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    15 March 2022, Volume 33 Issue 3
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    Opinion of the Editor in Chief
    Discussion on the scientific concepts of regional resources and environmental carrying capacity and its ecological basis.
    YU Gui-rui, ZHANG Xue-mei, ZHAO Dong-sheng, DENG Si-qi
    2022, 33(3):  577-590.  doi:10.13287/j.1001-9332.202203.020
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    The carrying capacity of resources and environment is an essential concept in ecology, the theoretical and practical research of which has become an important basis for measuring regional sustainable development. However, the scientific connection between the ecological foundation and the carrying capacity of resources and environment is still unclear. Moreover, it remains unknown which ecological theories played a supporting role in the development of the resources and environment carrying capacity, which makes the scientific concept of carrying capacity very vague. Based on the discussion of the scientific concepts and development of the carrying capacity of resources and environmen, we systematically discussed the basic concepts, such as the niche volume that organisms can occupy, the ecological threshold of ecosystems to withstand environmental stress, the potential resource capacity (supply capacity) of sustainable supply such as climate, water and nutrition, and the environmental capacity of buffering and purifying pollutants. Furthermore, from the biophysical point perspective of foundation pressure bearing capacity, spatial capacity carrying capacity and ecological threshold carrying capacity, the scientific concepts of Natural Resources Supply Carrying Capacity (NRSCC), Nature Environment Carrying Capacity (NECC), Carrying Capacity of Biological Population Development (CCBPD), Carrying Capacity of Social and Economic Development (CCSED) and Carrying Capacity of Environmental Stress in Ecosystems (CCESE) were defined. Finally, three basic issues of ecology were discussed in detail, including the theory of population growth and the ecological capacity of the ecosystem, the theory of ecosystem multi-functionality and resource and environmental effects, and the theory of alternative stable states, self-adaptability, and self-organization. Based on exploring the theory and method of regional resource environmental assessment, this study would provide theoretical basis for regional resource environment utilization, protection and social and economic sustainable development.
    Special Features of Impact of Global Change on Resource and Environmental Carrying Capacity in Ecologically Fragile Areas
    Evaluation theory and method of regional resources and environmental carrying capacity.
    ZHAO Dong-sheng, ZHANG Xue-mei, DENG Si-qi, YU Gui-rui
    2022, 33(3):  591-602.  doi:10.13287/j.1001-9332.202203.024
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    Our understanding of resources and environmental carrying capacity is deepened with the comprehensive effects of human needs and external stress. When human survival and development mainly depend on the supply of local resources and environmental conditions, the resources and environmental carrying capacity is largely controled by the dominant limiting factors. With sustainable development and environmental protection, the resources and environmental carrying capacity has gradually changed from supply restriction to demand support. There is an expression of capacity, threshold, intensity, and ability to characterize the resources and environmental carrying capacity. The impact of climate change and human activities on the resource and environmental system is increasing, altering resources and environmental carrying capacity. At present, the interrelationship and internal mechanism among resource and environmental carrying capacity, ecosystem vulnerability, and climate change risk are still unclear, which restricts the further development of theory and method. We preliminarily summarized and discussed the basic theory and method system of the research on carrying capacity of regional resources and environment. Furthermore, we advocated to develop the cascade relations of “carrying capacity of biological population development-carrying capacity of environmental stress in ecosystems-natural resources supply carrying capacity-natural environment carrying capacity-carrying capacity of social and economic development”. Moreover, the calculation method and conceptual model of multi-dimensional resource and environmental carrying capacity were put forward under each concept framework. This study provided new ideas for the research on the method of resources and environment carrying capacity.
    Theoretical basis of ecology for the influence of global change on resources, environment, and ecosystems.
    LI Yu-qiang, CHEN Yun, CAO Wen-jie, WANG Xu-yang, NIU Ya-yi
    2022, 33(3):  603-612.  doi:10.13287/j.1001-9332.202203.019
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    With the deepening of global change research, the applied problems such as global change risk and response for social sustainable development, temporal and spatial allocation of resources and environmental elements and impact assessment of ecosystem are becoming a new trend in the research field of global change. Based on the ecological framework, we focused on clarifying the connotations of resources and the environment and their components. Resources refer to all substances consumed by organisms in the process of producing organic matter from inorganic matter and transferring energy and matter among organisms. These include inorganic resources (e.g., solar radiation, CO2, O2, water, and mineral elements) and organic resources (as a source of food for other organisms). In contrast, the environment can not be consumed or depleted by organisms. In addition, we described the components of global change and the associated variations of resources and environmental factors, as well as current research progress on the responses of ecosystem to global change. We scientifically described the processes and mechanisms of global change in terms of their influence on resources, the environment, and ecosystems within a theoretical framework based on ecological principles. Our goal was to provide a strong theoretical foundation for future research on coping with the risks of global change.
    Research advances in critical transition and its ecological mechanisms of terrestrial ecosystems.
    ZHANG Tian-you, CHEN Zhi, WEN Zhong-ming, YU Gui-rui
    2022, 33(3):  613-622.  doi:10.13287/j.1001-9332.202203.021
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    With the exacerbating disturbances of climate changes and human activities to terrestrial ecosystems, more and more studies realize that ecosystems are at the risk of shifts without warning in structural and functional states and recovery from perturbations require more time. Developing an early warning model to identify critical transition and understanding its ecological mechanism of typical ecosystems have become hotspot in ecological researches. At present, based on theoretical and experimental researches across multiple spatiotemporal scales, a variety of theoretical frameworks and indicators of early warning signals (EWSs) were proposed to signal terrestrial ecosystem critical transition. Here, in order to more thoroughly understand and construct theoretical frameworks and indicators of early warning signals, we reviewed advances in critical transitions from aspects of theoretical methods and processing mechanisms. Catastrophe theory and critical slowing down (CSD) are the two basic theories for early-warning ecosystem state transitions. Self-organization and feedback mechanisms are the primary ecological mechanisms to shape alternative stable state. Understanding cascade effects networks (CENet) among biological and environmental elements, and clarifying the equilibrium relationships between input and output of key ecosystem parameters are theoretical foundation of critical transition model. These theoretical cognitions could provide useful references to early warning of ecosystem disasters, ecological environment management and restoration.
    Theories of ecosystem vulnerability, adaptability and catastrophe based on the mechanisms of ecological succession.
    XU Xing-liang, YU Gui-rui
    2022, 33(3):  623-628.  doi:10.13287/j.1001-9332.202203.025
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    With the increases in the breadth and depth of the impacts of climate change, the theories of ecosystem vulnerability, adaptability and catastrophe have gradually been widely applied in the field of ecology to explore and evaluate the sensitivity, vulnerability and adaptation of various ecosystems to climatic change. Based on such research, we can seek better ways to cope with the far-reaching impact of climatic change on ecosystems, and serve the sustainable management of national ecosystems and the construction of ecological security. Although a lot of achievements have been made to distinguish the sensitive regions responding to climatic change and potential tipping points in certain ecosystems, there are still multiple understandings and interpretations of these concepts in the academic community. To some extent, this affects the further development and application of related theories in ecological studies. Therefore, we combed the development history of related concepts, and analyzed the connotation of these concepts from the perspective of ecosystem ecology. Furthermore, we proposed a theoretical framework for ecosystem fragility, adaptability, and catastrophe based on the ecosystem evolution theory and corresponding calculation methods in order to promote the in-depth development of theories of ecosystem fragility, adaptability and catastrophe.
