Table of Content

15 October 2022, Volume 33 Issue 10

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Special Features of Terrestrial Ecosystem Carbon Sequestration and Sink Enhancement

Effects of addition of organic carbon with different chemical structure on the fate and accumulation of exogenous carbon in red and sandy soils

ZHANG Lin-mei, LI Meng-jiao, YUAN Fang-hui, HU Ya-lin

2022, 33(10):  2593-2601.  doi:10.13287/j.1001-9332.202210.041

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Plant litter input has important influences on soil CO₂ emission and soil organic carbon (SOC) formation in terrestrial ecosystem. However, it is not well known for the fate of carbon when exogenous organic matters with different chemical structures are added to soil with different textures. In this study, we added the uniformly ¹³C-labelled substrates of glucose, starch, and cellulose to red soil and sandy soil, and compared the net ¹³C accumulation and recovery and its proportions in soil releasing CO₂, SOC, dissolved organic carbon (DOC) and microbial biomass carbon (MBC) pools. The results showed that δ¹³C values increased after exogenous substrate additions in CO₂, SOC, DOC, and MBC, and that the peaks of δ¹³C in CO₂ pool appeared delay with increasing chemical structure complexity. The fate of exogenous C and its contributions of different C pools were significantly influenced by exogenous C types, soil types, and incubation times. In sandy soil, the added exogenous C was more mineralized as CO₂, with the net accumulation and recovery of ¹³C in CO₂ pool decreasing in the order of glucose>starch>cellulose. In red soil, more exogenous C was transferred to SOC pool, with the net accumulation and recovery of ¹³C in SOC pool decreasing in the order of glucose>starch>cellulose. Our results implied that the chemical structure of exogenous substrates and soil texture together controlled the fate and accumulation of exogenous organic carbon.

Effects of addition of leaf litter with different chemical properties on soil organic carbon mineralization and priming effect

CHEN Tian, YUAN Fang-hui, ZHANG Lin-mei, HU Ya-lin

2022, 33(10):  2602-2610.  doi:10.13287/j.1001-9332.202210.016

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Litter inputs can affect the mineralization of soil organic carbon (SOC). However, it is yet unknown how the input of leaf litter with different chemical properties drives SOC mineralization and priming effect. In this study, ¹³C-labeled leaf litter of six tree species were added to soil cores (10 cm depth) collected from a natural secondary forest in subtropical region. We examined the effects of different leaf litters on total soil CO₂, litter-derived and soil-derived CO₂ emission rates and accumulation and priming effect. We further examined the relationships between litter chemical properties and CO₂ accumulation and priming effect. Our results showed that leaf litter addition increased total soil CO₂ and soil-derived CO₂ emission rates and accumulations, and that there were positive priming effects ranging from 68% to 128%. Soil organic carbon mineralization and priming effects varied among tree species. The Pearson correlation and stepwise multiple linear regression analysis showed that the litter-derived CO₂ accumulation had negative correlation with leaf litter C, P and cellulose concentrations, whereas the soil-derived CO₂ accumulation were positively correlated to litter C:N and lignin:N. The results implied that tree species could influence SOC mineralization and litter-induced priming effect. Thus it could mitigate soil C loss when we afforested plantation with high quality leaf litter in subtropical region.

Responses of soil microbial carbon use efficiency to short-term nitrogen addition in Castanopsis fabri forest

DAI Hui, ZENG Quan-xin, ZHOU Jia-cong, PENG Yuan-zhen, SUN Xue-qi, CHEN Jing-qi, CHEN Wen-wei, CHEN Yueh-min

2022, 33(10):  2611-2618.  doi:10.13287/j.1001-9332.202210.013

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As an important parameter regulating soil carbon mineralization, microbial carbon use efficiency (CUE) is essential for the understanding of carbon (C) cycle in terrestrial ecosystems. Three nitrogen supplemental levels, including control (0 kg N·hm^-2·a^-1), low nitrogen (40 kg N·hm^-2·a^-1), and high nitrogen (80 kg N·hm^-2·a^-1), were set up in a Castanopsis fabri forest in the Daiyun Mountain. The basic physical and chemical properties, organic carbon fractions, microbial biomass, and enzyme activities of the soil surface layer (0-10 cm) were measured. To examine the effects of increasing N deposition on microbial CUE and its influencing factors, soil microbial CUE was measured by the ¹⁸O-labelled-water approach. The results showed that short-term N addition significantly reduced microbial respiration rate and the activities of C and N acquisition enzymes, but significantly increased soil microbial CUE. β-N-acetyl amino acid glucosidase (NAG)/microbial biomass carbon (MBC), microbial respiration rate, β-glucosidase (BG)/MBC, cellulose hydrolase (CBH)/MBC, and soil organic carbon content were the main factors affecting CUE. Moreover, CUE significantly and negatively correlated with NAG/MBC, microbial respiration rate, BG/MBC, and CBH/MBC, but significantly and positively correlated with soil organic carbon. In summary, short-term N addition reduced the cost of soil microbial acquisition of C and N and microbial respiration, and thus increased soil microbial CUE, which would increase soil carbon sequestration potential of the C. fabri forest.

Effects of different carbon addition modes on the soil priming effect of a subtropical Phyllostachys edulis forest under nitrogen deposition

XU Min, LIU Yuan-yuan, YUAN Xiao-cun, ZENG Quan-xin, LIN Hui-ying, WU Xiao-xia, CUI Ju-yan, CHEN Wen-wei, CHEN Yueh-min

2022, 33(10):  2619-2627.  doi:10.13287/j.1001-9332.202210.015

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Priming effect (PE) plays an important role in regulating terrestrial soil carbon (C) cycling, but the impact of different C addition modes on the PE in subtropical forest ecosystems with increasing nitrogen (N) deposition is unclear. In this study, we investigated the effects of C addition patterns (single or repeated C addition) on soil PE by adding ¹³C-labeled glucose for 90 d in an incubation experiment with different levels of N application (0, 20, and 80 kg N·hm^-2·a^-1). The different patterns of glucose addition significantly increased soil organic C (SOC) mineralization and produced positive PE. Single glucose addition resulted in stronger PE than repeated addition. PE was significantly weakened with increasing N application levels, indicating that N deposition inhibited soil excitation in Phyllostachys edulis forests. The cumulative PE was significantly negatively correlated with β-N-acetylaminoglucosidase (NAG) and peroxidase (PEO) activities, and was significantly positively correlated with microbial biomass P (MBP) and potential of hydrogen (pH). Our findings indicated that, when acting together on soil, N application and C addition could strongly affect soil C stocks by stimulating the mineralization of native soil organic matter in subtropical forests. The findings further indicated that single C addition model might overestimate the effect of exogenous readily decomposable organic C on PE and ignore the effect of N deposition on PE, which in turn would overestimate the mineralization loss of forest SOC.

Soil organic carbon density and its influencing factors in croplands with different cultivation years in the Northeastern Ulan Buh Desert, China

CAO Qi-qi, XIAO Hui-jie, LIU Tao, SUN Jing-kuan, XIA Jiang-bao, WANG Dong, XIN Zhi-ming, HE Wen-jun, ZHAO Dan-dan, HUANG Wen-wen

2022, 33(10):  2628-2634.  doi:10.13287/j.1001-9332.202210.017

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Understanding the changes and influencing factors of soil organic carbon density (SOCD) during the conversion of uncultivated natural soil to croplands is of great significance for the assessment of carbon sequestration in arid areas. In this study, we compared SOCD in the uncultivated soil and that in croplands with different cultivation years (2-5, 12-15, 25-30, 40-50 years) in the Northeastern Ulan Buh Desert. The change of SOCD and its influencing factors at 0-2 m soil depth during the conversion of uncultivated natural soil to croplands were explored by the method of replacing time with space. The results showed that SOCD at the shallow soil depth (0-0.4 m) in croplands increased continuously with cultivation years, but basically at low levels (0.990-1.983 kg·m^-2). The SOCD at deep soil (1.2-2 m) increased in the croplands with longer cultivation years (25-30 and 40-50 years), whereas no obvious change trends in both the croplands with shorter cultivation years (2-5 and 12-15 years) and the uncultivated natural soil. The SOCD at deep soil (1.2-2 m) were relatively large (28.9%-38.6%) of the 0-2 m soil depth of uncultivated natural soil and croplands with different cultivation years. The vertical distribution of SOCD in croplands with different cultivation years were well fitted by quadratic functions (with R² ranging from 0.757 to 0.972). It was noteworthy that soil clay and silt contents had dominant influences on SOCD at all the soil profile (0-2 m), and that cultivation years mainly contributed to the accumulation of SOC at the shallow soil (0-0.4 m).

