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    15 February 2023, Volume 34 Issue 2
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    Opinion of the Editor-in-Chief
    Ecosystem principles and main issues in regional ecological restoration and environmental governance in China
    YU Guirui, HAO Tianxiang, YANG Meng
    2023, 34(2):  289-304.  doi:10.13287/j.1001-9332.202302.030
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    Modern ecology is an analytical method and philosophical concept to solve major resource, environmental and ecological issues encountered during global sustainable development. In the long-term development processes, ecology constantly absorbed and integrated knowledge from related disciplines, forms a system of modern ecology and ecosystem science that closely related to climate system, biological system and socio-economic system, and raises ecosystem principles that directly support the practices of regional ecological restoration and environmental governance. The national needs in the new stage have given ecology a new mission. It is urgently needed to summarize and condense the principles of macro-ecosystems and apply them to regional ecological restoration and environmental governance with the aim to promote the high-quality development of society and economy. Against the background of the multiple severe challenges faced by global sustainable development, we comprehensively elaborated the logics and scientific mission of ecosystem science, organized the principle system of ecosystem science related to ecological restoration and environmental governance, and discussed major academic problems in regional ecological restoration and environmental governance of China. Finally, we emphasized that China has several regional macro-ecosystems of global significances. Conducting theoretical and practical research on macro-ecosystem is not only an urgent need for the construction of ecological civilization, but also the forefront of ecosystem science research, which is expected to make new contributions to theory development of ecology, and global ecological and environmental governance.
    Original Articles
    Effects of canopy density on understory plant diversity in Robinia pseudoacacia plantations on the Loess Plateau of China
    WANG Yirui, WANG Yanhui, DUAN Wenbiao, LI Pingping, YU Pengtao, ZHEN Li, LI Zhixin, SHANG Huijun
    2023, 34(2):  305-314.  doi:10.13287/j.1001-9332.202302.008
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    To solve the problems of understory plant shortage and biodiversity reduction caused by high tree density of Robinia pseudoacacia plantations on the Loess Plateau in northwest China, we analyzed the data collected by field survey and from literatures. We used the upper boundary line method to examine the impacts of canopy density on understory plant diversity. Based on field survey at the Guanshan Forest Farm of Jingchuan County of Gansu Pro-vince, the species number of understory plants in R. pseudoacacia plantations was higher than that in natural grassland (91 vs. 78). The dominant species varied with canopy density, which was completely different from that of natural grassland. A comprehensive analysis of both literature data and field survey data showed that, when mean annual precipitation (MAP) <550 mm or >550 mm, the increases in canopy density first led to a stable understory plant coverage and then a sharp or slight decrease, and understory plant biomass showed a sharp and continuous decrease or a slight increase and then decrease. Understory plant species richness and other diversity indices (Shannon, Simpson, and Pielou indices) first increase and then decrease, with bigger variation range under lower MAP. In all, the characteristics (coverage, biomass and species diversity, etc.) of understory plant community in R. pseudoacacia plantations were strongly affected by canopy density, with higher sensitivity under lower MAP. There was a general threshold range of canopy density of 0.45-0.6. When canopy density was above or below this thre-shold range, it would lead to a rapid decrease of the most characteristics of understory plant community. Therefore, keeping canopy density within the rational range of 0.45-0.6 in the management of R. pseudoacacia plantations is the key to make all the above-mentioned understory plant characteristics at relatively high level.
    Bark characteristics of Betula platyphylla at different heights and their environmental interpretation under fire disturbance
    SUN Xingyue, ZHANG Yujian, QIN Qianqian, BAI Yansong, LIU Yanhong
    2023, 34(2):  315-323.  doi:10.13287/j.1001-9332.202301.006
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    Betula platyphylla is a pioneer tree species after fire disturbance in forest communities in the Daxing'an Mountains of China. Bark, as an external structure of vascular cambium, plays an important role in protection and transport. To understand the survival strategy of B. platyphylla under fire disturbance, we analyzed the functional traits of inner and outer bark of B. platyphylla at different heights (0.3, 0.8 and 1.3 m) in natural secondary forest of the Daxing'an Mountains. We further quantified the explanation of three environmental factors (stand, topography and soil) and identified the key factors driving the changes in those traits. The results showed that the relative inner bark thickness of B. platyphylla in burned plot followed an order of 0.3 m (4.7%) > 0.8 m (3.8%) > 1.3 m (3.3%), which was 28.6%, 14.4% and 3.1% higher than that in the unburned plot (30-35 years without fire disturbance), respectively. The relative outer bark thickness and the relative total bark thickness showed similar pattern with tree height. Fire had different effects on other bark functional traits of B. platyphylla. The inner bark density of B. platyphylla in burned plot was significantly decreased by 3.8%-5.6% and water content was significantly increased by 11.0%-12.2%, compared with that in unburned plot across the three heights. However, the contents of carbon, nitrogen, and phosphorus in inner (or outer) bark were not significantly affected by fire. Further, the mean inner bark nitrogen content at 0.3 m in burned plot (5.24 g·kg-1) was significantly higher than that at the other two heights (4.56-4.76 g·kg-1). Environmental factors explained 49.6% and 28.1% of the total variation in inner and outer bark functional traits, respectively, with the highest single explanation (18.9% or 9.9%) of soil factors. Diameter at breast height was the most important factor affecting the growth of inner and outer barks. In summary, fire affected survival strategies of B. platyphylla (e.g., increased the resource allocation to the base bark) via changing the environment factors, which would help improve their defense ability under fire disturbance.