    Related theories of ecosystem risk under global change and their linkages.
    HOU Guo-long, HU Zhong-min
    2022, 33(3):  629-637.  doi:10.13287/j.1001-9332.202203.022
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    Global changes have a profound impact on ecosystems. If the disturbance caused by global change exceeds a certain degree, ecosystem resilience will be reduced, extreme events will be frequent, and ecosystem services will be degraded or even lost. Quantifying the risks of global change and developing appropriate adaptation strategies is an important way to deal with the risks of global change. Global change may reduce ecosystem resilience, leading to increased vulnerability and the risk of ecosystem degradation. The risk of ecosystem degradation is currently quantified mainly by the safe operating space assessment method based on planetary boundary theory. Understanding the concepts of ecosystem resilience, vulnerability, planetary boundaries, and safe operating spaces and their relationships is an important prerequisite for addressing the risks of global change. By summarizing the relevant theories of ecosystem vulnerability, we combined the concepts related to ecosystem resilience and vulnerability, global change risk and human adaptation, proposed a conceptual framework of ecosystem global change risk and human adaptation based on the vulnerability theory. Based on the logic of this proposed framework, we successively introduced the characteristics and mechanism of global change interference on ecosystem vulnerability, elaborated the assessment theories and methods of ecosystem vulnerability, and how to adopt human adaptation measures to alleviate the risk of global changes, aiming to provide ideas for coping with the risk of global change.
    Mathematical methods for analyzing ecosystem state evolution in ecologically vulnerable area.
    SUN Guo-dong, ZENG Xiao-dong, CUI Ming
    2022, 33(3):  638-647.  doi:10.13287/j.1001-9332.202203.026
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    Multiple ecosystems (grassland, desert and shrubs) always coexist in ecologically fragile areas. Influence by external environmental conditions and human activities, one ecosystem in ecologically fragile areas would be changed into another, called abrupt change. It is important to analyze the stability of each ecosystem in ecologically fragile areas under the condition of multiple ecosystems coexistence for understanding ecosystem changes. In this article, we reviewed several mathematical models that can describe the dynamic system and stability of multiple ecosystems in ecologically fragile areas. The dynamic system described by differential equations included the uniform and non-uniform ecosystems, as well as multi-ecosystems with the existence of forests, grasses, and deserts. There were three types of methods for analyzing the stability of the ecosystem. One type was the analysis method of ecosystem stability caused by the initial perturbation that could represent human activities, and the other type was the analysis method of ecosystem stability caused by the model perturbation that can represent the changes of environmental factors (precipitation, temperature, etc.), and the third type was the analysis method of ecosystem stability caused by the combination of initial perturbation and model perturbation. Finally, we introduced how to analyze the stabilities of ecosystem in ecologically fragile areas with those methods. These mathematical methods not only help us understand the stability of the ecosystems in the ecologically fragile area, but also provide theoretical guidance for the abrupt change of the ecological system, future prediction, and management.
    Innovative design of global change network control experiment: A case design of water and heat factors of grassland ecosystem in China
    ZHU Jun-tao, NIU Ben, ZONG Ning, ZHAO Bo, ZHENG Zhou-tao, ZHAO Guang, YU Qiang, WANG Chang-hui, ZHANG Yang-jian
    2022, 33(3):  648-654.  doi:10.13287/j.1001-9332.202203.023
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    Global changes have profound impacts on the structure and function of terrestrial ecosystems. It is a prerequisite to realize the sustainable use of ecosystem to clarify the response and adaptation mechanism of ecosystems to global changes. Network of control experiment is an important way to understand the response and adaptation of the structure and function of ecosystems to global change factors at regional and global scales. The scientific top-level design is conducive to the integration, comparison and analysis of integrative network-data, and then supports the development of universal ecological theory. We comprehensively expounded the theoretical basis, methodological principles and brand-new concepts of experimental network design for future global change control experiment networks design from several aspects, such as research progress, development needs, innovative design and research prospects. Taking Chinese grassland ecosystems as an example, based on the concept of space reference points (mean point of water and heat), the innovative design technology system of China's grassland ecosystem networking experiment was proposed, in order to promote the development of networking research of control experiments at both regional and global scales in the future.
    Methods and development trend for the measurement of plant species diversity in grasslands.
    SUN Yi, QIN Yu, WEI Tian-feng, CHANG Li, ZHANG Ren-ping, LIU Zhi-you, LYU Yan-yan, YI Shu-hua
    2022, 33(3):  655-663.  doi:10.13287/j.1001-9332.202203.010
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    Plant species diversity is one of the critical factors for maintaining multi-function and stability of terrestrial ecosystem. We reviewed the traditional methods for measuring plant species diversity of grassland (PSDG), and then introduced the new ideas and methods used for PSDG monitoring. Traditionally, PSDG monitoring depended heavily on ground-based investigation, which usually required large amounts of time, labor, and cost, and therefore was only suitable for small scale investigation. Grassland plant species were typically small in size and highly mixed. It was difficult to identify and measure by remote sensing due to the limitation of resolution. Consequently, most studies on PSDG were based on remote-sensing retrieval or habitat simulation. Characterized with high spatial-temporal resolution, flexible and low cost, the unmanned aerial vehicle (UAV) technology was regarded as the bridge between ground-based investigation and satellite remote sensing. It could be the breakthrough for monitoring PSDG accurately at large scales. In the future, we should establish PSDG monitoring network by combining the fixed monitoring sites and dynamic monitoring sites of UAV and satellite remote sensing, and integrating UAV and automatic target recognition organically.
    Special Features of Black Soil Protection and Agricultural Sustainable Development
    Effects of different amounts of straw return and nitrogen fertilizer application on soil CO2 emission from maize fields.
    WU Kai-kuo, ZHANG Zhe, WU Zhi-jie, FENG Liang-shan, GONG Ping, BAI Wei, FENG Chen, ZHANG Li-li
    2022, 33(3):  664-670.  doi:10.13287/j.1001-9332.202203.013
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    Understanding the effects of different amounts of straw returning and nitrogen fertilizer application on soil CO2 emission from maize field can provide theoretical support for carbon sequestration and CO2 emission reduction and the implementation of black soil region conservation plan. Three rates of straw returning were set up in the semi-arid area of northwest Liaoning Province, China, i.e. 3000 (S1), 6000 (S2) and 9000 kg·hm-2(S3, full amount of straw returned to the field); crossed with three nitrogen fertilizer application rates in the sub-region, respectively, i.e. 105 (N1), 210 (N2, conventional nitrogen application rate) and 420 kg N·hm-2(N3). In addition, there was a control treatment (CK) without nitrogen fertilizer and straw returning. Soil samples were collected after 4 years field experiment with maize plantation. The influence of different treatments on maize field soil CO2 emission and the relationship between CO2 emission and soil dissolved organic carbon (DOC) and microbial biomass carbon (MBC) were investigated in an incubation experiment. The results showed that both of straw returning and nitrogen fertilizer application promoted soil CO2 emission in maize field, which were increased significantly with the increases of straw returning amount and nitrogen application amount. Nitrogen fertilizer application was the most important factor promoting soil CO2 emission in maize field. Straw returning combined with nitrogen fertilizer promoted soil CO2 emission by increasing microbial biomass and increasing DOC consumption. MBC and DOC stimulated soil CO2 emission significantly in maize field, and were mainly affected by their contents in the early stage of incubation. From the perspective of ensuring the fertilization of straw return to the field while reducing CO2 emissions, results from our experiment showed that 210 kg N·hm-2 conventional nitrogen application in combination with 6000 kg N·hm-2 straw returning (N2S2) was the most promising mode in the semi-arid area of northwest Liaoning Province.