Characteristics and factors influencing organic carbon decomposition in sediment in check dams

WANG Zhen, LIU Ying, YANG Ming-yi, ZHANG Feng-bao

2022, 33(10):  2635-2643.  doi:10.13287/j.1001-9332.202210.018

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More than 56000 check dams have been built in the Loess Plateau, which capture around 0.95 Pg of organic carbon and act as an important carbon sink. However, the decomposition mechanism of organic carbon in the sediment in these dams is still poorly understood, and thus it is difficult to quantify their role in terrestrial carbon cycling. In this study, the mineralization culture was used as a simulated environment for the natural sediment environment. With the observations in the simulated environment, the decomposition rates of sediment organic carbon (SOC) were compared under different conditions to investigate the factors influencing the decomposition rate of SOC. The results showed that the average SOC decomposition rate of sediment under anoxic and aerobic conditions was (6.47±4.06) and (56.66±17.78) mg C·kg^-1·d^-1, respectively. The decomposition rate of SOC in dam sedi-ment under burial conditions was only 11.4% of that under the assumed aerobic condition, indicating that burial condition significantly reduced SOC decomposition. Under anoxic conditions, chemical compositions in the sediment had a greater effect on the decomposition rate of SOC than the microorga-nisms. In contrast, the effect of microorganisms on the decomposition rate of SOC was more significant under aerobic conditions. The physical properties of sediment had little effect on the decomposition rate of SOC under both anoxic and aerobic conditions. Under natural conditions, the siltation dam acted as a carbon sink. When the dam breaks, SOC stored in the sedimentary anoxic condition would be quickly exposed to the air, followed by a significant increase in the decomposition rate, and thus acting as a carbon source.

Spatio-temporal dynamics of gross primary productivity in China from 1982 to 2017 based on different datasets

CAO Yu-juan, SONG Zhen-hua, WU Zhi-tao, DU Zi-qiang

2022, 33(10):  2644-2652.  doi:10.13287/j.1001-9332.202210.027

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Understanding the spatio-temporal variations of gross primary productivity (GPP) of terrestrial ecosystem and its relationship with climatic factors can provide important basis for vegetation restoration and protection. Based on meteorological data and three public GPP datasets (EC-LUE GPP, GLASS GPP, and NIRv GPP), we syste-matically analyzed the spatial-temporal variations of GPP and its response to climate change in China during 1982-2017. All the results based on the three GPP datasets showed that the annual and seasonal GPP in China increased annually from 1982 to 2017, with that in 1998 and 2002 significantly being higher than the average level during the study period, and that in 1989 and 1992 significantly being lower than the average annual GPP. From 1982 to 2017, GPP showed a significant upward trend in most regions of China, with the regions with significant increases accounting for 75.7%, 73.0%, and 69.6% of the whole study area, respectively. There was a significant positive correlation between annual GPP and precipitation and temperature, but spatial heterogeneity was strong. Among them, the regions with positive correlation between GPP and temperature were mainly distributed in Northwest and Central China, while the regions with positive correlation between GPP and precipitation were mainly distributed in North China. There was obvious spatial-temporal heterogeneity in regions that GPP being affected by temperature and precipitation in different seasons. Temperature was the limiting factor of GPP in spring, autumn and winter, while summer GPP was mainly affected by precipitation.

Simulation of carbon sequestration and timber production in Larix olgensis plantation based on CO₂FIX model

DONG Ling-bo, CHEN Guan-mou, LIN Xue-ying, LIU Zhao-gang

2022, 33(10):  2653-2662.  doi:10.13287/j.1001-9332.202210.009

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Based on datasets from plot survey and bibliographic of Larix olgensis plantations in Maoer Mountain, the CO₂FIX model was used to quantitatively simulate the effects of different rotations (30, 40, 50, 60 years), site indices (12, 16, 20 m), and initial densities (2500, 3333, 4444 trees·hm^-2) on the stand level carbon flows among different carbon pools (i.e., biomass carbon pool, soil carbon pool, and product carbon pool). The results showed that the CO₂FIX model had high reliability for simulating the processes of L. olgensis plantation, with the average relative errors of stand biomass and volume between analog and measured values being 6.4% and 3.7%. Under the baseline conditions of initial density of 3333 trees·hm^-2, site index of 16 m and rotation of 40 years, the carbon stock of total and sub-pool of L. olgensis plantation changed periodically with rotation. The total stand carbon stock and volume for L. olgensis plantation increased with the extension of rotation, the improvement of site index, and the increase of initial density. The stand carbon stock and volume would be increased by 12.2% and 31.2%, 36.7% and 67.8%, respectively, when the reference rotation was correspondingly extended by 10 and 20 years. However, if the reference rotation was shortened by 10 years, stand carbon stock and volume would be correspondingly decreased by 20.9% and 40.4%, respectively. When the initial density was set as 3333 and 4444 trees·hm^-2, stand carbon stock and volume were increased by 27.8% and 50.9%, 27.4% and 49.1%, respectively. When the site index was under the range of 12 to 20 m, stand carbon stock and volume could be increased by 36.0% and 40.3%, 39.3% and 44.2%, respectively, with each increase of 4 m in site index. During one rotation, 271.57 t C per hectare could be fixed into L. olgensis plantation. At the end round of the rotation, 27.47 and 56.75 t C were transferred to soil and wood product carbon pools. Therefore, when the site condition was good, the management model with a higher initial density (4444 trees·hm^-2) and longer rotation (60 years) would be more beneficial to maximizing the carbon sink and timber benefits of L. olgensis plantation.

Change in nitrogen availability of northern peatlands and its effect on carbon sink function

GAO Jin-li, SONG Yan-yu, SONG Chang-chun, GONG Chao, MA Xiu-yan, GAO Si-qi, LIU Zhen-di

2022, 33(10):  2663-2669.  doi:10.13287/j.1001-9332.202210.008

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Northern peatlands are typical nitrogen-limited ecosystems, which are sensitive to global climate change and human activities. The increases of endogenous available nitrogen caused by climate warming and exogenous nitrogen input caused by human activities changed the nitrogen availability of northern peatlands, and would affect carbon and nitrogen cycling and carbon sink function of peatland. Here, we review the influence factors of carbon accumulation rate and carbon sink function in northern peatlands. The effects of nitrogen deposition, freezing and thawing, fire and other factors on nitrogen availability of northern peatlands were reviewed. The responses of plants and soil microorganisms to changes in nitrogen availability were elaborated from carbon fixation and carbon emission processes, respectively. The research related to carbon sink function of peat ecosystems under the influence of glo-bal change was prospected, aiming to help the implementation of the ‘double carbon' goal.