    Plasticity and coordination of branch and leaf traits in Ulmus pumila along a precipitation gradient
    ZHAO Yuhang, GONG Xuewei, NING Qiurui, ZHANG Chi, DUAN Chunyang, HAO Guangyou
    2023, 34(2):  324-332.  doi:10.13287/j.1001-9332.202302.007
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    We compared branch and leaf functional traits of Ulmus pumila trees inhabiting different climatic zones (sub-humid, dry sub-humid and semi-arid zones), aiming to investigate the role of trait plasticity and coordination in tree acclimation to different water conditions. The results showed that leaf drought stress of U. pumila increased significantly from sub-humid to semi-arid climatic zones, as indicated by a 66.5% reduction in leaf midday water potential. In the sub-humid zone with less severe drought stress, U. pumila had higher stomatal density, thinner leaves, larger average vessel diameter, pit aperture area and membrane area, which could ensure the higher potential water acquisition. With the increases of drought stress in dry sub-humid and semi-arid zones, leaf mass per area and tissue density increased, and the pit aperture area and membrane area decreased, indicating stronger drought tolerance. Across different climatic zones, the vessel and pit structural characteristics were strongly coordinated, while a trade-off between xylem theoretical hydraulic conductivity and safety index was found. The plastic adjustment and coordinated variation of anatomical, structural and physiological traits may be an important mechanism contributing to the success of U. pumila in different climate zones with contrasting water environments.
    Construction and precision analysis of individual tree biomass model of Larix olgensis considering random effects
    GAO Yu, XIE Longfei, HAO Yuanshuo, DONG Lihu
    2023, 34(2):  333-341.  doi:10.13287/j.1001-9332.202302.004
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    Accurate estimation of forest biomass in China is crucial for the study of carbon cycle and mechanisms underlying carbon storage in global terrestrial ecosystems. Based on the biomass data of 376 individuals of Larix olgensis in Heilongjiang Province, we used seemingly unrelated regression (SUR) method to build a univariate biomass SUR model with diameter at breast height as the independent variable and considering the random effect at the sampling site level. Then, a seemingly unrelated mixed effect (SURM) model was constructed. As the calculation of random effects of SURM model did not require the empirically measured values of all dependent variables, we analyzed the deviations from the following four types in detail: 1) SURM1, the random effect was calculated according to the measured biomass of stem, branch and foliage; 2) SURM2, the random effect was calculated according to the measured value of tree height (H); 3) SURM3, the random effect was calculated according to the measured crown length (CL); 4) SURM4, the random effect was calculated according to the measured values of H and CL. The results showed that the fitting effect of branch and foliage biomass models was improved significantly after considering the horizontal random effect of the sampling plot, with R2 being increased by more than 20%. The fitting effect of stem and root biomass models were improved slightly, with R2 being increased by 4.8% and 1.7%, respectively. When using five randomly selected trees to calculate the horizontal random effect of the sampling plot, the prediction performance of SURM model was better than that of SUR model and SURM model considering only fixed effects, especially SURM1 model (MAPE% of stem, branch, foliage and root was 10.4%, 29.7%, 32.1% and 19.5%, respectively). Except for SURM1 model, the deviation of SURM4 in predicting stem, branch, foliage and root biomass was smaller than that of SURM2 and SURM3 models. In actual prediction, although the prediction accuracy of SURM1 model was the highest, it needed to measure aboveground biomass of several trees, and the use cost was relatively high. Therefore, the SURM4 modelled on measured H and CL was recommended to predict the standing tree biomass of L. olgensis.
    Height to diameter ratio model of Larix gmelinii in Daxing'anling Mountains, China
    SHAO Weiwei, DONG Lingbo
    2023, 34(2):  342-348.  doi:10.13287/j.1001-9332.202302.005
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    Based on data from 56 plots of natural Larix gmelinii forest in Cuigang Forest Farm of Daxing'anling Mountains, we constructed the height to diameter ratio (HDR) model of L. gmelinii with exponential decay function as the base model. We used the tree classification as dummy variables and the method of reparameterization. The aim was to provide scientific evidence for evaluating the stability of different grades of L. gmelinii trees and stands in Daxing'anling Mountains. The results showed that except for diameter at breast height, the dominant height, dominant diameter, individual tree competition index all had significant correlations with the HDR. The involvement of these variables significantly improved the fitted accuracy of the generalized HDR model, with the adjustment coefficients, root mean square error and mean absolute error being 0.5130, 0.1703 m·cm-1 and 0.1281 m·cm-1, respectively. When the tree classification as a dummy variable was added to parameters 0 and 2 of the generalized model, the fitting effect of the model was further improved. The three above-mentioned statistics were 0.5171, 0.1696 m·cm-1 and 0.1277 m·cm-1, respectively. Through comparative analysis, the generalized HDR model with tree classification as dummy variable had the best fitting effect, which was superior to the basic model, and had higher prediction precision and adaptability.
    Altitudinal pattern and driving factors of soil fungal community in the tropical forest of Jianfengling, Hai-nan, China
    LIN Sinuo, SU Yangui, LYU Kun, WU Guopeng, HUANG Zhengyi, WANG Jingjing, HUANG Gang
    2023, 34(2):  349-358.  doi:10.13287/j.1001-9332.202302.033
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    Fungi are an important group of soil microorganisms. Exploring the altitudinal pattern and driving factors of fungal composition and diversity is an important topic in the field of biodiversity and ecosystem function. We employed the Illumina high-throughput sequencing technology to investigate the variation and environmental control of fungal α-diversity and β-diversity at the topsoil (0-20 cm) and subsoil (20-40 cm) across an altitudinal gra-dient of 400-1500 m in a tropical forest of Jianfengling Nature Reserve. The results showed that Ascomycota and Basidiomycota dominated soil fungal community, reaching a relative abundance of more than 90%. Fungal α-diversity at the topsoil exhibited no obvious altitudinal pattern, and that of the subsoil decreased with the increases in altitude. Higher fungal α-diversity was observed in the topsoil. Soil fungi β-diversity was significantly affected by altitude. Morover, temperature was the driving force of the altitude pattern of fungi β-diversity. The similarity of fungal community decreased significantly with the increases in geographical distance, but did not change with the increases in environmental distance. The similarity of rare phyla (Mortierellomycota, Mucoromycota and Rozellomycota) was significantly lower than that of rich phyla (Ascomycota and Basidiomycota), indicating that diffusion restriction determined the differentiation of fungal community structure along the altitude gradient. Our study demonstrated that the diversity of soil fungal community was affected by altitude. The rare phyla, rather than rich phyla, determined the altitudinal variation of fungi β-diversity in Jianfengling tropical forest.
