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Table of Content

    18 September 2024, Volume 35 Issue 9
    Academician's Viewpoint
    Carbon sink of forest ecosystems: Concept, time effect and improvement approaches
    ZHU Jiaojun, GAO Tian, YU Lizhong, YANG Kai, SUN Tao, LU Deliang, LIU Zhihua, CHU Yingdong, ZHANG Jinxin, TENG Dexiong, ZHU Yuan, SUN Yirong, WANG Xugao, WANG Gaofeng
    2024, 35(9):  2313-2321.  doi:10.13287/j.1001-9332.202409.025
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    The widespread utilization of fossil fuels has emitted large amounts of CO2 into the atmosphere since the Industrial Revolution, leading to climate warming and frequent occurrence of extreme climate events. To effectively alleviate climate change, the international community has made various efforts to reduce carbon emissions and eliminate CO2 from the atmosphere. In 2020, the Chinese government announced that carbon emission peaking and carbon neutrality will be achieved by 2030 and 2060, respectively. According to the current forecast, by the time carbon neutrality is achieved in 2060, even under the minimum conditions of fossil energy use, production, and living emissions, China will still have to emit about 1/4 of the current total emissions. These carbon must primarily be absorbed by ecosystems. Furthermore, approximately 140 ppm increase in CO2 in the atmosphere since the Industrial Revolution still needs to be removed by ecosystems. Forests are the main component of terrestrial ecosystems, contributing more than 80% of the carbon sequestration capacity of all terrestrial ecosystems. However, due to the long periodicity, complexity and dynamic variability of forests, the basic concepts of ecosystem carbon sink and its time effect are still unclear, leading to problems, such as lacking technologies for improving carbon sink capacity and disorganized rules in the carbon sink trading market. In this review, we introduced carbon sink concept according to the processes of absorbing and fixing CO2 by plant photosynthesis in forest ecosystems. Then, we analyzed the processes of time-scale-dependent carbon sinks of forest ecosystems, discussed the time effects of forest carbon sinks, and suggested using “t-year” as the unit of carbon sink (taking 3-6 months as the minimum measurement time, i.e., the beginning of carbon sequestration). Third, we proposed the approaches to improve the carbon sink capacity of forest ecosystems. One way is to improve the carbon sink capacity (expanding forest area, improving forest quality, and increasing forest soil carbon storage) of forest ecosystems. Another approach is to maintain the carbon sink of forest ecosystems as long as possible, i.e., to reduce temporary carbon sink (definition: carbon in the forest ecosystems emit into the atmosphere for a certain period) and to increase persistent carbon sink (definition: carbon in the forest ecosystems no longer emit into the atmosphere for a certain period; according to the relevant provisions of the Paris Agreement, the upper time limit for carbon sink measurement can be considered to be the year 2100. In order to maintain the persistent carbon sink, strateges such as efficient use of wood products (replace steel, cement, plastic with wood), control of forest fires or other disturbances-induced emissions, and turning forest biomass into biochar should be taken. Finally, we proposed to develop climate-smart forestry driven by artificial intelligence (AI), which would provide new theoretical and technical support for improving the carbon sink of forest ecosystems and facilitating sustainable forest management.
    Expert Insights
    Current status and research prospects of terrestrial ecosystem carbon sink in Northeast China
    WANG Xugao, LYU Xiaotao, XI Fengming, LIU Zhihua, LIANG Yu, GAO Tian, SUN Tao, YU Dapao, WANG Chao, MA Qiang, LIANG Chao, ZHENG Tiantian, WANG Jiaoyue, YIN Yan, JIAO Kewei, LIU Bo, ZHU Jiaojun
    2024, 35(9):  2322-2337.  doi:10.13287/j.1001-9332.202409.006
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    Increasing the carbon sink capacity of terrestrial ecosystems is a primary strategy to mitigate climate change and achieve the “carbon neutrality” goal. Clarifying the status and future dynamics of carbon sink of terrestrial ecosystems in Northeast China is crucial for achieving “carbon neutrality” as this region is a core contributor to carbon sink in China's terrestrial ecosystems. Here, we systematically summarized current research on carbon sink of terrestrial ecosystems across Northeast China, including the measurements and spatial-temporal patterns of carbon sinks, driving mechanisms of carbon sinks, the assessments of carbon sink potential, and technologies for increasing carbon sequestration. There are substantial uncertainties in quantifying terrestrial ecosystem carbon sink in Northeast China due to differences in data sources and methods, especially for forest carbon sink measurements, ranging from 0.020 to 0.157 Pg C·a-1. Carbon sink function depends on carbon exchange processes across plant-soil-atmosphere interfaces. The key pathways to enhance carbon sequestration in Northeast China under different temporal and spatial scales remains unclear. Improving terrestrial ecosystem quality is the key and core of carbon sequestration and sink enhancement. However, there is an urgent need to develop a multi-ecosystem collaborative carbon sequestration and sink enhancement technology system for the “dual carbon” goal. Future research needs to develop an accurate carbon sink measurement system that integrates multi-source data and multi-scale technologies to accurately assess the function and potential of carbon sink in Northeast China, focus on the multi-scale driving mechanism of carbon sink functions, develop new technical systems for coordinated enhancement of carbon sink for the Northeast terrestrial ecosystems, and carry out demonstrations of carbon sink enhancement technologies. These efforts will provide the scientific and technological supports for achieving the “carbon neutrality” goal.
    History, challenges, and prospects of researches on fish functional diversity
    KANG Bin
    2024, 35(9):  2338-2351.  doi:10.13287/j.1001-9332.202409.030
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    To complete the life cycle, species exhibit corresponding functional traits in morphology, physiology, ecology, etc. The eigenvalues, variation, and distribution of functional traits are the functional components of biodiversity, namely functional diversity, could maintain the service function and healthy operation of ecosystems. The application of functional diversity broadens our understanding of biodiversity and its temporal and spatial variations, and provides a breakthrough to the problem of how to combine morphological structure with ecological function. I reviewed the research process of functional diversity from the perspective of proposing, calculating, and applying the parameters of functional diversity, as well as the application of functional diversity from different purposes and perspectives. I put forward the challenges and countermeasures of related studies. In the future, researches should pay attention to establish a set of effective trait indicators, discover the internal and external mechanisms driving functional diversity variations, and map the redistribution of traits under environmental changes.
    Research advance in the effects of litter input on forest soil organic carbon transformation and stability
    GUO Xiaowei, ZHANG Yuxue, YOU Yeming, SUN Jianxin
    2024, 35(9):  2352-2361.  doi:10.13287/j.1001-9332.202409.033
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    The turnover and stabilization of soil organic carbon are tightly associated with the properties of litter input. Due to the complexity of litter decomposition and the high heterogeneity of forest soils, there are considerable uncertainties about how soil minerals, microorganisms, and environmental factors jointly regulate the transformation and stability of litter-derived soil organic carbon. Here, we present an overview of the “microbial efficiency-matrix stabilization” framework centered on microbial metabolism and organic carbon transformation, as well as the new “microbial carbon pump” and “mineral carbon pump” theories in forest soil organic carbon transformation and stabilization. We specifically highlighted a differential mechanism of “organo-organic interfaces” from the “organo-mineral interfaces” in the effects on soil organic carbon accumulation. We further expounded the transformation processes and stability of soil organic carbon based on the “carbon material cycling” and “energy fluxes”, aiming to provide theoretical support for the research on carbon sequestration in forest soils.