    Effects of long-term no-tillage and stover mulching on maize yield and its stability.
    XU Xin, WANG Xiao-ying, BAO Xue-lian, WANG Ying, LIU Ya-jun, HUO Hai-nan, HE Hong-bo, XIE Hong-tu
    2022, 33(3):  671-676.  doi:10.13287/j.1001-9332.202203.015
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    Clarifying the differences of maize yield and its stability under long-term no-tillage with different stover mulching amounts can provide theoretical and technical supports for establishing and evaluating long-term conservation tillage pattern and promoting grain production. Based on a long-term conservation tillage field experiment in the mollisol area of Northeast China since 2007, we analyzed the interannual variation, variation coefficient and stability of maize yield during 2013 and 2019 across five treatments, i.e., no-tillage stover-free mulching (NT0), no-tillage with 33% stover mulching (NT33), no-tillage with 67% stover mulching (NT67) and no-tillage with 100% stover mulching (NT100), with the traditional ridge cropping (RT) as the control. The results showed that compared with RT, long-term no-tillage with stover mulching treatments could increase maize yield. NT100 had the highest increasing rate of 11.4%, followed by NT67 and NT0, with the increasing rate of 11.0% and 10.4%, respectively. Maize yield exhibited a nonlinear relationship with the amount of stover mulch. The variation coefficient of maize yield under multi-year no-tillage with different stover mulching could be sorted as NT67<RT<NT100<NT33<NT0, and the yield sustainability index was NT67>NT0>NT100>RT>NT33, indicating that NT67 treatment could significantly reduce the interannual fluctuation of maize yield and had better sustainability of yield. No-tillage stover mulching significantly increased soil total carbon and total nitrogen contents, which were significantly positively correlated with maize yield. In conclusion, compared with traditional tillage, no-tillage stover mulching could increase maize yield and soil carbon and nitrogen contents. Appropriate stover mulching (NT67)had the potential to improve the stability and sustainability of maize yield.
    Effects of chemical fertilizer reduction combined with humic acid bio-fertilizer on soil biological properties and dry matter mass of maize.
    SUN Hai-yan, SUN Yi-zhuo, ZHOU Luan, DU Dan-feng, GUO Wei
    2022, 33(3):  677-684.  doi:10.13287/j.1001-9332.202203.014
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    A reduction of chemical fertilizers and improving fertilizer utilization rate are important for ensuring a balance between plant growth and minimizing the degradation of the black soil. We conducted a 2-year pot experiment with four treatments during 2019 and 2020, including T0: no fertilizer, T1: conventional use of chemical fertilizer, T2: 15% reduction of the chemical fertilizer combined with 400 kg·hm-2 of humic acid bio-fertilizer (HABF), and T3: 30% reduction of the chemical fertilizer combined with 600 kg·hm-2 of HABF, to examine the effect of reduction rates of chemical fertilizers combined with the HABF on soil microbial abundance, enzyme activity and nutrient content in maize cultivation. The results showed that the application of HABF significantly increased the abundance of soil bacteria and fungi, with the number of microbial colonies being positively correlated with the amount of HABF. When measured at the tassel stage of maize growth, T2 and T3 treatments significantly increased the activities of urease, sucrase, and catalase in soil by 11.4%-21.6%, 34.9%-46.7%, and 6.5%-13.4%, respectively. The available nitrogen contents in T2 and T3 treatments were higher than that in the T1 treatment by 8.2%-18.1%, which ensured the sufficient nitrogen supply to maize after the tassel stage. Soil available phosphorus and available potassium contents increased by 17.1%-121.0% and 9.6%-57.3%, respectively, compared with T1 treatment. With the increases of the amount of HABF, the activation effects of soil phosphorus and potassium and dry matter mass per plant increased significantly in T2 and T3 treatments compared with T1 treatment. In conclusion, HABF promoted the proliferation of soil bacteria and fungi, improved activities of catalase, urease, and sucrase, soil nutrient contents, and dry matter mass per plant. The 15% reduction of chemical fertilizer combined with 400 kg·hm-2 of HABF is the most suitable nutrient management strategy for maize production in black soil.
    Effects of soil erosion and deposition on the spatial distribution of soil microbial quantity in Mollisol area of Northeast China.
    MO Shuai-hao, ZHENG Fen-li, FENG Zhi-zhen, YI Yi
    2022, 33(3):  685-693.  doi:10.13287/j.1001-9332.202203.012
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    Revealing the responses of soil microbial community to soil erosion can provide guidance for agricultural ecosystem management. We investigated the impacts of soil erosion intensity on soil microbial quantity at the Binzhou River Basin, a typical thin layer Mollisol area in Bin County of Heilongjiang Province, using 137Cs tracer. The results showed that there were seasonal variations in soil microbial quantity. The abundance of soil microbes in summer was considerably higher than that in autumn. Bacteria was more sensitive to seasonal variation than fungi and actinomycetes, which was increased by 1.4-2.6 times and 1.4-2.2 times in summer compared with autumn in different parts of slope and watershed, respectively. The spatial variation of soil erosion intensity had an important effect on the spatial distribution of soil microbial community. The highest proportion of bacteria was found at lower deposition area of slope (84.4%) and at the lightly eroded area of the downstream (85.4%). The numbers of soil microbes, soil bacteria and actinomycetes were negative linearly correlated with soil erosion modulus, with correlation coefficients of -0.595, -0.554 and -0.291, respectively. Soil erosion and deposition induced spatial differences in soil physical and chemical properties, with consequences on spatial distribution of soil microbial community.
    Analysis of cropping pattern in black soil region of Northeast China based on geo-information Tupu.