    Effects of target tree management of Pinus massoniana plantation on soil nematode community structure at different soil depths
    YU Anwei, HU Wenting, WU Siying, YIN Haifeng, FAN Chuan, LI Xianwei
    2023, 34(2):  359-368.  doi:10.13287/j.1001-9332.202302.010
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    To understand soil nematode community structure at different soil depths and its responses to target tree management, we collected soil samples (0-10, 10-20, and 20-50 cm) and litter samples from the target tree management plots and control plots of Pinus massoniana plantation and analyzed community structure, soil environmental factors, and their relationship. The results showed that target tree management increased the abundance of soil nematodes, with the most significant effect at a depth of 0-10 cm. The highest abundance of herbivores was found in the target tree management treatment, while that of bacterivores was found in the control. Compared with the control, Shannon diversity index, richness index, maturity index of nematodes at 10-20 cm soil layer and Shannon diversity index at 20-50 cm soil layer of target trees were significantly improved. According to the results of Pearson correlation and redundancy analysis, soil pH, total phosphorus, available phosphorus, total potassium, and available potassium were the main environmental factors affecting community structure and composition of soil nematodes. In general, target tree management was conducive to the survival and development of soil nematodes and promoted the sustainable development of P. massoniana plantations.
    Characteristics and source of soil condensation water in Guanzhong Plain, China
    JIA Zhifeng, CHEN Danzi, WANG Zhi, LIU Pengcheng, LIU Peng, YAO Congcong
    2023, 34(2):  369-376.  doi:10.13287/j.1001-9332.202302.020
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    We determined the quantity and source of soil water condensation versus atmospheric vapor condensation in Guanzhong Plain and explored their role in water balance, using three different types of hand-made micro-lysimeters (open-ends, top-seal, and bottom-seal designs). Field monitoring of the vapor condensation process was carried out from late September to late October in 2018 and from March to May in 2019 using the weighing method. Results showed that during the monitoring period, condensation occurred every day without rainfall event. The maximum daily condensation for the open-ends, top-seal and bottom-seal designs were 0.38, 0.27 and 0.16 mm, respectively, indicating that vapor flow in soil pores was the main source of soil water condensation, and that the measurement using the open-ended micro-lysimeter could faithfully reflect the amount of condensation in Guanzhong Plain. During the monitoring period, total soil water condensation reached 14.94 mm, accounting for 12.8% of the precipitation in the same period (116.4 mm), and the ratio of atmospheric vapor condensation to soil vapor condensation was 0.59:1.
    Spatial variations and the key driving factors of soil losses on dolomite slopes
    MENG Qingmei, FU Zhiyong, DENG Yusong, CHEN Hongsong
    2023, 34(2):  377-386.  doi:10.13287/j.1001-9332.202302.023
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    We selected a typical dolomite slope and set up three micro-plots (projection length was 2 m, width was 1.2 m) on the upper, middle, and lower slopes to analyze the variations of soil losses and the key influencing factors during two hydrological years (2020-2021). The results showed that soil losses at different slope positions on dolomite slopes followed an order of semi-alfisol in lower slopes (386 g·m-2·a-1) > inceptisol in middle slopes (77 g·m-2·a-1) > entisol in upper slopes (48 g·m-2·a-1). Downward along the slope, the positive correlation gradually increased between soil losses and surface soil water content, as well as rainfall, while it gradually decreased with the maximum 30 min rainfall intensity. The meteorological factors affecting soil erosion on the upper, middle and lower slopes were the maximum 30 min rainfall intensity, precipitation, average rainfall intensity and surface soil water content, respectively. Soil erosion processes on upper slopes were mainly driven by raindrop splash erosion and infiltration-excess runoff, while that on lower slopes were mainly driven by saturation-excess runoff. The volume ratio of fine soil in the soil profile was the key factor of soil losses on dolomite slopes, with an explanation rate of 93.7%. The lower slope was the key site of soil erosion in the dolomite slopes. Subsequent rock desertification management should be based on the erosion mechanism of different slope positions, while control measures should be arranged according to local conditions.
    Development law of soil cracks in karst peak-cluster depressions under dry and wet alternations
    LUO Shuyu, DENG Yusong, CHEN Hongsong, WANG Jinyue, LIAO Dalan
    2023, 34(2):  387-395.  doi:10.13287/j.1001-9332.202302.018
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    In an experiment with alternating dry and wet conditions of soil in cultivated land, orchards and forest lands with limestone and dolomite in karst peak depression, combined with digital image processing technology, we investigated the development law of soil surface cracks under alternating dry and wet condition. The results showed that with the alternation of wet and dry, the average width of cracks decreased at a fast-slow-slower rate, with an order of limestone > dolomite under the same land use, and orchard > cultivated land > forest soil under the same soil-forming parent rock. In the first four dry and wet alternations, the degrees of soil fragmentation and connectivity were higher in dolomite development than in limestone, with significant differences in fracture development rose diagrams. In the subsequent cycles, soil fragmentation of most samples increased, the difference dominated by parent rock gradually decreased, the crack development rose diagram converged, and the connectivity showed the pattern of forest land > orchard > cultivated land. After the fourth cycle, the alternations of dry and wet seriously damaged soil structure. The physical and chemical properties of capillary porosity and non-capillary tube porosity were dominant in the development of cracks before that, but it was more dependent on the organic matter content and the sand composition after that.
