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Volume 37,Issue 22
  • Eutrophication in cold-water lakes driven by combined effects of climate change and human activities
  • Authors:LÜ Xiaotian, LÜ Yonglong, SONG Shuai and WANG Tieyu
  • Abstract:Eutrophication has become one of the most serious threats to aquatic ecosystems in the world, especially to water quality of lakes as drinking water sources, and further posed negative effects on the health of local residents. With the combined drivers of climate change and human activities, eutrophication has expanded from shallow lakes in temperature zone to water lakes in cold areas (named as cold-water lakes). Trends, characteristics and research advances in eutrophication of cold-water lakes throughout the world were summarized. Besides, influences of climate change and human activities, including agricultural activities, livestock farming and misguided policies, on eutrophication processes of cold-water were also analyzed. In the future research, eutrophication mechanism of cold-water lakes should be further explored and ecological restoration is desiderated to ensure the ecosystem health of the cold-water lakes and improve the quality of drinking water.
  • DownLoad:Eutrophication in cold-water lakes driven by combined effects of climate change and human activities.PDF
  • Studies on three-source partitioning of soil respiration
  • Authors:SONG Wenchen, TONG Xiaojuan, LI Jun and ZHANG Jinsong
  • Abstract:Partitioning soil respiration into three components (root respiration, rhizomicrobial respiration, and basal respiration) is called "three-source partitioning of soil respiration". These components are three different biological processes, and their responses to environment change are different. Therefore, it is important and significant to partition soil respiration into autotrophic and heterotrophic respiration to evaluate terrestrial ecosystem carbon balance quantitatively. Although there has been a general understanding of autotrophic and heterotrophic respiration affected by environment factors, the mechanisms underlying their role in the rhizosphere and their ecological significance are still not fully comprehended. To determine the mechanisms of the rhizosphere system response to environmental change, rhizosphere respiration should be partitioned into root respiration and rhizomicrobial respiration. In the present study, we discussed the significance, methods, and applications of three-source partitioning of soil respiration, and summarized the results under different conditions. Methods of three-source partitioning of soil respiration include physical excised method (such as the root excised method), isotopic tracer continuous labeling (such as 13C natural abundance), and isotopic tracer pulse labeling (such as 14C pulse labeling). The isotopic tracer pulse labeling method is more accurate than the other methods; however, it cannot be utilized in field studies and is expensive to undertake. The physical excised method is cheaper and requires no complex calculation; however, it greatly disturbs the soil and roots, which casts doubts on the relevance of the results. The isotopic tracer continuous labeling method has advantages for in situ measurements, accurate tracing, and causes almost no disturbance. However, this method can be utilized only under special conditions (such as when the plant organics are from C3 and the basal soil organic matter are from C4) and further study is required to improve its applicability. Therefore, it is difficult to partition soil respiration into the three components under field conditions. The excised roots and trenching method and 13C natural abundance method can be utilized in field studies, especially in forest ecosystems. The results showed that the proportion of root respiration and the proportion of rhizomicrobial respiration to rhizosphere respiration was approximately 45% and 55%, respectively, under laboratory conditions, and approximately 60% and 40%, respectively, under field conditions. Root respiration, rhizomicrobial respiration, and basal respiration varied with climate, depth, soil nutrition, and other environmental factors. Decomposition of rhizoorganisms, which causes rhizomicrobial respiration, has the potential to influence greatly basal respiration. The variation of the three components reflect the turnover rate of soil carbon, and affect the acquisition of competition and symbiosis by plants and microorganisms, thus maintaining nutrient balance among the various components of an ecosystem. The conventional three-source partitioning methods might produce great uncertainty by ignoring the root-microbial system processes in the soil. These processes include the adaptation of soil microbes, rhizosphere priming effects, nutrient partitioning, etc. Rhizomicrobial respiration is an important part of soil respiration in plantations and cannot be ignored. Three-source partitioning of soil respiration is a useful approach to quantitatively evaluate forest underground CO2 flux as the global climate changes. The outlooks of the present study on the three-source partitioning of soil respiration were also discussed and clarified.
  • DownLoad:Studies on three-source partitioning of soil respiration.PDF
  • Research advances on the ecological effects of microplastic pollution in the marine environment
  • Authors:LIU Qiang, XU Xudan, HUANG Wei, XU Xiaoqun, SHOU Lu and ZENG Jiangning
  • Abstract:Microplastic contamination of the marine environment has become a global environmental problem. Because of their small dimensions, microplastics can easily interact with a wide range of marine organisms, enter their bodies in various ways, and accumulate in and transfer between their tissues and organs, which results in toxic effects. Absorption and ingestion of microplastics, primary by lower trophic-level organisms, can be transferred along the marine food chain, threatening marine ecosystem health and stability. For this reason, the interaction between marine organisms and microplastics, and the ecological effects of marine microplastic pollution have become hotspots for current studies. Based on the review of biofouling of marine organisms on the microplastic surface, ingestion of microplastics, toxic effects of microplastics on marine organisms, and the combined toxic effects of microplastics with other chemical contaminants, this study proposed that future research on the ecological effects of microplastic pollution should focus on marine organism ingestion of microplastics in the marine environment of China, biological effects and toxicological mechanisms of microplastics on organisms, combined effects of microplastics with other contaminants, and the functions of microplastics in the marine ecological system and their biogeochemical behaviors.
  • DownLoad:Research advances on the ecological effects of microplastic pollution in the marine environment.PDF
  • Advances in landscape genetics of plants
  • Authors:SONG Youtao, SUN Zicheng and ZHU Jinghai
  • Abstract:Landscape genetics of plants is an important research direction of the newly emerged interdisciplinary landscape genetics, which lags behind that of animals. These studies are increasingly important for the conservation of biodiversity and reserve management. This article briefly summarizes the major advances in plant landscape genetics in the past ten years form two aspects:the effects of landscapes on migration, dispersal, and gene flow measured by neutral genetic variation; and the interaction between the environment and adaptive genetic variation in natural populations and individuals. In addition, it compares landscape genetics of plants with that of animals through different study designs and analytical approaches. Due to the complexity of plant dispersal, landscape elements and analytical approaches are not generally considered in landscape genetics studies. For example, the least cost path analysis, popular in animal studies, is rarely used in plant studies. Furthermore, this article elucidates five problems in current studies of plants:(1) many studies lack an explicit research design for evaluating the effect of landscape pattern on genetic structure; (2) genetic structure is often analyzed with regard to contemporary landscapes, but it may reflect historical landscapes; (3) misleading results could be produced when limited loci are matched roughly to a combination of environmental variables; (4) studies on gene flow and adaptation have not yet been combined; and(5) many statistical methods could be inappropriate for landscape genetics. Plant landscape genetics studies should focus on solving these problems in the future and move from the description of spatial genetic structure to quantifying and predicting the effect of landscape pattern on genetic variation.
  • DownLoad:Advances in landscape genetics of plants.PDF
  • Temporal-spatial analysis of vegetation coverage dynamics in Beijing-Tianjin-Hebei metropolitan regions
  • Authors:LI Zhuo, SUN Ranhao, ZHANG Jichao and ZHANG Chong
  • Abstract:Identifying the dynamics of vegetation coverage is important for the research of ecological security and ecosystem services. This study analyzed MODIS NDVI remote sensing data and identified the temporal-spatial dynamics of vegetation coverage during 2005-2015 in Beijing-Tianjin-Hebei metropolitan regions. The analysis methods included linear regression, coefficient of variation, R/S analysis, and other mathematical methods. The results showed that (1) the vegetation coverage increased by 0.065 from 2005 to 2015. The vegetation restoration experienced a stable fluctuation phase after two fast-improving periods. (2) The significantly improved area occupied 47.45% of the region and the insignificant area accounted for 33.9% of the region, which was mainly in the North China Plain. The degraded area accounted for 6.8% of the region and was scattered in the surroundings of big cities. (3) The sustainability of vegetation restoration was dominant (58.8%) in the Beijing-Tianjin-Hebei region. The vegetation area of anti-sustainability accounted for 34.4%, mainly distributed in Zhangjiakou, Cangzhou, and the south-east of Baoding. The continuous degradation area was only 4.8% of the region and distributed in the cities of Tianjin, Langfang, and Cangzhou. These results could be useful for identifying the dynamics of vegetation coverage and predicting the potential trends of ecological network connectivity.
  • DownLoad:Temporal-spatial analysis of vegetation coverage dynamics in Beijing-Tianjin-Hebei metropolitan regions.PDF
  • Dynamic response of the coastline and coastal landscape patterns to Hemeroby:A case study along the south coast of Yingkou
  • Authors:LIU Fuqiang, WU Tao, JIANG Guojun, Xuelian Meng, TONG Liying, ZHANG Yong, SUO Anning and ZHU Lidong
  • Abstract:Multi-temporal remote sensing data were used to extract coastline change information and calculate fractal dimensions from 1990 to 2015 for the south coast of Yingkou. Fishnet tools in Arcgis10.2 were used to create the analysis units. This study explored the dynamic response of the coastline and coastal landscape patterns to Hemeroby along the south coast of Yingkou using landscape pattern and Hemeroby indexes. The results showed that (1) Reclamation increased the shoreline and coastline fractal dimensions. Shoreline annual growth rate were 0.52%(1990-2000), 0.53%(2000-2005), 4.98%(2005-2010), and 0.96%(2010-2015); (2) The landscape pattern index reflected the landscape boundary, complexity, and fragmentation of the landscape, which increased prior to 2005, but exhibited a decreasing trend thereafter. (3) During the study period, the areas of low and high Hemeroby increased, whereas the area of moderate intensity decreased. (4) Synchronous changes occurred in Patch Density,Edge Density,Total Edge,Landscape Shape Index,Mean Fractal Dimension and the Hemeroby Index. The Shannon diversity index was inversely related to human disturbance intensity. (5) The change in shoreline length and shoreline fractal dimensions was negatively correlated with the degree of human disturbance, with correlation coefficients of -0.97 and -0.98, respectively. This indicated that the weaker human activity was, the longer and more complex the shoreline became.
