Table of Content

15 July 2023, Volume 34 Issue 7

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Special Features of Stable Isotope Ecology

Water use sources and its influencing factors of Pinus massoniana and Quercus acutissima community in hilly region of Southern China

ZHANG Suimeng, YE Limin, ZHOU Yizhi, WANG Xiaoxia, XU Yuanke, JIANG Jiang, LIU Ziqiang

2023, 34(7):  1729-1736.  doi:10.13287/j.1001-9332.202307.010

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The process of plant water use is complex and changeable, which is affected by various factors. Exploring the sources and influencing factors of plant water use can provide reference for clarifying the mechanisms of forest water adaptation under climate change. We chosen the typical forest communities in the hilly region of Sou-thern China, Pinus massoniana and Quercus acutissima mixed forest as the research object. By analyzing water sources of plants in different seasons, the factors affecting the changes of water sources were explored in combination with soil water, precipitation, and plant roots. The results showed that water use characteristics of P. massoniana and Q. acutissima were similar and both mainly utilized 0-40 cm soil water during the dry season, with proportions of 60.0% and 66.6%. During the rainy season, as soil water content of deep layers increased, the main water sources of both gradually shifted towards deep soil. The similarity proportion indices of P. massoniana and Q. acutissima were above 60%, indicating that there was an obvious water competition between them. Root system of Q. acutissima had plasticity in water absorption, and played a dominant role in absorbing shallow water during the dry season. Water was the main driving factor for water source transformation of Q. acutissima and P. massoniana during the rainy season. Compared with P. massoniana, Q. acutissima was more sensitive to the changes of water sources. Under the background of future warming and drying, the competition between the two species for shallow water sources might be intensified. Those two species should be sparsely planted or thinned to optimize forest structure to cope with water stress.

Anomalous stable hydrogen-oxygen isotope characteristics and water vapor sources of autumn precipitation in the Weihe River basin, Northwest China

WEI Haoyan, LU Yanwei, LI Min, LI Peiyue, CHENG Wenqing, SI Bingcheng

2023, 34(7):  1737-1744.  doi:10.13287/j.1001-9332.202307.013

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The extreme changes in autumn rain have significant impacts on the ecological environment of Weihe River basin. Based on 117 autumn rain samples and corresponding meteorological data from 2015 to 2021 at Yangling located in the middle of Weihe River basin, we investigated the stable hydrogen and oxygen isotope composition and water vapor sources of precipitation. The results showed that, (1) extreme changes in autumn rainfall in the study area occurred frequently in recent years, which could be divided into extreme-high autumn precipitation year (HAP, 2021), general autumn precipitation year (GAP, 2015-2017, 2019-2020) and extreme-low autumn precipitation year (LAP, 2018) based on the autumn rain index (ARI); (2) the stable isotopes of different types of precipitation differed significantly, with a pattern of LAP>GAP>HAP for both δ²H and δ¹⁸O values. the variations of d-excess values and the slopes and intercepts of the meteoric water lines of autumn rain showed opposite trends. The main factor controlling autumn rain anomaly was not the local meteorological parameters, but the El Nino-Southern Oscillation and the Indian Ocean dipole events, which could explain 99% and 93% of the autumn rain isotopic variations, respectively. These coupling phenomena affected water vapor transport intensity of the marine air mass to the northwest inland, which determined autumn rainfall amount and the stable hydrogen-oxygen isotope composition. Our results would be helpful for improving the understanding of autumn rain anomalies in West China, and provide basic data and theoretical support for regional hydrological model building, would thereby better serve water resources management and disaster prevention and reduction.

Nitrogen transformation and its microbial mechanism under co-composting of biogas slurry with garden waste

LIANG Xiaofeng, WANG Hong, LI Yuzhong, YANG Rui, ZHANG Dongdong, ZHOU Wanlai, QI Zhiyong, LIN Wei

2023, 34(7):  1745-1753.  doi:10.13287/j.1001-9332.202307.018

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Large amount of garden waste is consecutively produced in China every year. The composting with urea and microbial inoculum makes it possible to dispose garden waste in large quantities. However, composting accompanies with serious nitrogen loss and environmental problems. The biogas slurry contains considerable nitrogen nutrients and microorganisms, which theoretically could be used as alternative to urea and bacteria to reduce nitrogen loss, respectively. We set up three treatments of biogas slurry + garden waste (GB), biogas slurry + garden waste + urea (GBU), and biogas slurry + garden waste + urea + microbial inoculum (GBUM) to investigate the decomposition, nitrogen conversion and nitrogen loss in the co-composting process. The results showed that the high tempe-rature period of GB treatment was longer and more stable compared to that of GBU and GBUM treatments. The pH and EC value of GB treatment would benefit composting process and generated products with the highest germination index (GI) (221.8%). In addition, NH₃ and N₂O emission rates in the GB treatment were 2.59 mg·kg^-1·d^-1 and 3.65 μg·kg^-1·d^-1, respectively, being 99.0% and 50.0% lower than that in the GBU treatment and 99.4% and 40.7% lower than that in the GBUM treatment. The results of δ¹⁸O vs. δ¹⁵N^SP dual isotopocule plots approach analysis showed that the GB and GBU treatments were dominated by denitrification, and that the contribution of denitrification was higher in the GB treatment. In contrast, the GBUM treatment was dominated by nitrification. The degree of N₂O reduction in GB treatment (83.7%) was higher than the other two treatments. It was clear that GB treatment had the best maturity and lowest nitrogen loss in all treatments by enhancing the N₂O reduction process during denitrification to reduce N₂O emission. In conclusion, the biogas slurry and garden wastes could be directly co-composted without the limitation of C/N and microbial addition. The co-composting method could protect the environment and save resources leading to the recycling of waste in actual production.