    Characteristics of nitrogen wet deposition and flux with runoff during the spring freeze-thaw period in permafrost region watershed of Da Hinggan Mountains, Northeast China
    CAI Yushan, WANG Wenqian, XIAO Xiang, LANG Minghan, DUAN Liangliang
    2023, 34(2):  396-404.  doi:10.13287/j.1001-9332.202302.014
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    Nitrogen (N) transport is an important component of a watershed's nutrient cycle, which has significant impacts on global nitrogen cycle. In this study, we measured precipitation and daily stream N concentrations during the spring freeze-thaw period (April 9-June 30, 2021) in a small forest watershed (Laoyeling) in the permafrost region of Da Hinggan Mountains to calculate wet N deposition and stream N flux. The results showed the wet deposition fluxes of ammonium, nitrate, and total N were 695.88, 448.72 and 1947.35 g·hm-2, respectively, while the stream N fluxes were 86.37, 186.87 and 1160.78 g·hm-2, respectively over the whole study period. Precipitation was the main influencing factor of wet N deposition. During the freeze-thaw cycle period (April 9 to 28), the stream N flux was dominated by runoff and was affected by soil temperature through its influence on runoff. During the melting period (April 29 to June 30), it was affected by both runoff and runoff N concentration. The stream total N flux accounted for 59.6% of wet deposition during the study period, which indicated that the watershed had a strong N fixation potential. These findings would have important implications for understanding the impact of climate change on N cycling in permafrost watersheds.
    Effects of nitrogen input on N2O production and enzyme activity in Luoshijiang Wetland sediments, China
    LI Jiachen, HOU Lei, WANG Yanxia, LIANG Qibin
    2023, 34(2):  405-414.  doi:10.13287/j.1001-9332.202302.012
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    We examined the effects of nitrate (NO3--N) and ammonium (NH4+-N) input at different concentrations (0, 1, 5 and 25 mg·kg-1) on N2O production rate from the surface sediment (0-5 cm) of Luoshijiang Wetland, located upstream from Lake Erhai. The contribution of nitrification, denitrification, nitrifier denitrification, and other factors to the N2O production rate in sediments was studied by the inhibitor method. The relationships between N2O production and the activities of hydroxylamine (HyR), nitrate (NAR), nitric oxide (NOR), and nitrous oxide (NOS) reductases in sediments were analyzed. We found that NO3--N input significantly increased total N2O production rate (1.51-11.35 nmol·kg-1·h-1), which led to N2O release, whereas NH4+-N input decreased that (-0.80 to -0.54 nmol·kg-1·h-1), causing N2O absorption. NO3--N input did not change the dominant roles of nitrification and nitrifier denitrification in N2O production in sediments, but increased the contributions of these two factors to 69.5% and 56.5%, respectively. The NH4+-N input significantly changed N2O gene-ration process, and the nitrification and nitrifier denitrification changed from N2O release to uptake. There was a positive correlation between total N2O production rate and NO3--N input. NO3--N input significantly increased NOR activity and decreased NOS activity, thereby promoting N2O production. The total N2O production rate in sediments was negatively correlated with NH4+-N input. NH4+-N input significantly increased the activities of HyR and NOR, decreased NAR activity, and inhibited N2O production. Nitrogen inputs with different forms and concentrations changed the degree of contribution and mode of N2O production by affecting enzyme activities in sediments. NO3--N input significantly promoted N2O production, acting as a source of N2O, while NH4+-N input inhibited N2O production, resulting in an N2O sink.
    Mangrove forest fragmentation and its ecological service value in Tongming Sea of Zhanjiang, Guangdong, China during 2000-2018
    TANG Daobin, XIN Cunlin, CHEN Ning, LIU Xiangjun, ZHANG Liang
    2023, 34(2):  415-422.  doi:10.13287/j.1001-9332.202302.022
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    Mangrove forest has high ecological service value. Due to the destruction of human activities, mangrove forest has been greatly reduced and seriously fragmented, resulting in huge losses in the ecological service value. In this study, taking the mangrove forest in Tongming Sea of Zhanjiang as an example, we analyzed the characteristics of mangrove forest fragmentation and its ecological service value based on high-resolution distribution data from 2000 to 2018, and put forward suggestions for mangrove restoration. The results showed that the area of mangrove forest decreased by 1415.33 hm2 from 2000 to 2018, and the reduction rate (78.63 hm2·a-1) ranked the first among mangrove forests in China. The patch number and average patch size of mangrove forest changed from 283 and 1002 hm2 in 2000 to 418 and 341 hm2 in 2018, respectively. The largest patch in 2000 became twenty-nine small patches in 2018, with obvious fragmentation and poor connectivity. The total edge, edge density and mean patch size of mangrove forest were the main influencing factors for its service value. The landscape ecological risk of mangrove forest increased, the fragmentation rate in Huguang Town Region and the middle of the west coast of Donghai Island was faster than that in the other regions. During the study, the mangrove itself sevice value decreased by 1.35 billion yuan, and its ecosystem service value decreased by 1.45 billion yuan, especially for the significant reduction of regulation and support services. The mangrove forest in Tongming Sea of Zhanjiang urgently need to be restored and protected. It is necessary to implement protection and regeneration plans for vulnerable mangrove patches (such as ‘Island'). The effective methods were to return the pond to forest and beach afforestation. In summary, our results could provide important references for local government to carry out mangrove forest restoration and protection, and realize the sustainable development of mangrove forest.
    Trade-off and synergistic relationship of land use function and zoning in coastal saline-alkali area: A case study of Huanghua, Hebei, China
    YE Jing, GUAN Yu, CHEN Ying
    2023, 34(2):  423-432.  doi:10.13287/j.1001-9332.202302.024
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    Analyzing the multi-functional evolution of land use can help solve the confusion in the relationship between land use functions and unreasonable land use structure. From the perspective of ecological security, we integrated multi-source data on the basis of quantitative evaluation of various land use functions, and used the method of combining band set statistical model and bivariate local Moran's I to measure the dynamics of trade-off and synergy relationship between land use functions in Huanghua, Hebei from 2000 to 2018, and divided land use functional areas. The results showed that production function (PF) and life function (LF) showed the alternate evolution of the trade-off and synergy relationship, which mostly occured in the central urban areas such as the southern region. The PF and ecological function (EF) was mainly based on the synergistic relationship, which mostly occured in the traditional agricultural areas in the west region. The degree of synergy between LF and water conservation function (WCF) first increased and then decreased, with obvious regional differences in the degree of synergy. LF and soil health function (SHF)/ biological diversity function (BDF) was dominated by trade-off relationship, which mostly occured in western saline-alkali land and coastal areas. The performance of multiple EF was the mutual transformation of trade-offs and synergies. The land space of Huanghua could be divided into six types of areas, agricultural production area, urban development core area, urban and rural optimized development area, renovation and improvement area, nature reserve area, and ecological restoration area. There were differences in the dominant mode of land function and optimization strategies in each area. This research could provide scientific refe-rence for clarifying land function relationship and optimizing land spatial development pattern.