  • DownLoad:Dynamic response of the coastline and coastal landscape patterns to Hemeroby:A case study along the south coast of Yingkou.PDF
  • Correlation analysis between the spatial characteristics of land use/cover-landscape pattern and surface-water quality in the Ebinur Lake area
  • Authors:WANG Xiaoping, ZHANG Fei, LI Xiaohang, CAO Can, GUO Miao and CHEN Lihua
  • Abstract:To understand the effect of land use/cover-landscape on water quality, this study selected the Xinjiang Ebinur Lake region as the study area. We took 25 water sampling points to build five buffer zones, and combined land use/cover types with water-quality monitoring data, selected land-use types, and landscape index (landscape level) to monitor water quality. We tried to study the effects of a wide range of buffer land use/cover-landscape patterns on water quality indexes using the redundancy analysis method. Subsequently, we analyzed the specific location of the water-quality variables along the landscape gradient using the change-point analysis method. The results indicated:(1) the landscape pattern has different effects on the river-water quality indexes in different buffer zones. A 4 km buffer of land use/cover landscape pattern seems to be a threshold for differentiating the regional water quality. (2) The major environmental variables affecting the water quality of the lake area are the patch density, the patch density, and the degree of aggregation in a buffer of 4 km. (3) When the edge density (ED), of cultivation was 90-105 m/hm2, and the aggregation of forest and grassland index of water was 70%-90%, and the water quality in this region appeared to be better protected. This study performed the quantitative analysis of the land use/landscape pattern changes from multiple perspectives in the Ebinur Lake area, revealing the main regularities of the landscape ecology variation in the region. This study provides the theoretical basis for the optimization of regional landscape pattern and reasonable land planning. It improves the "Silk Road Economic-One Belt and One Road" initiative of the ecological environment and sustainable utilization of resources in the Ebinur Lake area in Xinjiang.
  • DownLoad:Correlation analysis between the spatial characteristics of land use/cover-landscape pattern and surface-water quality in the Ebinur Lake area.PDF
  • Evaluation on the intensive utilization of sea area based on ecosystem management theory:a case study on coastal cities of Hebei Province
  • Authors:KE Lina, HAN Xu, HAN Zenglin, WANG Hui, SUN Caizhi, WANG Quanming and XU Shuting
  • Abstract:Based on ecosystem management theory, an evaluation index system of the intensive utilization of sea area was constructed, which covered four aspects, namely marine input intensity, marine utilization intensity, marine economic benefits, and marine ecological environmental quality. This study used the fuzzy decision theory to calculate the weight of each index, obtained the composite index of the intensive utilization of sea area in coastal cities of Hebei Province from 2005 to 2014, and analyzed the regional difference characteristics of intensive utilization of sea area in Hebei Province by use of cluster analysis and coordination degree method. The results showed that:(1) The condition of the intensive utilization of sea area in coastal cities of Hebei Province was improved continually from 2005 to 2014. Except for the marine ecological environmental quality index criterion layer, the marine input intensity, marine utilization intensity and marine economic benefits were all on the rise, and the most obvious trend of continuous increase was observed in the marine economic benefits criterion layer. (2) The changes in the three coastal areas of Hebei Province were basically the same in the time-sequence variations in the intensity of intensive utilization of sea area and the criterion layers, but different regions still embodied different characteristics of change. Intensity of the intensive utilization of sea area in Cangzhou city was the highest, Tangshan city experienced a process of low to high intensity, and the situation of the intensive utilization of sea area in Qinhuangdao was roughly at an average level. (3) Hebei Province and the three coastal cities maintained a high degree of coordination on the whole, but the variation characteristics of different periods and regions were different also.
  • DownLoad:Evaluation on the intensive utilization of sea area based on ecosystem management theory:a case study on coastal cities of Hebei Province.PDF
  • Evaluation of the tourism efficiency loss due to the influence of carbon emissions from tourism in China
  • Authors:ZENG Yuxi, ZHONG Linsheng and YU Hu
  • Abstract:Tourism efficiency (TE) has received increasing attention in research and policy development. Considering that CO2-emission is one of the important factors influencing TE at both, international and regional levels, the need to understand its impact on TE is not only a managerial challenge, but also an issue of vital importance. This paper proposes a conceptual framework of tourism efficiency-loss (TEL), and calculates the TE and TEL of 30 Chinese provinces during 2001-2014 by utilizing the transcendental logarithmic production function, followed by the analysis of TEL variables using the panel regression model. Our results show that:(1) TEL can serve as an indicator of the impact of carbon emissions on TE. (2) For the entire study period, the CO2-emission has resulted in a high TEL value for all provinces, especially in central China. At the provincial level, most of the eastern provinces (e.g., Tianjing, Shandong, Zhejiang, Jiangsu, etc.), small parts of the central provinces (e.g., Henan), and parts of the western provinces (e.g., Qinghai and Inner Mongolia) showed a lower TEL value, while most of the central and western provinces, such as Shanxi, Hunan, Hubei, Gansu, etc., showed a relatively high TEL value.(3) An average increase was observed in the growth rates of both TE and TEL; however, the annual growth rate of TEL was relatively higher than that of TE. The general TEL levels have been experiencing a rising trend over the past 15 years in China, and the eastern region became the fastest region, followed by the western and northeast region. On the contrary, the central provinces experienced a decrease in the rate of TEL. (4) According to their TE and TEL values, the Chinese provinces can be categorized into four types:high-TE and low-TEL, high-TE and high-TEL, low-TE and high-TEL, and low-TE and low-TEL. The "high-TE and low-TEL" regions included Tianjing, Shanghai, Jiangsu, Zhejiang,Shandong,Guangdong, Henan, and Jilin, mostly in eastern China; the "high-TE and high-TEL" regions included Beijing, Hebei, Fujian, Shanxi, Anhui, Hubei, Hunan, Liaoning, and Chongqing, mostly in central China; the "low-TE and high-TEL" regions included Heilongjiang, Inner Mongolia, Sichuan, Yunnan, Shanxi, and Qinghai, mostly in northeast and northwest China; and the "low-TE and low-TEL" regions included Hainan, Jiangxi, Guangzhou, Gansu, Ningxia, and Xinjiang, mostly in central-western China. (5) The impacts of the infrastructure, reception capacity, attraction, industrial scale, industrial structure, and energy technology varied according to the type of region, making the selection of optimization measures different in each region. The "high-TE and low-TEL" regions should further improve the energy technology and optimize the structure of tourism industry. The "high-TE and high-TEL" regions should use energy-saving technology, reduce emissions from tourism transport, and speed up the transformation of the mode of traditional tourism development pattern to a more connotative and intensive growth pattern. The "low-TE and high-TEL" regions should focus on raising tourism scenic marginal benefit, optimizing the tourism industrial structure and improving the level of energy conservation and intensive utilization of resources and tourism management. The "low-TE and low-TEL" regions should adjust the structure of the tourism industry, pay attention to the protection of tourism resources and environment, and reduce the negative impact of transportation on the environment.
  • DownLoad:Evaluation of the tourism efficiency loss due to the influence of carbon emissions from tourism in China.PDF
  • Dynamic evolution and driving forces of ecological security in the Traditional Industrial Area of northeastern China
  • Authors:TANG Chengrui, LU Chengpeng, YANG Qing, JIANG Lu, REN Wanxia and XUE Bing
  • Abstract:Ecological security is as important as national, economic, and financial security and has become the main constraint of future socio-economic security. The Traditional Industrial Area of northeastern China is an important traditional industrial and grain production base of China, and its ecological security is related to the implementation of sustainable development strategies. Based on the emergy-ecological footprint model, the ecological security in Traditional Industrial Area of northeastern China was quantitatively evaluated from 2000 to 2014, followed by a scenario analysis on the driving forces of the ecological security using a principal component analysis method. The results showed that, the value of emergy ecological-capacity per capita decreased from 0.66 to 0.64 hm2/cap, whereas the emergy-ecological footprint increased from 10.58 to 19.85 hm2/cap, which indicated that an ecological deficit existed in the Traditional Industrial Area of northeastern China. The ecological pressure in this area increased, showing an unsustainable development trend from 2000 to 2014. The ecological pressure index and ecological security levels gradually increasing, ecological security situation is deteriorating, ecological security issues to be urgent resolved. The ecological stress tended to be serious as a result of a combination of several factors, such as social, economic, population, resource, environmental, technological level, and land use degree. Finally, effective management strategies and suggestions to improve the ecological security of the Traditional Industrial Area of northeastern China were proposed.
  • DownLoad:Dynamic evolution and driving forces of ecological security in the Traditional Industrial Area of northeastern China.PDF
  • Walk score method-based evaluation of social service function of urban park green lands in Futian district, Shenzhen, China
  • Authors:WU Jiansheng and SHEN Nan
  • Abstract:Green Lands in urban parks are important and indispensable parts of the contemporary cities. Whether citizens can conveniently enjoy facilities and services supplied by the urban parks is regarded as a significant indicator of the harmonious man-land relationship, urban modernization, and inhabitants' life quality. Furthermore, it embodies the social service function of the green lands in urban parks. This study selected Futian district as the study region. Single-point green land walk score was calculated to determine the walking accessibility of green lands. The population of Futian district was spatialized based on its land-use data. Combining the data of green lands and population distribution, this study evaluated the social service function of urban park green lands by determining the walking convenience of citizens in these green lands. Based on the isotropic area hypothesis, the overall walking accessibility of urban park green lands was found to be good in Futian. However, a huge difference was observed among different regions of Futian. A clear declining trend was observed from the eastern to the western parts of Futian. The green lands in Merlin Park, south Lianhuashan Park, Lychee Park, and Dahuang Park were considered highly accessible, whereas those in the northwestern and southwestern parts of Futian district were not. In addition, citizens could enjoy the services provided by these green lands conveniently and fairly in 70% of sub-districts; Huaqiangbei, Lianhua, Yuanling, and Huafu sub-districts had rather good open park space facility, and they performed a reasonable match between the green lands and population pattern. The status of green lands in the urban parks of Xiangmihu and Shatou sub-districts still needed to be improved. This manuscript presented a case study of the assessment of green land construction in urban parks using the walk score method. It particularly explored a new idea in applying walk score, providing useful reference for the construction of pedestrian city and spatial distribution optimization of green lands in urban parks.