Original Articles

Niche and interspecific association of dominant tree species in Michelia odora community

LIU Yi-peng, YE Xing-zhuang, YE Li-qi, CHEN Xu-hui, ZHENG Shi-qun, CHEN Shi-pin, ZHANG Guo-fang, LIU Bao

2022, 33(10):  2670-2678.  doi:10.13287/j.1001-9332.202210.007

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In order to understand the interspecific and ecological relationships of Michelia odora (extremely small population) community and strengthen the protection of wild M. odora resources in Junzifeng Nature Reserve, we studied the niche characteristics and interspecific associations of dominant tree species. The results showed that M. odora, Machilus chekiangensis, Schima superba, and Alniphyllum fortunei had obvious niche breadth advantages, which were the constructive species of the community. Among the 190 groups of species pairs among the 20 dominant tree species, 50.5% of species pairs had niche overlap value greater than 0.5. The degree of ecological niche differentiation among species was general. M. odora had large niche overlap with other 19 species, indicating a competitive risk when resources were insufficient. The overall associations of dominant tree species were significantly positive, indicating the community was at the late stage of relatively stable succession. The results ofχ² test, asso-ciation coefficient, and Pearson correlation coefficient showed that all the significance ratios of interspecific association were lower, and that the independence among species was relatively strong. There was a positive correlation between interspecific association and niche overlap. The M. odora community was relatively mature, with full utilization of resources and stable interspecific relationship. To promote the rejuvenation and create a good habitat of M. odora population, the population size with large overlap with M. odora niche and significant negative association could be appropriately limited, while that with positive interaction could be increased.

Effects of tree mortality on the spatial patterns and interspecific associations of individuals in karst evergreen deciduous broad-leaved mixed forests

LU Meng-zhen, ZENG Fu-ping, SONG Tong-qing, PENG Wan-xia, SU Liang, LIU Kun-ping, TAN Wei-ning, DU Hu

2022, 33(10):  2679-2686.  doi:10.13287/j.1001-9332.202210.002

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Tree mortality is an important ecological process in forests. It is crucial to understand how tree mortality affects spatial patterns and interspecific associations for revealing the mechanisms of tree mortality and community dynamics. We employed the correlation method of spatial point pattern analysis to analyse the variations in spatial patterns and interspecific relations before and after mortality using data obtained from two surveys of a 25 hm² plot in the Mulun National Natural Reserve, China. The results showed that most species had an aggregated distribution both pre- and post-mortality. The proportion of species with aggregated distribution reduced slightly post-mortality compared with that for pre-mortality. Increases in the number of species with random distribution at small scale indicated that tree death was not random. At the species level, there were significant positive associations between dead and live trees of the 13 common species at different levels of 0-30 m range, suggesting weak intraspecific and interspecific competition among dominant species. Pre- and post-mortality interspecific associations were mostly positive, which remained stable during the period of two surveys for most species, indicating that the community had reached a rather stable stage. Following tree mortality, the number of species with positive associations increased at 1-30 m scales, whereas the number of species with negative and no associations decreased at most scales. These results indicated that the pressure of interspecific competition was relieved to some extent after individual death.

Natural regeneration of Larix principis-rupprechtii plantations with different densities and its influencing factors

WEI Shu-ping, LIANG Wen-jun, WEI Xi, BU Rui-ying, YAO Jia-feng

2022, 33(10):  2687-2694.  doi:10.13287/j.1001-9332.202210.001

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In this study, we analyzed the natural regeneration of Larix principis-rupprechtii pure plantations with stand densities of 128, 240, 320, 400, 480, 560, 640 and 720 trees·hm^-2 in the Guandi Mountains and its influencing factors. The results showed that the regeneration index first increased and then decreased with the increases of stand density, and that the regeneration performance of stand with medium density (400-560 trees·hm^-2) was significantly better than other stands. Light conditions, herbaceous plants and litter of the understory had a dual effect on the regeneration of L. principis-rupprechtii. Excessive light, herbaceous plant cover or over-thick litter was not instrumental to the regeneration. Soil organic matter promoted stand regeneration by providing soft soil texture, adequate water content, low phosphorus but high nitrogen. The effects of the examined factors on the regeneration index were as follows: soil water content (0.798) > total nitrogen (0.621) > litter thickness (-0.597) > soil porosity (0.504) > soil organic matter (0.493) > total phosphorus (-0.404) > transmitted total light (-0.274) > herbaceous plants cover (-0.021). In the plantation management, stand density could be controlled at about 480 trees·hm^-2 by thinning or replanting, while litter could be cleared properly to improve soil condition and to promote natural regeneration of L. principis-rupprechtii.

Gravitational model-based competitive analysis of trees

DOU Xiao-wen, TANG Meng-ping

2022, 33(10):  2695-2704.  doi:10.13287/j.1001-9332.202210.004

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Whether the gravitational model can be used to analyze tree competition in forest community is a valuable question. A tree relative vitality circle based on the gravitational model can illustrate the magnitude of competitive tree vitality. A gravitational competition index based on the relative vitality circle of competitive trees can accurately depict the relationship between growth and competition. This study was conducted in the coniferous and broadleaf mixed forest of Tianmu Mountain National Nature Reserve in Zhejiang Province. We carried out correlation analyses between the V_Hegyi competition index and diameter at breast height (DBH), between the gravitational competition index and DBH, and between the two competition indices and the basal area increment. We further analyzed the correlation between the growth rate of DBH and the ratio of the two-phase gravitational competition index, that is, the ratio of the 2021 gravitational competition index to that of 2006. In addition, the correlation analysis was applied between the relative vitality circle diameter and DBH. We also compared the magnitudes of the competition indices between the living standing trees and the dead trees. The results showed that both competition indices were negatively correlated with DBH, and followed a power function relationship. The basal area increment was negatively correlated with each of the two competition indices. However, the gravitational competition index was better than V_Hegyi competition index for indicating the relationship between tree growth and tree competition. Compared with the ratio of the V_Hegyi competition indices, the ratio of the two-phase gravitational competition indices could better demonstrate the relationship between tree growth and tree competition. In the coniferous and broadleaved mixed forests, the correlation coefficient between the growth and competition of broadleaved species was greater than that of coniferous species. The dead trees were significantly influenced by competition. Tree relative vitality circle size was negatively correlated with DBH. The gravitational model was one of the critical models that reflect spatial interactions and could be applied to examine forest competition. The gravitational competition index could be used as a spatially structured indicator to evaluate tree competition and tree vitality, which could better indicate the relationship between tree growth and tree competition than the V_Hegyi competition index.

Simulated nitrogen deposition reduces potential nitrous oxide emissions in a natural Castanopsis carlesii forest soil

DENG Mi-lin, FENG Meng-meng, LIU Xiao-fei, CHEN Shi-dong, HE Ji-zheng, LIN Yong-xin

2022, 33(10):  2705-2710.  doi:10.13287/j.1001-9332.202210.005

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The reactive nitrogen deposition in subtropical region of China has been increasing annually, which affects biogeochemical processes in forest soils. In this study, three treatments were established, including control (no N addition, CK), low nitrogen deposition (40 kg·hm^-2·a^-1, LN), and high nitrogen deposition (80 kg·hm^-2·a^-1, HN) to study the response of denitrifying functional genes and potential N₂O emissions to simulated nitrogen deposition in the soils of a natural Castanopsis carlesii forest. Results showed that HN significantly decreased soil potential N₂O emission, while 8-year nitrogen deposition did not affect the abundances of nirS, nirK, nosZ Ⅰ and nosZ Ⅱ. However, the abundance of nosZ Ⅰwas significantly higher than nosZ Ⅱ in all the treatments, indicating that nosZ Ⅰ dominated over nosZ Ⅱ in the acidic soils. HN significantly decreased the ratio of (nirK+nirS)/(nosZ Ⅰ+nosZ Ⅱ), which was positively correlated with soil pH. The results suggested that long-term high nitrogen deposition reduced soil pH and the abundance ratio of (nirK+nirS)/(nosZ Ⅰ+nosZ Ⅱ), which subsequently reduced the potential N₂O emission.