    DU Guo-ming, ZHANG Rui, YU Feng-rong
    2022, 33(3):  694-702.  doi:10.13287/j.1001-9332.202203.017
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    Different cropping patterns have their own economic and ecological significance. Developing cropping patterns suitable for local conditions is needed to protect and make good use of black soils. At present, the cropping patterns and their spatial characteristics in the black soil region of Northeast China is poorly understood. Based on the crop classification data in 2017-2019, we used geo-information Tupu methods, distribution index model, and bivariate spatial autocorrelation to examine the cropping patterns. The results showed that: 1) The main cropping patterns in the black soil region of Northeast China were continuous maize cropping, continuous rice cropping, continuous soybean cropping, and maize-soybean rotation, accounting for 38.3%, 18.5%, 10.3% and 26.0%, respectively. The maize-soybean rotation included maize-soybean two-year rotation, maize-maize-soybean three-year rotation, and soybean-soybean-maize three-year rotation, accounting for 44.1%, 34.5% and 21.4% of the rotation area, respectively. 2) Various cropping patterns had obviously horizontal differentiation. For instance, continuous maize cropping had very obvious gradient differentiation characteristics in temperature and humidity, but soybean continuous cropping and maize-soybean rotation showed no gradient differentiation, while continuous rice cropping had gradient differentiation only in humidity. 3) Various cropping patterns had obviously spatial clustering characteristics. They had spatial transition characteristics from soybean continuous cropping, soybean-soybean-maize three-year rotation, maize-soybean two-year rotation, maize-maize-soybean three-year rotation, to continuous maize cropping. The cropping pattern in black soil region of Northeast China was dominated by continuous cropping. Understanding its distribution pattern can provide a basis for future spatial optimization of crop rotation.
    Paths of soil erosion controlled by typical soil and water conservation practices based on the SIMWE model: A case study of the Tongshuang watershed.
    CHEN Zu-ming, WANG Bin
    2022, 33(3):  703-710.  doi:10.13287/j.1001-9332.202203.016
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    Due to the basic topographical characteristics of the gentle and long slope lengths in the Mollisol region of Northeast China, severe soil erosion is easily aggravated by the concentration of surface flow. The spatial distribution of water depth and hydrological connectivity index were introduced to evaluate the effects of typical soil and water conservation practices on the overland flow path and hydrological connectivity based on the GIS and SIMWE (SIMulated Water Erosion) model. We analyzed the effects of different soil and water conservation practices on the hydrological connectivity, water flow path, and spatial distribution of soil erosion and sediment yield by quantifying the variations of soil infiltration rate and surface manning roughness, as well as by constructing an artificial terrain digital elevation model (DEM). The results showed that: 1) terraces could effectively affect the hydrological connectivity of the slope and regulate flow path, with significant differences between the responses of hydrological connectivity and flow path under different forms of terraced fields and ridges. The characteristics of spatial distribution of soil erosion and sediment yield varied with changes in water flow path, which would eventually lead to the intensification of local erosion; 2) practices of vegetated buffer strips and contour tillage presented limited effectiveness on runoff path controlling, though they played a significant role in sediment retention; and 3) conservation tillage could reduce the hydrological connectivity and improve the retention capacity of runoff by increasing surface roughness. This study quantified the effects of different soil and water conservation practices on the hydrological connectivity, flow path, and spatial distribution of soil erosion and sediment yield, and could provide a theoretical reference for scientific layout of soil and water conservation practices in black soil region.
    Original Articles
    Hydraulics and non-structural carbohydrate contents of Ginkgo biloba under different environmental conditions in Shenyang City, China.
    ZHENG Yue, WANG Ai-ying, SU Li-xin, GUO Jing-jing, DUAN Chun-yang, YIN Xiao-han, GONG Xue-wei, HAO Guang-you
    2022, 33(3):  711-719.  doi:10.13287/j.1001-9332.202203.006
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    Ginkgo biloba is an important urban ornamental tree species, but poor growth and damages often occur in urban environments. As a street tree species, the decline and death of G. biloba is particularly frequent, with the relevant physiological mechanism being unclear. In this study, we compared hydraulic characteristics, non-structural carbohydrate (NSC) contents and health status between G. biloba trees growing along the streets and those in parks in Shenyang City. The results showed that G. biloba growing along the streets showed higher degrees of branch and leaf mortality than those growing in the parks. Branches of G. biloba growing in both conditions showed lower degrees of xylem embolism. Branch hydraulic vulnerable curves of G. biloba under the two growing conditions also showed no significant difference, with the average P50 being lower than -2.8 MPa. G. biloba growing along the streets had lower leaf area specific conductivity, smaller tracheid diameter, smaller hydraulic diameter, lower soluble sugar content and total NSC than those growing in parks. Hydraulic failure was not the direct reason for the decline and mortality of G. biloba growing along streets. Under the more stressed growth conditions along the streets, G. biloba had smaller tracheid diameters in stems and lower Huber values, which limited the ability of water transport and photosynthetic carbon assimilation at the whole branch level. In addition, in order to deal with more serious stress such as greater heat and drought stresses, G. biloba might need to invest more NSC to repair damage, which further decreaded NSC contents in branches and increased the risk of carbon imbalance. At the same habitat (street or park), xylem hydraulics and NSC contents of G. biloba also showed relatively large difference among sampling sites, which reflected large heterogeneity of urban environment for tree growth.
    Responses of spatial distribution pattern of the dominant population Artemisia ordosica to enclosure restoration in desert steppe.
    LIU Jian-kang, FENG Xiang, ZHANG Ke-bin, LIU Shu-qin, LIU Xin-yue
    2022, 33(3):  720-726.  doi:10.13287/j.1001-9332.202203.005
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    Shrubs play an important role in maintaining biodiversity, stability and ecological service in grassland. Exploring the effects of enclosure on dominant shrub population can provide scientific guidance for grassland restoration and tending management. In this study, we investigated main growth characteristics and spatial distribution pattern of Artemisia ordosica population in four enclosed grasslands with duration of 0, 5, 15, and 25 years. The results showed that population density increased first and then decreased with time extension, and peaked after enclosed for 15 years, which was 3.7 times that of unenclosed plot. The crown and projected area showed opposite responses trend to that of density, which decreased by 31.7% and 52.3% after enclosed 15 years, respectively. The height decreased by 25.3% after 5 years of enclosure, and then increased gradually. Semi-variance function analysis showed that population distribution in all grasslands conformed to Gaussian model. The spatial variation decreased gradually in the early stage of enclosure, and then increased after enclosed for 15 years. Structure ratio in each plot was higher than 0.75, but nugget was relatively small, indicating that spatial autocorrelation of population was mainly affected by structural factors rather than random factors. Spatial distribution of A. ordosica population was patchy and striped. Enclosure reduced spatial variation of population at small scale. However, spatial heterogeneity and scale dependence of population enhanced after enclosed 25 years as plaque dissociating. Our findings suggest that enclosure duration is the key factor affecting plant growth and spatial distribution of dominant population in desert steppe. Long-term fencing enhances the spatial heterogeneity of dominant population. Appropriate human intervention should be carried out after 15 years of enclosure.
    Responses of stand growth, regeneration, and understory species diversity in Quercus mongolica secondary forest to stand density.