  • DownLoad:Walk score method-based evaluation of social service function of urban park green lands in Futian district, Shenzhen, China.PDF
  • Photosynthetic nitrogen-use efficiency of Manglietia glauca seedling leaves under different shading levels
  • Authors:TANG Jingchao, SHI Zuomin, LUO Da and LIU Shirong
  • Abstract:Photosynthetic nitrogen-use efficiency (PNUE), which is defined as the ratio of light-saturated photosynthesis (Amax) to nitrogen concentration in a defined leaf area (Narea), is considered an important trait for characterizing species regarding their leaf economics, physiology, and strategy. The light environment may influence photosynthetic capacity and leaf nitrogen content, and may also influence biochemical factors that affect PNUE such as nitrogen allocation to the photosynthetic apparatus, CO2 diffusion from the atmosphere to the site of carboxylation, and specific activity of the photosynthetic enzymes. The objective of this study was to describe the inherent PNUE variation in leaves of Manglietia glauca seedlings grown under varying light environments. An improved understanding of this process is of great importance for M. glauca seedling cultivation and artificial pure forest modification. The results showed that Amax of M. glauca seedlings grown under 60% shade (6.03 μmol m-2 s-1) was higher than that under other shading levels, mainly because of a higher maximum carboxylation rate (32.93 μmol m-2 s-1) and a higher maximum electron transport rate (61.83 μmol m-2 s-1). Thus, moderate shading may assist in the cultivation and planting of M. glauca seedlings because Amax improvement could significantly enhance their growth rate. No significant differences were observed in intercellular and chloroplast CO2 concentrations in M. glauca seedlings grown under different shading levels. Mesophyll conductance and stomatal conductance of M. glauca seedlings grown under 90% shade were lower than those under other shading levels. No significant difference was observed in the PNUE of M. glauca seedlings grown under different shading levels, because Narea changed synchronously with Amax, which was largely attributed to the lack of significant difference in the proportion of total leaf nitrogen allocated to Rubisco and bioenergetics in such seedlings. Shading significantly enhanced the proportion of total leaf nitrogen allocated to light-harvesting machinery (PL) in the following order:90% shade (0.296 g/g) > 60% (0.216 g/g) > 0 (0.132 g/g). However, enhanced PL under increased shade did not improve the PNUE. The proportion of total leaf nitrogen allocated to the photosynthetic apparatus (PP) was higher than that allocated to the cell wall (PCW); for M. glauca seedlings grown under 0, 60%, and 90% shade:PP was, respectively, 3.3, 5.8, and 6.0 fold higher than that of PCW. The PP of M. glauca seedlings grown under 90% shade was higher than that observed under 60% shade, and the lowest PP was observed under 0 shade. No significant difference in PCW was observed in seedlings grown under the different shading levels. The proportion of total nitrogen allocated to other plant organs (1-PP-PCW:POther) was higher than PP and PCW under all shading levels in the following order:0 shade (0.755 g/g) > 60% (0.683 g/g) > 90% (0.596 g/g). The relatively high POther under all shading levels implied sufficient nitrogen supply in the leaf for Rubisco, bioenergetics, light-harvesting machinery, and the cell wall. Thus, there was no relative change in the proportion of total nitrogen allocated to these components, and the PL increase was attributed to other nitrogen pools. In conclusion, for artificial pure forests where M. glauca seedlings are planted, forest gaps should be restricted, because the species is adapted to a moderately shaded light environment. In addition, when subject to shading, M. glauca seedlings should receive additional nitrogen to replenish leaf nitrogen consumption.
  • DownLoad:Photosynthetic nitrogen-use efficiency of Manglietia glauca seedling leaves under different shading levels.PDF
  • Phylogenetic development and functional structures during successional stages of conifer and broad-leaved mixed forest communities in Changbai Mountains, China
  • Authors:HOU Manman, LI Xiaoyu, WANG Junwei, LIU Shuai and ZHAO Xiuhai
  • Abstract:Community assembly has long been an important issue in community ecology. By quantifying the influence of habitat filtering, competitive exclusion, and random community assembly on the phylogenetic and functional traits, ecologists would gain a deeper understanding of community construction. In this study, based on the datasets of three 5.2 hm2 permanent plots at different successional stages (i.e., a Populus davidiana-Betula platyphylla secondary forest, a secondary conifer and broad-leaved mixed forest, and a Primary Tilia amurensis-Pinus koraiensis forest), we established the phylogenetic trees according to the Angiosperm Classification System (APG Ⅲ) and seven functional traits (i.e., leaf area, specific leaf area, leaf thickness, leaf nitrogen content, leaf phosphorus content, nitrogen-phosphorus ratio, and maximum tree height). We correlated the phylogenetic trees with the environmental variables to examine the patterns of the phylogenetic and functional structures of the forest communities at different successional stages in Changbai Mountains of China. The results showed that:(1) at each successional stage, significant phylogenetic signals were found for all seven functional traits, indicating that the functional traits were influenced by the phylogenetic history. (2) Both the phylogenetic and functional structures were non-random at all successional stages and stem classes. The phylogenetic and functional structures changed from "clustered" to "overdispersed" during the succession of forest community. Meanwhile, the degree of phylogenetic and functional clustering decreased with an increase in diameter class, indicating a significant increase in competitive exclusion with the succession of forest community. (3) The phylogenetic and functional turnovers were non-random, and the explanatory ability of the factors to interpret the phylogenetic and functional turnover was different. In the early succession stage, the spatial distance explained more than the environmental distance, indicating the importance of habitat filtering in community assembly. However, in the late succession stage, the environmental distance explained more than the spatial distance, indicating the importance of dispersal limitation in community assembly.
  • DownLoad:Phylogenetic development and functional structures during successional stages of conifer and broad-leaved mixed forest communities in Changbai Mountains, China.PDF
  • Relationships between forest canopy greenness and tree radial growth in the Mengshan Mountains of Shandong Province
  • Authors:WANG Zhou and FANG Ouya
  • Abstract:Forest canopy greenness and tree-ring widths are important indices describing the processes of forest growth. Questions about the relationships between the two indices and their temporal stability are still not completely answered. The canopy greenness index calculated from remote sensing maps is continuous in space, whereas tree-ring width is a comprehensive index that represents the health of the sample sites. Research concerning the relationship between canopy greenness and tree-ring width could enhance the understanding of growth conditions from multi-perspectives and help transform growth conditions of forests at different spatial scales. We collected increment cores from a Pinus densiflora forest at four sample sites with different health conditions in the Mengshan Mountains of Shandong Province and analyzed the relationships between enhanced vegetation indices and tree-ring widths. We found that 1) the variation in tree-ring width was significantly caused by the variation in forest canopy greenness in April and June for healthy forests as calculated using the Granger causality analysis, whereas the relationship was complicated for unhealthy forests. April and June represent the green-up period of the growth season, and according to the results, this green-up period was closely related to radical growth; 2) canopy greenness in other months and radial growth did not have a causality relationship, rather they were both driven by other environmental factors, especially climatic factors; and 3) we used superposed epoch analysis to determine the influence of canopy greenness decrease events on radical growth, and radical growth recovery following the canopy greenness decrease events. Moderate canopy greenness decreases were not always accompanied by a decrease in radial growth; however, if radial growth had already started to decline before the severe greenness loss, then the decrease would continue for five years after canopy greenness decrease event. Radial growth experienced difficult recovery after moderate canopy greenness decrease events. We identified two or three severe canopy greenness decrease events during 2000 to 2014. After these events, radial growth significantly decreased and continued to decrease for years. Radial growth was not completely recovered five years after severe canopy greenness decrease events. The results showed that changes in forest canopy greenness could not represent the beginning of forest stress or the process of forest restoration. Correlations between canopy greenness and tree radial growth existed only in healthy forests. Declines in canopy greenness strongly influenced radical growth and was difficult to recover after losses in greenness.
  • DownLoad:Relationships between forest canopy greenness and tree radial growth in the Mengshan Mountains of Shandong Province.PDF
  • Spatial variation characteristics of carbon density and storage in forest ecosystems in a typical subtropical region
  • Authors:DAI Wei, ZHAO Keli, GAO Zhiqun, LIU Kanghua, ZHANG Feng and FU Weijun
  • Abstract:Spatial pattern information of carbon density and storage in forest ecosystems plays an important role in the evaluation of carbon sequestration potentials and healthy forest management. Forest vegetation carbon, soil organic carbon, forest litter carbon and dead tree carbon are the four main carbon pools in forest ecosystems. Most of previous studies on carbon density and storage in forest ecosystems are based on the continuous forest inventory system in China or ecosystem models; however, there is little information on the spatial variation of forest ecosystems. Compared to traditional research methods, geostatistical methods combined with kriging spatial interpolation and Moran's I have been regarded as an effective tool to explore spatial variation, which have been successfully used to investigate the spatial variability of environmental variables and to incorporate this information into mapping. Therefore, it is widely applied to analyze spatial heterogeneity of forest and soil variables. In 2012, based on the annual data from the Forest Resources Monitoring Center in Zhejiang Province, a total of 838 forest sample plots were established based on a 4 km (south-north)×6 km (east-west) grid system in Zhejiang Province, and the area of each plot was 0.08 hm2. The portable global positioning system (GPS) was used to record the longitudes and latitudes. In this study, we analyzed the spatial variation characteristics of carbon density and storage of forest ecosystems in Zhejiang Province using geostatistical methods and Moran's I. The results showed that the average carbon density of forest ecosystems in Zhejiang Province was 145.22 t/hm2, and the forest vegetation layer, soil layer, forest litter layer, and dead tree layer carbon densities were 27.34 t/hm2, 108.89 t/hm2, 1.79 t/hm2, and 1.38 t/hm2. Kriging spatial interpolation and Local Moran's I showed that the spatial distribution of carbon density gradually decreased from southwest to northeast, similar to topographic changes in Zhejiang Province, which was influenced by both natural factors such as altitude, forest age, forest types, typhoon climate, and human activities. The carbon storage of forest ecosystems in Zhejiang Province was 877.19 Tg C, of which 203.88 Tg C was in the forest vegetation layer, 656.20 Tg C in the soil layer, 10.84 Tg C in the forest litter layer, and 6.27 Tg C in the dead tree layer, accounting for 23%, 75%, 1.3%, and 0.7% of the total carbon storage, respectively. The soil layer was the largest carbon pool in forest ecosystems, which was about three times as large as the forest vegetation layer, and which was the most important contributor to the carbon storage of forest ecosystems in Zhejiang Province. There are abundant forest resources in Zhejiang Province; most of the forests are young and middle-aged forests, which account for 76.76% of the total forest area in Zhejiang Province, and the young and middle-aged forests often have relatively low carbon density, but grow fast. Therefore, we should strengthen the healthy management of young and middle-aged forests and enhance the carbon sequestration potentials of forest ecosystems in Zhejiang Province in the future, in order to regulate the global carbon cycle, mitigate the increase in atmospheric CO2 concentrations, and maintain global climate.