Effects of warming on physicochemical property of Cunninghamia lanceolata branch and leaf litter in subtropical plantation

LI Ao-gui, LIN Cheng-fang, HU Ming-yan, LIU Xiao-fei, SONG Hao-wei, ZHANG Lei, YANG Yu-sheng

2022, 33(10):  2711-2717.  doi:10.13287/j.1001-9332.202210.003

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At the regional scale, substrate properties are the key factors driving litter decomposition rate. In this study, soil temperature was increased by buried heating cables to explore the impacts of climate warming on the physical and chemical properties in branch and leaf of Cunninghamia lanceolata litter. The results showed that after 5 years of soil warming (4 ℃), the contents of nitrogen (N), phosphorus (P) and water-soluble substance in branch litter increased by 35.2%, 40.8% and 7.6%, while that in leaf litter increased by 41.2%, 45.9% and 5.9%, respectively. The contents of carbon (C), cellulose and C/N in branch litter decreased by 5.1%, 11.6% and 28.8%, and in leaf litter decreased by 5.3%, 11.3% and 33.3%, respectively. Soil warming led to 29.8% increase in specific leaf area (SLA) and 40.7% decrease in tensile strength (LTS) of leaf litter. However, warming did not affect lignin content and pH value in both branch and leaf litter. ¹³C NMR and infrared spectrum analysis showed that the contents of amino acids, polysaccharides, polyphenols and aliphatic compounds in litter changed significantly after warming. Warming effect differed between litter organs, in that polysaccharides increased significantly only in leaf litter and the increase of amino acids in branch litter was greater than that in leaf litter. Overall, soil warming significantly changed the physical and chemical properties in C. lanceolata branch and leaf litter, which might accelerate the decomposition rate at the initial stage due to the increase of N, P contents and the decrease of LTS, but might decelerate the decomposition rate at the later stage due to an increase of complex polymers content in the litter.

Effects of manure combined with nitrogen fertilizer on yield and quality of winter wheat and soil biological characteristics in drylands of Northwest China

MA Long, WANG Shu-ting, SHI Lei, ZHANG Ran, WANG Kai, ZHENG Wei, LI Zi-yan, ZHAI Bing-nian

2022, 33(10):  2718-2724.  doi:10.13287/j.1001-9332.202210.014

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We conducted an experiment with five treatments in winter wheat of the dryland of Northwest China, i.e. 30 t·hm^-2 cow dung (M) plus different doses of nitrogen fertilizer (0, 75, 150, 225, and 300 kg N·hm^-2), denoted by M+N₀, M+N₇₅, M+N₁₅₀, M+N₂₂₅, and M+N₃₀₀, respectively. After three years of treatment, wheat yield, grain quality, and soil biological characteristics were measured in two consecutive years (2018 and 2019). The results showed that the combination of manure with nitrogen fertilizer significantly increased wheat yield compared with the manure-only treatment (M+N₀). Compared with the manure-only treatment, the combined treatments significantly increased wheat grain protein content, wet gluten, sedimentation value, and extensibility, but not for starch content. Neither wheat yield nor grain quality had significant differences among the M+N₁₅₀, M+N₂₂₅, and M+N₃₀₀ treatments, but both were prominently higher than those of M+N₇₅. Soil microbial biomass carbon (MBC) and nitrogen (MBN) reached highest in M+N₁₅₀ for both years, which were distinctly higher than those of M+N₀, M+N₂₂₅, and M+N₃₀₀. In 2018, soil β-1, 4-glucosidase, cellobiohydrolase, L-leucine aminopeptidase, β-1,4-N-acetyl glucosaminidase, and alkaline phosphatase activities in M+N₁₅₀ treatment were higher than those of other treatments. In 2019, soil enzyme activities (excluding L-leucine aminopeptidase) in M+N₁₅₀ were higher than those of M+N₀ and M+N₂₂₅. MBC significantly positively correlated with MBN, and both significantly positively correlated with the activities of cellobiohydrolase, β-1, 4-N-acetyl glucosaminidase, and alkaline phosphatase. MBN significantly positively correlated with total nitrogen content and negatively correlated with NO₃^-. Considering winter wheat yield, grain quality, and soil biological characteristics, M+N₁₅₀ was conducive to sustainable production of winter wheat in drylands of Northwest China.

Alleviating effect of exogenous melatonin and calcium on the peroxidation damages of cucumber under high temperature stress

XU Chen-xiao, ZHANG Xiao-yu, LIU Chao-yue, LIU Kun, BI Huan-gai, AI Xi-zhen

2022, 33(10):  2725-2735.  doi:10.13287/j.1001-9332.202210.010

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To explore whether there is an interaction between melatonin (MT) and calcium (Ca²⁺) in regulating heat tolerance of plants, we analyzed the response of endogenous MT and Ca²⁺ to heat stress, and examined the effect of MT and Ca²⁺ on the reactive oxygen (ROS) accumulation, antioxidant system, and transcripts of heat shock factor (HSF) and heat shock proteins (HSPs) of cucumber seedlings under high temperature stress. Seedlings were foliar sprayed with 100 μmol·L^-1 MT, 10 mmol·L^-1 CaCl₂, 3 mmol·L^-1 ethylene glycol tetraacetic acid (EGTA, Ca²⁺ chelating agent) +100 μmol·L^-1 MT, 0.05 mmol·L^-1 chlorpromazine (calmodulin antagonist, CPZ) +100 μmol·L^-1 MT, 100 μmol·L^-1 p-chlorophenylalanine (p-CPA, inhibitor of MT) +10 mmol·L^-1 CaCl₂ or deionized water (H₂O), respectively. The results showed that both endogenous MT and Ca²⁺ in cucumber seedlings were induced by high temperature stress. The seedlings treated with exogenous MT showed significant increases in the mRNA expression of calmodulin (CaM), calcium-dependent protein kinase (CDPK5), calcineurin B-like protein (CBL3) and CBL interacting protein kinase (CIPK2) compared with the control at normal temperature. The mRNA levels of tryptophane decarboxylase (TDC), 5-hydroxytryptamine-N-acetyltransferase (SNAT) and N-acetyl-5-hydroxytryptamine methyltransferase (ASMT), key genes of MT biosynthesis and endogenous MT content were also induced by Ca²⁺ in cucumber seedlings. Exogenous MT and CaCl₂ alleviated the heat-induced oxidative damage through increasing antioxidant ability, reducing the accumulation of reactive oxygen species (ROS), and upregulating the mRNA abundances of HSF7, HSP70.1 and HSP70.11, as evidenced by mild thermal damage symptoms, lower heat injury index and electrolyte leakage under heat stress. The positive effect of MT-induced antioxidant capacity and mRNA expression of HSPs was removed by adding EGTA and CPZ in stressed seedlings. Similarly, the mitigating role of Ca²⁺ in the peroxidation damage to high temperature stress was reversed by p-CPA. These results suggested that both MT and Ca²⁺ could induce heat tolerance of cucumber seedlings, which had crosstalk in the process of heat stress signal transduction.