    Research progress on isotope tracing on the sources and transformations of reactive nitrogen in the earth-atmosphere system
    SONG Wei, LIU Xueyan
    2024, 35(9):  2362-2371.  doi:10.13287/j.1001-9332.202409.031
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    Since the Industrial Revolution, human activities have led to a rapid and sustained increase in reactive nitrogen production, resulting in nitrogen enrichment at the Earth's surface and triggering many ecological and environmental issues. Stable isotopes are effective tools for tracing the sources and mechanisms of environmental processes. The nitrogen isotope values in surface environments integrate the isotope signatures of different nitrogen sources and the isotope fractionation effects of transformation processes. The composition of nitrogen isotopes can thus be utilized to trace the sources and cycling of nitrogen at the surface, aiding the development of strategies to reduce reactive nitrogen emissions, and assess the ecological effects of nitrogen enrichment. We reviewed the research progress on nitrogen isotope in the sources of reactive nitrogen in atmospheric systems, plant nitrogen utilization, and tracking of nitrogen processes in forest ecosystems. We further discussed how to gain a more systematic and accurate understanding of nitrogen cycle within and between the various spheres of the surface environment.
    Application and prospect of landscape ecology in territorial spatial planning
    LIU Miao, SHI Sixue, ZHANG Tingshuang, LI Dikang, YU Yang, ZHANG Zhibin
    2024, 35(9):  2372-2381.  doi:10.13287/j.1001-9332.202409.038
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    Territorial spatial planning could achieve the integration of various plans, resulting in a unified “multi-plan integration” map. Such planning emphasizes the efficient use of territorial spatial patterns and structures to ensure functional perfection, and serves as the spatial framework for building a modern socialist country, particularly in the areas of ecological security and ecological civilization. The past few decades have seen rapid advances in the development of landscape ecology in China. The core concept of “pattern-process-function” has gained significant progress and been widely applied in the initial phase of territorial spatial planning at various levels. We outlined the advancements in the territorial spatial planning system and the core research theories and technologies in landscape ecology. We discussed the progress and shortcomings of key theories and methods of landscape ecology in practical applications of territorial spatial planning, such as ecological security patterns, pattern and process, and scale effects. We proposed the future application of landscape ecology theories and technologies in territorial spatial planning, including overall ecological effects, scale effects, and regional ecological network optimization. Future developments in landscape ecology, especially research on the “human-place-ecology” coupling based on the latest Big Data and AI technology for sustainable development, will provide robust theoretical and methodological supports for the scientific formulation of territorial spatial planning in China.
    Microbiological mechanism of hydrogen fertilizer effect in soil
    FENG Qingshan, MAO Qinjiang, MA Jianguo, LI Yuman, YANG Xiaoqian, LU Xingxin, WANG Xiaobo
    2024, 35(9):  2382-2391.  doi:10.13287/j.1001-9332.202409.012
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    For a long time, intercropping and rotation of leguminous with non-leguminous crops is widely used to reduce the application of nitrogen fertilizer and increase yield in agroecosystems. At present, most researchers considered that this management measure is helpful for reducing fertilizer consumption and increasing its efficiency, as it can improve nutrient supply of legumestonon-legumes, the spatial nutrient utilization efficiency by enhancing soil spatial heterogeneity, and improve soil structure and disease resistance. However, current theories cannot fully explain the positive effect of crop rotation and inter-cropping systems involving legumes. A large amount of hydrogen (H2) can be produced as an obligatory by-product of nitrogenase responsible for nitrogen (N2) fixation in the root nodules of leguminous plants. Despite of substantial amounts of H2 enriched in the rhizosphere of legumes, only a minor proportion of H2 is found to leak to soil surface. Increasing evidence showed that most H2 released in soil is immediately depleted in the surrounding of N2-fixing nodules by H2-oxidizing bacteria (HOB) thriving in soil. HOB can use H2 as an electron donor to assimilate and fix CO2 through redox reactions to synthesize cellular substances and consequently promote plant growth. To date, however, little is known about the biological mechanism and ecological process behind the “hydrogen fertilizer effect”. Therefore, we review the H2-induced plant growth-promoting effects and its microbiological mechanisms. Our aims were to explore a new way for enhancing agroecosystem production, and to provide scientific basis for future utilization of H2 in agricultural production practices.
    Application of species distribution models in predicting the distribution of marine macrobenthos
    CONG Jiayi, LI Xinzheng, XU Yong
    2024, 35(9):  2392-2400.  doi:10.13287/j.1001-9332.202409.029
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    Species distribution models (SDMs) are valuable tools in predicting species distribution ranges and the suitable habitats, which are based on environmental conditions and species distribution data. These models encompass correlative models, mechanistic models, and mechanistic-correlative models. In the field of marine science, SDMs have been extensively used for predicting the spatial distribution patterns of various marine organisms including fish, mammals, algae, et al. However, the application of SDMs in predicting the distribution of macrobenthos remains scarce. Understanding the distribution of macrobenthos, the integral components of marine ecosystems, has significant implications for ecological conservation and resource management. We reviewed common methodologies employed in SDMs and presented case studies using different models to predict the distribution patterns of marine macrobenthos. Further, we emphasized the use of correlative and mechanistic models to analyze the impact of climate change on the spatial distribution of marine macrobenthos. Finally, we discussed the challenges and prospects associated with SDMs. With the advances in remote sensing technology and modeling techniques, SDMs are becoming increasingly pivotal in marine ecological research, which could offer a robust scientific foundation for addressing climate change and preserving marine biodiversity.
    Process and mechanism of termite impact on soil and plant
    JIANG Chuan, ZENG Xiaoling, JIN Yanqiang, FENG Defeng, LIN Fangmei, CHEN Yuanyang, TANG Jianwei, LIU Chenggang
    2024, 35(9):  2401-2412.  doi:10.13287/j.1001-9332.202409.028
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    Termites, as a kind of nesting social insects, are often confused as worldwide “pests” because some of their groups have great destructive effects. The vast majority of termites can regulate ecosystem functions and ser-vices by participating in biogeochemical cycles, known as “ecosystem engineers”. We reviewed studies on the effects of termites on the physical, chemical and biological characteristics of mound soil ecosystems and the composition and diversity of plant communities. Termites could form unique soil “biogenic aggregates” and “resource heterogeneity patches”, which affect microbial community structure, extracellular enzyme activity, physicochemical property and greenhouse gas emission, thereby affecting plant growth, community composition and structure, and vegetation productivity. However, this effect significantly differed among termite groups and functional groups, and was dependent on regional soil environment and microclimate conditions. Meanwhile, termite-mound could effectively improve ecosystem adaptation or resistance to environmental stress through the above process. Future research should focus on the following directions: 1) studying the trophic cascading effect of termite-centered soil multilevel biological network and the potential effect on biogeochemical cycle from microscale (aggregate level) to macroscale (landscape level); 2) exploring the potential of termite mound soil as a fertility amendment in tropical regions, and mining beneficial microbial functional genes to develop related products for termite control.