    HU Yan-chen, ZHANG Xiao-lin, HAN Xiao-yi, WAN Xiao-liang, LIANG Tai-ming, LU Xiu-jun
    2022, 33(3):  727-732.  doi:10.13287/j.1001-9332.202203.003
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    Six Quercus mongolica plots with an area of 0.1 hm2 were thinned in 2018. A field survey was carried out in 2020 to examine the effects of different stand densities (high: 900 trees·hm-2; medium: 720 trees·hm-2; low: 600 trees·hm-2) on growth and regeneration of stands and understory species diversity of secondary Q. mongolica forests in Qingyuan, Liaoning Province. Due to the short interval after thinning, there was no significant difference in tree height and diameter at breast height under different densities. However, the crown symmetry index under low stand density was significantly higher than that of high stand density, indicating that crown growth was more sensitive to stand density than trunk growth. The abundance of seedlings was the highest in the medium density, and the basal diameter of the seedlings with the same height was significantly higher, and the seedling regeneration and growth at the medium density were much better than the other two densities. A total of 70 species were recorded, belonging to 41 families and 67 genera. Quercus mongolica, Lespedeza bicolor, Melampyrum roseum, and Potentilla freyniana were the dominant species of trees and herbs, respectively. Simpson index, Pielou index and Shannon index of shrub layer and herb layer were the highest at the medium density. It indicated that the stand density of 720 trees·hm-2 could help maintain the sustainable development of Q. mongolica secondary forest in the mountainous area of eastern Liaoning.
    Effects of groundwater depth on functional traits of young Haloxylon ammodendron.
    LIU Shen-si, XU Gui-qing, CHEN Tu-qiang, MI Xiao-jun, LIU Yan, MA Jian, LI Yan
    2022, 33(3):  733-741.  doi:10.13287/j.1001-9332.202202.025
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    Groundwater is an important water source for phreatophytic shrubs in arid desert areas. In order to understand the impacts of groundwater depth on functional traits of phreatophytic shrubs, two groups of groundwater levels (2 and 3.5 m) were set up using lysimeter with automatic water replenishing instrument. We measured hydraulic traits, gas exchange characteristics, and root morphological parameters of young Haloxylon ammodendron during the growing season. The results showed that predawn assimilating branch water potential, osmotic potential at full turgor, and root length ratio of young H. ammodendron in the groundwater depth of 3.5 m were lower by 48.2%, 41.5% and 56.7% than that under groundwater depth of 2 m, respectively, while maximum net photosynthetic rate of late growing season, root volume, specific root length and specific root area of fine root were 75.7%, 41.0%, 273.7% and 67.7% higher, respectively. Midday water potential and water content of assimilating branch tended to decrease first in the early growing season and then increase in the late growing season. Root distribution of young H. ammodendron along soil profile showed a significant positive correlation between the average root diameter and soil depth, while the proportion of fine root surface area showed a significant negative correlation with soil depth at both groundwater levels. There was synergy of aboveground assimilating branch hydraulic traits and photosynthetic capacity with belowground root morphological traits in young H. ammodendron. Under the condition of increasing groundwater depth, young H. ammodendron adopted the ecological strategies of reducing predawn assimilating branch water potential and osmotic potential at full turgor, and increasing root diameter and length to enhance water deficit tolerance and expanding the area of water uptake to sustain their survival.
    Plant diversity on different types of slope ecological engineering and its responses to environmental factors in mining areas.
    QIAO Ou-meng, CHEN Zhang
    2022, 33(3):  742-748.  doi:10.13287/j.1001-9332.202203.004
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    With three types of ecological slope protection projects of rock slope, soil slope and rock soil mixed slope (geotechnical slope) in Xishan mining area of Taiyuan as the object, CCA ranking was used to examine the relationship between environmental factors and species distribution of different types of slopes, and analyze the impacts of environmental factors such as soil and topography on plant diversity. The results showed that geotechnical slope was rich in vegetation composition (8 families, 17 genera, and 19 species), including Asteraceae, Gramineae, Fabaceae, Vitaceae, Lamiaceae, Simaroubaceae, etc. The species richness, Shannon index, Simpson index, and Pielou evenness index of the geotechnical slope were significantly higher than that of soil slope and rocky slope. The artificial soil nutrient contents of the three types of slopes were significantly higher than that of the control. The ave-rage contents of total nitrogen (1.24 g·kg-1), organic matter (21.28 g·kg-1), and available potassium (0.21 g·kg-1) of geotechnical slope were higher than that of rocky slope (1.02, 15.56 and 0.14 g·kg-1) and soil slope (0.80, 11.65 and 0.15 g·kg-1), respectively. Vegetation diversity was significantly related to soil factors, with organic matter and soil water content as the main limiting factors. Soil factors had greater impacts on vegetation restoration than topographical factors. Results of structural equation modeling showed that topographical factors, such as slope gradient, indirectly affected vegetation restoration by affecting soil moisture and nutrients.
    Effects of organic matter addition on the stoichiometric homeostasis of soil microbes in Pinus tabuliformis forest in Taiyue Mountain, China.
    XIA Wei, ZHOU Zhi-yong, SHEN Ying, SUN Mei-jia
    2022, 33(3):  749-756.  doi:10.13287/j.1001-9332.202203.002
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    In Taiyue Mountain of Shanxi Province, five types of organic matter, i.e., biochar, maize straw, leaves of Quercus mongolica and Pinus tabuliformis, and sawdust of wood stem, were separately added to the soils of a P. tabuliformis forest. Nutrient content, enzyme activity, and microbial biomass were analyzed to elucidate the characteristics of soil ecoenzymatic stoichiometry and the element homeostasis of soil microorganisms. The results showed that the addition of woody sawdust significantly increased soil nitrogen and phosphorus content by 17.1% and 37.6%, and enhanced carbon, nitrogen, and phosphorus contents of soil microbial biomass by 118.0%, 41.0%, and 176.6%, respectively. The activities of carbon-, nitrogen- and phosphorus-targeting enzymes (i.e., β-1, 4-glucosaminosidase, β-1,4-N-acetylglucosaminosidase, leucine aminopeptidase and acid phosphatase) generally increased with the C:N of the added organic matter (biochar<Q. mongolica leaf< P. tabuliformis leaf < maize straw < woody sawdust). This indicated that ecoenzymatic stoichiometry was controlled by soil nutrient content and micro-bial biomass. The limitation of soil microbial growth by phosphorus was not alleviated after the addition of different organic matters, as indicated by the results of enzymatic ratio and its vector value. Soil microbial biomass carbon and nitrogen contents and their stoichiometry (C:N, C:P, N:P) were homeostatic, whereas the microbial biomass phosphorus content fluctuated slightly. The stabilities of microbial element contents and their proportion were mainly ascribed to the allocation of extracellular enzyme production. The susceptibility of soil microbial biomass phosphorus to the addition of organic matter indicated phosphorus limitation of microbial growth.
    Effect of elevated atmospheric CO2 concentration and temperature on volatile halogenated organic compound content in soils of Schima superba and Cunninghamia lanceolata seedlings.