  • DownLoad:Spatial variation characteristics of carbon density and storage in forest ecosystems in a typical subtropical region.PDF
  • Hydrogen and oxygen stable isotopic composition in a deciduous forest ecosystem in Canada
  • Authors:ZHU Shanxian, XIAO Wei, ZHANG Mi, WANG Wei, SHEN Jing, XU Jiaping, HU Yongbo, WEN Xuefa and LI Xuhui
  • Abstract:Hydrogen and oxygen stable isotopes in terrestrial ecosystems can provide unique trace information for studies on water exchange between land and the atmosphere and the hydrological cycle in terrestrial ecosystems. We observed stable isotopic composition and environmental factors in a Canadian deciduous forest during the 2009 growing season. The spatial pattern and temporal variability in isotopic composition for various ecosystem water pools and atmospheric water vapor were analyzed. Further, the variability of the isotopic composition of ecosystem evapotranspiration, and soil evaporation, and their isoflux were analyzed. The main controlling environmental factors were discussed. The results indicated that the isotopic composition varied in different water pools. The isotopic composition of leaf water was more enriched and more variable with comparison to twig and soil water. The H218O and HDO composition of atmospheric water vapor (δ18Ov and δDv) decreased with increasing height, and the opposite occurred for deuterium-excess. The diurnal pattern of water vapor isotopes showed a "W" pattern, decreased during the morning, rose and fell slightly at noon, and increased in the afternoon. The isotopic composition of water vapor was significantly correlated with atmospheric moisture, and the mid-day means of the deuterium excess of atmospheric water vapor were both negatively correlated with surface relative humidity and the water vapor mixing ratio, with correlation coefficients of -0.61 (P < 0.01) and -0.57 (P < 0.01), respectively. The H218O composition of evapotranspiration was higher at noon and in the evening and lower in the afternoon because of the influence of evapotranspiration rate and leaf-water enrichment. The isoflux indicated that evapotranspiration could promote the isotopic enrichment of atmospheric water vapor, with a maximum isoflux of 147.5 mmol m-2 s-1 ‰. Our results could provide data support and theory reference to the development of isotopic hydrological models.
  • DownLoad:Hydrogen and oxygen stable isotopic composition in a deciduous forest ecosystem in Canada.PDF
  • Characteristics of sap flow and correlation analysis with environmental factors of Acer wangchii in the karst area
  • Authors:WU Peng, YANG Wenbin, CUI Yingchun, ZHAO Wenjun, SHU Deyuan, HOU Yiju and DING Fangjun
  • Abstract:The Thermal Dissipation Probe (TDP) method was used to conduct long-term continuous observations from February 2012 to March 2014 on the sap flow velocity of Acer wangchii in karst regions. In addition, environmental factors including air temperature (Ta), relative humidity (RH), solar radiation (Solar), wind speed (WS), rainfall, soil water content (SWC), and the characteristics of A. wangchii sap flow were investigated, and correlations between environmental factors and different temporal scales were determined. The findings revealed the following:1) sap flow velocity in relation to different weather conditions, in descending order, was sunny, cloudy, and rainy days, and the sap flow was generally high in the daytime and low at night; 2) the average amount of sap flow was 5.08 kg/d, with the sap flow quantity varying in different seasons, in descending order of (8.38 ±5.32) kg/d in summer, (5.16 ±3.99) kg/d in autumn, (4.86 ±3.77) kg/d in spring, and (1.94 ±1.40) kg/d in winter; 3) the monthly sap flow was 153.64 kg and the annual sap flow was 1838.40 kg, on average; 4) on the hourly scale, solar radiation over 1 day was the main environmental factor influencing sap flow regardless of the weather conditions, while the influence of the other environmental factors on sap flow varied in the daytime, at night, and in different seasons and rainfalls; and 5) over 1 year:on the hourly scale, 63.50% of the sap flow could be interpreted jointly by the environmental factors including solar radiation, Ta, RH, SWC10cm and WS. On the daily scale, 68.50% of the sap flow could be interpreted jointly by the environmental factors including solar radiation, Ta, SWC10cm and rainfall. On the monthly scale, the sap flow quantity could be interpreted with the single environmental factor, Ta, which contributed 74.80% to the total. With the time scale reducing, the more environmental factors were involved in the regression equation, the lesser interpretation of sap flow quantity (R2) would be. In comparison to similar findings from other regions, the impact of environment factors on sap flow diverged greatly. However, on temporal scales, solar radiation or PAR and Ta were the two major factors that affected sap flow, and no environmental factor contributed in the interpretation of sap flow on rainy days, which is consistent with the present study. Therefore, estimates of the impact of environmental factors on sap flow on rainy days deviate, and particular attention should be paid to the role of soil water content.
  • DownLoad:Characteristics of sap flow and correlation analysis with environmental factors of Acer wangchii in the karst area.PDF
  • Dynamics and quality of leaf litter fall in pure Pinus massoniana plantations
  • Authors:LU Xiaohui and DING Guijie
  • Abstract:Litter is an important component of forest ecosystems, and its production and substrate quality influence the cycling of nutrients among plants and the soil. Therefore, to explore the relationships among litter production, litter chemistry, and meteorologic factors, three Pinus massoniana stands with different stand densities (low, medium, and high) were selected and compared on a monthly basis. The production of leaf litter exhibited a bimodal distribution pattern, with a smaller peak in February and a higher peak during October and November. The concentration of N and P varied considerably among months (P < 0.05), with peak values observed from April to June and significantly lower values observed from August to December. The concentration of lignin (L) varied considerably among months (P < 0.05), with the highest concentration observed in February and subsequent decreases until July or August. The C/N, C/P, L/N, and L/P ratios also varied between months (P < 0.05), with significantly lower value in April, May, and June and significantly higher values in September, November, and December. The ranges spanned nearly two-fold or three-fold differences, and all were above critical values, which generally inhibits the release of N and P. Meanwhile, stand density significantly influenced litter quantity and N concentration (P < 0.05), with significantly more litter produced by the medium-density stand and a significantly lower N concentration in litter from the low-density stand. The substrate quality of the litter were closely related to litter quality and were influenced by temperature and precipitation, whereas monthly litter production was negatively correlated with the litter's N and P concentrations and positively correlated with its C/N, C/P, L/N, and L/P ratios. Therefore, greater litter production was associated with lower litter quality and, subsequently, slower decomposition.
  • DownLoad:Dynamics and quality of leaf litter fall in pure Pinus massoniana plantations.PDF
  • Estimation of ecological water demand of a desert riparian forest using tree rings of Populus euphratica in the Lower Tarim River
  • Authors:ZHOU Honghua, LI Weihong, LI Yupeng, WANG Yuyang and HUANG Xiang
  • Abstract:Estimation of the ecological water demand of natural plants is a key issue for the restoration and reconstruction of a fragile ecological region in arid areas. Tree rings of Populus euphratica in the Yingsu section of the lower reaches of the Tarim River and their responses to climate change and hydrological conditions were analyzed using the nonparametric Mann-Kendall trend test, Mann-Kendall-Sneyers test, moving t-test, one-way ANOVA, and Pearson correlation. The ecological water demand of a desert riparian forest in the Yingsu section was then estimated based on the tree ring characteristics using regression and stepwise regression models. The results showed that the abrupt temporal changes of temperature and precipitation were different from that of the standard chronology of P. euphratica in the lower reaches of the Tarim River. Moreover, there was no significant relationship between temperature and standard chronology of P. euphratica or between precipitation and standard chronology of P. euphratica in the lower reaches of the Tarim River. The Pearson correlation analysis also revealed no significant relationship between temperature and groundwater depth or between precipitation and groundwater depth in the lower reaches of the Tarim River. However, the width indexes of tree rings of P. euphratica were significantly and negatively related to the groundwater depth, and they were significantly and positively related to the amount of ecologically conveyed water from August to July in the Yingsu section of the lower reaches of the Tarim River. These results proved that historical information regarding water conditions could be accurately reproduced by the tree rings of P. euphratica in the lower reaches of the Tarim River. Therefore, the tree rings of P. euphratica could be used for quantitatively assessing the restoration effects of ecological water conveyance to desert riparian forests and calculating the ecological water demand for natural vegetation in the lower reaches of the Tarim River. The average contribution of ecological water conveyance to the increased tree ring width index was 42.96% in the Yingsu section of the lower reaches of the Tarim River. Estimated from the equation of the tree rings of P. euphratica and the amount of ecologically conveyed water, an annual ecological water conveyance of 0.84×108 m3 was expected to maintain the average growth (i.e., average tree ring index of 0.997 during 1933-2015) of P. euphratica in the Yingsu section within a distance of 300 m to the river channel in the lower reaches of the Tarim River. Furthermore, an annual water conveyance of 0.91×108 m3 was estimated to keep P. euphratica at an average radial growth rate of 0.972 during the period of 1933-1974 (i.e., before the main channel of the Tarim river near Yingsu section dried up).