    Research advance on soil organic carbon stabilization mechanisms during vegetation restoration on the Loess Plateau, Northwest China
    AN Shaoshan, HU Yang, WANG Baorong
    2024, 35(9):  2413-2422.  doi:10.13287/j.1001-9332.202409.013
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    The Loess Plateau is renowned for its deep soil layer and rich in organic carbon (C). In recent years, numerous ecological restoration projects have been undertaken on the Loess Plateau, with consequence on the stability of soil organic carbon (SOC). The SOC stability is pivotal for its capacity to sequestrate and store C. However, comprehensive review on the characteristics of SOC stability and its mechanisms during vegetation restoration on the Loess Plateau is scarce. Therefore, we summarized the dynamics of SOC stability during vegetation restoration on the Loess Plateau, discussed the mechanisms of SOC stabilization, including mineral protection, physical protection, and biological mechanisms. Furthermore, we prospected the future development directions and research focus of SOC stability research during vegetation restoration on the Loess Plateau to provide scientific support for theory and technology of soil C sequestration and stabilization during vegetation restoration, and to provide scientific reference for achieving the “double-carbon” goals.
    Some critical thinking on the integrative assessment of ecosystem service supply and demand relationships
    TAO Yu, OU Weixin, SUN Xiao
    2024, 35(9):  2423-2431.  doi:10.13287/j.1001-9332.202409.039
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    In the past decade, research on the relationships between the supply and demand of ecosystem services has been flourishing. To address issues such as the misuse of supply and demand concepts, methods, and results in current research, we proposed five key aspects that need to be considered to enhance the scientific rigor and practical value in assessing relationships between ecosystem service supply and demand. Firstly, it is essential to clarify the distinctions and connections between the concepts related to ecosystem service supply and demand, which are crucial prerequisites and starting points for assessing their relationships. Secondly, it is necessary to integrate relevant environmental standards or policy objectives to develop reliable methods for assessing the demand for ecosystem regulating services. Furthermore, it is important to properly address the modifiable areal unit problem by determining the most appropriate spatial scale and unit for evaluating relationships between ecosystem service supply and demand. Additionally, it is crucial to differentiate between quantitative and qualitative methods for characterizing (im)balances or (mis)matches between ecosystem service supply and demand, particularly avoiding the use of qualitative methods to represent quantitative relationships between supply and demand. Lastly, it is imperative to integrate ecosystem service flows into the assessment of supply and demand relationships, and evaluate the dynamic supply and demand relationships of regional ecosystem services from a coupled “supply-flow-demand” perspective.
    Effects of simulated warming on content, fractions and chemical structure of soil organic carbon:Progress and prospects
    SUN Ruifeng, HAN Guangxuan
    2024, 35(9):  2432-2444.  doi:10.13287/j.1001-9332.202409.010
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    Soil organic carbon (SOC) represents the largest terrestrial organic carbon pool and plays an important role in mitigating global climate change. Warming can change the stabilization process and the balance of inputs and outputs of the SOC pool, thereby affecting the content, fraction, and chemical structure of SOC. It has become a research hotspot to reveal the mechanisms underlying the effects of warming on SOC stability by analyzing the fraction and molecular structure of C. Here, we reviewed the warming effects on the SOC pool from three aspects, e.g., the content, fraction, and chemical structure of SOC. We also summarized the response of key ecosystem processes to warming, including plant productivity and community composition, microbial activity and community structure. We highlighted the importance of prospective and systematic research focusing on elucidating the microbial mechanism, identifying SOC source and turnover processes, establishing long-term dynamic networked experiments, and mining and optimizing key parameters in C cycle models. This would provide theoretical support for better understanding the change and mechanism of SOC under global warming and predicting the alterations of SOC pool under climate change.
    Effects of simulated precipitation changes on soil respiration:Progress and prospects
    LI Xinge, ZHU Lianqi, ZHU Wenbo, HAN Guangxuan
    2024, 35(9):  2445-2454.  doi:10.13287/j.1001-9332.202409.014
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    Soil respiration, the main pathway for transferring terrestrial carbon pool to atmospheric carbon pool, is profoundly affected by the intensification in global precipitation variability in the context of climate change. Nowadays, variable controlling methods and field manipulation experiments are two main methods widely used to investigate the effects of simulated precipitation changes on soil respiration. Yet, due to the heterogeneity of soil properties, vegetation types, and the magnitude of precipitation change, there is substantial inconsistency in the conclusions of simulated precipitation change effects on soil respiration. Here, we analyzed data from domestic and foreign literature, and examined the effects of simulated precipitation change on soil respiration. Firstly, we described the response pattern of soil respiration to soil moisture fluctuation and pointed out that the magnitude and direction of the response of soil respiration to simulated precipitation change depended on whether soil moisture was optimally conditioned at different precipitation treatments. Second, we summarized the response patterns of soil respiration to symmetric increase and decrease in precipitation, which mainly included symmetric and asymmetric responses (positive and negative asymmetric). Meanwhile, the adaptation of plants and soil microorganisms to drought stress and soil oxygen limitation, as well as the reduction of organic substrates, were the main mechanisms accounting for the shifts of soil respiration response patterns to simulated precipitation change from symmetric to asymmetric responses. Third, we identified a significant effect of ambient climate on soil respiration in response to precipitation treatments as increasing duration of the experimental treatments. In addition, cumulative or buffering effects of ambient climatic conditions on precipitation treatment could affect the sensitivity of soil respiration along precipitation gradient by altering hydrothermal conditions. Finally, to accurately assess the implications of precipitation changes on soil carbon balance processes, we proposed three aspects of future precipitation effects on soil respiration for attention: 1) focusing on the phenomenon of “threshold effects” in the asymmetric response of soil respiration along precipitation gradients; 2) distinguishing the intrinsic mechanisms of autotrophic and heterotrophic components in soil respiration in response to precipitation changes; and 3) focusing on the impacts of intensified precipitation variability on soil respiration in the context of future climate extremes. In conclusion, with the intensified variability in global precipitation patterns, clarifying the response mechanism of soil respiration to precipitation changes is of great significance for accurately predicting and evaluating the alterations of soil carbon cycle processes and carbon balance in the context of global changes.
    Research progresses on the effects of light, temperature and water conditions on primary and secondary growth of trees
    ZHOU Minghui, ZHANG Ting, LI Rongping, YAN Qiaoling
    2024, 35(9):  2455-2462.  doi:10.13287/j.1001-9332.202409.008
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    Tree growth includes primary growth and secondary growth. The growth activity and dormancy cycle of trees can affect forest productivity and carbon sequestration capacity. Therefore, it is of great significance to examine the effects of environmental conditions (e.g., photoperiod, temperature and water) on tree growth for understanding the responses of trees to climate change and predicting forest productivity and carbon sequestration capacity under the background of global climate change. We reviewed the effects of photoperiod, temperature and water conditions on the primary and secondary growth of trees, and revealed the physiological mechanisms underlying their impacts on the synchronization or asynchronization between primary and secondary growth of trees. The shortcomings of the existing research were pointed out. For example, less attention had been paid to the enrionmental response and adaptation of root growth, as well as the physiological mechanism of the effect of light, temperature and water on tree growth. Research on the growth of underground roots should be strengthened in the future, and more attention should be paid to the physiological changes in the process of tree growth affected by environmental factors. Furthermore, the source and sink limitation theory and the process-based prediction model should be improved, aiming to provide a scientific basis for predicting forest productivity and carbon sequestration capacity and putting forward scientific policies of forest management.
