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    15 May 2021, Volume 32 Issue 5
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    Opinion of the Editor-in-Chief
    Discussion on the multi-disciplinary dimensional basic problems and methodology systems of macroecosystem science research.
    YU Gui-rui, CHEN Zhi, ZHANG Wei-kang, YANG Meng
    2021, 32(5):  1531-1544.  doi:10.13287/j.1001-9332.202105.040
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    The urgent requirement of human society to solve major resource and environmental pro-blems at the regional and global scales promotes the rises of macroecosystem science (MES) and the multidisciplinary fusions of natural science and humanities. Furthermore, it facilitates the innovation of macroecosystem scientific theory, as well as the development of continental and global scale knowledge fusion methodology and key technology. With the aim to serve the construction and deve-lopment of continental and global scale knowledge fusion methodological system for the changes of ecosystem status and resource environmental effect studies, we systematically elaborated the multi-disciplinary dimensional basic scientific problems, logic relationships and frontiers in the macroecosystem science, discussed the ideology and content of constructing the continental and global scale research methodological system, proposed to develop the networked observation-networked experiment-numerical simulation-knowledge fusion four-in-one infrastructures. This study would provide theoretical references for the network design of ecosystem observation research in China and at the global scale.
    Special Features of Landscape Ecology
    Construction of ecological network in Qinling Mountains of Shaanxi, China based on MSPA and MCR model.
    CHEN Nan-nan, KANG Shuai-zhi, ZHAO Yong-hua, ZHOU Yu-jie, YAN Jin, LU Ya-ru
    2021, 32(5):  1545-1553.  doi:10.13287/j.1001-9332.202105.012
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    Rapid urbanization destroys the ecological network connectivity among habitat patches. The research on the construction of regional ecological network at the patch level is obviously insufficient. The morphological spatial pattern analysis (MSPA) and minimum cumulative resistance (MCR) were used to identify ecological sources and to extract potential ecological corridors in Qinling Mountains, respectively. The ecological network was effectively constructed. We analyzed the structural characteristics and landscape compositions of the network. Based on the gravity model, the importance of patches in the ecological network was graded and the structural characteristics and landscape composition of the network were analyzed. The results showed that there were 10 ecological sources, 45 potential ecological corridors and 38 stepping stones in the ecological network of Qinling Mountains in Shaanxi Province, with a total area of 29686.15 km2. There were good connectivity in potential ecological corridors and ecological network nodes as indicated by network closure (0.11), line point rate (1.18), network connectivity (0.42) and cost ratio (0.99). The connectivity between ecological source was low, but the cost of network reconstruction was high. The important ecological corridors were mainly composed of forest, grassland, and cultivated land. Fore-sts accounted for 89.2% of the total corridor area (571.00 km2), indicating the good landscape structure in Qinling Mountains. The protection of ecological source areas must be strengthened, and priority should be given to the establishment and protection of important ecological corridors and ecological nodes. Our results would provide the scientific reference and basis for the ecological environment protection and high-quality development in Qinling Mountains.
    Comprehensive evaluation of the evolution of ecological network structure in Tianjin, China from a multi-dimensional perspective.
    LIU Xiang-ping, ZHANG Zhen, LI Ling-yu, LI Ming-xin
    2021, 32(5):  1554-1562.  doi:10.13287/j.1001-9332.202105.017
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    Based on the construction of ecological network in Tianjin in 2000, 2010 and 2020, we evaluated the structural evolution of Tianjin ecological network from the multi-dimensional perspective of source-corridor-node-whole, using complex network evaluation index and landscape pattern index integrated with the stability, uniformity and connectivity indices. The results showed that from 2000 to 2020, the ecological source areas in Tianjin significantly shrank and degraded, be uneven in spatial distribution. Ecological corridors became sparse. Landscape fragmentation and shape complexity first increased and then decreased. The average length of corridors in 2000 and 2010 was shorter, with the bioflow efficiency being relatively high. In 2000, 2010, and 2020, the number of nodes with high significance accounted for 35.7%, 29.4% and 21.4% of the statistical nodes respectively. In 2020, the network connectivity robustness and vulnerability robustness showed substantial fluctuation, and the network was the most unstable. In 2010, the ecological network was of high connectivity and complexity, while in 2000 and 2020, it was more general. In 2000, the network uniformity was the highest, followed by 2010, and lowest in 2020.
    Evaluation of land ecosystem health in Shaanxi Province, Northwest China based on PSR Model.
    WANG Tong-da, CAO Jin-xue, ZHAO Yong-hua, HAN Lei, LIU Zhao
    2021, 32(5):  1563-1572.  doi:10.13287/j.1001-9332.202105.013
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    Based on the pressure-state-response (PSR) model and entropy method, we analyzed the health status of land ecosystem and the temporal and spatial variations from 2009 to 2017 in ten cities and one district in Shaanxi Province. The driving factors affecting the health of the land ecosystem was examined. Results showed that during 2009-2017, the overall health of the land ecosystem in Shaanxi Province was improved, which was lower during 2009-2014 and being obviously improved after 2014. The health level of land ecosystems in Xi'an, Baoji, Weinan and Hanzhong was high and with substantial variation, while that in Yan'an, Yulin, and Ankang was low and stable, decreasing in order of South Shaanxi, Guanzhong region and North Shaanxi. Overall, the pressure, state and response indices of the land ecosystem in Shaanxi Province increased during 2014-2017 with a gentle growth, which were basically flat after 2014. Those results indicated that the land ecosystem in Shaanxi Province was at a stable and healthy state. Population growth, urbanization level, fertilizer load per unit of arable land, forest coverage rate, industrial wastewater discharge compliance rate and comprehensive utilization rate of industrial solid waste were the main driving factors for the health of land ecosystems in Shaanxi. Controlling the use of fertilizers and pesticides, optimizing the structure of land use and improving land use efficiency are necessary strategies to promote the construction of ecological civilization and implement the red line of ecological protection for Shaanxi Province.
    Conception and framework of land ecological restoration for a new stage in China.
    ZHANG Ying-wen, SU Teng, ZHANG Fu-gang, LI Kai, LIU Xuan-he
    2021, 32(5):  1573-1580.  doi:10.13287/j.1001-9332.202105.016
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    Based on the theories of geography and landscape ecology, land ecological restoration is an important strategy to promote ecological civilization and build a beautiful China. Land ecological restoration in China has the characteristics of multi-disciplinary theoretical system, diverse work mode, integration of technology and methods, and diversified practice and exploration. The overall effectiveness of the work coexists with arduous tasks. Based on the new challenges in land ecological restoration, we summarized the overall framework and technical path of land ecological restoration, the working mechanism and mode of regional land ecological restoration, the content system and technical standards of land ecological restoration. In the new stage, the top-level design of land ecological restoration in China should focus on the work system, business boundary and institutional system, identify the responsibility boundary of different business processes, and realize the closed management of the whole work chain from the perspective of theory, system, engineering and technology. Rural settlement area, urban built-up area, industrial and mining gathering area, ecological function area and blue ocean area are the five major elements of regional scale land space, which correspond to five different ecological restoration modes, namely, comprehensive land improvement, urban renewal and double repair, mine geological environment restoration, mountain-river-forest-farmland-lake-grassland restoration, and blue bay restoration. It is necessary to comprehensively use the thinking of “Three Integrations” (information, technology, and process) to build a set of regional land ecological restoration work mode covering the integration of investigation, monitoring and evaluation, land space planning, project implementation, project acceptance and ecosystem monitoring and evaluation.
    Spatial and temporal variations of vegetation coverage in the middle section of Yellow River Basin based on terrain gradient:Taking Yan'an City as an example.
    HAN Lei, HUO Hong, LIU Zhao, ZHAO Yong-hua, ZHU Hui-li, CHEN Rui, ZHAO Zi-lin
    2021, 32(5):  1581-1592.  doi:10.13287/j.1001-9332.202105.014
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    Vegetation restoration is an important requirement for ecological protection and high-quality development in the Yellow River Basin. In-depth understanding the temporal and spatial differentiation of vegetation has important practical significance. With the four Landsat TM/OLI remote sensing images as the data source, the pixel binary model was used to estimate vegetation coverage. The transfer matrix, geological information map, and the center of gravity migration model were used to analyze the temporal and spatial variations of vegetation coverage in Yan'an City in the middle of the Yellow River Basin from 1988 to 2018. The spatial variation of vegetation cover to elevation and slope was explored using terrain distribution index combined with terrain data. The results showed that vegetation coverage in Yan'an was low in the north region and high in the south region. The vegetation coverage increased significantly due to policy changes. From 1988 to 2018, the vegetation change pattern in Yan'an was dominated by continuous improvement and stability. Vegetation coverage increased in about 50% of the area. 83% of the study area with high vegetation coverage remained stable. At each elevation and slope level, the advantage of high vegetation cove-rage increased with time. At each slope level, vegetation cover increased with slope. The transition direction of vegetation cover of different levels in Yan'an was basically consistent with the overall spatial change trend of vegetation cover, with the overall shift being from north to west. The vegetation construction in Yan'an has achieved remarkable results, though the vegetation coverage in the north still needs to be improved. Optimizing vegetation types and structures is an important direction for future vegetation construction.