The planting effect of cover crop in Sanjiang Plain, Northeast China

CAI Li-jun, ZHANG Jing-tao, GAI Zhi-jia, LIU Jing-qi, GUO Zhen-hua, ZHAO Gui-fan, MENG Qing-ying

2022, 33(10):  2736-2742.  doi:10.13287/j.1001-9332.202210.011

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The planting effect and the planting potential of 12 cover crops (Leguminous: alfalfa, smooth vetch, hairy vetch, red clover, white clover, common vetch; non-leguminous: sudangrass, green radish, Nitro radish, rape, kale, endive) in the Sanjiang Plain of Northeast China were comprehensively evaluated by soil penetration resistance, pre-winter biomass, root characteristics, and plant nitrogen accumulation. The results showed that all the 12 cover crops grew normally during the experimental sowing period. Compared with the control, all the cover crops successfully reduced soil compactness. The planting of green radish, nitro radish, and sudangrass decreased soil penetration resistance by 47.1%, 43.4% and 33.4%, respectively. The pre-winter total fresh biomass of cover crop populations was between 3.38 and 13.98 kg·m^-2, and the total dry matter mass was between 0.78 and 2.43 kg·m^-2. The biomass of non-leguminous cover crops was significantly higher than that of the leguminous cover crops. The group roots of radish, rape and endive had large volumes. In particular, the nitro radish roots had a vo-lume of 4018.5 cm³·m^-2, and the root system of sudangrass extended over the widest horizontal range. The ash content of leguminous cover crops was significantly lower than that of non-leguminous species, which could provide more organic matter with high decomposability. The total nitrogen accumulation of cover crops varied from 18.72 to 53.09 g·m^-2. Kale and endive accumulated the highest amount of nitrogen and large biomass, which could facilitate nitrogen fixation and accumulation. According to the type of main crops in Sanjiang Plain and canopy structure, planting leguminous (clover, vetch, and alfalfa) and non-leguminous (radish, kale and sudangrass) cover crops to plant inter-row or in a line mixed cropping pattern could regulate soil structure and promote nutrient cycing, with positive effects on the fertility of black soil in the Sanjiang Plain.

Responses of plant C:N:P stoichiometry to soil properties on unstable slopes of dry-hot valley

YANG Liu-sheng, GAO Ruo-yun, YU Chen-hui, HAN Run-yu, TIAN Xue, SUN Fan, LIN Yong-ming, WANG Dao-jie

2022, 33(10):  2743-2752.  doi:10.13287/j.1001-9332.202210.023

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In this study, we examined plant C:N:P stoichiometry of herbaceous plants in different sections (stable area, unstable area and deposition area) of the unstable slope on both shade and sunny aspects of dry-hot valley with different soil properties. The results showed that C concentration (320.59 g·kg^-1), N concentration (12.15 g·kg^-1), and N:P ratio (25.37) of shoot on the unstable slope were significantly higher than those of root, with 254.01 g·kg^-1, 6.12 g·kg^-1 and 13.43, respectively. The average value of the C:N ratio was significantly higher in root (43.09) than shoot (31.90). The C content and N:P ratio of shoot and root in stable and unstable areas were significantly higher than in deposition area, whereas the N content in unstable area was significantly higher than that in deposition area on the sunny slope. In addition, the N and P contents of shoot and the root P content in deposition area were significantly higher than in stable and unstable areas, whereas the C content of root in stable and unstable areas were significantly higher than in deposition area on the shade slope. Moreover, the shoot growth of plants was mainly limited by P, whereas root growth was mainly limited by N and the limitation gradually increased as the section goes down. Soil water content (SWC) was an important factor controlling the C, N, and P contents change of shoot with the relative influence ratios of 28.8%, 20.8%, and 19.9%, respectively. Soil organic carbon (SOC) had a significant impact on the C and P contents of root with the relative influence ratios of 49.5% and 22.1%. The change of root N content was mainly affected by soil pH (24.3%). Our results revealed that nutrient allocation of plant was significantly affected by slope aspects, sections and soil factors, which were mainly constituted by SWC, SOC, and soil pH.

Soil respiration rate and its influencing factors in artificial land-bridge islands system

YANG Xi-xi, XU Xiao-zhong, RUAN Zhen, GE Xiao-gai, WANG Bin, WU Dong-hao, WANG Zhi-ping, YU Ming-jian

2022, 33(10):  2753-2759.  doi:10.13287/j.1001-9332.202210.012

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It is of great significance to understand the pattern of soil respiration rate in fragmented forests for further revealing terrestrial ecosystem carbon cycling. With different habitats (island vs. mainland, island edge vs. island interior) of the artificial land-bridge island system in Thousand Island Lake (TIL) region as the objects, we analyzed the seasonal dynamics of soil respiration rate and its relationships with soil physicochemical factors. The results showed that: 1) Soil respiration rates varied significantly across different seasons, with an order of summer (3.74 μmol·m^-2·s^-1) > autumn (2.30 μmol·m^-2·s^-1) > spring (1.82 μmol·m^-2·s^-1) > winter (1.40 μmol·m^-2·s^-1). 2) Forest fragmentation had significant effects on soil respiration rate, with soil respiration rate of island (2.37 μmol·m^-2·s^-1) being significantly higher than that of mainland (2.08 μmol·m^-2·s^-1) and the soil respiration rate of island edge (2.46 μmol·m^-2·s^-1) being significantly higher than that of island interior (2.03 μmol·m^-2·s^-1). 3) Soil temperature significantly promoted soil respiration rate, explaining 56.1% of the total variation. 4) There was a significant positive correlation between soil respiration rate and soil total carbon, ammo-nium nitrogen content, and vegetation coverage. The soil total carbon and ammonium nitrogen content of island edge were significantly higher than those of island interior. In all, forest fragmentation promoted soil respiration rate, with soil physicochemical factors as the drivers for its variation.

Spatio-temporal relationship between vegetation restoration and ecosystem services in the Loess Plateau of Northern Shaanxi, China

YE Xuan, KANG Shuai-zhi, ZHAO Yong-hua, HAN Lei, XIANG Xi-ming, LI Fan

2022, 33(10):  2760-2768.  doi:10.13287/j.1001-9332.202210.022

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As the core region of the “Grain to Green” Program, the Loess Plateau of Northern Shaanxi became an example with the most dramatic changes in earth surface pattern and vegetation cover. Evaluating the effectiveness of vegetation restoration is important for promoting regional ecological environment. In this study, the fractional vegetation coverage (FVC) was used as the index to analyze the changes in vegetation coverage in this area. Soil conservation service, carbon sequestration service, habitat quality, and water yield were used to characterize the regional ecosystem services (ESs). The effects of FVC on ESs were analyzed based on the bivariate spatial autocorrelation model. The trade-off synergies and spatio-temporal variations of different scales of those indices were discussed. The results showed that the FVC of the study area presented a fluctuating upward trend from 2000 to 2020, with the annual average value increasing from 31.7% to 47.1%. Carbon sequestration service and soil conservation service were increased, habitat quality was stable. Water yield increased firstly and then decreased, with an overall upward trend. The ESs changes were scale-dependent. There was an obvious synergistic relationship among ESs. There was a significant spatial dependence between FVC and ESs, with some differences in the degree of correlation. FVC had the strongest impact on soil conservation, followed by carbon sequestration service. However, the increase of vegetation coverage and water consumption of forest and grass led to the negative effect of water yield reduction. In gene-ral, FVC in the Loess Plateau of Northern Shaanxi had achieved remarkable success, and the ecological environment had been significantly improved.

Temporal and spatial variation of vegetation net primary productivity and its driving factors in Ningxia, China from 2000 to 2019

HONG Le-le, SHEN Yan, MA Hong-bin, ZHANG Peng, HUO Xin-ru, WEN Hua-chen

2022, 33(10):  2769-2776.  doi:10.13287/j.1001-9332.202210.019

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Ningxia is an important agriculture-pastoral area in China. Research on the temporal and spatial variations of net primary productivity (NPP) in this area and its driving factors would help understand the trends and leading factors of NPP variations, and reveal vegetation restoration status and causes. Based on the NPP data of MODIS, we used Theil-Sen Median trend analysis, correlation analysis, overlay analysis and other methods to analyze the spatiotemporal variations and driving factors of NPP in Ningxia. The results showed that NPP of Ningxia vegetation showed a fluctuating upward trend during 2000-2019, with a linear growth rate of 5.46 g C·m^-2·a^-1. The NPP presented a spatial characteristics of “two high and two low”, with the highest in the southern mountain area, followed by the Yellow River irrigation area, and the lowest in the hilly area of the central arid zone and Helan Mountain. 84.2% of the NPP in the study area was under significant restoration, mainly distributed in the central and southern mountainous and hilly areas. The NPP varied significantly with altitude and was significantly affected by the terrain. NPP center of gravity had generally moved to the south, with the increase and growth rate of NPP of vegetation in the south being greater than that in the north. The annual precipitation in Ningxia had shown an increasing trend, while the average annual temperature had slightly decreased. The NPP was significantly affec-ted by precipitation (R²=0.291), whereas the correlation between mean annual temperature and NPP was weak. 96.9% of the study area was at a state of vegetation restoration, which was promoted by both climate change and human activities.