    LIU Gui-zhen, SUN Hao-zhao, ZHAO Lin, MA Fang-yuan, CHEN Lin-yi, HUANG Xing-ran, FANG Xiong, YI Zhi-gang
    2022, 33(3):  757-764.  doi:10.13287/j.1001-9332.202203.001
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    Global changes caused by the increases of atmospheric CO2 concentration and temperature have important effects on soil biogeochemical processes. The synthesis and release of volatile halogenated organic compounds (VOXs) is an important pathway for soil to participate in the global material cycle and energy flow. In this study, Schima superba and Cunninghamia lanceolata seedlings in the southern subtropics were selected as the research objects. Four treatments, including control (CK), elevated CO2 concentration (EC), elevated temperature (ET) and elevated both factors (EC+ET) were set up. The effects of EC and ET on soil VOXs formation were studied by an open-top chamber system coupled with a purging and trapping gas chromatography/mass spectrometry. The results showed that VOXs content in the soil of S. superba seedlings was 0.065-0.252 ng·g-1, which was higher than that of C. lanceolata (0.038-0.136 ng·g-1). At the EC, ET and EC+ET treatments, VOXs contents were reduced in soils of both species. The effect of ET was the most significant, with the decrease rates of 74.2% and 72.1% in both soils, respectively. The change of VOXs content with increasing temperature mainly attributed to the changes of soil moisture and nitrogen content. The content of VOXs in the soils of S. superba seedlings decreased more than that of C. lanceolata under different treatments. In CK, EC, ET and EC+ET treatment, bromodichloromethane (BDCM) (27.5%, 36.7%, 32.9%, 32.6%) and tetrachloromethane (TCM) (9.0%, 16.8%, 22.7%, 15.8%) were the main VOXs in the soil of S. superba seedlings, respectively, while BDCM and dibromomethane (DBM) were the main VOXs in the soil of C. lanceolata seedlings. BDCM accounted for 31.9%, 38.2%, 40.9% and 37.2% of the VOXs content in each treatment, and DBM accounted for 17.9%, 16.5%, 19.2% and 16.0% of the VOXs content, respectively. Simulating elevated atmospheric CO2 concentration and temperature was conducive to more comprehensive reflection of the ecological effect of global climate change, and it could provide data support for improving the VOCs flux model.
    Distribution and enrichment characteristics of soil nutrients in the nebkhas profile of Nitraria tangutorum in Gahai Lake Area, Qaidam Basin.
    WANG Xiang, JIAO Ju-ying, CAO Xue, LI Jian-jun, BAI Lei-chao, SUN Xiao-chen
    2022, 33(3):  765-774.  doi:10.13287/j.1001-9332.202203.011
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    As a special bio-geomorphic landscape in the Qaidam desert area, Nitraria tangutorum nebkhas play a critical role in fixing quicksand, improving soil quality, and maintaining the stability of regional ecological environment. Taking the N. tangutorum nebkhas with coverage of approximately 15%, 25%, 45% and 60% in Gahai Lake area of Qaidam Basin as the research objects, we analyzed the vertical distribution and enrichment characteristics of soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkali-hydrolyzable nitrogen (AN), available phosphorus (AP) and available potassium (AK). The results showed that the contents of SOM, TN, TP, TK, AN, AP and AK varied in the range of 1.67-10.22 g·kg-1, 0.05-0.42 g·kg-1, 0.31-0.54 g·kg-1, 15.87-18.84 g·kg-1, 2.26-11.68 mg·kg-1, 0.80-15.00 mg·kg-1 and 45-161 mg·kg-1, respectively. Vertically, soil nutrients in the N. tangutorum nebkhas with 15% coverage showed a decreasing trend first then increased, and then decreased again with the increase of soil depth, except for TP, which did not show any significant change. In the nebkhas with 25%, 45% and 60% coverage, SOM, TN, AN, TP and AP all showed a decreasing trend with increasing soil depth ,whereas TK and AK did not change significantly with soil layer. Above the nebkhas ground level of N. tangutorum, SOM, TN, TK, AN, AP and AK were all enriched, especially in the surface layer.Aamong all the nutrients, the enrichment rate of AN reached 5.19. In addition, below the nebkhas ground level of N. tangutorum, TN, AN, TK, AK and AP also showed enrichment. SOM, TN, AN, TP, AP, TK and AK were all significantly positively correlated with soil water content, and negatively correlated with altitude. All nutrients except TP were mainly affected by altitude. In conclusion, soil nutrient content of N. tangutorum nebkhas was the highest in the surface layer, the enrichment effect of which was not only reflected in the interior of the nebkhas, but also below the ground level of the nebkhas. Our results could provide reference for the scientific utilization of N. tangutorum nebkhas and ecological environment protection in Qaidam Basin area.
    Simulation of the responses of spring wheat yield to the rates and depths of nitrogen application in dryland based on APSIM model
    YIN Jia-de, ZHANG Jun-ying, HOU Hui-zhi, ZHANG Xu-cheng, MA Ming-sheng, GUO Hong-juan, FANG Yan-jie, LEI Kang-ning
    2022, 33(3):  775-783.  doi:10.13287/j.1001-9332.202202.029
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    Nitrogen limitation is an important factor for the improvement of crop water production potential in rain-fed areas of the Loess Plateau. The reasonable deep application of nitrogen fertilizer is a promising method to increase yield of rain-fed crop. Based on APSIM model, this study simulated spring wheat yield under different nitrogen application rates and depths, by using meteorological observation data from 1990 to 2020 in the semiarid areas of central Gansu Province, aiming to provide theoretical reference for optimizing wheat fertilization strategy. The results showed that the determination coefficient of simulated spring wheat yield, biomass and soil water content in 0-200 cm soil profile was greater than 0.80, the normalized root mean square error was less than 0.2, and the model validity index was greater than 0.5. These results indicated that the model had good fitting and adaptability in the test area. Across all the levels within the experimental design, increasing nitrogen application rates could significantly increase the yield of spring wheat in different precipitation years, and increasing nitrogen application depth could significantly increase spring wheat yield in wet and normal years, but had no effect in dry years. The rate and depth of nitrogen application had significant interaction effects on spring wheat yield in wet and normal years, but not in dry years. According to the binary quadratic regression fitting equation, when the potential maximum yield reached 2749 kg·hm-2 in wet year, nitrogen application depth was 22.7 cm, and nitrogen application rate was 245 kg·hm-2. When the maximum potential yield reached 2596 kg·hm-2 in normal year, nitrogen application depth was 20.6 cm, and nitrogen application rate was 235 kg·hm-2. Integrating the effects of nitrogen application rate and depth on yield, biomass and agronomic efficiency of nitrogen fertilizer, and farmer's fertilizer application habits, the recommended nitrogen application depth was 20-23 cm, and nitrogen application amount was 120-150 kg·hm-2, which could further improve water productivity and nitrogen use efficiency of spring wheat in arid areas of central Gansu Province.