  • DownLoad:Estimation of ecological water demand of a desert riparian forest using tree rings of Populus euphratica in the Lower Tarim River.PDF
  • Reconstruction of March-June mean air temperature along the timberline of Mount Taibai, Qinling mountains, northwest China, over the last 144 years
  • Authors:QIN Jin, BAI Hongying, LIU Rongjuan, ZHAI Danping, SU Kai, WANG Jun and LI Shuheng
  • Abstract:Since the vegetation of the timberline area at Mount Taibai in the Qinling mountains is of high elevation and rarely disturbed by anthropogenic activities,it is sensitive to climate change, thereby providing a proxy resource of past climate change information. However, to date, there have been no investigations that have integrated dendrochronological methods with Arcgis spatial analysis techniques to reconstruct the past climate change at specific elevations and locations. Herein, we presented a reconstruction based on extracted meteorological data from spatial interpolation and Larix chinensis tree ring widths. Climate growth response analysis revealed that the air temperature,particularly from March to June, was the principle factor that limited the radial growth of L. chinensis. By using dendrochronology techniques, we obtained a reconstruction of the March to June mean air temperature for the timberline of Mount Taibai over the period from 1870 to 2013. The reconstruction captured 57.2% of the temperature variance(55.5% after the degree of freedom is adjusted) after removing the tree-ring width values of 1997 and 1998 during the calibration periods. On the decadal scale, the pattern of cool-warm fluctuations exhibited frequent repetitive features., On average, the cold periods (16 years) always persist longer than the warm periods(10.8 years).The years 1870-1881, 1903-1918, and 1977-1996 were colder periods, whereas the years 1882-1892, 1919-1929, 1950-960, and 1997-2013 were relatively warmer. The temperature variations indicated three quasi-periodic changes on scales of 22-31 a,18-22 a and 10-13 a, which suggested that the Mount Taibai region may be associated with a huge-scale climate drive and solar activity. Our reconstruction exhibited good consistency with local historical records and reconstruction results from similar climatic regions for the same intervals.
  • DownLoad:Reconstruction of March-June mean air temperature along the timberline of Mount Taibai, Qinling mountains, northwest China, over the last 144 years.PDF
  • Effects of local landscape fragmentation on species richness at a macroecological scale
  • Authors:QIU Lian, TAO Tingting, HAN Shanrui, YANG Wenyu, LUAN Xiali, QIU Yanning, LIU Maosong and XU Chi
  • Abstract:Geographical patterns of biodiversity and their underlying mechanisms have been the focus of macroecological and biogeographical studies. Many hypotheses have been proposed to explain macro-scale geographic patterns of species richness, such as the water-energy, habitat heterogeneity, and evolutionary history hypotheses. Extensive studies have shown that at landscape scales, habitat fragmentation has important effects on spatial patterns of species diversity, but it is still unclear whether these effects on geographical patterns of biodiversity are pronounced at macroecological scales. Recent research has focused on the role of local landscape attributes in driving macro-scale biodiversity patterns. However, several different studies have drawn contradictory conclusions. In the present study, we used the distribution range data of 575 mammal species and 1328 avian species in mainland China extracted from the database of China's Species Information System to generate the geographical patterns of species richness per 100 km×100 km grid cells. We further used ordinary least squares (OLS) models and simultaneous autoregressive (SAR) models to examine the relationship between species richness and climate (including 19 bioclimatic variables), habitat heterogeneity (including 20 variables), and landscape fragmentation (including 24 patch-and landscape-level metrics representing fragmentation). Results showed that the SAR models could effectively solve the spatial autocorrelation problem, as indicated by the substantially reduced Moran's I index. The landscape fragmentation factors were significantly correlated with the species richness of both birds and mammals, presenting explanatory power of 30%-50% (non-spatial OLS models) or 60%-80% (SAR models), which is slightly lower than that of the climate and habitat heterogeneity factors. This indicates that the effect of local landscape fragmentation is non-trivial regarding macro-scale patterns of species richness. We further used the variation partitioning technique to quantitatively compare the relative importance of the three groups of influencing factors, i.e., climate, habitat heterogeneity, and local landscape fragmentation. The results showed that landscape fragmentation had largely overlapped explanatory power of 20%-40% with climate and habitat heterogeneity. The explanatory power of landscape fragmentation was higher for mammal than for bird species richness. In summary, our results suggested that local landscape fragmentation plays an important role in driving macro-scale species richness patterns. Therefore, local landscape attributes that model large-scale biodiversity patterns should be considered in future research. Our research will facilitate a better understanding of the drivers of biodiversity patterns at macroecological scales, and provides important implications for biological conservation.
  • DownLoad:Effects of local landscape fragmentation on species richness at a macroecological scale.PDF
  • Selection mechanism of rodents on the removal and predation microhabitats of seeds from different tree species
  • Authors:KANG Haibin, WANG Dexiang, CHANG Mingjie, KANG Bing, HU Youning, YU Fei, PANG Yue and TENG Qinglin
  • Abstract:Different types of seeds could be dispersed in various ways. Rodents show a significant preference in the microhabitats of predation sites and caching methods after seeds removal. Understanding the relationship between storing behavior and microhabitat is the key to study seedling establishment. The objective of this study was to reveal the effects of small rodents on seed dispersal patterns of constructive species in pine-oak mixed forests. Field experiments were conducted in the Huoditang forest region in the middle of the Qinling Mountains, Shaanxi Province, northwestern China. Coded plastic tags were used to study the seed fates of Quercus aliena var. acuteserrata, Pinus tabuliformis, and Pinus armandii. The results showed that the in situ seed predation rate of P. tabuliformis seeds was significantly higher than the seeds of the other three types of seeds. P. armandii seeds had the highest predation rate (60%) and cache rate (4.33%) after removal by rodents, and the longest average dispersal distance of predation sites (2.49 m). The small acorns of Q. aliena var. acuteserrata had the longest dispersal distance of cache sites after removal by rodents (4.92 m). All types of seeds except P. armandii seeds had over 85% of the sites were used as predation sites. P. tabuliformis seeds had no cache sites. Over 90% of the cache sites of the other three types of seeds contained a single seed. Most of the seeds were discarded after removal by rodents. The proportions of seeds that were cached under shrubs were higher for large and small acorns of Q. aliena var. acuteserrata and P. armandii seeds, which were 87.5%, 78.57% and 53.33% of the total number of seeds after cache by rodents, respectively. A lower proportion of seeds was cached on bare land. Most of seeds were eaten under shrubs. Only P. armandii seeds were eaten in the holes after removal by rodents. A higher proportion of P. tabuliformis seeds were eaten in situ than the other three types of seeds. Except P. tabuliformis seeds, the predation rates for the other three types of seeds tended to decrease along microhabitat changing from simple to complex (shrub to grass to shrub edge to bare land). The nutritive value of the seeds and the cost of the rodents' predation and removal process were the key factors affecting the fates of seeds, and rodents showed obvious preference in the microhabitats of seed storage and predation sites.
  • DownLoad:Selection mechanism of rodents on the removal and predation microhabitats of seeds from different tree species.PDF
  • The composition and vertical distribution characteristics of soil seed banks in soil coverage with biocrusts in the Shapotou Region
  • Authors:CHEN Mengchen, ZHANG Jingguang, FENG Li and TENG Jialing
  • Abstract:Using random sampling in the field and observing the emergence of seedlings, we studied the structure, the density and vertical distribution of soil seed banks in moss crusts, lichen crusts, and bare sands in the artificially re-vegetated region of Shapotou. We found that the soil seed banks of this region were mainly composed of annual herbs and had a simple species composition and a significantly higher seed density in soil covered by biocrusts than in bare sands (P < 0.01). However, the existence of biocrusts decreased the species diversity of soil seed banks and the similarity of soil seed banks with corresponding ground vegetation. Furthermore, although the total density of soil seed was not significantly different between the two types of crusts, there were differences in the distribution within the different soil layers. Specifically, the soil seed density in the 0-2 cm soil layer of lichen crusts was significantly higher than in the corresponding layer in moss crusts (P < 0.05), while that of moss crusts was higher in the 2-5 cm and 5-10 cm soil layers. Finally, the effects of biocrusts on vertical distribution of soil seed banks varied with biocrust types. For example, germinative seeds were primarily distributed in the 0-5 cm soil layer for moss crusts and in the 0-2 cm soil layer for lichen crusts and bare sands, and their abundance decreased with soil depths. These results suggest that biocrusts increase the soil seed bank density, but also change the vertical distribution pattern of soil seed banks in artificially re-vegetated regions. A substantial proportion of small seeds are present in soil covered by biocrusts, and these seeds lack germination potential and contribute little to the above-ground vegetation. However, they play a significant role in ecosystem stability and the sustainable development of deserts.
  • DownLoad:The composition and vertical distribution characteristics of soil seed banks in soil coverage with biocrusts in the Shapotou Region.PDF
  • Effect of controlled-release fertilization on nitrous oxide emission:a case study of a wheat-maize rotation system in the North China Plain
  • Authors:ZHANG Jing, LI Hu, ZHU Guoliang, XIA Guangli, MU Xiaoling, WANG Ligang, HUANG Chengcheng and JIANG Yuqian
  • Abstract:Nitrous oxide (N2O) plays an important role in global warming. N2O is long-lived and cause harm to the stratospheric ozone. The concentration of N2O has increased from 270 ppbv during the preindustrial period to 319 ppbv in 2005. The greenhouse effect of N2O is 296 to 310-fold higher than that of carbon dioxide, although its contribution is only 5% (2.6 Tg) of the total annual man-made greenhouse gas emissions in 2010. Use of fertilizer is a major factor in the increase in N2O levels in agricultural systems. The wheat-maize rotation system is one of the most popular cultivating systems in the North China Plain. In recent years, a new method of fertilization (controlled-release fertilization) has been introduced in this region to reduce N fertilizer losses and to save labor inputs; this has mainly been used in crop lands, such as paddy fields, wheat and maize growing systems, but also in vegetable fields, such as tomato fields. The reported results mostly focus on crop growing and nitrogen leaching, but rarely on the N2O emissions characteristics related to controlled-release fertilizers in wheat-maize rotation systems, and even more rarely on exact quantities of various controlled-release fertilizers being applied in the North China Plain. This study was conducted from October 2013 to October 2014, with the major focus on the effects of application of controlled-release fertilizers on nitrous oxide and crop yields. The N2O emission driving factors, such as the soil temperature, soil moisture, and the content of soil NO3--N, were also analyzed together with N2O fluxes. Five treatments were included in this study:control treatment (CK), controlled-release fertilization treatment 1 (CRF1), optimized controlled-release fertilization treatment 1 (80%CRF1), optimized controlled-release fertilization treatment 2 (80%CRF2), and controlled-release fertilization treatment 3 (CRF3+Urea). The results show that the high N2O peaks usually following the basal fertilization can be attributed to irrigation or precipitation. Irrigation during the period of wheat seeding establishment, and precipitation during the later period of maize cultivation may also result in weak N2O peaks. The N2O fluxes changed from -235.61 μg N2O m-2 h-1 to 2625.01 μg N2O m-2 h-1, and daily mean N2O fluxes ranged from 23.88 μg N2O m-2 h-1 to 51.39 μg N2O m-2 h-1. N2O fluxes were positively correlated to soil temperature at a depth of 5 cm for CK and CRF3+Urea; the correlation coefficient (r2) was 0.38 and 0.30, respectively. N2O fluxes were positively correlated to soil water filled pore space (WFPS) during wheat and whole rotation system for CRF1 and 80%CRF1 (for wheat:r2=0.50, P < 0.01; r2=0.39, P < 0.05; for whole system:r2=0.39, P < 0.05; r2=0.43, P < 0.05). For the same fertilizer type, compared to CRF1 treatment, 80%CRF1 reduced the annual N2O emission by 14.23%. For the same fertilizer rate, there was no significant difference between CRF1 and CRF3+Urea, but 80%CRF1 significantly reduced the annual N2O emission by 16.16% compared to 80%CRF2 (P < 0.05). There was no significant difference in crop yields between these treatments and the treatments practiced by farmers. In conclusion, controlled-release fertilizer management could reduce N2O emission from the wheat-maize rotation system while maintaining cropping yields.