    Relationship between urban atmospheric environment and surrounding two-dimensional and three-dimensional landscape pattern in China.
    LI Di-kang, LIU Miao, LI Chun-lin, HU Yuan-man, WANG Cong, LIU Chong
    2021, 32(5):  1593-1602.  doi:10.13287/j.1001-9332.202105.015
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    Atmospheric environment in urban built-up area is severely influenced by the surrounding landscape pattern. Understanding the relationship between air pollution and surrounding landscape pattern at small scale has great significance for mitigating air pollution from the perspective of urban construction. The annual average concentrations of NO2, SO2, PM2.5 and PM10 from 266 air pollution monitoring stations in 30 provincial capitals of China in 2017 were chosen as dependent variables. Ten two-dimensional and three-dimensional landscape pattern indices (number of buildings, building aggregation, building density, impervious water ratio, quantitative density of catering, building footprint area, high building ratio, floor area ratio, total building area and building type Shannon diversity index) within the 3 km area around the monitoring stations were used as independent variables. The effects of landscape pattern on the concentration of four air pollutants were analyzed using the boosted regression trees model. The results showed that the concentration of four air pollutants in the central and northern cities were significantly higher than that in the southeast coastal cities and southwest cities. The most important factor affecting the concentrations of NO2, SO2, PM2.5 and PM10 was the impervious ratio, with relative contribution rates of 40.7%, 36.3%, 51.0% and 51.8% respectively. The results of sub-region analysis showed that the most important influencing factor differed in different regions, including the impervious ratio in the East and Central China; the number and density of buildings in South China; the impervious ratio and diversity of building types in North China; the impervious ratio and the number of buildings in Northeast China, the density of buildings in Northwest China. Such differences were mainly caused by climate, topography, urban planning, and other factors.
    Landscape ecological risk assessment and influencing factors in ecological conservation area in Sichuan-Yunnan provinces, China.
    GAO Bin-pin, LI Chen, WU Ying-mei, ZHENG Ke-jun, WU Yan
    2021, 32(5):  1603-1613.  doi:10.13287/j.1001-9332.202105.018
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    It is important for preventing and resolving landscape ecology risk and promoting regional sustainable development to explore the characteristics of temporal and spatial variations of landscape ecology risk of key ecological function zone and to reveal the potential influence of human activity on aggravation of landscape ecological risk. Based on the land cover data of 2000, 2010, and 2020, we constructed a model of risk assessment on landscape ecology, incorporating a landscape index and an assessment of ecological vulnerability, with the support of ArcGIS 10.8 and Fragstats 4.2. The spatial analysis method was used to examine the temporal and spatial variations of landscape ecology risk in ecological conservation in Sichuan-Yunnan provinces. We used the Geodetector to quantify the impacts of natural and social-economy factors in different ranges of region on landscape ecological risk. The results showed that from 2000 to 2020, the area of artificial land surface, water body, shrubland in the study area showed an upward trend, while the area of forest, cultivated land, grassland, wetlands, barren land, and permanent snow cover and glacier showed an downward trend. There was remarkable transfer of landscape types among forest, grassland and cultivated land, especially for the transfer from cultivated land to artificial surface. The mean value of landscape ecological risk had been reducing. The classes of landscape ecological risk was consistent with the changes and shifts of landscape. Landscape ecological risk was mainly at lower, low, and high levels in ecological conservation in Sichuan-Yunnan provinces. Natural factors, including elevation and precipitation, generally drove the temporal-spatial variations of landscape ecological risk. In addition, factors such as economy, society and regional accessibility could contribute to prominent impacts on local area suffering from pejorative risk.
    Landscape pattern of built-up land in a typical mining city, Datong, Shanxi, China from 1986 to 2018.
    HAN Ya-hui, SUN Wen-bin, FU Ying, YANG Yi
    2021, 32(5):  1614-1622.  doi:10.13287/j.1001-9332.202105.011
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    Analyzing the landscape spatial layout and evolution characteristics of built-up land in a mining city is helpful to solve the environment problem, and can provide scientific basis for optimizing the urban land structure and taking timely intervention measures for transformation. Taking Datong, a typical mining city as the case, we examined the spatiotemporal characteristics of landscape of built-up land based on the spatial distribution data of built-up land from 1986 to 2018 with the landscape index analysis method, and detected the landscape change period with graphs obtained by Fourier transform and wavelet transform. The results showed that, during the study period, the area of built-up land in Datong City increased continually, with the growth rate gradually slowing down and the extent spreading from a “northeast-southwest” belt zone to the east. The fragmentation and complexity of the landscape pattern were increasing. The physical connectivity gradually decreased, while functional connectivity alternated between high and low values. The space expansion of Datong City and the fragmentation and complication of landscape pattern of its built-up land may all have a cycle of about 35 years, while the functional connectivity had a longer cycle than the physical connectivity.
    Spatiotemporal variations of ecosystem service values and landscape ecological risk and their correlation in forest area of Loess Plateau, China:A case study of Ziwuling region.
    JIN Tian-tian, ZHANG Yun-xia, ZHU Yue-hua, GONG Jie, YAN Ling-ling
    2021, 32(5):  1623-1632.  doi:10.13287/j.1001-9332.202105.030
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    Although the awareness of ecosystem services provided by natural landscape is increa-sing, few studies integrate ecosystem services value (ESV) into ecological risk management and its control. With Ziwuling region as an example, we carried out the gridding resampling of landscape pattern types in the forest area of Ziwuling region in 1980, 1990, 2000, 2010 and 2017. We quantified the ESV and landscape ecological risk and their spatiotemporal variations, based on the 2.5 km×2.5 km grid. The spatial correlation between the ESV and landscape ecological risk was examined. The results showed that the ESV decreased from the center to the outside of Ziwuling region, which increased from 12.345 to 12.633 billion yuan from 1980 to 2017. The landscape ecological risk increased from the center to the outside edge of Ziwuling region, indicating that the landscape ecological risk of Ziwuling region was reduced and the overall ecological situation was improved. There was a significant negative correlation and negative spatial correlation between ESV and landscape ecological risk in this area. The high value-low risk area was mainly located in Ziwu-ling forest area, while the ESV might be maintained in the future.
    Research progress on the cascade effect of ecosystem service.
    ZHANG Cheng, LI Jing, ZHOU Zi-xiang, LIU Xian-feng
    2021, 32(5):  1633-1642.  doi:10.13287/j.1001-9332.202105.029
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    The ecosystem services cascade (ESC), which connects the components of ecosystem services with social value and builds a bridge between natural science and social science, can help decision-makers better integrate the concept of ecosystem services into decision-making. We reviewed the concept and the research progress of ESC. From the perspective of theory, the theoretical research of ESC mainly focused on how to accurately define each component and the causal relationship among different components, improve the practicability and applicability of ESC model, and how to effectively connect stakeholders and ecosystem service structure. From the perspective of application, ESC played an important role in ecosystem services mapping, ecosystem services assessment, and policy making. There were still great uncertainties in index selection and mutual feedback mechanism. Future research should be strengthened from the following aspects: to pay more attention to the structure process and classification standard of ecosystem services, to make up the lack of ESC of the feedback mechanism through multi-model fusion and regional survey, and to provide scientific guidance for human-earth coupling and sustainable development combined with regional characteristics .
    Sea-land hydrological connectivity of coastal wetlands based on water salinity and hydrological structure.
    XU Jia-yi, LI Yu-feng, QIU Chun-qi, LIU Hong-yu, ZHOU Yi, SONG Qing-nan, WU Han
    2021, 32(5):  1643-1652.  doi:10.13287/j.1001-9332.202105.019
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    In this study, with water salinity as the core index, sea-land hydrological connectivity index was constructed by integrating the hydrological structure connectivity index (water surface ratio, intake and outtake density, sea-land distance, and ditch distance). Based on multi-scale spatial analysis, we carried out the spatial quantitative analysis and classification of sea-land hydrological connectivity in the study area under an evaluation unit of 150 m×150 m grid. The results showed that sea-land hydrological connectivity gradually decreased from sea to land, with different decreasing rates. The spatial differentiation of water salinity in the study area was substantial, with certain impacts on the change rate of hydrological connectivity. The sea-land hydrological connectivity was divided into four grades, which was excellent, good, medium, and poor. The areas under excellent and good grades were mainly distributed in offshore areas, with saltwater aquaculture ponds and farmland as the main land use types. The regions with moderate and poor land use were mainly distributed in inland areas, with freshwater aquaculture ponds and farmland as the land use types. The hydrological process of coastal wetlands was complex. Quantitative coastal wetland hydrological connectivity could provide reference for coastal wetland status assessment and wetland restoration.