    Differentiation of grazing pressure expressions and its applicable scenarios
    GU Changjun, ZHANG Yili, LIU Linshan, WEI Bo, GONG Dianqing, CUI Bohao
    2023, 34(2):  433-441.  doi:10.13287/j.1001-9332.202302.003
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    High intensity grazing is considered as an important cause of grassland degradation. Numerous studies have explored effects of grazing activities on grassland ecosystems. Nevertheless, the research regarding grazing activity itself, especially the quantification methods and gradient division of grazing pressure, is relatively insufficient. Based on a total of 141 Chinese and English papers containing keywords such as ‘grazing pressure', ‘grazing intensity', and giving specific quantification methods and classification standards, we sorted out the definition, quantification methods, and grading standards of grazing pressure. The results showed that the definition of grazing pressure in current studies could be classified into two categories: considering the number of livestock carried in the current grassland ecosystem only from the perspective of the amount of grazing livestock; or considering the impacts or consequences on grassland ecosystems. Small-scale manipulative experiments mainly quantified and divided gra-zing pressure by controlling the number of livestock, grazing duration, grazing area, etc. Ecosystem responses to grazing activities were also converted by the above indicators, while the large-scale data spatialization method only considered number of livestock per unit area. The method of remote sensing inversion focused on ecosystem responses, that is, the impacts of grazing activities on grasslands, and it was difficult to separate the role of climatic factors. The quantitative standards of grazing pressure in different grassland types were quite different, even in the same grassland type, and such difference was directly related to grassland productivity.
    Effects of combined application of biochar and nitrogen fertilizer on soil quality of summer maize-winter wheat system
    SHI Duopeng, YE Zizhuang, LI Huitong, LYU Shenqiang, WANG Linquan, ZHOU Chunju
    2023, 34(2):  442-450.  doi:10.13287/j.1001-9332.202302.013
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    The effects of nitrogen fertilizer and biochar on topsoil quality in the drylands of northwest China were studied in field trials for two years. A split plot design with two factors was adopted, with five nitrogen rates (0, 75, 150, 225 and 300 kg N·hm-2) as main plots, and two rates of biochar (0 and 7.5 t·hm-2) as submain plots. We collected soil samples at 0-15 cm depth after two years of winter wheat-summer maize rotation and measured physical, chemical, and biological properties. The minimum data set (MDS) was established by using principal component analysis and correlation analysis to analyze the responses of soil quality to nitrogen fertilizer and biochar addition. The results showed that the combined application of nitrogen fertilizer and biochar could improve soil physical properties, increase macroaggregate content, reduce soil bulk density, and increase soil porosity. Both fertilizer application and biochar application had a significant effect on soil microbial biomass carbon and nitrogen. The application of biochar could improve soil urease activity and the contents of soil nutrients and organic carbon. Six out of 16 indicators (urease, microbial biomass carbon, total phosphorous, total nitrogen, pH, and available potassium) relating to soil quality were used to construct MDS, and soil quality index (SQI) was calculated. The variation range of SQI was 0.14-0.87, with that of 225 and 300 kg N·hm-2 nitrogen application combined with biochar application being significantly higher than other treatments. Soil quality could be significantly improved by application of nitrogen fertilizer and biochar. Interactive effect was observed, which was particularly stronger under high nitrogen application rate.
    Effects of phosphorus application rates on photosynthetic and senescence characteristics and yield of diffe-rent stems and tillers of wheat under water-saving supplementary irrigation
    HUI Kaishan, WU Zhaohan, ZHANG Yongli
    2023, 34(2):  451-462.  doi:10.13287/j.1001-9332.202302.015
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    To clarify the physiological mechanism underlying grain yield of different stems and tillers of wheat in response to phosphorus application under water-saving supplementary irrigation and to determine the suitable phosphorus fertilization rate, we set water-saving supplementary irrigation (irrigation to the soil water content of 0-40 cm soil layer shall be supplemented to 70% of the field saturation capacity during the jointing stage and flowering stage, W70) and no irrigation (W0) on wheat variety ‘Jimai 22', and three phosphorous application rates, low (90 kg P2O5·hm-2, P1), medium (135 kg P2O5·hm-2, P2), and high (180 kg P2O5·hm-2, P3), with no phosphorus application as the control (P0). We examined the photosynthetic and senescence characteristics, the grain yield of the different stems and tillers, as well as water and phosphorus use efficiency. The results showed that under both water-saving supplementary irrigation and no irrigation, the relative content of chlorophyll, net photosynthetic rate, sucrose content, sucrose phosphate synthase activity, superoxide dismutase activity, and soluble protein content of flag leaf of the main stem and tillers Ⅰ and Ⅱ (first degree tillers arising from axils of the 1st and 2nd true leaf of the main stem) under P2 were significantly higher than those under P0 and P1, which contributed to the higher grain weight per spike of main stem and tillersⅠ and Ⅱ, but did not differ from P3. Under water-saving supplementary irrigation, P2 increased grain yield of main stem and tillers Ⅰ, Ⅱ and Ⅲ (first degree tillers arising from axils of the 3rd true leaf of the main stem) compared with that under P0 and P1, and increased grain yield of tillers Ⅱ and Ⅲ compared with P3. Grain yield per hectare under P2 was 49.1%, 30.5% and 8.9% higher than that under P0, P1 and P3, respectively. Similarly, water use efficiency and phosphorus fertilizer agronomic efficiency under P2 were the highest among the phosphorous treatments under water-saving supplementary irrigation. Under no irrigation condition, P2 increased grain yield of main stem and tillers Ⅰ and Ⅱ compared with P0 and P1, yet grain yield of tiller Ⅱ was higher than that of P3. Furthermore, under P2, the grain yield per hectare, water use effi-ciency, and phosphorus fertilizer agronomic efficiency were higher than those under P0, P1 and P3 under no irrigation. Under each phosphorous application rate, grain yield per hectare, phosphorus fertilizer agronomic efficiency, and water use efficiency of water-saving supplementary irrigation treatment were higher than those of no irrigation treatment. In conclusion, medium phosphorus application rate (135 kg·hm-2) under water-saving supplementary irrigation would be the optimal treatment for both high grain yield and efficiency under the experimental condition.