  • DownLoad:Effect of controlled-release fertilization on nitrous oxide emission:a case study of a wheat-maize rotation system in the North China Plain.PDF
  • Spatial-temporal variations and influencing factors of carbon dioxide evasion from the Yellow River:An example of the Toudaoguai Gauging Station
  • Authors:LI Lingyu, YU Ruihong, TIAN Mingyang, HU Haizhu, ZHANG Xiaoxin, RAN Lishan, YANG Xiankun and LÜ Xixi
  • Abstract:The oceanic carbon pool and terrestrial carbon pool are connected by rivers. Carbon dioxide (CO2) evasion from rivers to the atmosphere represents a substantial flux in the global carbon cycle. The CO2 efflux (FCO2) and CO2 partial pressure (pCO2) in large rivers have been widely evaluated. Most studies concerning CO2 emission from the Yellow River, a typical river containing high sediment concentrations, focused on the lower reach and its estuary, but less is known about its upper and middle reaches. In this study, a river cross-section at the Toudaoguai Gauging Station in Inner Mongolia, the dividing point between the upper and middle reaches of the Yellow River was chosen as a study site. Evasion of CO2 was measured four times each year using Li-7000 static chamber method from 2013 to 2015 at four sampling points in a river cross-section. The spatial and temporal variations of FCO2 were analyzed. The relevant hydrological indexes, including water temperature, pH,and wind velocity as well as current velocity were measured at the four sampling points. The hydrochemical indicators, including ALK and DOC in water samples, were analyzed in the laboratory and pCO2 was estimated. The possible influential factors of FCO2 were further discussed using correlation analysis. The CO2 evasion from the river cross-section ranged from 14 to 186 mol m-2 a-1 and its average was 84 mol m-2 a-1. The pCO2 in the Yellow River at the Toudaoguai Gauging Station was within the range of 467-2101 μatm and the average value was 995 μatm. The concentration of DOC ranged from 2 to 13 mg/L. The FCO2 exhibited obvious seasonal variations, with the maximum FCO2 of 456 mmol m-2 d-1 occurring in summer and the minimum of 33 mmol m-2 d-1 occurring in winter. The FCO2 values were markedly different at sampling points, with the maximum value of 392 mmol m-2 d-1 at S4 near the right bank, similar values at S2 and S3 in the middle of the river section, and the minimum of 86 mmol m-2 d-1 at S1 near the left bank. The analysis of factors influencing FCO2 indicated that FCO2 was positively correlated with current velocity and pCO2, and negatively correlated with pH. There was no obvious correlation between FCO2 and wind speed. Results also showed that current velocity contributed more to FCO2 than to pCO2 in the river cross-section. In this study, evasion of CO2 from the Toudaoguai cross-section was determined on a relatively fine scale. The results suggested that a distinct spatial variation in FCO2 exists even at the level of river cross-section, with the maximum FCO2 found at the point with the highest current velocity. Thus, typical sampling points in a river cross-section should be chosen for FCO2 measurement. The study provided a scientific reference for both FCO2 evaluation in the upper and middle reaches of the Yellow River and FCO2 sampling in a river cross-section.
  • DownLoad:Spatial-temporal variations and influencing factors of carbon dioxide evasion from the Yellow River:An example of the Toudaoguai Gauging Station.PDF
  • Study on spatial heterogeneity and reserve estimation of soil organic carbon in a small karst catchment
  • Authors:ZHANG Zhenming, ZHOU Yunchao, TIAN Xiao and HUANG Xianfei
  • Abstract:Using a grid-based sampling method, 2755 soil profiles consisting of 23536 soil samples were sampled and analyzed to study the spatial distribution of soil organic carbon (SOC) in the karst basin of Guizhou Province. Further, we established an estimation method of SOC stock exclusively for karst after correcting for soil distribution area, particle content, percentage of exposed rock, and soil thickness, and optimizing the calculation formula. The results showed that there were obvious differences in the SOC content of different soil types and at different soil depths. The content of SOC decreased with an increase in soil depth, but the extent of the decrease differed in soils of different types. The content of SOC in soils on shady slopes was higher than that in soils on sunny slopes. The content of SOC at different slope positions decreased in the following order:upper-middle, top, middle, lower-middle, and bottom. There was extensive SOC heterogeneity in the karst area. The order of SOC content under different land use patterns was as follows:woodland > shrub grassland > dry land > paddy field. SOC content showed a very significant positive correlation with slope, elevation, and percentage of exposed rock, and a significant negative correlation with soil thickness and soil bulk density. There was a large spatial variability in SOC in the karst area, with the influences of different indicators for SOC reserve estimation being as follows:soil thickness > percentage of exposed rock > particle content > content of SOC > soil bulk density. Using the revised formula to make estimations, the SOC density of the surface 20 cm of soil in a small watershed of the Houzhai River catchment in Pudin was 3.53-5.44 kg/m2, with an average value of 1.24 kg/m2. The SOC of the surface 100 cm of soil was 4.44-14.50 kg/m2, with an average value of 12.12 kg/m2, and the SOC storage was 5.39×105 t.
  • DownLoad:Study on spatial heterogeneity and reserve estimation of soil organic carbon in a small karst catchment.PDF
  • Priming effect of dissolved organic matter in the surface soil of a Cunninghamia lanceolata plantation
  • Authors:ZHANG Zheng, CAI Xiaozhen, TANG Caidi and GUO Jianfen
  • Abstract:Dissolved organic matter (DOM) is one of the main carbon and nutrient pools in the forest ecosystem. Its effect on carbon sequestration in forest soil has received great attention. However, the influence of DOM on the organic carbon mineralization in forest soil is still unclear. Here, a short-term (36 h) incubation experiment was conducted to measure δ13C within soil CO2 efflux following soil priming effects caused by the addition of DOM from leaf and root litter of Castanopsis carlesii and Cunninghamia lanceolata. The results showed that CO2 efflux from Castanopsis carlesii leaf litter DOM and Cunninghamia lanceolata leaf litter DOM peaked at 12 h, being 8.0 and 3.4 times higher than that at 2 h, and 4.6 and 7.0 times higher than that at 36 h, respectively. The CO2 efflux from soil organic carbon (SOC) was also highest at 12 h and was 10.1 and 6.3 times higher than that in the control. The use of 13C-labeled DOM additions allowed the total respired CO2 to be distinguished into that derived from the added DOM and that from SOC mineralization. The cumulative CO2 emission from added litter DOM was significantly greater than that from the added root litter DOM. In addition, the cumulative emission of CO2 from Castanopsis carlesii leaf litter DOM was significantly greater than that from Cunninghamia lanceolata leaf litter DOM. There was a significant positive relationship between soil CO2 efflux and the content of dissolved organic carbon. DOM from different sources had different priming effects (PEs) on SOC mineralization. During the 36 h of incubation, soils amended with leaf litter DOM always had a higher PE than those amended with root litter DOM. At 5 h, for all soils amended with DOM, the PE reached the peak. At 36 h, soil amended with Cunninghamia lanceolata root litter DOM changed from positive to negative PE. The microbial mechanisms of the priming effects of DOM inputs on SOC mineralization will be studied in future.
  • DownLoad:Priming effect of dissolved organic matter in the surface soil of a Cunninghamia lanceolata plantation.PDF
  • Effects of long-term fertilizer treatments on CH4 fluxes and key functional microorganisms in a double-cropping paddy field
  • Authors:TANG Haiming, XIAO Xiaoping, TANG Wenguang, SUN Jimin, LIU Jie, WANG Ke, LI Chao, CHENG Kaikai, LI Weiyan and SUN Geng
  • Abstract:Methane (CH4) fluxes and their key functional microorganisms in a double-cropping paddy field are affected by long-term fertilizer treatment; thus, it was important to utilize and evaluate different fertilization regimes on rice growth. A manual static chamber-gas chromatography (GC) technique was used to verify the effects of different fertilizer treatments, which included mineral fertilizer alone (MF), rice residues plus mineral fertilizer (RF), 30% organic matter plus 70% mineral fertilizer (LOM), 60% organic matter plus 40% mineral fertilizer (HOM), and a control without fertilizer (CK), on CH4 emissions from double-cropping paddy fields in subtropical regions of China and on the microbial mechanisms driving them. The results showed that the flux of CH4 from the HOM, LOM, RF, and MF treatments was higher than that of the CK treatment, and it varied with different fertilizer treatments in the following order:HOM > LOM > RF > MF > CK. Further, CH4 emissions were significantly greater during the entire growth period for early and late rice in the HOM, LOM, RF, and MF treatments than in the CK treatment (P < 0.05). CH4 emissions from paddy fields in the HOM, LOM, and RF treatments increased by 105.56%, 72.97%, and 54.17%, respectively, compared with the CK treatment. At the main growth stages of early and late rice, the abundance of methanogens under the different fertilizer treatments ranged from 3.18×103 cfu/g to 81.07×103 cfu/g, while that of methanotrophs ranged from 24.82×103 cfu/g to 379.72×103 cfu/g. The results indicated that the abundance of the methanogens and methanotrophs were significantly greater in the HOM, LOM, RF, and MF treatments at the main growth stages of early and late rice than they were in the CK treatment. Additionally, the abundance of methanogens and methanotrophs varied under the different fertilizer treatments in the following order:HOM > LOM > RF > MF > CK. Moreover, the abundance of methanogens and methanotrophs was significantly greater in the HOM, LOM, and RF treatments at the main growth stages than they were in the MF or CK treatments. CH4 emissions were significantly correlated with the abundance of methanogens and methanotrophs during the whole growth period. Our results clearly demonstrated that CH4 emissions from paddy fields and the abundance of key functional microorganism were promoted by the application of inorganic fertilizer combined with organic manure practices in a double paddy field ecosystem.