    Research advance in effects of solar radiation on litter decomposition in terrestrial ecosystems
    ZHANG Juanjuan, LI Xingzhi, WANG Yanan, DENG Jiaojiao, ZHOU Li, ZHOU Wangming, YU Dapao, WANG Qingwei
    2024, 35(9):  2463-2472.  doi:10.13287/j.1001-9332.202409.009
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    Litter decomposition significantly influences the carbon (C) dynamics of terrestrial ecosystems. Solar radiation is not only essential for photosynthetic C fixation and primary productivity, but also can directly or indirectly promote litter decomposition through photodegradation. Recently, photodegradation has been identified as a key factor driving litter decomposition and potentially impacts terrestrial C cycle. To enrich and develop the theory of litter decomposition, we summarized the mechanisms and main driving factors of photodegradation, and compared the responses of photodegradation to environment and climate changes at different scales. Photodegradation primarily includes photomineralization, photoinhibition, and photofaciliation, each affecting litter decomposition differently under various environmental conditions. Photodegradation is closely related to factors such as solar radiation, litter traits, temperature, moisture, microorganisms, and vegetation cover. The interactions among these factors complicate the patterns of photodegradation. Finally, we identified the main issues in litter photodegradation research and prospected future research directions. We emphasized the needs for in-depth exploration of photodegradation pathways and intrinsic mechanisms, quantification of its interactive effects with environmental factors, and optimization of traditional carbon turnover models.
    Principle, structure and application progress of the forest landscape model FireBGCv2
    SONG Jia, CHEN Hongwei, WU Zhiwei, SUN Xuebin
    2024, 35(9):  2473-2482.  doi:10.13287/j.1001-9332.202409.020
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    Forest landscape model can quantitatively simulate the spatiotemporal variations in forest structure and function at the landscape scale based on traditional field survey data and mathematical models, providing a reference for the formulation of scientific forest management strategies. FireBGCv2 is one of the representative models currently used in the research area of forest landscape changes. It can simulate ecological processes at various scales, including trees scale (tree growth, establishment, and mortality), stand scale (carbon and nitrogen pools, fuel treatment, decomposition), site scale (resource competition and species phenology), and landscape scale (seed dispersal and wildfire disturbances), and the effects of those processes on forest landscape structure and function. The advantage of this model lies in its ability to simulate multiple ecological processes while considering the diversity and complexity of ecosystems. However, it also has drawbacks, such as high computational demands and complexity of use. We summarized the basic principles and structure of FireBGCv2 and introduced its application progress in forest landscape research and management. Currently, the application of the FireBGCv2 model, both domestically and internationally, mainly focused on exploring the interactions between fire, climate, and vegetation, quantifying the spatial and temporal dynamics of fires, and describing potential fire dynamics under future climate scenarios and land management strategies. With the in-depth development of forest landscape model theories and applications, the future prospects of FireBGCv2 include improving and updating the model's algorithms, adding new functional modules to explore fire management issues, and meeting the needs of different users.
    Research Reports
    Azimuthal and radial variations in sap flow and its effects on the estimation of transpiration for Picea mongolica
    LIU Xin, SONG Lining, ZHANG Jinxin, ZHU Xinwei, ZHAO Yumin, ZHENG Qing-shan
    2024, 35(9):  2483-2491.  doi:10.13287/j.1001-9332.202409.005
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    In this study, we applied thermal dissipation probe technology to examine sap flow in various directions (east, south, west, and north) and at different depths (0-2, 2-4, 4-6 cm) within the stem of natural Picea mongolica trees in the eastern of Otindag Sandy Land to provide a scientific basis for accurately quantifying water consumption of P. mongolica forests through transpiration and to enhance the understanding of water relations. The results showed that the diurnal variation of sap flow in different directions displayed a unimodal curve, with the sap flow sequence being south>east>west>north. The sap flow at different sapwood depths exhibited an obvious unimodal curve, with a significant decrease as sapwood depth increased. Compared with that calculated from the mean sap flux density in four directions (23.57 kg·d-1), water consumption calculated using the mean value in south-east, east-west, south-west, north-east, north-south, and north-west was overestimated by 10.2%, 5.5%, 14.5%, and underestimated by 12.3%, 8.2%, 9.8%, respectively. The water consumption calculated using the values from the east, south, and west was overestimated by 6.1%, 14.4%, and 15.4%, respectively, and underestimated by 30.7% in the north. In addition, compared with the water consumption calculated from the mean value in three sapwood depths (48.51 kg·d-1), that calculated using sap flux density at sapwood depths of 0-2, 2-4, and 4-6 cm were overestimated by 18.8%, underestimated by 1.7%, and underestimated by 62.9%, respectively. These results indicated that sap flow of P. mongolica had significant azimuthal and radial variations, which considerably influence the estimation of tree water consumption. Installing probes at 0-2 cm simultaneously in both the north and east of the trunk could effectively reduce the estimation error of whole-tree water consumption by 4.2%. This approach enabled the accurate quantification of water consumption of individual P. mongolica trees in sandy areas, thereby improving the precision of transpiration water consumption estimates scaling up from individual level to stand level.
    Spatial structure and individual competition characteristics of secondary Mongolian oak mature forests in the mountainous area of eastern Liaoning Province, China
    ZHANG Huidong, MAO Yixin, WANG Ruizhao, ZHU Jian, XIA Hang, YU Dapao, YOU Wenzhong
    2024, 35(9):  2492-2500.  doi:10.13287/j.1001-9332.202409.004
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    The community structure of natural mature forests is determined by long-term forest succession, characterized by rational structure, rich biodiversity, and high ecological function. Understanding the spatial structure and formation mechanisms of mature forests is a fundamental prerequisite for forest management. We analyzed four structure parameters, including diameter structure, angular scale, size ratio, and mixture degree, as well as the Hegyi competition index, of secondary Quercus mongolica (Mongolian oak) mature forests in the mountainous area of eastern Liaoning Province. The results showed that Q. mongolica predominated the tree layer. In the sapling layer, Q. mongolica, Tilia amurensis, and Acer pictum were the dominant species. In the seedling layer, Acer pseudosieboldianum, T. amurensis, and A. amurensis dominated, with very few Q. mongolica seedlings. The overall diameter distribution of the stand showed an inverse “J” shape, while the diameter distribution of Q. mongolica, the dominant tree species, followed a normal distribution. The horizontal spatial structure of the stand was generally randomly distributed, with an average angle scale of 0.505, size ratio of 0.219, and mixture degree of 0.670 for Q. mongolica. From the perspective of spatial structure binary distribution, Q. mongolica individuals which had a random distribution exhibited greater growth advantages and higher levels of mixing, in comparison to other distribution types. Randomly distributed dominant and subdominant individuals made up nearly half individuals in the stand, and showed a high degree of mixing with surrounding trees. The stand-level individual tree competition index decreased with increasing diameter classes. When the diameter at breast height exceeded 20 cm, the competition index tended to stabilize (ΔCI<2). The competitive radius of individual Q. mongolica trees was 8 m, with intraspecific competition as the main pressure. Other species experienced competition pressure primarily from interspecific sources. Our results suggested that competition played an important role in shaping the spatial structure of secondary Q. mongolica mature forests.