Estimation method of urban green space living vegetation volume based on backpack light detection and ranging

LI Xiao-xiao, TANG Li-yu, PENG Wei, CHEN Jian-xin, MA Xia

2022, 33(10):  2777-2784.  doi:10.13287/j.1001-9332.202210.020

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Living vegetation volume (LVV) can objectively and accurately reflect the urban greenery quality, and provide a reliable data foundation for the quantitative study aiming to reveal the mechanisms underlying urban greenery ecological functions. According to the characteristics of dispersion and small scale of unit affiliated green space, we proposed a LVV estimation scheme for such urban green space, which included data acquisition, processing, entity segmentation, classification, single tree canopy extraction, and LVV calculation. First, point cloud data was obtained with a backpack LiDAR system, and the ground point clouds were eliminated by a multi-scale algorithm. Second, the Density Based Spatial Clustering of Application with Noise (DBSCAN) algorithm was used to cluster the non-ground point clouds, and density feature-based competitive algorithm was used to re-segmented for the overlapping area to generate independent objects. Third, the PointNet++ network model was used to extracted plant point clouds. Then, the canopy point clouds were extracted using the similarity of principal direction between neighboring points and distribution density of branch and leaf points. Finally, the LVV of individual tree canopy was calculated by the convex hull method, and then the LVV of the accessory greenland was summed up. Taking a science and technology park as an example, its total LVV was 21034.95 m³, among which the number of mango trees was the highest, and the total LVV was the largest (4868.64 m³, accounting for 23.2%). The tree species with the largest LVV per plant was Terminalia neotaliala tree, with an average of 120.37 m³ per plant. The relative error between LVV of trees estimated by this scheme compared with traditional method and convex hull method was 10.7%-33.7% and 2.7%-16.0%, with average value of 20.9% and 8.7%, respectively. This scheme could make full use of the characteristics of the three-dimensional point cloud and use a convex polyhedron to simulate the original form of the tree crown, which was more consistent with the actual situation of trees. The measurement and estimation solution of the LVV provided new ideas for rapid and accurate estimation of urban LVV.

Evaluation of gap-filling methods for CH₄ flux data based on eddy covariance method in the Lake Taihu, China

QIU Ji-li, ZHANG Mi, PU Yi-ni, ZHANG Zhen, JIA Lei, ZHAO Jia-yu, XIAO Wei, LIU Shou-dong

2022, 33(10):  2785-2795.  doi:10.13287/j.1001-9332.202210.021

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Eddy covariance method has become a key technique to measure CH₄ flux continuously in lakes. A large number of CH₄ flux data was missing due to variable reasons. In order to reconstruct a complete time series of CH₄ flux, it is necessary to find an appropriate gap-filling method to insert the CH₄ flux data gap. Based on the routine meteorological data and CH₄ flux data measured at Bifenggang site in the eastern part of the Taihu eddy flux network during 2014 to 2017, we analyzed the control factors of CH₄ flux at the half-hour scale and daily scale. With those data, we tested that whether nonlinear regression method and two machine learning methods, random forest algorithm and error back propagation algorithm, could fill the CH₄ flux gap at the half-hour scale and daily scale. The results showed that CH₄ flux at the half-hour scale was mainly influenced by sediment temperature, friction velocity, air temperature, relative humidity, latent heat flux and water temperature at 20 cm in the growing season, and was mainly affected by relative humidity, latent heat flux, wind speed, sensible heat flux and sediment temperature in non-growing season. The CH₄ flux at the daily scale was mainly affected by latent heat flux and relative humidity. Random forest model was the best in CH₄ flux data gap filling at both time scales. The random forest model with the input variables of day of year, solar elevation angle, sediment temperature, friction velocity, air temperature, water temperature at 20 cm, relative humidity, air pressure, and wind speed was more suitable for filling the CH₄ flux data gap at the half-hour scale. The random forest model with the input variables of day of year, sediment temperature, friction velocity, air temperature, water temperature at 20 cm, relative humidity, air pressure, wind speed, and downward shortwave radiation was more suitable for filling CH₄ flux data gap at the day scale. The interpolation models could fill the data gap better at daily scale than that at the half-hour scale.

Precipitation variation reconstructed based on tree-ring width data for the past 399 years in the eastern Yinshan Mountains, China

LI Ming-qi, SHAO Xue-mei, NIE Wen-zheng

2022, 33(10):  2796-2804.  doi:10.13287/j.1001-9332.202210.006

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Based on the tree-ring increment cores of Pinus tabuliformis collected from the eastern Yinshan Mountains, the tree-ring width chronology was developed. The correlation coefficients were calculated between the chronology and monthly mean temperature and monthly precipitation during the instrumental period of AD 1952-2007. The results showed that the highest correlation was found between the total precipitation from September of previous year to June of current year and the chronology (r=0.73, n=56, P<0.01). Based on the correlation, the September of previous year to June of current year total precipitation variation was reconstructed in the eastern Yin-shan Mountains during the past 399 years (AD 1619-2017). The reconstruction explained 54.9% of the variation in the total precipitation from September of previous year to June of current year for the calibration period (AD 1952-2007). Both the ‘leave-one-out' cross validation and split-period validation showed that the model was relatively robust, with sufficient skills of estimation and high reliability. At the decadal scale, there were four wet periods (AD 1619-1663, AD 1705-1711, AD 1945-1963, and AD 1979-2017)) and four dry periods (AD 1734-1767, AD 1786-1814, AD 1839-1867, and AD 1888-1942) in the past 399 years. Among those periods, the AD 1979-2017 was the wettest period, and AD 1888-1942 was the longest dry duration with the driest period at the late 1920s. Results of power spectral analysis revealed cyclic fluctuations of precipitation series on 2-7 years and 125 years. In addition, the comparison with other reconstructions and spatial correlation analysis indicated that the reconstructed precipitation series well represented regional scale precipitation variation.

Characteristics of climate change and its impacts on water resources in Qilian Mountains, China

WANG You-heng, LI Dan-hua, LU Guo-yang, JIANG You-yan, HUANG Peng-cheng

2022, 33(10):  2805-2812.  doi:10.13287/j.1001-9332.202210.024

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Qilian Mountains, is an important ecological function area, an important ecological security barrier, the river runoff region in Northwest China, as well as a sensitive area to global climate change and fragile area of ecological environment. The ecological environment in this area played an important role in the economic development of Northwest China. Based on the observation data of temperature and precipitation in Qilian Mountains, MOD10A2 snow products and the flow data of Shiyang River, Heihe River and Shule River, we systematically analyzed the characteristics of climate change from 1961 to 2020, and the impacts of climate change on water resources under the scenario of climate warming. The results showed that, from 1961 to 2020, the annual average temperature increased significantly, with the rate reaching 0.39 ℃·(10 a)^-1. The warming rate was the highest in the western part of Qilian Mountains, followed by the middle and eastern regions. The warming trend was the strongest in winter and the lowest in spring. The average temperature changed abruptly in 1997. The annual average precipitation increased with flucturation, with a rate of 10 mm·(10 a)^-1, which increased most obviously in the middle of Qilian Mountains. After 2004, it entered a rainy period, with a warm and humid trend. The precipitation in the four seasons showed an increasing trend and the increase of precipitation in summer contributed the most to the annual precipitation. Annual precipitation was dominated by interannual scale change, and the contribution rate of 2.8-year was approximately 64.3%. The snow cover of Qilian Mountains was obviously affected by temperature and snowfall, which was negatively correlated with summer temperature and positively correlated with snowfall. From 2016 to 2020, the temperature increase had slowed down in Qilian Mountains, the snowfall had increased, and the snow cover tended to increase. After 2000, the temperature and precipitation increased more obviously, the meltwater from glacier and snow increased, the mountainous runoff of Shiyang River, Heihe River and Shule River had an increasing trend. Our findings are of great significance to the construction of ecological civilization and coping with climate change in Qilian Mountains.