  • DownLoad:Effects of long-term fertilizer treatments on CH4 fluxes and key functional microorganisms in a double-cropping paddy field.PDF
  • The bacterial community structure associated with a copper-tolerant plant, Artemisia capillaries Thunb., and its influencing factors
  • Authors:SHAO Zongyuan, WANG Yue, ZHANG Ju, YANG Cheng, ZHOU Gang and YANG Ruyi
  • Abstract:The properties and roles of indigenous heavy metal-tolerant microbes have been extensively investigated for plant growth promotion and ecological remediation at contaminated sites, but these studies seldom address the community-level features of the microbes. Three soil samples were collected from the rhizosphere of a Cu-tolerant plant, Artemisia capillaries Thunb., grown on a Cu mine spoil. The MiSeq high-throughput sequencing technique, targeting the V3-V4 region of the bacterial 16S rDNA gene, was used to investigate the bacterial community structure and analyze the links between the bacterial community and soil environmental parameters. The results showed that sampling site Cu3 contained higher concentrations of Cu and Zn than Cu1 and Cu2 did. The Shannon-Wiener diversity index, richness, evenness, ACE index, and Chao1 index of the bacterial communities in Cu3 were all lower than those of Cu1 and Cu2, but coverage by the bacterial communities in Cu3 was higher than that of Cu1. The top 10 dominant phyla of bacteria accounted for 95% of the total relative abundance and 8 out of the top 10 dominant phyla were the same across all three sampling sites; these were Proteobacteria, Acidobacteria, Bacteroidetes, Gemmatimonadetes, Actinobacteria, Verrucomicrobia, Planctomycetes, and Unclassified. The relative abundances of Proteobacteria, Bacteroidetes, and Gemmatimonadetes were higher in Cu1 than in Cu2 and Cu3, but the opposite was true for Acidobacteria, Actinobacteria, Verrucomicrobia, Chloroflexi, and Unclassified phyla, indicating that different bacteria responded differently to Cu stress. The relative abundance of Chloroflexi, which only accounted for 0.54% of the bacterial community in Cu1, was 4.54% and 15.27% in Cu2 and Cu3, respectively. Bacterial communities were clustered into three different groups, according to principal coordinates analysis (PCoA) and redundancy analysis (RDA). The variation in bacterial communities was controlled by 11 principal coordinates, among which the first and second coordinates explained 74.3% and 14.8% of the total variance, respectively. Soil environmental parameters were closely related to the differences in bacterial community and explained 97.5% of the total variance. Total Cu, total P, pH, available P, and organic matter were the significant parameters; altogether, they accounted for 93.9% of the total variance in bacterial community. Total Cu was the most powerful factor, and explained 60.6% of the total variance independently. However, the dominant parameters differed across sampling sites. The RDA bioplots revealed that the bacterial community in Cu3, which showed the highest Cu tolerance, was positively related to total Cu. In contrast, the relatively Cu-sensitive bacterial community in Cu1 was positively correlated with pH and negatively correlated with total Cu. It is of vital importance to study how bacterial communities in the plant rhizosphere change with the environment and screen functional bacteria for plant-microbe remediation of heavy metal contamination.
  • DownLoad:The bacterial community structure associated with a copper-tolerant plant, Artemisia capillaries Thunb., and its influencing factors.PDF
  • Effects of nitrogen and phosphorus fertilizers on carbon, nitrogen, and phosphorus stoichiometry of oasis cotton in the upper reaches of Tarim River, Xinjiang, China
  • Authors:GONG Lu, LI Honglin, LIU Yutong and AN Shenqun
  • Abstract:C, N, and P are the basic elements required for plant growth and regulation and their balance and stability plays an important role in many physiological functions. Ecological stoichiometry combines the first law of thermodynamics, the theory of evolution by natural selection, and the central dogma of molecular biology and has organically integrated biological studies at the scales of molecules, cells, species groups, communities, and ecosystems. C, N, and P stoichiometry of plants reflects a complex interplay that is the result of adaptation of plants to changing biological and abiotic environments during the process of evolution. Therefore, it is important to investigate the patterns of stoichiometric flexibility within and among plant species. Homeostasis and the growth rate hypothesis (GRH) have always been considered as the two important theories of ecological stoichiometry. Homeostasis is the ability of organisms to maintain relatively stable chemical compositions regardless of the environmental changes. The growth rate hypothesis considers that there is a close relationship between C:N:P stoichiometry and growth rate and it proposes that fast-growing organisms have low biomass C:P and N:P ratios. Fertilization by the addition of exogenous substances directly disturbs the migration of elements and circulation of crop in the farmland ecosystem. To further understand the response of crop growth to fertilization, in this study, we measured the cotton C, N, and P contents and the biomass of cotton plant in a pot experiment involving the addition of N and P fertilizers, conducted in the upper reaches of Tarim River. Our results showed that the mean content of C, N, and P was 388.7, 20.97, and 3.43 g/kg, respectively. The growth rate of cotton decreased with increasing leaf N:P or C:P, and the growth of cotton was consistent with GRH. Plants with higher H (H is the homeostasis index) have stronger homeostasis, that is, they have stronger control over element change. The values of H in cotton ranged from 1.02 to 5.28 for N and from 1.01 to 4.55 for P. Researchers have reported that homeostasis is gradually enhanced from prokaryotic to eukaryotic organisms. H of cotton was between those of prokaryotic and eukaryotic organisms, and was consistent with the results of earlier studies. The leaf N:P ratios have been widely used to indicate the availability and limitation of soil nutrients. Cotton growth was mainly restricted by N and P. For cotton, the value of leaf N:P was 13 at the maximum growth rate, which was the standard of judging the limiting element. It conformed to the law of demand for cotton growth.
  • DownLoad:Effects of nitrogen and phosphorus fertilizers on carbon, nitrogen, and phosphorus stoichiometry of oasis cotton in the upper reaches of Tarim River, Xinjiang, China.PDF
  • Estimating biomass of emergent aquatic plants based on UAV SfM data
  • Authors:JING Ran, GONG Zhaoning, ZHAO Wenji, DENG Lei, A Duo and SUN Weidong
  • Abstract:Biomass is an important ecological parameter that is used to evaluate the growth condition of emergent plants in wetlands during ecosystem health assessments. This study used SfM (Structure from Motion) data generated from UAV images and field measurements of emergent plant biomass to establish a quantitative relationship between the SfM data and biomass, which was then used to map biomass in the study area. The influence of emergent plant types on the spatial distribution of biomass was analyzed. Our results show that a Stepwise Linear regression (SWL) model based on the SfM data had the best forecasting accuracy and ability (P < 0.01), with a coefficient of determination (R2) of 0.86 and an rRMSE of 6.1%. Emergent plant types had a significant influence (P < 0.05) on the spatial distribution of biomass in the study area. The results of this study provide a new quantitative method for retrieving growth parameters for emergent aquatic plants.
  • DownLoad:Estimating biomass of emergent aquatic plants based on UAV SfM data.PDF
  • Effects of desiccation on chlorophyll fluorescence characteristics in the fronds and receptacles of emersed Hizikia fusiformis and their recovery upon re-submersion
  • Authors:WANG Longle, ZHANG Xin, ZOU Dinghui and CHEN Binbin
  • Abstract:The fronds and reproductive tissues (female and male receptacles) of intertidal-grown Hizikia fusiformis exposed to air and faced desiccation when the tide is low during sexual reproduction period. In this study, we determined photosystem Ⅱ (PS Ⅱ) effective quantum yield[Y(Ⅱ)] and the parameters of rapid light curves of desiccation tissues:fronds, and female and male receptacles, at different desiccated states. We also measured Y(Ⅱ) of desiccation tissues upon rewetting after 50% and 75% water loss. Our objective was to reveal whether there are differences of desiccation tolerance or not among fronds and reproductive tissues of H. fusiformis when exposed to air during sexual reproduction period. The results showed that Y(Ⅱ) exhibited no significant changes within the range of 0-73% water loss from fronds, and within the range of 0-60% water loss from female and male receptacles. However, the values of Y(Ⅱ) were sharply reduced with the water loss more than 73% in fronds, and more than 60% in receptacles. Severe dehydration of 75% water loss reduced Y(Ⅱ) values by 12%, 31%, and 37% in fronds, and female and male receptacles, respectively. The values of Y(Ⅱ) of submersed tissues (fronds and receptacles) followed by 50% always remained high levels. However, the values of Y(Ⅱ) of both severe-desiccated female and male receptacles could not recover, and continued to decrease even after re-submersion, suggesting that the PS Ⅱ reaction center in receptacles of H. fusiformis underwent irreversible damage when water loss reached up to 75%. Our results showed that PS Ⅱ reaction center in fronds of H. fusiformis exhibited greater desiccation tolerance of than that in receptacles. The maximum relative electron transport rates (rETRmax), light use efficiency (α), and the tolerance of high irradiance (Ik) for emersed fronds and receptacles of H. fusiformis exhibited no significantly differences at the initial desiccation state. Both rETRmax and Ik decreased significantly with increased water loss. Particularly, rETRmax were reduced by 33%, 67%, and 78% in fronds, and female and male receptacles, respectively, after 75% of water loss. Furthermore, α were hardly affected by 50% of water loss, but it were reduced by 16%, 42%, and 59% of their initial value when fronds, and female and male receptacles lost 75% water, respectively. The values of Y(Ⅱ), rETRmax, Ik, and α of the fronds were higher than those of the receptacles, and the parameters of the female receptacles were always higher than those of the male receptacles after 60% water loss of desiccation tissues under emersed state, and the results showed the same trends when followed by submersed state. Those indicated that male receptacles were the most susceptible, while the fronds were relative less susceptible by severe dehydration. It was concluded that severe desiccation is an important factor affecting the reproduction success of H. fusiformis during the sexual reproduction period, and the factors alleviating desiccation such as sea spray and shingle-overlapping would benefit the emersed fronds and receptacles of H. fusiformis.