    Population dynamics and its relationship with functional traits in different succession stages of temperate mixed coniferous broad-leaved forest in Northeast China
    SHAN Weiqiang, FANG Shuai, YIN Jin, REN Jing, LIN Fei, MAO Zikun, HAO Zhanqing, WANG Xugao
    2024, 35(9):  2501-2510.  doi:10.13287/j.1001-9332.202409.003
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    Functional traits regulate plant response to environmental changes, with consequences on population dynamics. However, how plant functional traits impact population dynamics, including growth, mortality, and recruitment, remains elusive in temperate forests across different successional stages. In this study, we compiled data on population dynamics and eight functional traits, encompassing hydraulic, wood, and leaf traits, from 35 species commonly found in a secondary poplar-birch forest and a broad-leaved Korean pine forest in Northeast China. We quantified the intrinsic relationships between plant population dynamics and assessed how plant functional traits influenced these dynamics. The results demonstrated a gradual increase in the correlation among population dynamics as forest succession progressed. In the secondary forest, tree growth rate and mortality rate were negatively correlated, while growth-death rate and growth-recruitment rate were not related. Conversely, in the broad-leaved Korean pine forest, there was a significant negative correlation between tree growth rate and mortality rate, as well as between growth rate and recruitment rate, while tree mortality rate positively correlated with recruitment rate. Additionally, functional traits effectively predicted population dynamics, but the predictive ability varied across successional stages. Functional traits, particularly xylem hydraulic traits (e.g., Huber value) and anatomical traits (e.g., mean xylem conduit diameter), were stronger predictors of tree growth, mortality, and recruitment rates at the late successional stage compared with the early stage. These findings indicated that population dynamics and functional traits exhibited strong regularity in the late successional stage of broad-leaved Korean pine forests.
    Latitudinal responses of litter decomposition to solar radiation
    WU Jinju, SU Baoling, LI Xingzhi, SUN Xuekai, TAN Xiangping, NIE Yanxia, DU Wenzhi, ZOU Renshuang, DENG Jiaojiao, ZHOU Li, YU Dapao, WANG Qingwei
    2024, 35(9):  2511-2517.  doi:10.13287/j.1001-9332.202409.002
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    Photodegradation driven by solar radiation has been confirmed as an important driving factor for litter decomposition. However, previous single-site studies could not quantify the relative contribution of variation in solar radiation to litter decomposition. To address it, we conducted a field experiment in Heshan National Field Research Station of Forest Ecosystem, Guangdong (Heshan Station, south subtropical climate), Jigongshan Ecological Research Station, Xinyang, Henan (Jigongshan Station, north subtropical climate) and Daqinggou Ecological Research Station, Institute of Applied Ecology, Chinese Academy of Sciences (Daqinggou Station, temperate climate) at intervals of 10 degrees. We examined litter decomposition of Populus davidiana and Larix olgensis, two species with significant differences in initial litter quality through an in-situ spectral-attenuation experiment. Treatments included full-spectrum, No-UV-B (attenuating UV-B radiation <315 nm) and No-UV & Blue (attenuating all UV and blue wavelengths <500 nm). After nearly 1-year decomposition, litter dry mass remaining of P. davidiana and L. olgensis under full-spectrum treatment was lowest at Heshan (30.2% and 36.3%), and highest at Jigongshan (37.3% and 45.8%). Among all sites, litter dry mass remaining was lowest under the full-spectrum, and lower than that of No-UV-B and No-UV & blue. UV and blue light significantly increased litter mass loss of P. davidiana and L. olgensis, with contributions of 59.7% and 57.0% (Heshan), 46.4% and 42.1% (Jigongshan), and 39.0% and 45.9% (Daqinggou), respectively. The contribution of UV-A and blue light (315-500 nm) was greater than UV-B (280-315 nm); the cumulative irradiance, soil temperature and moisture were the main driving factors for litter photodegradation.
    The stoichiometric characteristics of carbon, nitrogen, and phosphorus in soil aggregates of Cryptomeria japonica plantation with stand ages in the Rainy Area of Western China
    WU Aomiao, HONG Zongwen, YOU Chengming, XU Lin, XU Hongwei, XU Zhenfeng, LUO Ziteng, TAN Bo
    2024, 35(9):  2518-2526.  doi:10.13287/j.1001-9332.202409.018
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    Understanding the variations in soil aggregate composition, as well as the contents and stoichiometry of organic carbon (C), total nitrogen (N) and total phosphorus (P), in the surface layer of Cryptomeria japonica plantations with different stand ages can provide a theoretical basis for the optimized management of plantations and the improvement of soil fertility in the Rainy Area of West China. With the dry-sieving method, we measured the contents of soil aggregates with different sizes in the 0-15 and 15-30 cm soil layers across C. japonica plantations with five distinct developmental stages at Hongya Forestry Farm, Sichuan Province, including young stands (7 years old), middle-aged stands (13 years old), nearly mature stands (24 years old), mature stands (33 years old), and over-mature stands (53 years old). We further analyzed the C, N and P contents and ecological stoichiometric characteristics of soil aggregates. The results showed that the particle size composition of soil aggregates in C. japonica plantations varied among stand ages. The nearly mature and mature stands had higher proportion of large aggregates (0.5-1 and 1-2 mm), whereas the nearly mature stand had a lower proportion of micro-aggregates (0.053-0.25 mm) and the silt-plus-clay fraction (<0.053 mm). Moreover, the C, N and P contents and stoichiometric ratios in soil aggregate showed a unimodal pattern, which increased initially and then decreased with stand age, with peak values in the nearly mature and mature plantations. Furthermore, the C, N and P contents in aggregates in 0-15 cm soil layer were higher than that in the 15-30 cm soil layer. The highest C and N contents were found in the aggregates with particle sizes of 0.5-1 and 0.25-0.5 mm. In conclusion, the near-mature and mature stands of C. japonica plantations have higher nutrient content in soil aggregate, underscoring these stages was critical for maintaining soil fertility and advancing sustainable management practices.