    Relationship between accumulation of autotoxins and soil fertility factors under long-term continuous cropping of cucumber in solar greenhouse
    WANG Shuang, ZHENG Shi-wei, LI Xiao, ZHANG Yi-di, WU Tong, FU Hong-dan, SUN Zhou-ping
    2022, 33(3):  784-792.  doi:10.13287/j.1001-9332.202202.030
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    In this study, we investigated the effects of long-term continuous cucumber cropping on phenolic acids in rhizosphere soil, as well as their link to soil chemical characteristics, enzyme activities, and microbiological activities, using rhizosphere soil from the 2nd, 6th, 10th, 14th, 18th, 20th, 24th, and 26th round of cucumber cultivation in solar greenhouse. The results showed that contents of phenolic acids increased significantly with increasing continuous cropping rounds. The increase amount per round of total phenolic acid was significantly higher in the early stage (0-2 rounds) and late stage (20-26 rounds) than middle stage (10-14 rounds) of continuous cropping. Soil nutrient contents were enriched, while invertase enzyme activity and microbial activities were decreased. Redundancy analysis showed that organic matter, total phosphorus, total nitrogen, available nitrogen, microbial biomass carbon and microbial metabolic entropy were main soil fertility factors correlating with the accumulation of phenolic acids. Results of structural equation model showed that soil phosphorus enrichment directly led to the accumulation of phenolic acids, and that nitrogen enrichment indirectly facilitated the accumulation of phenolic acids by altering the activity of microorganisms. As a result, proper nitrogen and phosphorus fertilizers application would reduce the accumulation of phenolic acids and alleviate the cucumber continuous cropping obstacles.
    Effects of intercropping and nitrogen application on soil microbial metabolic functional diversity in maize cropping soil.
    WANG Ding, YI Wen-bo, LI Huan, CHEN Lin-kang, ZHAO Ping, LONG Guang-qiang
    2022, 33(3):  793-800.  doi:10.13287/j.1001-9332.202202.038
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    Soil microorganism is an important indicator of soil health and plays a critical role in biogeochemical processes. We collected soil samples from a multi-year in-situ field experiment with two cropping modes (maize monocropping and maize-potato intercropping) subjected to four nitrogen (N) levels (N0, 0 kg·hm-2; N125, 125 kg·hm-2; N250, 250 kg·hm-2; N375, 375 kg·hm-2). By using the Biolog-ECO microplate method, soil microbial metabolic activity, diversity and utilization of six carbon groups were analyzed. The results showed that N application significantly increased the average well color development (AWCD) values, Simpson and Shannon indices, with the highest value at N250 in mono- and inter-cropped soils. Moreover, N application promoted the utilization of amino acids, amines and phenolic compounds, but decreased the utilization of polymers. Compared with monocropping at the same N level, intercropping improved the AWCD values, Simpson and Shannon indices, with a maximal improvement at N250. Intercropping and nitrogen application significantly affected the metabolic activities of the six carbon-source groups. In addition, intercropping improved the utilization of labile carbon sources, such as amino acids and carbohydrates. Results of the redundancy analysis and linear regression showed that intercropping and N application elevated AWCD values by increasing soil temperature, water content, and soil organic carbon content. Therefore, the changes in soil physicochemical properties after intercropping were the main reason for the enhancement of microbial metabolic activity under N application.
    Evaluation of agricultural drought in Luanhe River Basin based on the standardized soil moisture index.
    YANG Wen-jing, LI Jian-zhu, FENG Ping
    2022, 33(3):  801-807.  doi:10.13287/j.1001-9332.202202.019
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    Drought is one of the main disasters causing agricultural production losses. Accurate and effective agricultural drought monitoring is of great significance to reduce agricultural production losses. In this study, the standardized soil moisture index for agricultural drought evaluation was established by using the historical time series of soil moisture. Based on the index, the temporal and spatial distribution of drought events in the Luanhe River Basin from 2002 to 2019 were analyzed, and the agricultural drought was quantitatively evaluated. The results showed that soil moisture of most grid units in the Luanhe River Basin obeyed normal distribution during the study period, and that the soil moisture of a few grid units obeyed generalized extreme distribution. The changes of drought and flood in each grid unit had good temporal consistency, that is, the changes of drought and flood was consistent. The changes of drought and flood in the middle of the basin was relatively significant, while the agricultural drought generally showed a trend of reduction. The spatial distribution of agricultural drought severity was not obvious. Relatively speaking, the drought characteristics (the frequency, duration and intensity of drought) were higher in the middle and northwest of the basin and lower in the southeast. The results could provide a reference for agricultural drought prediction and the formulation of drought prevention and mitigation measures in the Luanhe River Basin.
    Effects of simulated insect herbivory on defense traits of Galinsoga parviflora.
    ZHOU Ying, LIU Jie, YAN Xiao-hui, HU Shi-jun
    2022, 33(3):  808-812.  doi:10.13287/j.1001-9332.202202.036
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    To understand mechanisms underlying Galinsoga parviflora invasion and its responses to simulated insect herbivory, individuals of Galinsoga parviflora were treated with different concentrations of methyl jasmonate (MeJA) before blooming. We measued plant height, abundance of leaves and inflorescences, biomass, specific leaf area, trichome density, condensed tannins, total polyphenols, and flavonoids in leaves and inflorescences. The growth and reproduction parameters of G. parviflora treated with 5 mmol·L-1 MeJA were not significantly different from those of control, higher than those of control when treated with 10 mmol·L-1 MeJA, with significant difference except plant height, and declined when treated with 20 mmol·L-1 MeJA. The trichome density of leaf upper epidermis increased and specific leaf area decreased with increasing MeJA concentration, with both being significantly different from that of control. The contents of flavonoids, total polyphenols, and condensed tannins in leaves treated with 5 mmol·L-1MeJA were not significantly different from those of control. These defensive substances in leaves and inflorescences were highest under 10 mmol·L-1MeJA treatment. The contents of flavonoids and total polyphenols in inflorescences being higher than those of leaves, while condensed tannins was opposite. The defensive substances in leaves declined under 20 mmol·L-1MeJA treatment. The results suggested that G. parviflora could use tolerance and resistance strategies comprehensively, and adopted a variety of defense strategies such as compensatory growth, physical defense, and chemical defense, which was conducive to its success in invasion.
    Effects of cultivating Coptis chinensis and Paris polyphylla on soil microarthropod communities.
    HOU Chun-yu, WEI Xue, WU Peng-fei
    2022, 33(3):  813-820.  doi:10.13287/j.1001-9332.202202.035
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    In recent years, the area of herbal medicine planting is rapidly increasing. The effects of planting herbal medicines on soil invertebrate communities are still unclear. To reveal the effects of planting different herbal medicines on the soil microarthropod communities, soil microarthropods in two fields of planting Coptis chinensis and Paris polyphylla for 3-year and 5-year, respectively, were investigated in Pengzhou, Chengdu in July 2020. A total of 526 individuals of soil microarthropods were recorded and classified into 4 classes, 17 orders, 69 families, and 98 genera or taxonomic groups. The communities were dominated by Isotoma, Piatynothrus, Folsomia, and Paranura. The community structure of soil microarthropods differed obviously among the two herbal medicine fields, with the main influencing taxonomic groups of Proisotoma, Ocesobates and Epicridae. The total taxonomic group richness of soil microarthropods were richer in C. chinensis field than P. polyphylla field. There was no significant difference in the abundance and diversity index between the two fields. With the increases of cultivating years, the abundance of soil microarthropods in C. chinensis field declined significantly, and Shannon index increased significantly in P. polyphylla field. The redundancy analysis showed that the community structure of soil microarthropods was mainly affected by soil available N, pH, total K, and available K. It suggested that the effects of cultivating herbal medicines on soil microarthropod communities differed between herbal medicine species. Therefore, we recommended to intercrop C. chinensis and P. polyphylla for maintaining the stability of soil microarthropod diversity and promoting ecosystem function.