    Effects of small irrigation facilities on hydrological connectivity of ditches in North Jiangsu Plain, China.
    WU Yu-qin, QIU Chun-qi, XU Jia-yi, LI Yu-feng, LIU Hong-yu, WANG Gang
    2021, 32(5):  1653-1662.  doi:10.13287/j.1001-9332.202105.020
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    Hydrological conditions in the plains irrigation area are complex, which are strongly affected by small irrigation facilities and human management. In this study, the connectivity index of ditch network and the influence index of rural small irrigation facilities were constructed to quantitatively analyze the hydrological connectivity of a typical plain irrigation area, Fudong irrigation area, in north Jiangsu Province. The self-organizing feature map (SOM) analysis method was used to identify the effects of small irrigation facilities on the spatial heterogeneity of ditch network structure connectivity. The results showed that the hydrological structure connectivity differed in different regions of Fudong. The connectivity in the north of the irrigation area was the best, but the worst in the central and southern part of the irrigation area. There were 876 pumps, 633 gates and 2420 culverts in the study area. Without the effects of small irrigation facilities, there were 13 villages with poor hydrological structure connectivity and 48 villages with good and best hydrological structure connectivity. Under the effects of small irrigation facilities, the number of villages with poor connectivity was reduced to 8, while the number of villages with good and best connectivity was increased to 53. Due to the influence of gates and culvert, the hydrological connectivity of 26 villages in Fudong became poor. The hydrological connectivity of 39 villages had been enhanced due to the existence of pump.
    Original Articles
    Seasonal dynamics of energy and nutrients of Pinus koraiensis seedlings in different successional stages of broadleaved Korean pine forest in Changbai Mountain, China.
    ZHOU Guang, XU Wei-ze, WAN Jing, WANG Yan-nan, LIU Li-ting, LIU Qi-jing
    2021, 32(5):  1663-1672.  doi:10.13287/j.1001-9332.202105.001
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    We examined the seasonal variations of growth and nutrient accumulation of two-year-old Korean pine (Pinus koraiensis) seedlings in the primary broadleaved Korean pine forest (primary forest) and poplar birch forest (secondary forest) in Changbai Mountain. The seasonal changes of photosynthetically active radiation (PAR), seedling biomass, nonstructural carbohydrate (NSC), total nitrogen (N), and total phosphorus (P) were measured in both forests. The effects of understory light and its seasonal variations in both forests on the growth and nutrient accumulation of understory Korean pine seedlings were also explored. The results showed that the seasonal variations of monthly cumulative PAR under both forests showed a double-peak pattern. In summer, light conditions under the two forests were poor because of the closed canopy. In spring and autumn, light conditions were better due to the deciduous characteristics of canopy broadleaved trees, with light conditions under the secondary forest being obviously better than that of the primary forest. The seasonal variations of biomass, NSC, total N and total P concentrations of Korean pine seedlings in the primary and secondary forests were basically consistent with that of understory light. All those variables increased significantly in spring and autumn, and decreased in summer. In spring, starch concentration increased. In summer, starch and soluble sugar concentrations decreased gradually, and touched bottom in August. In autumn, soluble sugar concentration increased significantly. The biomass and NSC concentration of seedlings under secondary forest were significantly higher than those under primary forest in spring and autumn, but without difference in summer. Therefore, the diffe-rence of understory light conditions in spring and autumn between the two forests might be the key factor driving nutrient accumulation, growth and regeneration of Korean pine seedlings.
    Dynamics and influencing factors of stem diameter micro-variations during the growing season in two typical forestation species in the loess hilly region, China.
    LIU Mei-jun, LYU Jin-lin, CHEN Qiu-wen, YANG Jie, LI Guo-qing, DU Sheng
    2021, 32(5):  1673-1680.  doi:10.13287/j.1001-9332.202105.005
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    Using DC3 high-resolution dendrometer and Granier-type thermal dissipation probes, we measured stem diameter micro-variations and xylem sap flow of two typical forestation species, Quercus liaotungensis and Robinia pseudoacacia, for a growing season in the loess hilly region of China. The main environmental factors (soil water content, solar radiation, air temperature and relative humidity) were monitored. The linkage between diameter micro-variations and transpiration water use were analyzed with respect to their responses to environmental factors. The results showed that the variations in stem diameter and sap flux density of both species had obvious diurnal rhythms. The maximum daily shrinkage was positively correlated with daily sap flux density. The micro-variation of stem diameter at the daily scale was affected by transpiration during the day. The maximum daily shrinkage of stem diameter was positively correlated and well fitted with transpiration driving factors (solar radiation, vapor pressure deficit, and the integrated variable VT). The difference in slopes of regression curves suggested that the daily variation of stem diameter in Q. liaotungensis was greater and more sensitive to meteorological factors than that in R. pseudoacacia. The sap flux densities of both tree species were higher during the period with relatively higher soil water content than that with lower soil water content. The difference of maximum daily diameter shrinkage between different soil water conditions was statistically significant in Q. liaotungensis, but not in R. pseudoacacia. These differences may be related to water use strategies, including transpiration regulation and stem water replenishment.
    Effects of environment and canopy structure on stem sap flow in a Larix principis-rupprechtii plantation.
    QIN Hao-ping, LIU Ze-bin, GUO Jian-bin, WANG Yan-hui, YU Song-ping, WANG Lei
    2021, 32(5):  1681-1689.  doi:10.13287/j.1001-9332.202105.007
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    Accurately quantifying the impacts of environmental factors and canopy structure on stem sap flow is of great significance for deeply understanding water use strategies of trees in changing environment. The stem sap flow of Larix principis-rupprechtii plantation was observed using thermal diffusion probes from June to September of 2019 in the Xiangshuihe small watershed of Liupan Mountains, with the meteorological conditions, root-zone soil water content and canopy structure being simultaneously recorded. We first analyzed the relationships of sap flow rate (Jc) to potential evapotranspiration (PET), relative extract water (REW) and canopy leaf area index (LAI), and then quantified their relative contribution to Jc. The results showed that the response of Jc to PET, LAI, and REW conformed to binomial, linearly increase and saturated exponential function, respectively. The Jc model coupling multiple factors was established as a continuous multiplication of the response functions of Jc to PET, REW and LAI, which had good simulation precision. PET was the main factor leading to the difference of Jc in different weather conditions. The average contribution rate of PET had obvious difference in sunny (with a contribution rate of 40.3%), cloudy (4.3%), and rainy days (-26.3%). PET and LAI were the leading factors affecting the Jc variation among months. The ranges of the contribution rates of PET and LAI were from -23.1% to 16.8% and from -12.3% to 11.0%, respectively. The Jc model coupling the multi-factor effect developed in this study could be used to predict Jc, and quantify the impacts of each leading factor, which had the potential to be an effective tool to analyze the water use of trees in the changing environment.
    Changes of light response indicators and its impact factors of Larix principis-rupprechtii on Saihanba Forest Farm, China.
    ZHOU Ying, ZHANG Ze-wen, WEN Shuo, SUN He, LIU Qiang
    2021, 32(5):  1690-1698.  doi:10.13287/j.1001-9332.202105.002
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    We examined the differences of maximum light use efficiency (LUEmax), most effective light intensity (PARe), light compensation point (LCP) and light saturation point (LSP) in diffe-rent vertical positions and different phenological periods of tree crown in Larix principis-rupprechtii plantation in Saihanba Mechanical Forest Farm of Hebei Province. We analyzed the main influencing factors for all the variables. The results showed that LUEmax increased with the increasing crown depth, and that PARe, LCP and LSP decreased with the increasing crown depth. Such a result indicated that upper crown had higher utilization efficiency to strong light and that the lower crown was more efficient to adapt to weak light environment. During the leaf development in the growth period, the LUEmax approximately increased except in July, while the changes of other photosynthe-tic-light factors showed a tendency of unimodal curve. Environmental factors were significantly correlated with the indices of light response, mainly due to the stress reaction of leaf stomata to surrounding environment. Understanding the spatial and seasonal changes of the photosynthetic-light indicators was important for formulating scientific management measures, optimizing stand structure, improving local microenvironment and maximizing forest productivity.