    Responses of plant carbon, nitrogen, and phosphorus content in terrestrial ecosystems to warming: A Meta-analysis
    HUANG Lulu, ZHOU Huiling, WANG Qifan, ZHAO Xinran, CHEN Jinhui, YOU Chengming, XU Lin, TAN Bo, XU Zhenfeng, XU Hongwei
    2024, 35(9):  2527-2534.  doi:10.13287/j.1001-9332.202409.001
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    We conducted a Meta-analysis with 264 datasets from 55 publications to investigate the effects of warming duration and intensity on plant carbon, nitrogen and phosphorus contents. The results showed that warming significantly reduced shoot carbon (effect value of -1.7%), root carbon (-4.0%), litter carbon (-3.7%), shoot nitrogen (-7.0%) and litter nitrogen contents (-6.4%). For different ecosystem types, warming significantly decreased shoot carbon (-0.8%), shoot nitrogen (-5.9%), root carbon (-7.4%), litter carbon (-2.1%), and litter nitrogen content (-13.4%) in grasslands, while significantly increased shoot carbon (2.7%) in scrublands and litter phosphorus content (42.4%) in forests. Short-term warming (<5 years) decreased shoot carbon (-0.4%), shoot phosphorus (-0.4%) and litter nitrogen (-13.4%) contents, while medium- to long-term warming (5-10 years) increased shoot carbon (0.6%), shoot phosphorus (20.2%) and litter nitrogen (6.2%) contents. The 0-2 ℃ warming intensity increased shoot phosphorus (10.1%) and root phosphorus (27.4%) contents of plants, while the >2 ℃ warming intensity decreased shoot phosphorus (-3.7%) and root phosphorus (-6.5%) content. The effect values of plant shoot carbon and shoot nitrogen were significantly and positively correlated with humidity index. Warming showed negative effects on plant carbon, nitrogen and phosphorus contents in terrestrial ecosystems, and such effects were moderated by the duration and intensity of warming.
    Effect of pH on the growth and competition of Trichoderma spp. and Fusarium spp
    BAO Wenjie, SHEN Lingjie, XIA Shangwen, YANG Xiaodong
    2024, 35(9):  2535-2542.  doi:10.13287/j.1001-9332.202409.032
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    Collar rot caused by Fusarium spp. is a serious threat to the production of Passiflora edulis. However, biocontrol methods are lacking. Trichoderma spp., as the most widely applied biocontrol fungus, can be effective in managing crop diseases. The effectiveness is significantly influenced by environmental factors, such as soil pH. To screen potential biocontrol strains against collar rot of P. edulis, and to explore the effect of pH on the inhibition rate of Trichoderma spp., we selected four Trichoderma species and four Fusarium species isolated from P. edulis planting area in Xishuangbanna. The growth dynamics of different strains under different pH conditions were determined using the mycelial growth rate method. The effect of pH on the growth inhibition of Fusarium spp. by Trichoderma spp. was investigated using the plate confrontation assay. The results showed that the optimal growth pH range was 4-6 for Trichoderma spp. and 7-9 for Fusarium spp. All four Trichoderma strains exhibited significant inhibitory effects on the growth of the four Fusarium strains. T. harzianum showed the most notable inhibition, reaching up to a 72% inhibitory rate. Moreover, pH significantly influenced the inhibitory effect of Trichoderma spp., with variations observed depending on the specific species of Trichoderma spp. and Fusarium spp. Therefore, it is essential to consider the environmental pH impact on the efficacy of biocontrol agents when applying biological control measures in the field, tailored to the specific pathogen and biocontrol agent involved.
    Characteristics of soil viral communities in Cunninghamia lanceolata plantations with different stand ages
    HE Li, YAN Yuting, YUAN Chengyu, LIN Qiusha, YU Danting
    2024, 35(9):  2543-2551.  doi:10.13287/j.1001-9332.202409.007
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    We investigated the dynamics of soil viral community in Cunninghamia lanceolata plantations with different stand ages (8, 21, 27, and 40 years old) in a subtropical region. The viral metagenomics and bioinformatics analysis were used to analyze the compositional and functional differences of soil viral communities across different stand ages, and to explore the environmental driving factors. The results showed that tailed phages dominated soil viral community in subtropical C. lanceolata plantations, with the highest proportion of Siphoviridae (19.6%-39.5%). There was significant difference in soil viral community structure among different stand ages, with the main driving factors being electrical conductance and available phosphorus. The metabolic functional genes encoded by viruses exhibited higher relative abundance. The α-diversity of soil viral function in mature C. lanceolata plantations was higher than other stands. There were significant differences in soil viral functional structure among different stand ages, which were mainly driven by ammonium nitrogen. During the development of C. lanceolata plantations, auxiliary metabolic genes encoded by virus related to nitrogen and phosphorus may regulate the metabolism of host microorganisms, thereby potentially impacting biogeochemical cycling of these elements.
    Distribution characteristics of soil moisture and temperature under different land use types in the deep profile of loess area in northern Shaanxi, China
    LI Minghui, LI Yangyang, FAN Jun
    2024, 35(9):  2552-2560.  doi:10.13287/j.1001-9332.202409.019
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    Understanding the effects of different land use modes on the spatial and temporal variations of soil moisture and temperature in the deep profile and revealing the regulatory effects of various vegetation covers on regional water and heat resources can provide a theoretical basis for the optimization of land management and vegetation restoration. Taking the advantage of different land use patterns in the Liudaogou watershed in the northern part of Loess Plateau, we monitored soil moisture content as well as temperature in the 0-1000 cm soil layer in 2022 to analyze the temporal variation and vertical profile distribution characteristics of soil moisture and temperature under four land use modes (woodland, grassland, farmland, and wild grassland). The results showed that soil moisture and temperature distributions varied significantly across different land use types. In the growing season (April-October), total soil water storage in the 0-1000 cm soil layer of the four land use types, in a descending order, was as follows: soybean farmland (1393 mm), wild grassland (1374 mm), Caragana korshinkii forest (1218 mm), and alfalfa grassland (557 mm). Soil moisture of C. korshinkii forest and soybean farmland changed obviously in the 0-300 cm soil layer, and that of wild grassland and alfalfa grassland was in 0-500 and 0-200 cm soil layers, respectively, while soil moisture of deep soil layers fluctuated little. The impact of land use modes on soil temperature was primarily manifested in the 0-200 cm soil layer, and the depth was up to 300 cm. The depth of precipitation infiltration replenishment of the four land use modes was approximately 200 cm. The depth of soil moisture depletion was 200 cm in both C. korshinkii forest and alfalfa grassland, and was 100 cm in soybean farmland and wild grassland. Soil hydrothermal processes in the deep profile varied across vegetation types.
    Change trend and attribution analysis of leaf area index in the East African Plateau from 1982 to 2020
    MA Yan, CHEN Tiexi, CHEN Xin, XIAO Yinmiao, ZHOU Shengjie, WANG Shengzhen
    2024, 35(9):  2561-2570.  doi:10.13287/j.1001-9332.202409.021
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    The ecosystems on the East African Plateau are crucial for maintaining the biodiversity, water resource balance, and ecological equilibrium of the African continent. However, the spatiotemporal variations of vegetation and the driving factors remain unclear. We analyzed leaf area index (LAI) change trends in the East African Plateau based on the GIMMS LAI4g dataset and further conducted attribution analysis combining temperature and precipitation data, as well as 10 Dynamic Global Vegetation Models (DGVMs) in TRNEDY v9. The results showed that LAI of the East African Plateau had a modest change trend from 1982 to 1999 (2.5×10-3 m2·m-2·a-1), but significantly increased from 2000 to 2020 (5.2×10-3 m2·m-2·a-1), which was 2.1 times faster than that during 1982-1999. Temperature and precipitation had weak correlations with LAI from 1982 to 1999, but showed significant correlations from 2000 to 2020. The DGVMs demonstrated consistent attribution results, with temperature and precipitation contributing significantly more to the LAI variations from 2000 to 2020 compared to the period from 1982 to 1999. The results highlighted the key role of climate change in driving vegetation greening on the East African Plateau during 2000-2020, which could provide important evidence for ecological conservation and sustainable development strategies in the region.