    Hyperspectral monitoring on proline content in winter wheat under water stress
    XIE Yongkai, SONG Jinyao, LIU Min, MENG Wanzhong, FENG Meichen, WANG Chao, YANG Wude, QIAO Xingxing, YANG Chenbo
    2023, 34(2):  463-470.  doi:10.13287/j.1001-9332.202302.021
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    Frequent occurrence of drought disaster will seriously affect the growth and development of winter wheat (Triticum aestivum). We set different water stress treatments (80%, 60%, 45%, 35%, 30% of field water capacity) to simulate the severity of drought disaster. We measured free proline content (Pro) of winter wheat, and investigated the responses of Pro to canopy spectral reflectance under water stress. Three methods, i.e., correlation analysis and stepwise multiple linear regression (CA+SMLR), partial least squares and stepwise multiple linear regression (PLS+SMLR), and successive projections algorithm (SPA) were used to extract the hyperspectral cha-racteristic region and characteristic band of proline. Furthermore, partial least square regression (PLSR) and multiple linear regression (MLR) methods were used to establish the predicted models. The results showed that Pro content of winter wheat was higher under water stress, and that the spectral reflectance of canopy changed regularly in different bands, indicating that Pro content of winter wheat was sensitive to water stress. The content of Pro was highly correlated with the red edge of canopy spectral reflectance, with the 754, 756 and 761 nm bands being sensitive to Pro change. The PLSR model performed good, followed by the MLR model, both showing good predictive ability and high model accuracy. In general, it was feasible to monitor Pro content of winter wheat by hyperspectral technique.
    Soil carbon and nitrogen sequestration and associated influencing factors in a sustainable cultivation system of fruit trees intercropped with cover crops
    LI Wenhui, LIN Yanmin, NAN Xiongxiong, WANG Fang, ZHU Lizhen
    2023, 34(2):  471-480.  doi:10.13287/j.1001-9332.202302.017
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    We comprehensively quantified the influence of cover crops on soil carbon and nitrogen storage in Chinese orchards by a meta-analysis based on the literature published during 1990 to 2020. The factors influencing soil carbon and nitrogen storage were also analyzed. The results showed that compared with clean tillage, soil carbon and nitrogen storage under the cultivation of cover crops considerably increased by 31.1% and 22.8%, respectively. Intercropping legumes enhanced soil organic carbon storage by 4.0% and total nitrogen storage by 3.0% compared with non-legumes. The effect of mulching duration was most prominent at 5-10 years, with 58.5% and 32.8% increases in soil carbon and nitrogen storage, respectively. The largest increase in soil carbon and nitrogen storage (32.3% and 34.1%, respectively) occurred in areas with low initial organic carbon (<10 g·kg-1) and total nitrogen (<1.0 g·kg-1). In addition, suitable mean annual temperature (10-13 ℃) and precipitation (400-800 mm) markedly contributed to soil carbon and nitrogen storage in the middle and lower reaches of the Yellow River. The findings indicated that multiple factors influence the synergistic changes in soil carbon and nitrogen storage in orchards, while intercropping with cover crops is an effective strategy for enhancing soil carbon and nitrogen sequestration.
    Effects of partial substitution of chemical fertilizer with organic fertilizer on arbuscular mycorrhizal fungal community of Mangifera indica
    JIANG Shangtao, LI Han, PENG Haiying, MEI Xinlan, CHEN Tingsu, XU Yangchun, DONG Caixia, SHEN Qirong
    2023, 34(2):  481-490.  doi:10.13287/j.1001-9332.202302.011
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    Nutrient enrichment caused by fertilization would reduce the diversity of arbuscular mycorrhizal fungi (AMF). To explore whether partial substitution of chemical fertilizer with organic fertilizer would alleviate the negative effects of nutrient enrichment on AMF, we conducted a two-year mango (Mangifera indica) field experiment to examine the effects of different fertilization regimes on AMF communities in roots and rhizospheric soils by using high-throughput sequencing. The treatments included chemical-only fertilization (control), and two kinds of organic fertilizer (commercial organic fertilizer and bio-organic fertilizer) with replacing 12% (low) and 38% (high) chemical fertilizer. The results showed that under equivalent nutrient input, partial substitution of chemical fertilizer with organic fertilizer had positive effects on the yield and quality of mango. The application of organic fertilizer could effectively increase AMF richness. AMF diversity was significantly positively correlated with some indices of fruit quality. Compared with chemical-only fertilization, high replacement ratio of organic fertilizer could significantly change root AMF community, but did not affect AMF community in the rhizospheric soil. Bio-organic fertilizer could enrich more AMF species and form a more complex AMF co-occurrence network than commercial organic fertilizer. In all, replacing chemical fertilizer with a high proportion of organic fertilizer could improve the yield and quality of mango while maintain AMF richness. The changes of AMF community caused by organic fertilizer substitution pre-ferably occurred in roots rather than soils.