    Nitrogen and phosphorus dynamics along the primary succession in the Hailuogou Glacier retreat area, eastern Tibetan Plateau, China.
    YANG Dan-li, LUO Ji, JIA Long-yu, SHI Wen-bo
    2021, 32(5):  1699-1708.  doi:10.13287/j.1001-9332.202105.009
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    In this study, seven sampling sites (glaciers retreated for 0, 10, 30, 40, 50, 80 and 127 years) were chosen along a primary succession sequence in the Hailuogou glacial retreat area in the eastern margin of the Tibetan Plateau, China. The accumulation and cycling characteristics of N and P under different succession stages were analyzed by measuring biomass and N and P contents in surface soil and each vegetation layer. The N and P contents in leaves, branches and roots of tree layers decreased along the succession sequence, whereas the N and P contents in stems were higher in the late succession stage. The changes of N and P contents in litter and soil O layer were consis-tent with those in the leaves and branches of tree layers. Ecosystem N and P storage increased along the succession sequence. Ecosystem N accumulation was mainly dependent on the vegetation layer in the early succession stage. After the community reached the climax, soil became the main N pool of the ecosystem. Vegetation P storage was higher than that in the surface soil after 80 years of glacial retreat. The nutrient accumulation rate in each layer of the ecosystem was rapid in the middle succession stage, with an order of surface soil > tree layer > understory vegetation layer. The nutrient cycling coefficients of N and P in broadleaved forest in the middle stage were higher than those in coniferous forest in the late stage, whereas the N and P utilization efficiency was lower than that in coniferous forest. Therefore, the mechanism of low nutrient cycling and high utilization efficiency of coniferous trees was conducive to the their competition with other species, thus finally forming the climax community.
    Changes of nutrient release and enzyme activity during the decomposition of mixed leaf litter of Larix principis-rupprechtii and broadleaved tree species.
    WANG Chun, DONG Xue-ting, DU Rui-peng, ZHANG Zhi-dong, HUANG Xuan-rui
    2021, 32(5):  1709-1716.  doi:10.13287/j.1001-9332.202105.008
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    Litter is an important contribution to forest soil. Litter decomposition plays an important role in nutrient cycling of forest ecosystem. A field litterbag experiment was conducted to examine the dynamics of decomposition rate, nutrient release and enzyme activity during litter decomposition in the pure forests of Larix principis-rupprechtii (L) and mixed forests, including L and Betula platyphylla (B), L and Quercus mongolica (Q), as well as LBQ, in Saihanba area, Hebei Pro-vince, China. The results showed that the decomposition rate of leaf litter in L forest was significantly lower than that in mixed forests during the 720 d decomposition. The LB had the highest decomposition rate of L leaf litter. All treatments had the same change trend of nutrient contents, with the contents of N and P being increased and that of C, K and C/N being decreased. Contrast to pure leaf litter of L, leaf litter in mixed forests could promote the release of C and K, and inhibit litter N and P release. During the litter decomposition, the activities of catalase, urease and acid phosphatase increased, while that of sucrase decreased in all leaf litter of forests. The decomposition rate of leaf litter was positively correlated with the activities of catalase, urease and acid phosphatase, negatively correlated with that of sucrase. Our results showed that leaf litter mixture of L. principis-rupprechtii, B. platyphylla and Q. mongolica could enhance the litter decomposition of L. principis-rupprechtii, and that enzyme activities were closely related to litter decomposition.
    Species-abundance distribution patterns of Quercus aliena var. acutiserrata forest in Taibai Mountain, China.
    YU Wen, SONG Wen-chao, GUO Yi-chun, ZHANG Hou-fa, YAN Yan, ZHANG Shuo-xin
    2021, 32(5):  1717-1725.  doi:10.13287/j.1001-9332.202105.010
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    The statistical model (log-normal model), niche models (Zipf model, broken stick mo-del, niche preemption model), and neutral model were used to fit the species-abundance distribution patterns based on the measurements of environmental factors and inventory data of trees with DBH≥1 cm in a 1.5 hm2 plot in the primary forest (PF) and a 1.5 hm2 plot in the secondary forest (SF). The results showed that species-abundance distribution was affected by habitat heterogeneity in Q. aliena var. acutiserrata forest. Topography had a predominant impact on the species-abundance distribution in PF. Species distribution was affected by both neutral and niche processes, with neutral process having a less prominent effect in large convexity habitats. While the neutral model was rejected by the K-S and Chi-square test in low convexity habitats, the species-abundance distribution satisfied the assumption of niche theory. Niche process and neutral process were equally important in the community in areas with steep slopes, while niche differentiation was the dominant in flat areas. In SF, the main factors affecting species distribution were soil nutrients. The niche process was the mainly ecological process affected species-abundance distribution in habitats with high soil available phosphorus, while the niche and neutral processes existed simultaneously in habitats with low soil phosphorus availability. There was a significant scale effect on the species-abundance distribution pattern of Q. aliena var. acutiserrata forests in Taibai Mountain. The niche and neutral processes could protect the species-abundance distribution at the 20 m×20 m scale in PF, while the niche process could explain the species-abundance distribution at the 40 m×40 m and 70 m×70 m scales. The niche and neutral processes combined acted on the species abundance distribution at the 20 m×20 m, 40 m×40 m and 70 m×70 m scales in SF, with niche process being more important than neutral process. Moreover, besides the scale and habitat heterogeneity, the species-abundance distribution patterns of Q. aliena var. acutiserrata forests differed significantly between primary forest and secondary forest under anthropogenic disturbance.
    Root architecture of main tree species and the effects on soil reinforcement in typical black soil region.
    ZHANG Yang, LI Cheng-yuan, HAN Shao-jie, CHEN Xiang-wei
    2021, 32(5):  1726-1734.  doi:10.13287/j.1001-9332.202105.003
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    To explore root architecture and its effects on soil reinforcement of main tree species in typical black soil region, we measured root spatial distribution characteristics, root fractal characte-ristics, and geometric morphological characteristics of Amygdalus triloba, Caragana microphylla, Betula platyphylla, Acer negundo, Picea koraiensis, Pinus sylvestris var. mongolica, using whole root excavation method and WinRHIZO Pro LA2004 root analysis system. All the examined species are distributed widely in typical black soil region. The vertical uprooting force was determined by in-situ uprooting tests. The results showed that inclined roots were dominant in A. triloba, horizontal roots were dominant in C. microphylla, B. platyphylla, A. negundo and P. koraiensis, and the horizontal and vertical distribution of roots were commensurable in P. sylvestris var. mongolica. Except for the total root surface area of B. platyphylla and the total root length of P. koraiensis, the total root length and root surface area of shrub species were significantly greater than those of arbor species, while deciduous broad-leaved trees were significantly larger than coniferous evergreen trees. The total root volume of B. platyphylla was significantly larger than that of C. microphylla, A. negundo, P. koraiensis and P. sylvestris var. mongolica. The root fractal dimension and abundance of A. triloba, C. microphylla, B. platyphylla were significantly higher than those of P. koraiensis and P. sylvestris var. mongolica. The average maximum uprooting force of A. triloba, C. microphylla, and A. negundo was significantly higher than that of B. platyphylla, P. koraiensis, and P. sylvestris var. mongolica. Due to the role of total root length, total root surface area and the number of inclined roots, root system of A. triloba, C. microphylla and A. negundo showed strong soil reinforcement capacity. A. triloba, C. microphylla and A. negundo could be used as the option-preferred tree species when constructing soil and water conservation vegetation in typical black soil region.
    Responses of the spatial distribution of Stipa breviflora to stocking rate at different scales.
    ZHANG Feng, SUN Jia-wei, SUN Yu, ZHENG Jia-hua, QIAO Ji-rong, ZHAO Tian-qi, CHEN Da-ling, ZHAO Meng-li
    2021, 32(5):  1735-1743.  doi:10.13287/j.1001-9332.202105.006
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    We conducted an experiment to test the characteristics and differences of the spatial distribution of constructive species Stipa breviflora at different scales under different stocking rates in the S. breviflora desert steppe in Siziwang Banner, Inner Mongolia. The spatial distribution of S. breviflora under four treatments (control, light grazing, moderate grazing, and heavy grazing) at different scales (small scale as 1 m×1 m and mesoscale as 5 m×10 m) were analyzed. The results showed that the population density of S. breviflora at mesoscale in the control and light grazing was significantly lower than that at the small scale. Grazing significantly increased the population density of S. breviflora in the meso- and small scales. At the small scale, the population distribution of S. breviflora in the control, light grazing, moderate grazing, and heavy grazing treatments conformed to linear, exponential, exponential and exponential models, respectively, and Gaussian, exponential, Gaussian and exponential models at mesoscale fitted by semi-variance function. The spatial distribution pattern at small scales in the control was simple and better but was more complex and poorer under the heavy grazing. At the mesoscale, it was simple and better under the heavy grazing but complex and poor under the moderate grazing. The spatial heterogeneity of S. breviflora population reduced and were more uniform under the moderate and heavy grazing at meso- and small scales. In addition, the trend of population distribution in the enclosure, moderate and heavy grazing were generally the same, while light grazing showed inconsistent trend at different scales.