    Distribution and prediction of biocrusts under the canopy of typical vascular plants on the Loess Plateau, Northwest China
    LIU Ning, YU Shunyao, ZHANG Caiyue, ZHAO Yunge
    2024, 35(9):  2571-2580.  doi:10.13287/j.1001-9332.202409.017
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    Vascular plants exert significant effects on micro-environment, thereby affecting the distribution of biological soil crusts (biocrusts). The relationship between vascular plants and the spatial distribution characteristics of biocrusts is largely unknown. We investigated the distribution characteristics of biocrusts under the canopy of vascular plants in the water-wind erosion crisscross area of the Loess Plateau, where larger areas of biocrusts had been formed since the implantation of “Grain for Green” project. We analyzed the relationship between the canopy characteristics of different vascular plants and the spatial distribution of biocrusts using correlation analysis and random forest importance ranking methods, and further constructed a predictive model for the area of biocrusts under the canopy of vascular plants. The results showed that: 1) Cyanobacteria crust was the predominant biocrusts, followed by moss crust. 2) The canopy of vascular plants affected the spatial distribution of biocrusts, with notable differences in distribution pattern across different directions under the canopy of vascular plants. Biocrusts were primarily distributed in the 270°-315° and 315°-360° directions, while was less frequent in the 90°-135° and 135°-180° directions. 3) Radially, the coverage of biocrusts gradually increased from the root-base to the edge of the canopy of vascular plants. 4) The coverage of biocrusts under canopy was significantly related to the characteristics of vascular plants, including canopy area, long crown width, short crown width, litter area and plant height. 5) The relative importance of canopy area, long crown width, and short crown width to the biocrusts under the canopy was 13.7%, 12.1%, and 11.9%, respectively, while the relative importance of plant height and species type was relatively low, being 6.7% and 4.4%, respectively. 6) Results of the random forest model demonstrated strong predictive performance for biocrusts distribution based on canopy characteristics of vascular plants, with a prediction accuracy of 0.59 (R2) and a root mean square error of 1.2 m2. This model could be applied to predict and estimate the area of biocrusts under the canopy of vascular plants. This study provided a theoretical basis for in-depth understanding of the relationship between vascular plants and biocrusts in semi-arid climate regions, as well as for predicting the spatial distribution of biocrusts.
    Spatial variations of annual net ecosystem productivity and its trend over Chinese terrestrial ecosystems based on spatial downscaling
    ZHU Xianjin, LIU Chenchen, CHENG Shihao, WANG Qiufeng
    2024, 35(9):  2581-2591.  doi:10.13287/j.1001-9332.202409.026
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    Annual net ecosystem productivity (NEP), the amount of net carbon sequestration during a year, serves as the basis of terrestrial carbon sink. Quantifying the spatial variations of NEP and its trend would enhance our understandings on the response and adaption of ecosystems to environmental change, which also serves for the regional carbon management targeting at carbon neutrality. Based on process-based model and data-driven model simulating NEP, we selected the optimal simulating NEP mostly representing NEP spatial variations with multiple site eddy covariance measurements to develop the spatial downscaling method and generate high resolution NEP data of China, which was used to examine the spatial variations of NEP and its trend and driving factors during 2000-2017. Compared with process-based model results, data-driven model simulating NEP could mostly represent the spatial variation of site measurements. The random forest regression based on climate, soil, and biological data combining with the simple scaling could successfully downscale NEP to a high spatial resolution. From 2000 to 2017, the total amount of NEP in China was (1.30±0.03) Pg C·a-1, showing a decreasing-increasing pattern with the inflection point in 2009. Chinese NEP decreased from southeast to northwest, showing a descending latitudinal distribution and an ascending longitudinal distribution, with the combined effects of climate and biotic factors. NEP trend decreased from east towards west, which was only accompanied with a slightly ascending longitudinal distribution, while photosynthetically active radiation and soil organic carbon content dominated the spatial variations of NEP trend. Therefore, the spatial patterns of generated NEP obviously differed from those of NEP trend, suggesting the obvious difference between the responses and adaptions of ecosystems to environmental changes.
    Contribution of soil microbial necromass carbon to soil organic carbon in grassland under precipitation change and its influencing factors in loess hilly region, Northwest China
    ZHOU Yue, LI Yayun, LI Na, LI Huijun, ZHANG Yuhan, AN Shaoshan, WANG Baorong
    2024, 35(9):  2592-2598.  doi:10.13287/j.1001-9332.202409.011
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    To investigate the contribution of microbial necromass carbon (MNC) to soil organic carbon (SOC) and its influencing factors under precipitation changes in grassland, we conducted a precipitation experiment with seven different precipitation levels in the Bothriochloa ischaemum restoration area in the loess hilly region. We analyzed the contents and characteristics of fungal necromass carbon (FNC), bacterial necromass carbon (BNC), and MNC in different fractions of SOC under different treatments, including natural precipitation (CK), and increased and decreased 20%, 40%, 60% of natural precipitation (I20, I40, I60, D20, D40, D60) . The results showed that 1) MNC content in mineral organic carbon (MAOC) ranged from 1.62 g·kg-1 to 2.17 g·kg-1, which was higher than that in particulate organic carbon (POC) ranging from 0.69 g·kg-1 to 1.31 g·kg-1. The former was approximately 1.4 to 2.8 times as that of the latter. 2) FNC and MNC exhibited similar changes in both MAOC and POC fractions. BNC content in MAOC was approximately 1-3.1 times as that of FNC. FNC content in POC was generally higher than BNC except for I40 and I60 where BNC exceeded FNC. 3) Overall, both increases and decreases in precipitation resulted in elevated MNC/MAOC and BNC/MAOC ratios, but decreased MNC/POC and FNC/POC ratios. The MNC/MAOC ratios in I60 and D60 were 33.2% and 18.1% higher than CK, respectively. The BNC/MAOC ratios in D60, I40 and I60 were 28.0%, 23.0% and 19.1% higher than those in CK, respectively. Except for D60, the FNC/POC and MNC/POC ratios were significantly lower than CK under other treatments. In terms of POC fractions, the MNC/POC ratios of D40, D20, I20, I40 and I60 were 28.4%, 23.3%, 28.8%, 23.3% and 32.2% lower than that of CK, respectively. The FNC/POC ratio of D40, D20, I20, I40 and I60 was found to be lower by 23.3%, 16.1%, 21.0%, 27.0% and 31.0% compared to that of CK, respectively. 4) NH4+-N and pH were the primary factors influencing the content of MNC in different carbon fractions under varying precipitation conditions. In summary, alterations in precipitation (either increase or decrease) enhanced the contribution of BNC-dominated MNC to MAOC, but reduced the contribution of FNC-dominated MNC to POC. This study was of significance for understanding the distribution of microbial necromass across different organic carbon fractions under precipitation alterations.