    Spatiotemporal variations of fish feeding guilds in Yellow River basin
    WANG Yu-zhu, PAN Bao-zhu, GONG Zheng, LI Dian-bao, JIANG Xiao-ming, CHEN Yue, LI Ke
    2022, 33(3):  821-828.  doi:10.13287/j.1001-9332.202202.037
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    Conservation of fish resources is the key to ecological protection and high-quality development of Yellow River basin. From 1960 to 2019, Yellow River basin distributed 201 fish species, belonging to 16 orders, 35 families. The species number of Cypriniformes was the largest (accounting for 60.7%), followed by Perciformes (accounting for 10.0%). From 1960 to 1980, there were 182 fish species belonging to 15 orders, 28 families. During 1980-2019, there were 112 species, belonging to 10 orders, 23 families. The total number of fish species in source area, midstream and downstream decreased significantly, while that in the upper reaches increased slightly. Jaccard's similarity index of source area, upstream, midstream and downstream between two periods were 34.2%, 46.0%, 42.4% and 35.7%, respectively. Based on feeding preference characteristic, fish species could be divided into eight feeding guilds: phytobenthivores, herbivores, phytoplanktivores, zooplanktivores, omnivorous, insectivores, zoobenthivores, and piscivores. Compared with the period from 1960 to 1980, the proportion of insectivores decreased significantly in the Yellow River basin during 1980-2019, while that of phytobenthivores, herbivores, phytoplanktivores, omnivorous and piscivores increased significantly. From 1960 to 1980, the proportion of insectivores was higher than other reaches at source area and upstream, then began to decrease along the river continuum from reaches with elevation of 2000-3000 m; while the proportion of piscivores was lower than other reaches at source area and upstream, then began to increase along the river continuum from reaches with elevation of 2000-3000 m. From 1980 to 2019, the proportion of insectivores decreased along river continuum from source area, and that of piscivores increased from source area to midstream but decreased in downstream. Development of cascade hydropower, water pollution, insufficient water flow, overfishing and invasion of alien fish were important factors causing the spatiotemporal variations of fish feeding guilds in Yellow River basin.
    Ecosystem structure and function of Sanmen Bay based on Ecopath model.
    KONG Ye-fu, YIN Cheng-jie, WANG Lin-long, LIU Yang, LIN Li, KANG Bin
    2022, 33(3):  829-836.  doi:10.13287/j.1001-9332.202202.034
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    Ecosystem structure determines material circulation, energy flow, and system function. Based on field investigation data in the Sanmen Bay, East China Sea from 2017 to 2018, ecological channel model was constructed by Ecopath, describing energy flow routes and functional characteristics of the Sanmen Bay ecosystem. Results showed that grazing food chain was the main energy circulation channel, and the trophic level of each functional group ranged from 1 to 3.80. Energy flow of the system was mainly concentrated in the first five levels, with an average energy conversion efficiency of 13.0%. Energy conversion efficiency was 12.8% and 14.5% from primary producers and debris, respectively. Connectance index (CI) and system omnivory index (SOI) were 0.40 and 0.24 respectively. Finn's cycling index (FIC) was 0.40, and Finn's mean path length (MPL) was 2.06. The ratio of total primary productivity to total respiration was 13.59. In conclusion, Sanmen Bay ecosystem was immature in material circulation and energy flow. This work is helpful to understand the structural and functional traits of coastal ecosystems in China.
    Influence of species interaction on species distribution simulation and modeling methods.
    WANG Yan-ge, ZHANG Bo-ran, ZHAO Rui
    2022, 33(3):  837-843.  doi:10.13287/j.1001-9332.202202.024
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    The species distribution models (SDMs) simulate and predict the potential distribution of species in geographical space by quantifying the relationships between species distribution and environmental variables, and extrapolating these relationships to unknown landscape units, which makes them important tools in ecology, biogeo-graphy, and conservation biology. Current SDMs mainly take abiotic factors as prediction variables, whereas biotic factors, especially species interactions, are often ignored due to the difficulties in data quantification and modeling. Incorporating species interactions into SDMs is considered as the main challenge of SDMs. We reviewed the influence of species interactions on species distribution simulations, clarified the necessity of incorporating species interactions into SDMs, summarized four main ways to incorporate species interactions into SDMs, analyzed their strengths and limitations, and discussed the future development direction of incorporating species interactions into SDMs. The study showed that incorporating species interaction into SDMs was based on the premise that the spatial scale of species distribution simulation was consistent with that of species interactions, and that the training data should be collected from large environmental heterogeneous space to ensure the diversity of species interactions in heterogeneous habitats. In order to eliminate the influence of multicollinearity on the prediction of SDMs, all abiotic and biotic factors should be fully considered and accurately quantified. Modeling the complex population/community dynamics would be an important development direction of incorporating species interactions into SDMs.
    Reviews
    Research advances in histone modification-regulated plant stress memory and defense priming.
    ZHENG Yue-qin, WANG Qiong-li, CHEN Dao-qian, CHEN Dong-mei, ZENG Ren-sen, SONG Yuan-yuan
    2022, 33(3):  844-854.  doi:10.13287/j.1001-9332.202202.039
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    Plants, grown in the immobile soils, have evolved various strategies in response to environmental stresses, including the “stress memory” and “defense priming” mechanisms. The environmental stresses cannot immediately change the DNA base sequence in plants in the short-term. Therefore, epigenetic inheritance is a key mechanism for stress memory and defense priming. In particular, histone modification is considered to be the most important mechanism, which offers the possibility of stress memory. We summarized research advances in plant histone modifications involved in stress memory and defense priming under biotic and abiotic stresses, and proposed pro-blems in the field and the focus and directions in the future research. In-depth understanding of the relationship between histone modification and environmental stresses would facilitate the quick adaptation of plants to harsh environments, and provide theoretical and technical guidance for plant phenotype shaping, organ regeneration, and crop genetic improvement.
    Research progress on sensitivity of indices for ecotoxicological assays using rotifers.
    ZHANG Gen, CHEN Bao-rui
    2022, 33(3):  855-864.  doi:10.13287/j.1001-9332.202206.028
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    Human activities have severely polluted environments during industrialization. Rotifers are commonly used as model species for ecotoxicological assays. The sensitivities of ecotoxicological indices of rotifers highly depend on different pollutants. We summarized available ecotoxicological indices of rotifers, and reviewed their sensitivity to commonly investigated pollutants. Under the stress of heavy metals, the life-table demographic parameters, physiological and biochemical indices generally show high sensitivity. In response to persistent organic pollutants, sexual indices generally show higher sensitivity than asexual ones. Some studies showed that swimming speed revealed higher sensitivity after exposure to several pollutants compared with life-table demographic and population growth indices. We suggested to consider swimming speed of rotifer as an alternative index for ecotoxicological assays. Overall, this study would provide a guideline for rotifer ecotoxicological studies in the future.