    Characteristics and influence factors in leaf and soil carbon stable isotopes of Caragana jubata.
    AI Zhe, XU Ting-ting, LI Yuan-yuan, MA Fei
    2021, 32(5):  1744-1752.  doi:10.13287/j.1001-9332.202105.004
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    In order to explore the relationship of plant carbon (C) cycling with its habitat in the high-altitude regions, a leguminous shrub, Caragana jubata, that mainly distributed in those areas was studied. We collected leaf and soil samples of C. jubata from 35 sites along an east-west transect across the alpine regions of China. We measured leaf carbon stable isotope (δ13C), soil δ13C, and the difference between leaf and soil δ13C (Δδ13C) of each sampling site. We further analyzed the effects of climatic factors, leaf and soil elements on leaf δ13C, soil δ13C and Δδ13C. Results showed that leaf δ13C ranged from -30.9‰ to -27.1‰, with a mean value of -28.4‰, soil δ13C ranged from -26.2‰ to -23.2‰, with a mean value of -25.3‰, and Δδ13C ranged from 2.0‰ to 7.7‰, with a mean value of 3.1‰. δ13C values of leaf was significantly lower than that of soil. Soil δ13C initially decreased and subsequently increased with increasing leaf δ13C. Leaf δ13C was negatively correlated with growing season temperature and leaf C content. Soil δ13C was negatively correlated with relative humidity and mean temperature of the warmest month, and was positively correlated with soil carbon:nitrogen (C:N). Soil δ13C firstly decreased and subsequently increased with soil C content. Δδ13C was positively correlated with leaf C content, soil C content, and soil C: N. Climatic factors directly affected leaf δ13C and Δδ13C, and indirectly affected leaf δ13C, soil δ13C and Δδ13C through their effects on leaf and soil elements. The C cycle of C. jubata was affected by climatic factors, leaf and soil elements in the alpine regions.
    Effects of tillage and fertility on soil nitrogen balance and greenhouse gas emissions of wheat-maize rotation system in Central Henan Province, China.
    ZHANG Dai-jing, HU Xiao, MA Jian-hui, GUO Yu-xin, ZONG Jie-jing, YANG Xue-qian
    2021, 32(5):  1753-1760.  doi:10.13287/j.1001-9332.202105.027
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    Energy saving, emission reduction, and efficiency improvement are important directions for agricultural development in Central Henan Province, the main grain production area in the Huang-huai-hai Plain. Based on the tillage and fertilization positioning experiment in 2010, we investigated the effects of three tillage methods (deep tillage, shallow tillage, and no-tillage) and two fertilization methods (nitrogen fertilizer and nitrogen fertilizer+organic fertilizer) on soil nitrogen balance and greenhouse gas emissions from 2018 to 2019. The results showed that soil nitrogen accumulation increased with organic fertilizer addition. During wheat and maize maturation, soil total nitrogen accumulation in the 0-60 cm layer was the highest under the treatment of shallow tillage+organic fertilizer, being 8058.53 and 8299 kg N·hm-2, respectively, being 3.2%-27.4% and 4.3%-7.2% higher than other treatments. The treatment with organic fertilizer addition resulted in nitrogen surplus. The shallow tillage+organic fertilizer treatment led to the highest nitrogen surplus (13.57 kg N·hm-2), which was 9.52 and 0.18 kg N·hm-2 higher than deep tillage+organic fertilizer and no tillage+organic fertilizer treatments. Nitrate leaching was the main way of nitrogen losses, accounting for 73.4%-76.9% of the total losses. The amount of nitrate leaching was the highest in deep tillage+organic fertilizer treatment (48.37 kg N·hm-2), being 18.9%-35.1% higher than other treatments. Results of greenhouse gases emission during 2018-2019 showed that global warming potential was the highest under the treatment of deep tillage+organic fertilizer, which was 33070 kg N·hm-2, being 6.6%-26.8% higher than other treatments. The treatment of organic fertilizer addition increased the emission of N2O and CO2 and reduced the absorption of CH4. The annual grain yield was highest under the treatment of deep tillage+organic fertilizer, which was 5.0%-17.1% higher than other treatments. The crop harvest index was the highest under the treatment of shallow tillage+organic fertilizer. The recommended cropping mode in Central Henan Pro-vince is shallow tillage+organic fertilizer, which could ensure crop yields, maintain soil nitrogen balance, and reduce greenhouse gas emissions.
    Impacts of arbuscular mycorrhizal fungi (AMF)on growth, N bio-fixation, and phosphorus uptake of legume crop.
    LIU Yun-long, QIAN Hao-yu, ZHANG Xin, ZHENG Cheng-yan, DENG Ai-xing, JIANG Yu, ZHANG Wei-jian
    2021, 32(5):  1761-1767.  doi:10.13287/j.1001-9332.202105.022
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    To explore the effects of arbuscular mycorrhizal fungi (AMF) on the growth of legume crop, pot and field experiments with soybean were conducted. Treatments of inoculation (+AMF) and non-inoculation with AMF (-AMF) were set up for the pot experiment, and AMF mycelium non-limited and limited for the field experiment. Results of the pot experiment showed that inoculation with AMF significantly increased soybean aboveground biomass (16.5%) and root nodules number (131.4%), above-ground plant phosphorus and nitrogen concentrations and uptakes. In the field trial, the above-ground and root biomasses and root nodules number under AMF mycelium non-limited were significantly increased by 123.6%, 61.5%, and 212.5% compared with those under the limited condition, respectively. Plant phosphorus uptake, nitrogen concentration and uptake, and soil available nitrogen and phosphorus concentrations were significantly higher under AMF mycelium non-limited than the limited both in both shoot and root. Our findings provide theoretical reference for further understanding the relationship between legume crop and AMF, as well as the efficient utilization of phosphorus fertilizer.
    Responses of photosynthesis and P/Fe traits to P application in soybean under stress of low Fe.
    ZHAO Jing, MENG Fan-gang, YU De-bin, ZHANG Ming-hao, RAO De-min, CONG Bo-tao, YAN Xiao-yan, ZHANG Wei, QIU Qiang
    2021, 32(5):  1768-1776.  doi:10.13287/j.1001-9332.202105.025
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    We examined the effects of phosphorus (P) levels on photosynthetic and P/Fe traits of soybean under the stress of low Fe and their genotypic differences, to provide a theoretical basis for rational application of P and Fe fertilizer. Six P-efficient and six P-inefficient soybean varieties screened in the early stage were used as experimental materials. Four treatments of P:Fe ratio were set, including 0:30, 30:30, 150:30 and 300:30 (μmol·L-1). We measured chlorophyll fluorescence traits and P-Fe utilization efficiency in soybean. A stepwise regression equation was established with seed weight per plant. Pathway analysis was performed, with the response of P-efficient and P-inefficient soybean genotypes to different P:Fe treatments being comprehensively evaluated by factor scores. The results showed significant main and interactive effects of genotype and P:Fe on the relative electron transfer rate of photosystem Ⅱ (ETR) at beginning of flowering stage (R1), the proportion of the energy absorbed by photosystem Ⅱ dissipated into heat (NPQ) at R1 stage, and proportion of energy absorbed by photosystem Ⅱ devoted to the photochemical reaction (qL) at R1 stage. Results of canonical correlation analysis showed a negative correlation between P utilization efficiency of seed at full maturity stage (R8) and photosynthetic rate at R1 stage of P-efficient genotypes. Seed Fe utilization efficiency of P-inefficient genotypes at R8 stage was positively correlated with NPQ at R1 stage, but negatively correlated with qL at R1 stage. The actual photochemical efficiency of PSⅡ (ΦPSⅡ) at R1 stage was negatively correlated with P-efficient genotypes, but positively correlated with P-inefficient genotypes, which indicated that ΦPSⅡ at R1 stage was an important indicator for identifying soybean genotypes with different P efficiency under stress of low Fe. The comprehensive performance of P-efficient soybean genotypes decreased first and then increased with P level, while P-inefficient soybean genotypes increased first and then decreased. The inflection point of both genotypes appeared in P:Fe of 30:30. Thus, P:Fe ratio of 30:30 could be used as a threshold to identify soybean genotypes with different P efficiency under stress of low Fe. In conclusion, P fertilizer application should be equal to or greater than 1:1 (P:Fe) when planting P-efficient soybean genotypes in low Fe area, while P fertilizer application should not exceed 1:1 (P:Fe) when planting P-inefficient soybean genotypes.