    Influences and mechanisms of iron input for methane productions in peatlands
    HU Xinyi, WANG Hong-yan, ZHAN Tian, XU Yijie, SUN Guoxin, YU Zhiguo
    2024, 35(9):  2599-2608.  doi:10.13287/j.1001-9332.202409.016
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    Atmospheric deposition provides a stable iron source for peatlands. The influences of Fe input on methane (CH4) productions and the underlying mechanisms remain unclear. We conducted a microcosm experiment with peat sediments collected from the Qinghai-Tibet Plateau of China to explore the effects of ferrihydrite reductionfor CH4 productions in peatlands by using geochemical analyses including 57Fe Mössbauer spectroscopy and three-dimensional fluorescence spectroscopy (3D-EEM) in combination with high-throughput sequencing of 16S rRNA and real-time fluorescence quantitative PCR (qPCR). Results showed that ferrihydrite reduction significantly increased CH4 production, being 30 times of that under the control. Selective extractions for iron oxides and 57Fe Mössbauer spectroscopy measurements revealed that no crystalline secondary iron minerals were formed during the ferrihydrite reduction process. The addition of ferrihydrite enhanced the degradation of dissolved organic matter (DOM) in peat soil, resulting in a reduction in the concentration of dissolved organic carbon (DOC). Furthermore, the relative abundance of typical fermentative microorganisms in peat sediments, including Acidobacteriota and Bacteroidota, significantly increased. Such a result indicated that reduction of ferrihydrite accelerated organic matter decomposition and increased substrate concentration required for methanogenesis. Furthermore, a co-increase in relative abundance of Geobacter, Geothrix, and Methanobacterium in the ferrihydrite-amended group suggested a potential synergistic interaction that may promote the CH4 production. Our results demonstrated that ferrihydrite reduction could significantly enhance CH4 production and play a vital role in regulating CH4 emissions in peatlands.
    Different organic composts application in dryland Mollisol:Residual effect and soil CO2 emission
    WU Zhi-yang, CHEN Zengming, LIU Yulian, CHEN Yizhou, XU Shiqi, ZHANG Jiuming, ZHANG Yongcheng, GUO Xiaojun, DING Weixin
    2024, 35(9):  2609-2619.  doi:10.13287/j.1001-9332.202409.015
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    Organic compost application plays an important role in improving the fertility of Mollisol. However, the effects of different organic composts on carbon sequestration varies greatly and its internal mechanism are unclear. We conducted a field experiment to explore the residual proportion of different organic composts and their effects on carbon emissions in dryland Mollisol in Northeast China. There were a total of seven treatments, including chemical fertilizer control (SNF), organic composts from cattle excreta (CRH), sheep excreta (SHP), chicken excreta (CKN), residue after corn starch production (BCS), residue with crop straws (HRS) and mushroom residue (WMC). We monitored annual soil CO2 flux by static chamber method, as well as the changes of environmental factors and soil dissolved carbon and nitrogen. The regulatory mechanism of organic component characteristics on carbon residual porprotion of organic composts were examined by neural network analysis. The results showed that compared with the SNF treatment, soil dissolved organic carbon (DOC) and extractable organic nitrogen increased by 26.3%-103.5% and 21.4%-150.0%, respectively. The aromaticity of soil DOC was significantly reduced. Heterotrophic respiration flux was mainly affected by soil temperature and DOC content, while its temperature sensitivity was significantly reduced in the CKN treatment. Annual accumulation of heterotrophic respiration increased from 203 g·C·m-2 of the control to 234-334 g·C·m-2 under treatments with organic composts applications, with the CKN and HRS treatments showing the strongest impact. The annual carbon residual proportion of different organic composts in Mollisol was in an order of CRH (91.2%)> WMC (82.9%)> BCS (82.6%)> SHP (78.1%)> CKN (70.2%)> HRS (69.3%). Hemicellulose content and C/N of organic composts were the key factors, which explained 58.8% and 32.9% of the total variations of carbon residual proportion. Organic compost from cattle excreta had higher residual proportion due to lower C/N, hemicellulose content and soluble polyphenol content, and thus did not significantly affect Mollisol heterotrophic respiration. Therefore, the application of organic compost from cattle excreta was more efficient to improve organic carbon in dryland Mollisol.
    Spatio-temporal pattern and coordinated development of eco-compensation performance of 101 cities in the Yangtze River Economic Belt
    YAN Haijuan, HU Xiaofei, ZHANG Jianing
    2024, 35(9):  2620-2630.  doi:10.13287/j.1001-9332.202409.027
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    Eco-compensation is an important component of ecological civilization construction. Therefore, it is of great significance to elucidate the spatial and temporal pattern of eco-compensation performance and its internal coupling and coordinated features to promote ecological civilization construction. We proposed that eco-compensation performance consists of benefit and efficiency, and used the projection pursuit and super-efficiency SBM-DEA models to measure the eco-compensation benefit and efficiency of 101 cities in the Yangtze River Economic Belt from 2010 to 2021 and to analyze their spatial and temporal patterns. Finally, we used the coupling coordination degree model to reveal the coupling and coordinated features of eco-compensation performance. The results showed that the temporal trends of eco-compensation benefit and efficiency were “W” and “U” shaped. The eco-compensation benefit in eastern or mega-cities was the highest, whereas the eco-compensation efficiency in western or small/medium-sized cities was the highest. Coupling coordination degree of eco-compensation performance was in the coordinated development stage from 2010 to 2012, with a concentration of agglomeration effects in the central region. It was in the transition/adjustment stage from 2013 to 2020, with low-value areas concentrated and scattered high-value areas, and smaller regional differences. It was in the coordinated development stage in 2021, with a clear agglomeration effect in the eastern region. Cities in the Yangtze River Economic Belt should incorporate the eco-compensation performance coupling coordination mechanism into their optimized eco-compensation policy plans based on the stage of coordinated development, to achieve their environmental improvement goals.
    Remembering the Ancestor
    The neglected giant Tchen-Ngo Liou:The enlightenment of his dynamic geobotany theory to current studies in vegetation ecology and biodiversity
    ZHANG Jian, HAO Zhanqing
    2024, 35(9):  2631-2638.  doi:10.13287/j.1001-9332.202409.034
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    Prof. Tchen-Ngo Liou is one of the founders of China's botany, geobotany, and forest ecology. Theory of dynamic geobotany, established by Prof. Liou, can track back from his doctoral work in Alps in France, and was developed based on his long-term field works in northeast, southeast, north, northeast parts of China, India, North Korea and other regions. In the short course on dynamics geobotany in 1962, he gave a series of lectures which formed a synthesized system. The key elements of this theory are the comprehensive review and critical thinking on climax theory of vegetation science and community succession. Prof. Liou has applied this theory into the establishment of artificial vegetation, the improvement of natural vegetation, forest harvesting and regeneration, and the prevent and control of desertification in China. Here, we gave a short summary about this theory, and discussed its potential influence on important topics in vegetation ecology and biodiversity science, including mountain biodiversity, natural forest conservation, forest management, global change, and vegetation classification.