  • DownLoad:Effects of desiccation on chlorophyll fluorescence characteristics in the fronds and receptacles of emersed Hizikia fusiformis and their recovery upon re-submersion.PDF
  • Comprehensive effects of tetracycline hydrochloride concentration on life history traits of Brachionus calyciflorus under different food densities
  • Authors:XIANG Xianling, ZHU Yelin, XU Qiulei, ZHU Lingyun and XI Yilong
  • Abstract:Increasing attention has been paid to the challenging issue of environmental pollution by antibiotics in recent years, and the structure and functioning of aquatic ecosystems could be disturbed by residues remaining in the environment. To date, however, few attempts have been made to investigate the effects of tetracycline hydrochloride on life history traits of rotifers under different food densities. In this study, the effects of tetracycline hydrochloride concentration on life table demography of Brachionus calyciflorus under different Scenedesmus obliquus densities were studied. The results showed that tetracycline hydrochloride concentration and food density had significant effects on life expectancy at hatching, net reproductive rate, generation time, intrinsic rate of population increase, average lifespan, and proportion of sexual offspring of B. calyciflorus. In addition, the interaction of tetracycline hydrochloride concentration and food density had a marked influence on five demographic parameters, except for the intrinsic rate of population increase, in rotifers. The peak of age-specific fecundity in B. calyciflorus increased to a maximum and then decreased with increasing concentration of tetracycline hydrochloride under each food density. The effects of tetracycline hydrochloride on the growth and reproduction of B. calyciflorus presented a pattern of hormesis. Mixis rate of offspring in rotifers increased at the high concentration of tetracycline hydrochloride under the three food densities, and there were significant dose-effect relationships between tetracycline hydrochloride concentration and the proportion of sexual offspring at the 1.0×106 cells/mL food density. Levels of food density played an important role in the poisoning effects of tetracycline hydrochloride on B. calyciflorus.
  • DownLoad:Comprehensive effects of tetracycline hydrochloride concentration on life history traits of Brachionus calyciflorus under different food densities.PDF
  • Spatial and temporal distribution of phytoplankton community and its relationship with environment factors in Nansha's Rivers, Pearl River estuary
  • Authors:REN Hui, TIAN Tian, YANG Yufeng and WANG Qing
  • Abstract:The concept of urban ecological health has increased concern over the ecological health of urban rivers. Therefore, in order to study the spatial and temporal distribution of phytoplankton communities and the water quality of Nansha's rivers, Pearl River estuary, eight sites were sampled on a monthly basis from March 2015 to February 2016. During this period, 164 phytoplankton species, from 7 phyla and 73 genera, were recorded. The most diverse group was the green algae (79 spp., 33 genera), which accounted for 48.17% of the total recorded species, followed by diatoms (41 spp., 17 genera), which accounted for 25% of the total recorded species, and the dominant species included Cyclotella meneghiniana, Pseudanabaena sp., and Chlorella vulgaris. The overall abundance ranged from 0.19×106 to 101.34×106 cells/L and exhibited a unimodal pattern of seasonal variation. The peak abundance corresponded to an algal bloom that occurred in April 2015, during which the dominant species, Schroederia nitzschioides, reached 87.38×106 cells/L at site 14 (S14) and then rapidly decreased over the next month. The seasonal succession of the phytoplankton community structure in Nansha's rivers conformed to the Plankton Ecology Group (PEG) Model, with Chlorophyta dominating during the spring and summer, Cyanophyta dominating during the end of summer and autumn, and Bacillariophyta dominating during the winter. The temporal variation of phytoplankton density was significant (P < 0.01), as was the positive correlation of the proportion of Chlorophyta cells in total phytoplankton abundance (r=0.454, P < 0.01). The Shannon-Wiener diversity, Margalef abundance, Pielou evenness, and trophic state indices indicated that Nansha's rivers were experiencing moderate eutrophication. Cluster analysis indicated that the phytoplankton communities possessed high temporal heterogeneity but low spatial heterogeneity. Human activities maybe the key factor for spatial differences. Meanwhile, redundancy analysis (RDA) indicated that chlorophyll a, salinity, dissolved oxygen, water temperature, total nitrogen, and pH were most closely related to the phytoplankton community structure, and pH significantly affected the abundance and species of Bacillariophyta, with alkaline environments benefiting Melosira, in particular. Salinity, water temperature, and total nitrogen were the driving factors of the spring algal bloom.
  • DownLoad:Spatial and temporal distribution of phytoplankton community and its relationship with environment factors in Nansha's Rivers, Pearl River estuary.PDF
  • Population genetic structure of Schizopygopsis kialingensis inferred from mitochondrial D-loop sequences
  • Authors:WANG Tai, DU Yanyan, YANG Zhuoyu, ZHANG Yanping, LOU Zhongyu and JIAO Wenlong
  • Abstract:Schizopygopsis kialingensis is an endemic fish of the Bailong River, which is a tributary of the Jialing River. The species' population has been largely reduced in recent years as a result of overfishing, river pollution, and dam construction. To develop effective strategies forpreserving the species'germplasm, it is first necessary to understand the species' genetic variation and population structure. Therefore, in the present study, a 706-bp segment of the mitochondrial control region was sequenced from 147 S. kialingensis specimens that were collected from six populations in the Bailong and Weihe Rivers. Seventeen variable sites and 14 haplotypes were identified. The six populations exhibited high haplotype diversity (0.810) and low nucleotide diversity (0.00698), and the genetic diversity of the Zhouqu County Chengguan Township population was highest, whereas that of the Weiyuan County Qiaoyu Township population was the lowest. AMOVA indicated that significant difference among populations, with 44.29% molecular variation among the populations and 55.71% molecular variation within populations. Pairwise fixation index (Fst) values indicated that all the populations were significantly different, except the Tanchang County Nanhe Township and Zhouqu County Chengguan Township populations. Meanwhile, gene flow estimates suggested high levels of gene flow, and the Mantel test indicated that the genetic and geographic distances were significantly correlated. In addition, the construction of a neighbor-joining phylogenetic tree and a minimum spanning network indicated that the 14 haplotypes formed two main groups that corresponded to the Bailong River and Weihe River systems, and mismatch distribution and neutrality analyses indicated that the population has not under gone recent expansion. According to these findings, we suggest that the S. kialingensis population in the Bailong River should be protected and that the protection of the Weihe River population should be prioritized, owing to the group's high genetic differentiation and very low genetic diversity.
  • DownLoad:Population genetic structure of Schizopygopsis kialingensis inferred from mitochondrial D-loop sequences.PDF
  • Macrobenthic species distribution modeling based on a binary logistic regression:a case study of freshwater restoration wetlands in the Yellow River Delta of China
  • Authors:YANG Wei, LI Xiaoxiao, LI Ming and SUN Tao
  • Abstract:Studies on changes in the macrobenthic species distribution could help to understand the ecological restoration efficiency of wetlands and elucidate the ecological succession process. Based on the results of field samplings and species identification from 2014-2015 in the Yiqianer national nature reserves in the Yellow River Delta wetlands of China, in which freshwater release has been implemented since 2010, we selected three characteristic, dominant macrobenthic species, namely, Chironomidae species, Sinocorophium sinensis, and Alitta succinea, corresponding to freshwater species, euryhaline species and brine species, respectively. We selected salinity, pH, water moisture, total organic carbon (TOC), and median particle size of sediment as environmental variables. Based on the binary logistic regression approach, in which a binary variable (0/1) indicates whether the target species were found at the sampling sites, 80 groups of the field sampling data were used to calibrate the parameters of the distribution possibility model for the three species, whereas the other 20 groups were used to verify the simulated accuracy of models. Based on the simulated distribution possibility of the target species at the sampling sites, we spatialized their occurrence possibility using inverse distance weighted interpolation and characterized their changes on a regional scale. We found that the models for Chironomidae species and A. succinea corresponded well with the survey results and their precision rates reached 84.9% and 77.9%, respectively. In contrast, the accuracy of the simulated occurrence probability of S. sinensis reached only 26.7%, which may be because of the mobility traits of S. sinensis and small sampling data, and because the selected environmental variables could not cover the main limited survival factors for S. sinensis. The distribution possibility for A. succinea showed no significant difference between before and after freshwater release. In general, the distribution possibilities of A. succinea in the study region were lower than 0.55. Furthermore, the areas with distribution probabilities between 0.4 and 0.55 accounted for about 28.2% of the study region and were concentrated in the intertidal zone. The main high distribution possibility area for Chironomidae species was the freshwater restoration area with the implementation of freshwater release. The area with a distribution possibility > 0.5 for Chironomidae has increased 9.9-to 10.8-fold after the ecological restoration. Owing to the low accuracy of the simulated distribution possibility, we did not spatialize its occurrence possibility of S. sinensis on a regional scale. The steep increase in the occurrence possibility of Chironomidae species after freshwater release indicated that the restoration wetlands increasingly showed obvious freshwater characteristics, consistent with the significant reed growth and increase in the freshwater habitat patches observed during field investigation. Although the freshwater habitat succession was unpredictable owing to significant fluctuations with respect to release periods, we should take essential measures, such as continuous freshwater release, long-term monitoring system, quality improvement of released freshwater, and cost reduction and high frequency of freshwater release, to maintain the long and difficult transition.
  • DownLoad:Macrobenthic species distribution modeling based on a binary logistic regression:a case study of freshwater restoration wetlands in the Yellow River Delta of China.PDF

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