    Effects of different forms of microbial agents on the growth and quality of Brassica rapa L. ssp. chinensis Makino (non-heading Chinese cabbage).
    WEN Dan, WANG Xiao, SUN Kai-ning, WANG Ke-an, GAO Jian-wei, ZHANG Wei, YANG Ning
    2021, 32(5):  1777-1782.  doi:10.13287/j.1001-9332.202105.021
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    Reasonable application of microbial agents can significantly improve soil environment and increase the yield and quality of vegetables. In this study, we examined the effects of different forms of microbial agents on the growth and quality of Brassica rapa L. ssp. chinensis Makino (non-heading Chinese cabbage) under the conditions of no microbial agent application, liquid and solid microbe agents application. The results showed that compared with no microbial agent, application of liquid and solid microbial agent significantly improved soil urease activity, plant nitrogen content, leaf area, SPAD value, and net photosynthetic rate, and increased vegetable production by 26.9% and 34.4% respectively. Meanwhile, the total phenol content and ascorbic acid content of non-heading Chinese cabbage were increased and nitrate content was significantly decreased by applying microbial agents. Thus, rational application of microbial agents promoted the yield and quality of non-heading Chinese cabbage. From the perspective of vegetable growth, liquid microbial agents work fast, solid microbial agents had good long-term efficacy. The cooperating application with organic and inorganic fertilizers would facilitate the excellent quality and high yield of vegetables.
    Responses of root exudates to intercropping of Chinese milk vetch with rape.
    WANG Ya-jun, WANG Teng-qi, HOU Zhi-jie, WANG Xue-hao, SU Gao-jie, LIU Yi-qiang, ZHOU Quan
    2021, 32(5):  1783-1790.  doi:10.13287/j.1001-9332.202105.024
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    Root exudates are important carriers for material exchange and information transfer between plant and soil, and important regulators of crop-soil-microorganism interaction in intercropping systems. We examined the interaction between crops in intercropping system by setting three treatments, monoculture Chinese milk vetch, monoculture rape and Chinese milk vetch intercropped with rape. The responses of root exudates were emphatically analyzed. The results showed that 391 root exudates were detected, with 93 of which being identified and divided into nine types of metabo-lites. Among them, organooxygen compounds were the most abundant, mainly in the form of ribitol. Under different planting patterns, root exudates of Chinese milk vetch and rape were significantly different. The characteristics of root exudates in intercropping were similar to monoculture rape, but significantly different from monoculture Chinese milk vetch. Among the root exudates in different planting modes, only 9-fluorenone 1 was negatively correlated with others. The differential root exudates were mainly benzenoids, lipids and lipid-like molecules, organic acids and derivatives, and organooxygen compounds. The benzenoids, lipids and lipid-like molecules were important types that characterized the changes of root exudates of Chinese milk vetch and rape. Chinese milk vetch intercropping with rape changed the characteristics of root exudates, which were closely related to benzenoids, lipids, and lipid-like molecules.
    Effects of Astragalus sinicus combined with chemical fertilizer on nitrogen absorption and utilization of rice and nitrogen distribution and residue of Astragalus sinicus in rice-soil system.
    LIU Chun-zeng, ZHANG Cheng-lan, LI Ben-yin, LYU Yu-hu, NIE Liang-peng, ZHANG Lin
    2021, 32(5):  1791-1798.  doi:10.1328/j1001-9332.202105.026
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    Clarifying the pattern of nitrogen absorption and utilization of rice under the treatments of Astragalus sinicus combined with chemical fertilizer application and the pattern of absorption, utilization, distribution and residue of A. sinicus nitrogen in rice-soil system could provide basis to rational fertilization for rice planting area in southern Henan. In this study, undisturbed soil column simulation and isotope tracer technology of 15N were used to examine the differences of nitrogen uptake and utilization of rice, nitrogen nutrient balance of rice-soil system and nitrogen uptake, utilization, distribution and residue of A. sinicus nitrogen after mineralization and decomposition among seven treatments. The treatments involved 1) no fertilization (CK); 2) chemical fertilizer+22500 kg·hm-2 A. sinicus (FM1); 3) chemical fertilizer+30000 kg·hm-2 A. sinicus (FM2); 4) chemical fertilizer+37500 kg·hm-2 A. sinicus (FM3); 5) chemical fertilizer+22500 kg·hm-2 A. sinicus +lime (FM1+CaO); 6) chemical fertilizer+30000 kg·hm-2 A. sinicus lime (FM2+CaO); 7) chemical fertilizer+37500 kg·hm-2 A. sinicus +lime (FM3+CaO). Results showed that compared with CK, fertilization significantly increased nitrogen uptake of grain and rice stalks, apparent nitrogen loss, and nitrogen surplus. The grain nitrogen uptake, rice straw nitrogen uptake and nitrogen use efficiency of rice increased firstly and then decreased with the increasing A. sinicus application rates, while the apparent nitrogen loss and nitrogen surplus showed the opposite trend. The best performance was presented under the treatment of chemical fertilizer combined with 30000 kg·hm-2 of A. sinicus. Lime addition could increase grain nitrogen uptake, rice straw nitrogen uptake, and nitrogen use efficiency of rice, while reducing apparent nitrogen loss and nitrogen surplus, with the best performance of FM2+CaO. For all the treatments, the proportion of nitrogen absorbed by rice from A. sinicus was 6.3%-13.2%, while that from soil and chemical fertilizer was 86.8%-93.7%. The utilization ratio of A. sinicus nitrogen by rice was 23.8%-33.6%. The utilization ratio of A. sinicus nitrogen in different parts of rice was grain > stem and leaf > root. The residue rate of A. sinicus nitrogen in soil was 37.6%-62.4%. The loss rate of A. sinicus nitrogen was 7.8%-38.6%. Comprehensively considering nitrogen absorption and utilization of rice, nitrogen nutrient balance of rice-soil system, and the distribution situation of nitrogen from A. sinicus in rice, FM2+CaO was the optimum fertilization pattern in the study area.
    Effects of activated coke on soil properties and growth of two plant species in saline alkali soil in northern Shanxi Province, China.
    QIN Wen-fang, SONG Hui-ping, FAN Yuan, CHENG Fang-qin
    2021, 32(5):  1799-1806.  doi:10.13287/j.1001-9332.202105.028
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    Solid waste-based improver is one of the effective means to improve properties of saline-alkali soil. As a kind of porous waste, activated coke is expected to improve soil properties and alleviate salt-alkali stress. In order to understand the improvement effect of activated coke on saline alkali land in northern Shanxi Province, we examined the effects of different addition rates of activated coke (CK, 0 g·kg-1; A10, 10 g·kg-1; A20, 20 g·kg-1; A50, 50 g·kg-1) on the properties of saline alkali soil and the growth of two plant species. The results showed that activated coke addition could increase the content of water soluble soil aggregates, reduce soil salt content, soil pH, and the electrical conductivity (EC). Compared with CK, the mean weight diameters of the aggregates for the saline-alkali soils grown with Puccinellia distans and maize were increased by 5.1%-32.2%, soil pH was decreased by 0.4%-4.1%, sodium adsorption ratio (SAR) was decreased by 4.8%-18.7%, and the EC was decreased by 7.4%-8.2%. Applying appropriate amount of activated coke could promote plant growth through reducing the plasma membrane damage of plant cells, increasing plant chlorophyll and Ca2+ contents. The biomass of Puccinellia distans and maize both reached the maximum under the A20 treatment. It suggested that the application of 20 g·kg-1 activated coke (A20) in saline alkali soil could improve soil quality in the rhizosphere soil, increase plant selective Ca2+ absorption, thereby reducing salt damage to plant cells and promote plant growth in saline-alkali habitat.
    Effects of different nitrogen application rates on dry matter accumulation, distribution and yield of grape under alternate partial root-zone drip irrigation.