    Comparison on the stormwater runoff effects of roof greening in different urban functional areas
    LING Ziyao, PENG Lihua, WEN Hui
    2023, 34(2):  491-498.  doi:10.13287/j.1001-9332.202303.019
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    Global climate change and the expansion of impervious surface in urban areas have increased the risk of urban flood. As a measure with low impact development (LID), roof greening can effectively reduce stormwater runoff, serving as the first barrier to prevent rainwater from entering the urban drainage system. We used the CITYgreen model to simulate and analyze the impacts of roof greening on hydrological parameters (e.g., surface runoff) in the new and old residential areas and the commercial areas in Nanjing City, and further investigated the variations in stormwater runoff effects (SRE) among these functional areas. We compared the SRE between different green roof types, and between green roofs and ground-level green spaces. The results showed that the proportion of permeable surface would increase by 28.9%, 12.5% and 49.2% respectively in the old residential area, new residential area and commercial area if all building roofs were greened. In a rainfall event with a return period of two years and a duration of 24 hours (precipitation=72 mm), the implementation of roof greening in all buildings in the three sampling areas could reduce surface runoff by 0-19.8% and reduce peak flow by 0-26.5%. The reductions in runoff by green roofs could be translated to a rainwater storage capacity of 223-2299 m3. The commercial area had the highest SRE by installing green roofs, followed by the old residential area, while the new residential area had the lowest SRE. The rainwater storage volume by per unit area of extensive green roof was about 78.6%-91.7% that of the intensive green roof. The storage capacity by per unit area of green roof was 31%-43% of that in the ground-level greenery. The results would provide scientific references for the site selection, sustainable design and incentive development of roof greening from the perspective of stormwater management.
    Influencing factors and scenario forecasting of carbon emissions in Liaoning Province, China
    NIU Le, ZHAGN Lixia, XI Fengming, WANG Jiaoyue
    2023, 34(2):  499-509.  doi:10.13287/j.1001-9332.202302.001
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    Liaoning is a province with large energy consumption and carbon emissions. Management of carbon emissions in Liaoning Province is crucial to realizing China's carbon peaking and carbon neutrality goals. To clarify the driving factors and trends of carbon emissions in Liaoning Province, we analyzed the impacts of six factors on carbon emissions in Liaoning Province through STIRPAT model based on carbon emission data from 1999 to 2019. The impact factors included population, urbanization rate, per-capita GDP, secondary industry ratio, energy consumption per unit GDP, and coal consumption ratio. Nine forecasting scenarios with three economic and population growth models and three emission reduction models were set up, and their carbon emission trends under the above nine forecasting scenarios were predicted. The results showed that the main driving factor of carbon emissions in Liaoning Province was per-capita GDP, and that the main inhibitor was energy consumption per unit GDP. The carbon peak year in Liaoning Province would fluctuate between 2020 and 2055 under the nine forecasting scenarios, with peak values ranging from 544 to 1088 million tons CO2. The medium economic development growth and high carbon emission reduction scenario would be the optimal carbon emission scenario in Liaoning Province. Under this forecasting scenario, Liaoning Province could achieve carbon peak (611 million tons CO2) by 2030 without affec-ting economic development through optimizing energy structure and controlling the intensity of energy consumption. Our results would be helpful for seeking the best path for carbon emission reduction in Liaoning Province and providing a reference for its realization of carbon peaking and carbon neutrality goals.
    Seasonal change of habitat selection of Hydropotes inermis in Yancheng coastal wetlands, China
    CHEN Guoyuan, WANG Cheng, CHEN Hao, SU Yue, YU Ran, XU Xiaohua
    2023, 34(2):  510-518.  doi:10.13287/j.1001-9332.202302.026
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    Yancheng coastal wetlands are one of the main habitats and breeding grounds of wild Chinese water deer (Hydropotes inermis). Based on GPS-GSM tracking data, we used the habitat selection index and MaxEnt model to simulate and analyze the distribution of suitable habitat of H. inermis in different seasons as well as the main influencing factors. The results showed that H. inermis mainly used reed marshes, with the usage rate in spring-summer and autumn-winter being 52.7% and 62.8%, respectively. The area under receiver operating characteristic curve value simulated by MaxEnt model in different seasons was 0.873 and 0.944, which showed high prediction accu-racy. In spring and summer, the sub-suitable and most suitable habitats were mainly reed marshes, farmland, and ponds. In autumn and winter, the main habitat types were reed marshes and ponds, with an area equivalent to only 5.7% and 8.5% of that in spring and summer. Distance to reeds, distance to Spartina alterniflora, habitat types, distance to water and distance residential area were the main environmental variables affecting the distribution of H. inermis in spring and summer. The above five variables and vegetation height were the main environmental variables affecting the distribution of H. inermis in autumn and winter. This study would provide an important reference for the conservation of Chinese water deer and the fine management of their habitats in Yancheng coastal wetlands.
    Spatiotemporal distribution of Lophius litulon in the southern Yellow Sea and East China Sea
    YUAN Xingwei, JIANG Yazhou, GAO Xiaodi, YANG Linlin, LIU Zunlei, CHENG Jiahua
    2023, 34(2):  519-526.  doi:10.13287/j.1001-9332.202302.034
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    In order to investigate the temporal-spatial distribution of yellow goosefish in the open waters of the southern Yellow Sea (SYS) and East China Sea (ECS), according to the fishery data by bottom-trawl surveys and environmental data including sea bottom temperature (SBT), sea bottom salinity (SBS), bottom concentration of dissolved oxygen (BDO) and depth during 2018-2019, we established habitat suitability index (HSI) models by arithmetic mean (AMM) and geometric mean (GMM) methods, and compared the model outputs by cross validations. Especially, the weight of each environmental factor was evaluated by boosted regression tree (BRT). Results showed that the area with the highest habitat quality varied among seasons. The yellow goosefish mainly inhabited in the adjacent area of the Yangtze River Estuary and coastal waters of Jiangsu Province with depth ranged from 22 to 49 m in spring. The optimal inhabitation was located in the SYS, with the bottom temperature ranged from 8.9-10.9 ℃ in summer and autumn. Particularly, the optimal inhabitation extended from the SYS to the ECS with bottom temperature ranged from 9.2-12.7 ℃ in winter. Results of BRT models showed that depth was the most important environmental factor in spring and bottom temperature was the crucial one in the other three seasons. Results of cross validation showed that the weighted AMM-based HSI model performed better for yellow goosefish in spring, autumn and winter. The distribution of yellow goosefish was closely related to its biological traits and environmental factors in the SYS and ECS, China.