Spatial heterogeneity and driving factors of ecosystem water yield service in Yunnan Province, China based on Geodetector

HUANG Xin, PENG Shuang-yun, WANG Zhe, HUANG Bang-mei, LIU Jing

2022, 33(10):  2813-2821.  doi:10.13287/j.1001-9332.202210.025

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Water yield is an important ecosystem service. It is the key to maintain ecological security and sustainable development to accurately grasp the spatial heterogeneity characteristics and identify the key driving factors of water yield in different regions. Taking Yunnan Province with significant geospatial heterogeneity as the research area, we used InVEST model to simulate the temporal and spatial variations of water yield in Yunnan Province from 1992 to 2019. The spatial characteristics of driving factors, such as climate, vegetation, soil, terrain, land use, on water yield service were analyzed through Geodetector. The results showed that water yield of Yunnan Province showed a fluctuating trend of increasing at first and decreasing later from 1992 to 2019, with a similar spatial distribution pattern in each year, and an overall trend of gradually decreasing from northwest, west and southwest to central and east. Climatic factors (precipitation and actual evapotranspiration) were the main driving factors leading to spatial differentiation of water yield. In different watershed divisions, the impact of each driving factor on water yield had significant spatial heterogeneity: the watersheds dominated by precipitation were mainly distributed in the west of Yunling-Yuanjiang line, the Irrawaddy River, the upper reaches of Nujiang River, the lower reaches of Nujiang River, the upper reaches of Lancang River, the upper reaches of Jinsha River, Yuanjiang River and Lixian River areas. As for the east of Yunling-Yuanjiang line, in karst landform areas (Nanguang River, Chishui River, Wujiang River, Youjiang River and Panlong River) and the lower reaches of Jinsha River with high population density and shortage of cultivated land, actual evapotranspiration and land use type were the leading factors controlling the spatial pattern of water yield. The results could provide a reference for water resources management policy and ecological civilization construction in Yunnan Province, with a certain guiding significance to promote the optimization and sustainable development of ecosystem services in complex plateau-mountain area.

Evaluation of ecological-economic-social synergy in urban area of China

LIU Yan-bing, KONG Ling-qiao, LU Fei, OUYANG Zhi-yun

2022, 33(10):  2822-2828.  doi:10.13287/j.1001-9332.202209.021

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To understand the synergetic features of economy, society, and ecology in cities, we established an urban ecological-economic-social synergetic index evaluation system from three aspects (per capita green area, per capita GDP, and life expectancy per capita) and created an urban ecological-economic-social synergetic index eva-luation method. We analyzed the synergetic features by comparing the ecological-economic-social synergetic index and comprehensive function scores of 35 typical cities in China. The differences in ecological-economic-social synergy and function score for different city sizes and administrative divisions were investigated, while the synergy level of cities were classified. The results showed that the average ecological-economic-social synergetic index of 35 cities in China was 28.79, with the highest of 3.83 and the lowest of 63.04 in 2016. The synergetic index, urban econo-mic function, and social function were significantly positively correlated with urban population sizes and economic sizes. There were significant differences in synergetic index among cities with different population sizes, economic sizes, and administrative functions. The urbanization in China was still in the status of functional imbalance. Urban development was conducive to improve cities' function, but did not effectively improve the synergy of ecology, economy, and society. The ecological function of cities significantly affected urban synergy, which indicated that the poor urban ecological function was the main restrictive factor for urban synergy in China.

Soil nematode community characteristics of alfalfa field with different growing ages in the semi-arid Loess Plateau of Central Gansu, Northwest China

TIAN Jian-xia, LUO Zhu-zhu, LI Ling-ling, NIU Yi-ning, CAI Li-qun, LIU Jia-he, SUN Peng-zhou, WANG Xiao-fei

2022, 33(10):  2829-2835.  doi:10.13287/j.1001-9332.202210.032

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To clarify the impacts of long-term alfalfa plantation on the soil nematode community, soil samples were collected from different alfalfa growing ages (2 a, 9 a, 18 a) in the semi-arid area of Loess Plateau in Central Gansu by Illumina Miseq sequencing technology. The main controlling factors affecting its community change were also explored. The results showed that soil nematode belongs to 2 classes, 7 orders, 16 families and 21 genera. Among them, Chromadorea was the dominant group (44.6%-81.4%), the relative abundance of which decreased with alfalfa growing ages. Paratylenchus, Helicotylenchus, Xiphinema, Pristionchus, Ditylenchus, Panagrolaimus, Longidorus, Aprutides, Isolaimium and Aglenchus were the special nematode species of alfalfa, among which Paratylenchus (54.1%), Helicotylenchus (23.9%) and Xiphinema (21.9%) were the dominant nematodes in 2 a, 9 a and 18 a alfalfa soil respectively. Plant-parasitic nematode was the dominant group in alfalfa soil (31.8%-67.1%), and its relative abundance decreased at first and then increased with alfalfa growing ages. Results of redundancy analysis showed that soil available phosphorus and total nitrogen were the dominant environmental factors affecting community structure of soil nematodes in the region.

Behavioral and physiological responses to hypoxia stress in male and female Macrobrachium rosenbergii

QIU Xiao-long, JIANG Ying-lin, CAI Ya-shuang, CHEN Hui, LYU Xiao-jing, LIN Li, LI Jiang-tao

2022, 33(10):  2836-2844.  doi:10.13287/j.1001-9332.202210.030

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To explore the physiological and behavioral responses of male and female Macrobrachium rosenbergii under hypoxia stress, an experiment with three dissolved oxygen (DO) levels (6.46, 4.48 and 3.27 mg·L^-1, 6.46 mg·L^-1 as control) was conducted. The enzyme activities of energy metabolism in hepatopancreas and muscles of male and female M. rosenbergii were measured after six days of hypoxia stress. The results showed that the enzyme activities of aerobic metabolism in muscles and swimming abilities were significantly decreased as DO decreased from 6.46 mg·L^-1 to 4.48 mg·L^-1, with the decreases being less in males than females. There was no significant difference in enzyme activities of anaerobic metabolism. When DO was further decreased to 3.27 mg·L^-1, the enzyme activities of aerobic metabolism and anaerobic metabolism in muscles significantly decreased. The activity of lactate dehydrogenase (LDH) in anaerobic metabolism of hepatopancreas and tail-flipping speeds significantly decreased in males and females, with less decrease in females than that in males for LDH activity of hepatopancreas. The swimming ability was positively correlated with the enzyme activities of aerobic metabolism in pleopods muscles. There was significant correlation between tail-flipping abilities and enzyme activities of anaerobic metabolism. M. rosenbergii could reduce its reliance on energy metabolism during hypoxia stress, but with negative consequences on locomotor abilities. The muscles were preferentially powered to meet energy requirements of locomotion in males, while females gave priority to energy supply for hepatopancreas under insufficient oxygen conditions.