    CHEN Li-nan, LIU Xiu-chun, SUN Zhan-xiang, RONG Chuan-sheng, ZHOU Yan-qi, SHU Liang-zuo
    2021, 32(5):  1807-1815.  doi:10.13287/j.1001-9332.202105.023
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    To get an optimal mode of irrigation and nitrogen supply for table grape production in North China, a pot experiment was conducted to investigate the effects of different irrigation modes and N application rates on dry matter accumulation and distribution, yield, water use efficiency, and nitrogen use efficiency of table grape. The irrigation modes included conventional drip irrigation (CDI, with sufficient irrigation), alternate partial root-zone drip irrigation (ADI, with 50% amount of the irrigation water of CDI) and fixed partial root-zone drip irrigation (FDI, with 50% amount of the irrigation water of CDI). The nitrogen application rates were set at 0.4 (N1), 0.8 (N2) and 1.2 (N3) g·kg-1 dry soil. The results showed that compared with CDI, ADI and FDI reduced new shoot pruning amount by 34.8% and 11.2%, respectively. New shoot pruning amount increased with increasing N application rates, being highest under CDIN3. Dry matter accumulation of ADI was the highest, being 5.1% and 12.8% higher than CDI and FDI. Dry matter accumulation was higher under N2 and N3 than N1. Compared with CDI and FDI, leaf to fruit ratio reduced but harvest index significantly increased in ADI, while those variables showed no significant difference among diffe-rent N application rates. The ratio of pruning amount to the biomass accumulated in the current year in ADIN2 was the lowest among the treatments. Compared with CDI and FDI, ADI increased grape fruit yield by 6.0% and 10.4%, respectively. Fruit yield was enhanced with increasing nitrogen application rates under the same irrigation condition, with the highest yield under the ADIN2 and ADIN3. Water use efficiency (WUE) increased significantly in ADI compared with CDI and FDI, with the highest value being observed in ADI coupled with N2 or N3. Nitrogen use efficiency (NUE) showed a trend of ADI＞CDI＞FDI. In addition, NUE decreased with increasing nitrogen supply level across the irrigation modes. In conclusion, ADIN2 could reduce the redundant growth of grape tree, promote the transfer of dry matter to fruit, which increased yield and use efficiency of both water and nitrogen, which is a suitable coupling water and nitrogen supply mode for grape production in northern China.
    Effects of salinity on soil bacterial diversity and assembly processes in coastal soils.
    CHEN Rui-rui, ZHANG Jian-wei, DONG Yang, LIN Xian-gui, FENG You-zhi
    2021, 32(5):  1816-1824.  doi:10.13287/j.1001-9332.202105.039
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    Coastal saline soil is an important reserve resource of agricultural land. Soil microorganisms play a key role in soil nutrient cycling. However, it is still far from clear about the effects of salinity on soil microbial community. We examined the effects of salinity on soil bacterial abundance, diversity, and community assembly, by collecting soil samples in coastal areas with three salinity levels (non-, mild-, and severe-salinity). Our results showed that the activity of dehydrogenase and the abundance of bacteria significantly decreased in the severe-saline soils, while the diversity of bacteria remained unchanged, compared with non- and mild-saline soils. Bacterial communities were clustered by salinity. Null model was used to infer bacterial community assembly processes. Salinity was the main driving factor for bacterial community assembly. Deterministic process driven by salinity played a leading role in controlling bacterial community composition in coastal saline soil. These findings suggested that coastal saline soils contain abundant microbes within the salinity range, and have a biological basis for soil improvement. Due to the high deterministic process of microbial community assembly, it would be difficult for alien species to colonize coastal saline soils. Salt-tolerant and indigenous strains are recommended when using microbial technology to reclaim coastal saline soils.
    Compositions and metabolic footprints of soil nematode communities under different alfalfa-crop planting patterns in semi-arid region of the Loess Plateau, Northwest China.
    HUO Na, HUANG Jing-hua, GENG De-zhou, WANG Nan, YANG Pan-pan, ZHAO Shi-wei
    2021, 32(5):  1825-1834.  doi:10.13287/j.1001-9332.202105.033
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    Soil nematode communities play an important role in ecosystem material cycling and energy flow. In this study, soil samples were collected from three rotation systems in southern Ningxia mountainous region, including alfalfa continuous cropping (A-A), alfalfa-corn rotation (A-C), alfalfa-potato rotation (A-P). Soil physicochemical properties, nematode community composition and their metabolic footprints were measured. Compared with the A-A plot, the concentrations of soil organic carbon (SOC) and total nitrogen (TN) were significantly increased by 4.6% and 7.4% for SOC, 4.0% and 5.2% for TN in the A-C and A-P plots, respectively. Soil microbial biomass carbon and nitrogen were significantly higher in the A-C and A-P plots when compared with the A-A plot. The total abundance of soil nematodes in the A-C and A-P plots was higher by 49.5% and 93.7% than that in the A-A plot, respectively, with the dominant trophic group being changed to omnivores-predators from plant parasite. Compared to the A-A plot, the plant parasite index (PPI) was decreased significantly in the A-C and A-P plots, indicating that the harm of plant-parasites was reduced in soil food web. The nematode channel ratio (NCR) in the A-C and A-P plots were higher than that in the A-A plot, indicating that the role of bacterial decomposition was enhanced in soil organic matter decomposition. The maturity index (MI), the total nematode metabolic footprint, enrichment footprint, structure footprint in the A-C and A-P plots were all significantly higher than those in the A-A plot, suggesting that the structure and function of soil food web were more mature and stable, and the productivity and metabolic activity of nematodes were significantly enhanced. In general, the alfalfa-crop rotations improved soil nutrient status and reduced the disturbance degree of soil food web. Furthermore, soil ecosystem developed in the stable and healthy direction, which would be beneficial to the sustainable development of agriculture.
    Effects of cadmium stress on growth and cadmium enrichment of Chlorophytum comosum and Chlorophytum comosum var. variegatum.
    WANG Fei, XIAO Yu, CHENG Xiao-mao, HUANG Xiao-xia
    2021, 32(5):  1835-1844.  doi:10.13287/j.1001-9332.202105.031
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    We examined the growth and physiological characteristics of Chlorophytum comosum and Chlorophytum comosum var. variegatum by hydroponics at different Cd2+ concentrations (0, 20, 80, 200 μmol·L-1). The results showed that 20 μmol·L-1 Cd2+ did not affect those two varieties, with no changes of single leaf area, total leaf area, chlorophyll (Chl) a content, Chl (a+b) content, carotenoid content, Chla/Chlb value, intercellular carbon dioxide concentration (Ci) and transpiration rate (Tr) compared with the control (CK). Under the 80 μmol·L-1 Cd2+ stress, the initial fluorescence (Fo) and non-photochemical quenching coefficient (NPQ) were the highest for both varieties. As for Cd2+ at 200 μmol·L-1, the biomass, chlorophyll content, maximum net photosynthetic rate (Pn), stomatal conductance (gs), maximum photochemical quantum yield (Fv/Fm), actual photochemical quantum yield Y(II), the transfer factor (TF) of both varieties and all parts biomass decreased to the lowest, while peroxidase (POD), ascorbic acid peroxidase (APX) and catalase (CAT) activities of two varieties and MDA content of C. comosum var. variegatum increased in different degrees. With the increases of Cd2+ stress, the Cd content in organs of two varieties showed an increasing trend, with higher Cd accumulation in roots. C. comosum had higher Cd content and bioconcentration factor (BCF) in all organs than C. comosum var. variegatum. It suggested that two varieties had the ability to resist Cd stress. The tolerance of C. comosum was stronger, and thus could be considered as a green plant to remediate Cd contaminated water or soil.
    Seasonal variations and driving factors of phytoplankton community shift in Datun Lake with long-term stress of arsenic contamination.
    SHANG Li, CHEN Li, ZHANG Tao, ZHENG Xin, ZHAO Shuai-ying, KONG Ling-yang, CHEN Guang-jie
    2021, 32(5):  1845-1853.  doi:10.13287/j.1001-9332.202105.032
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    Heavy metal is an important environmental stress that threatens water quality and ecological health of surface waters. Therefore, it is vital to identify the responses of lake community to long-term pollution for sustainable ecological restoration of polluted lakes. From June 2017 to March 2018, we conducted a seasonal survey of phytoplankton and environmental factors in Datun Lake, which had a decadal history of tailing-related arsenic contamination. Consistent with results from previous studies, phytoplankton were dominated by As-tolerant taxa such as Cyanophyta. Results of the analysis of similarities and analysis of variance showed that there were significant temporal variations in phytoplankton community structure and biomass, but without spatial variation. Results of the Pearson correlation analysis demonstrated that the total phytoplankton biomass was positively related to lake-water soluble orthophosphate and arsenic, which was consistent with the differential effect of arsenic on algae growth (e.g. promotion at low concentration and suppression at high concentration). The increases of phosphate might alleviate the toxic impacts of arsenic on phytoplankton. Redundancy analysis showed that the soluble nutrients and arsenic were significant factors driving phytoplankton community variations. The results of variation partitioning demonstrated that nutrients and water temperature explained 17.6% and 3.8% of community variations, respectively, with strong interaction with arsenic (15.1%). Arsenic did not affect phytoplankton community assembly, indicating that the dominant algae were tolerant to arsenic and thus highly insensitive to the arsenic stress. Therefore, the seasonal variations of phytoplankton dominated by As-tolerant algae in Datun demonstrated that the low-As promotion effect on phytoplankton should be considered in ecological restoration of polluted lakes.