    Discriminant analysis of two Branchiostegus species in the East China Sea based on otoliths and shape morphology
    XUAN Wendan, XIE Yu, ZHU Kai, ZHU Wenbin, LI Pengfei, ZHAO Yixiang
    2023, 34(2):  527-534.  doi:10.13287/j.1001-9332.202302.031
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    Population discrimination is the basis of fishery stock assessment. To effectively distinguish Branchiostegus japonicus and Branchiostegus albus in the East China Sea, we measured 28 morphometric characteristics of otolith and 55 morphometric characteristics of shape for 399 Branchiostegus samples (187 B. japonicus and 212 B. albus)collected by deep water drift net in 27°30′-30°00′ N and 123°00′-126°30′ E from August to October 2021. The data were then analyzed by the variance analysis and stepwise discriminant analysis (SDA). The otolith of the two Branchiostegus species was different in the anterior, posterior, ventral and dorsal sides, while the shape morpholo-gical differences were observed in the head, trunk and caudal areas. The SDA results showed that the discriminant accuracy based on otoliths and shape morphological parameters was 85.1% and 94.0%, respectively. The comprehensive discriminant accuracy was 98.0% based on those two morphological parameters. Our results suggest that otolith or shape morphology could effectively distinguish the two species of Branchiostegus, and that incorporating various morphological parameters could further increase the discrimination accuracy.
    Reviews
    Spawning substrates of cuttlefish: Type, function, and application
    LIANG Jun , WU Tian, ZHOU Yongdong, HU Yangjie, XU Kaida, ZHANG Tao
    2023, 34(2):  535-546.  doi:10.13287/j.1001-9332.202302.032
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    The fertilized eggs of cuttlefish are sticky eggs. Cuttlefish parents prefer to lay eggs on the attached substrates, which help increase the number of eggs and the hatching rate of fertilized eggs. If egg-attached substrates are sufficient, cuttlefish spawning will be reduced or even delayed. With the advances in the construction of marine nature reserves and research on artificial enrichment techniques, domestic and international experts have conducted research on different types and configurations of attachment substrates around cuttlefish resource enhancement. Based on the source of the substrates, we classified cuttlefish spawning substrates into two types, natural and artificial. By summarizing the differences, advantages, and disadvantages of the common economic cuttlefish spawning substrates in offshore areas worldwide, we sort out the functions of two different types of attachment bases, and discussed the practical applications of natural and artificial egg-attached substrates in spawning ground restoration and artificial enrichment. We proposed several thoughts on the future research directions of cuttlefish spawning attachment substrates, aiming to provide reasonable suggestions for cuttlefish habitat restoration, cuttlefish breeding and sustainable development of fishery resources.
    Progress on eco-technology classification in ecologically vulnerable regions of China
    ZHANG Peng, WU Chunsheng, ZHU Bisheng, LIU Fang, LU Rongrong , ZHAO Zhongxu
    2023, 34(2):  547-554.  doi:10.13287/j.1001-9332.202302.019
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    Ecological technology is the core of ecological environment governance and restoration in ecologically vulnerable regions. A reasonable classification method is the basis for induction and summary of ecological techno-logy, which is of great significance to classify and solve ecological environmental problems and evaluate the effects of ecological technology implementation. However, there is still no standard method for the classification of ecological technology. From the perspective of ecological technology classification, we summarized the concept of eco-technology and related classification methods, in view of current situation and deficiency of ecological technology related classification, we put forward a system suitable for defining and classifying ecological technology in ecologically vulnerable regions of China, and analyzed the practicality and application prospect. Our review would provide reference for the management and promotion of ecological technology classification.
    Research progress on calculation method and impact factors of carbon sequestration capacity in urban ecosystems
    SHI Tiemao, WANG Di, TANG Yu, LI Peiying, CHU Yaqi
    2023, 34(2):  555-565.  doi:10.13287/j.1001-9332.202302.002
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    Achieving carbon neutrality is an urgent, complex and arduous task in China. How to effectively exert carbon sequestration and improve carbon sequestration capacity of urban ecosystems should be solved. Compared with other terrestrial ecosystem types, frequent anthropogenic activities lead to more abundant carbon sink elements of urban ecosystems and more complex factors affecting their carbon sequestration capacity. Based on researches at multiple spatial and temporal scales, we analyzed key factors affecting the carbon sequestration capacity of urban ecosystems from different perspectives. We illuminated the composition and characteristics of carbon sinks of urban ecosystems, summarized the methods and characteristics of carbon sequestration capacity of urban ecosystems, and revealed the impact factors of carbon sequestration capacity of different carbon sink elements and the comprehensive impact factors of carbon sinks of urban ecosystems under the influence of human activities. With the continuous improved understanding of carbon sinks of urban ecosystems, it is necessary to further improve the accounting method of carbon sequestration capacity of artificial carbon sink systems, explore the key impact factors of comprehensive carbon sequestration capacity, change the research method from global to spatially weighted, discover the spatial coupling relationship between artificial and natural carbon sink systems, find out the optimal artificial-natural spatial configuration to achieve carbon sequestration capacity enhancement, break the limitations of increasing carbon sink of urban ecosystems, and finally contribute to the achievement of the urban carbon neutrality goal.
    Methodology and application of precipitation isoscapes of stable hydrogen and oxygen isotopes
    WANG Shengjie, WANG Liwei, ZHANG Mingjun
    2023, 34(2):  566-576.  doi:10.13287/j.1001-9332.202302.016
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    The precipitation isoscapes of stable hydrogen and oxygen isotopes combine isotope tracing technology with spatial perspective, which are useful to examine the source and sink of water in different regions, to understand the isotope fractionation in atmospheric, hydrological and ecological processes, and to reveal the pattern, process, and regime of water cycle on the earth's surface. We reviewed the development of database and methodo-logy for precipitation isoscape mapping, summarized the application fields of precipitation isoscape, and put forward the key research directions in the future. At present, the main methods in mapping precipitation isoscapes include spatial interpolation, dynamic simulation, and artificial intelligence. In particular, the first two methods have been widely used. The applications of precipitation isoscapes can be classified into four fields including atmospheric water cycle, watershed hydrological process, animal and plant traceability, and water resources management. The future works should focus on the compilation of observed isotope data as well as the data evaluation of spatiotemporal representativeness, and pay more attention to develop the long-term products and quantitatively assess the spatial connection among various water types.