Effects of ultrasound on the physiological characteristics and competitive growth between Microcystis aeruginosa and Chlorella pyrenoidosa

TAN Xiao, XU Yang-xue, LI Nie-gui, DUAN Zhi-peng, JIANG Yu-ji, ZENG Qing-fei, QIANG Juan

2022, 33(10):  2845-2852.  doi:10.13287/j.1001-9332.202210.028

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Microcystis aeruginosa is a common bloom-forming cyanobacterium, which generally coexists and competes with Chlorella pyrenoidosa in lakes. Sonication can be used for emergency management of algal blooms. Ultrasound influences algal growth and physiological parameters, as well as interspecific competition in algal community. To explore the effects of ultrasonic stress (35 kHz, 0.035 W·cm^-3) on physiological characteristics and interspecific competition of algae, M. aeruginosa and C. pyrenoidosa were sonicated in mono- and co-cultures (1:1 mixture, according to cell concentration). Results showed that M. aeruginosa was more sensitive to ultrasonic stress. After the sonication for 600 s, both photosynthetic activity (F_v/F_m) and esterase activity of M. aeruginosa showed significant changes, with F_v/F_m values in mono- and co-cultures being decreased by 51.8% and 64.7%, respectively. In comparison, F_v/F_m values of C. pyrenoidosa changed slightly. M. aeruginosa released more chromophoric dissolved organic matter (CDOM, including tryptophan-, tyrosine-, and fulvic-like substances) than C. pyrenoidosa. The cell concentration of C. pyrenoidosa showed little changes regardless of sonication time, while the cell concentration of M. aeruginosa decreased at different degrees. The cell concentration of M. aeruginosa in co-cultures decreased by 42.6% after sonication for 600 s, which might be responsible for the dominance of C. pyrenoidosa during 8 days after sonication. M. aeruginosa inhibited C. pyrenoidosa in other treatments, but mutual inhibition appeared in the 600 s sonication treatment. After ultrasonic treatment, the activity of M. aeruginosa could recover gradually. The treatment should be conducted again within a week to improve the persistence of algal control.

Inhibitory effects of Bellamya aeruginosa on common algae in freshwater blooms

QIU Yu, WANG Jiang-nan, MA Zeng-ling, CHEN Yu-tao, ZHANG Zi-yi, WANG Min

2022, 33(10):  2853-2861.  doi:10.13287/j.1001-9332.202210.033

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The increasingly frequent algal blooms in freshwater have become a major environmental problem in the world. In recent years, algae removal by the biological method is receiving more attention for its eco-friendly characteristics. In this study, we examined the effects of Bellamya aeruginosa, a common macrobenthic snail in eutrophic lakes in China, on the growth and photosynthesis activities of the common algae occurred in freshwater blooms, including cyanobacterium Microcystis aeruginosa, coupled with green algae Chlorella vulgaris and Scenedesmus obliquus. The main aims were to clarify the interactive relationships between B. aeruginosa and algae, and to verify feasibility of using B. aeruginosa as an algal-removing organism. The results showed that B. aeruginosa could feed a large amount of algae cells in a short period after inoculation, and reached the maximal removal rate of toxic and non-toxic M. aeruginosa as well as S. obliquus within 12 hours, which were 73.7%, 73.2%, and 51.1%, respectively. Furthermore, its feeding on C. vulgaris was stronger than on other algae, with the removal rate reaching 99.2% by the end of the experiment. The microcystins produced by the toxic M. aeruginosa accumulated in the body of B. aeruginosa induced the histopathological changes in the liver tissue, and thereby hindered the feeding of B. aeruginosa. In the late stage of the experiment, the photosynthetic activities of the algal cells under each treatment were significantly lower than that in the control, indicating that the feeding of B. aeruginosa damaged algal cells and inhibited their proliferation. In addition, in the mixture of non-toxic M. aeruginosa and S. obliquus, the selective feeding of B. aeruginosa caused the dominance of non-toxic M. aeruginosa to be replaced by S. obliquus. Therefore, B. aeruginosa could inhibit the photosynthesis and reduce the biomass of algae through feeding, and thus would eliminate or mitigate the formation of algal blooms.

Spatiotemporal distribution and multi-source characteristics of microplastics in the soil and water environment of Poyang Lake Wetland, China

LI Wen-gang, JIAN Min-fei, NIE Jia-min, WU Xi-en, YANG Wen-jing, LIU Shu-li, WU Yu-bing, CHU Zhong-ren

2022, 33(10):  2862-2870.  doi:10.13287/j.1001-9332.202210.034

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The increasing microplastics (MPs) pollution in freshwater wetlands has received global concerns. To investigate the spatiotemporal dynamics of MPs in the wetlands of Poyang Lake, surface water and sediment samples were collected from five rivers entering the lake as well as the confluence of Poyang Lake into the Yangtze River, in both dry and wet seasons. The MPs in water and sediment were extracted by the digestion-filtration method and flotation-separation-digestion-filtration method, respectively. Light microscope, Fourier transform infrared spectroscopy, and scanning electron microscope were used for microplastic characterization. The results showed that the abundance of MPs ranged from 32.1 to 127.3 n·L^-1 in water samples, and from 533.3 to 1286.6 n·kg^-1 in sediment samples during the wet season. In the dry season, the abundance of MPs ranged from 87.1 to 295.5 n·L^-1 in water and from 460.0 to 1368.0 n·kg^-1 in sediment. Compared with other freshwater wetlands, Poyang Lake had higher abundance of MPs. There were temporal and spatial differences among regions. The main forms of MPs included beads, fragment, film and fiber, and the corresponding polymer components were mainly polystyrene, polypropy-lene and polyethylene. Beads (35.7% in wet season and 52.0% in dry season) were the main form of MPs in water, while fragment (45.8% in wet season and 69.7% in dry season) was the main form of MPs in sediment. Small size (<0.1 mm) MPs were dominant (>50%) in water and sediment in both seasons. The abundance of MPs with different sizes decreased with the increases of size. The potential main sources of MPs in the wetlands of Poyang Lake included the discharge of industrial wastewater, discharge from urban and rural domestic sewage treatment plants, agricultural and fishing activities, and improper disposal of domestic wastes.

Reviews

Research progress on the application of quorum sensing in the colonization and degradation enhancement of bioaugmentation functional bacteria

WANG Ya-jun, SI Yun-mei, LI Yan-juan

2022, 33(10):  2871-2880.  doi:10.13287/j.1001-9332.202210.031

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Due to the impacts of refractory organic pollutants and environment on the water treatment system, the sewage quality can not reach the standard. It is an effective measure to improve the efficiency of wastewater treatment by introducing exogenous engineering strains with relevant functional genes and the ability of horizontal gene transfer. In sewage treatment system, there are bacteria secreting signal molecules with quorum sensing. When population density reaches induction threshold, the bacteria would activate the related genes expression (such as biofilm formation, bioluminescent, antibiotics synthesis and virulence factor expression, etc.) through releasing signaling molecules, and thus trigger the behavior of other groups. Previously, researches about quorum sensing mainly concentrated on signal transduction, microbial social behavior, and medical microbiology. In recent years, stu-dies found that quorum sensing plays an important role in wastewater biological treatment and affects the colonization of the microorganism strain and pollutants degradation. Therefore, the regulation of quorum-sensing behavior is the key factor in the bioaugmentation performance. Here, we review the signaling molecules mechanism, the release of signaling molecules and its influence factors, the colonization of microbial community and the removal of pollutants. We further discussed the research from the perspective of quorum sensing biological process. The aim was to provide new idea for the effective implementation of bioaugmentation technology and the improvement of wastewater treatment efficiency, and to provide a theoretical reference for the in-depth understanding of quorum sensing regulation behavior in the process of bioaugmentation.