    Effects of dung beetles on decomposition of cattle dung in spring and autumn in a Seriphi-dium-dominated desert, China.
    GUO Ya-ya, CAO Jia-min, CHE Zhao-bi, YANG Han-jun, HUANG Xing-yu, LU Wei-hua
    2021, 32(5):  1854-1862.  doi:10.13287/j.1001-9332.202105.034
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    To understand the decomposition of cattle dung in Seriphidium-dominated desert, the changes of dung physical and chemical properties were determined by setting different stacking times (0, 7, 29, 48, 58 h) in May (spring) and September (autumn), respectively. Mesh cage with different openings (no mesh cage, opening up and down, opening up, totally enclosed) were set up to explore the effects of different ecological functional groups of dung beetles on decomposition. The results showed that species richness of dung beetles in spring was significantly higher than that in autumn, and that the abundance of dung beetles in autumn was significantly higher than that in spring. The losses of moisture, total carbon, total nitrogen and total phosphorus in dung were mainly concentrated during 0-29 h in spring, being decreased by 39.4%, 13.9%, 32.1% and 26.7% at 29 h, respectively. Neutral detergent fiber and acid detergent fiber of the dung stacked for 58 h decreased significantly by 8.0% and 16.0% respectively. In autumn, moisture, neutral detergent fiber and acid detergent fiber decreased most rapidly during 0-7 h, being decreased by 85.6%, 10.2% and 20.2% at 7 h, respectively. The concentrations of neutral detergent fiber and acid detergent fiber increased during 7-58 h by 20.0% and 13.7%, respectively. The decomposition of total carbon, total nitrogen and total phosphorus mainly concentrated during 0-29 h, being reduced by17.5%, 55.0% and 64.8%, respectively. The mesh cage with different openings effectively prevented the entering of dung beetles from the corresponding ecological functional groups. With the increases of functional groups of dung beetles, the decomposition rate accelerated, with cattle dung of no mesh cage being significantly higher than other treatments. The species richness and abundance of dung beetles and the stacking time of dung significantly affected the decomposition of cattle dung.
    Diversity and community characteristics of organic phosphate-mineralizing bacteria in the sea area between Minjiang Estuary to Pingtan.
    SHE Chen-xing, LIN Hong, SU Yu-ping, ZHANG Yong, LIN Wan-zhen, LAN Rui-fang
    2021, 32(5):  1863-1872.  doi:10.13287/j.1001-9332.202105.038
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    Microbial mineralization of organic phosphorus is an important component of marine phosphorus cycle. The research on organic phosphate-mineralizing bacteria (OPB) is helpful to reveal microbial driving mechanism of organic phosphorus mineralization in eutrophic sea area. The diversity and community characteristics of OPB were examined by Illumina high-throughput sequencing using the primer sets phoX in the sea area between Minjiang Estuary to Pingtan in April (spring) and July (summer) 2019. The results showed that the Shannon index of OPB in the surface seawater samples ranged from 3.21 to 7.91, and that the diversity at each station was greater in spring than that in summer. Shannon index of OPB in the sediment samples ranged from 2.04 to 8.70, which was greater in summer than that in spring. Shannon index of OPB in surface seawater of each station was higher than that of sediment in spring, while it was in adverse in summer. Nine phyla of OPB were detected in surface seawater, with Proteobacteria and Cyanobacteria being the most abundant. Tweleve phyla of OPB were detected in the sediments, with Proteobacteria and Bacteroidetes being the most dominant. OPB community composition at the genus level showed obvious spatio-temporal variation. Leisingera, Phaeobacter, Thalassococcus, and Pseudomonas were the major genera in the seawater in spring, while Synechococcus, Halioglobus, Roseovarius, Phaeo-bacter, Sulfitobacter, and Hyphomonas were the major genera detected in summer. Leisingera, Phaeobacter, Vibrio, and Sulfitobacter were major genera in the sediment in spring, while Azospirillum, Aminobacter, Sulfurifustis, Burkholderia, and Thiohalobacter were the major genera in summer. A large number of unclassified OPB were detected in both surface seawater and sediment. The redundancy analysis results showed that dissolved oxygen, water temperature, pH, dissolved inorganic nitrogen, NO2--N, and NO3--N had great influences on community distribution of OPB in the surface seawater. The abundant OPB in the surface seawater and sediment might play an important role in phosphorus cycle in this sea area.
    Age and growth characteristic of Sepia officinalis in the West Africa based on cuttlebones.
    QU Jun-yue, ZHOU Min-hua, HAN Pei-wu, FANG Zhou, CHEN Xin-jun
    2021, 32(5):  1873-1880.  doi:10.13287/j.1001-9332.202105.035
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    Common cuttlefish is mainly distributed in the eastern North Atlantic and the coastal waters of Africa, which is an important fishing target for trawl fisheries and the most important commercial species in the Atlantic sepia family. In this study, based on the cuttlefish samples collected from the west Africa coast in July-August 2015, we measured the outer morphological parameters of 283 cuttlebones. Combined with the age information of cuttlebones, we examined the growth characteristics of cuttlefish of different genders. The results showed that there were significant differences in body length and body weight between different genders. The dominant age group of female and male was both 80-100 days. Among the fitting functions of the outer shape of cuttlebone and the age, the logistic function was the best one. The females' maximum likelihood estimates of the outer morphological parameters of cuttlebone were larger than that of males. The absolute and instantaneous relative growth rates of the cuttlebone length and width of male and female cuttlefish peaked at 110-120 days and 100-110 days, respectively. The age of males and females at first sexual maturity was 111 days and 104 days, respectively. The growth difference between genders might be related to environment.
    Factors influencing beak morphology of Sthenoteuthis oualaniensis in the northwest Indian Ocean.
    HE Jing-ru, LU Hua-jie, CHEN Xuan-yu, LIU Kai, WANG Hong-hao, CHEN Xin-jun
    2021, 32(5):  1881-1889.  doi:10.13287/j.1001-9332.202105.037
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    With 1009 Sthenoteuthis oualaniensis samples collected by Chinese light falling-net fishery during February to May in the northwest Indian Ocean, we analyzed the influencing factors of the morphology change of the beak. There were significant differences in the morphologic growth between genders, different gonad maturity stages, and different mantle length. The increment of characteristic parameters growth peaked in the mantle length between 201 and 250 mm, and in the Ⅱ and Ⅲ stages of gonad maturity for females and males, respectively. There was no significant difference in the ratio of morphometric parameters to crest length (CL) between the genders, diffe-rent gonad maturity stages, and different mantle length, except for the ratio of upper hood length to upper crest length (UWL/UCL) and lower hood length to lower crest length (LHL/LCL). The ratio of each characteristic parameter to CL was nearly stable with the change of sex, gonad maturity and mantle length, suggesting consistent growth of each dome of beak. Our results suggested the mantle length of 201 mm to 250 mm seemed to be the threshold for the morphologic growth of beak on the body size, while the gonad maturity of Ⅱ and Ⅲ stages seemed to be the threshold for the morphologic growth of beak on the gonad maturity.
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    The suppression effect and mechanism of arbuscular mycorrhizal fungi against plant root rot.
    HUANG Yong-ming, JIANG Ying-chun, WANG Zhi-jing, SONG Fang, HE Li-gang, TIAN Rui, WU Li-ming
    2021, 32(5):  1890-1902.  doi:10.13287/j.1001-9332.202105.036
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    Root rot is a serious soil-borne disease, with negative consequences on crop yield and quality. Arbuscular mycorrhizal (AM) fungi are a group of soil microorganisms, which play important physiological and ecological functions by establishing symbionts with plant roots. AM fungi could induce plant resistance against root rot by regulating physiological and biochemical processes. As a biological agent, AM fungi are used to antagonize soil-borne diseases such as root rot, which is a hotspot in the field of plant-microorganism interaction. We comprehensively reviewed the suppression effect of AM fungi on plant root rot, and the effect of AM fungi on root morphology of host plant, plant nutrition levels, as well as their role in competing with pathogens for ecological sites, activating plant defense systems, and regulating root exudates. Finally, we discussed the potential mechanism of AM fungi inhibiting root rot, as well as the practical problems in the efficient utilization of AM fungi were discussed, in order to provide the theoretical basis for the biological control protocol to antagonize root rot with AM fungi.