Seasonal differences of feeding ecology of Uroteuthis edulis in the East China Sea based on fatty acid and stable isotope

GUO Rongpei, ZHANG Baihao, LI Nan, FANG Zhou

2023, 34(7):  1754-1762.  doi:10.13287/j.1001-9332.202307.017

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Uroteuthis edulis, an important fishery target species, plays an important role in the food web of the East China Sea. We collected U. edulis samples in the East China Sea from September 2020 to January 2021 to examine their feeding differences in autumn and winter based on fatty acid and stable isotope analyses. The results showed that the content of polyunsaturated fatty acids (PUFA) was the highest, followed by saturated fatty acids (SFA), and the lowest content of monounsaturated fatty acids (MUFA) in autumn and winter. Results of the similarity ana-lysis showed significant differences in PUFA and MUFA contents but no differences in SFA contents between autumn and winter. Results of non-metric multidimensional scale analysis showed that C18:1n9 could be used as signature fatty acids in autumn samples and C22:6n3 as characteristic fatty acids in winter samples. There was significant difference of δ¹⁵N between autumn and winter, but no difference of δ¹³C. The total area (TA), range of δ¹⁵N (NR), standard ellipse area (SEA) and the corrected version of the standard ellipse area (SEA_C) in autumn were all smaller than those in winter, but range of δ¹³C (CR) was on the contrary. Results of the Spearman rank correlation test showed that there were differences between fatty acid content and stable isotope ratio of U. edulis and the dorsal mantle length in autumn and winter. Our results could provide basic data for understanding material and energy flow of the East China Sea food web, which is conducive to the sustainable development and utilization of U. edulis.

Seasonal variations of macrozoobenthic community trophic structure in the waters adjacent to the seaweed beds of Dalian Island in the North Yellow Sea

DONG Shiqi, ZHANG Heye, SUN Guoqing, LI Lei, AN Wencong, ZHANG Yanchao, WANG Zhaoguo, GAO Dongkui, TIAN Tao, WU Zhongxin

2023, 34(7):  1763-1770.  doi:10.13287/j.1001-9332.202307.029

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To investigate the effects of algal detritus export on the trophic structure of macrozoobenthic community in the adjacent benthic habitat during the bloom and decline of macroalgae, we collected macrozoobenthos from the adjacent sea area of Dalian Island in the North Yellow Sea in May (the algal bloom period) and August (the algal decay period) of 2020. We quantifyied the seasonal changes in the trophic structure of macrozoobenthic community by using carbon and nitrogen stable isotope techniques. Results showed that δ¹³C and δ¹⁵N values of macrozoo-benthos in May ranged from -23.14‰ to -14.24‰, 6.21‰ to 12.90‰, respectively, and -22.36‰ to -14.13‰, 5.33‰ to 12.00‰, respectively in August. Results of PERMANOVA analysis showed that δ¹³C values of macrozoobenthos differed significantly between the two months, while δ¹⁵N values were not significantly different. Based on the Euclidean distance, the macrozoobenthic communities in both months could be classified into five trophic functional groups. The trophic levels of macrozoobenthos ranged from 2.00 (Nitidotellina minuta) to 3.97 (Glycera onomichiensis) in May and from 2.00 (N. minuta) to 3.96 (G. onomichiensis) in August. The δ¹³C range, δ¹⁵N range, mean centroid distance, total area and corrected standard ellipse areas which represented community trophic structure indices in August were higher than those in May. Our results indicated that the trophic diversity level and trophic niche width of the macrozoobenthic community in the adjacent sea area of the seaweed bed were higher in the algal decline season.

Original Articles

Niche and interspecific association of dominant tree species in karst forest of Junzi Mountain, Eastern Yunnan, China

LIU Yuting, HOU Manfu, HE Luyan, TANG Wei, ZHAO Jun

2023, 34(7):  1771-1778.  doi:10.13287/j.1001-9332.202307.006

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To understand the interspecific relationships of tree species in the karst forest of Junzi Mountain in Eas-tern Yunnan, we evaluated the niche and interspecific association of dominant tree species based on field survey plot data with the combining approaches of niche determination, χ² test, association coefficient (AC), and Spearman rank correlation test. The results showed that the niche breadth of Quercus glaucoides was the largest and that of Juglans mandshurica was the smallest. The ranking of niche breadth was more consistent with the ranking of frequency than with that of importance values. The degree of niche overlap was generally low, with a mean value of 0.21, suggesting a low similarity in resource utilization among tree species. The overall association of dominant tree species was significantly positive, and the ratio of positive and negative association was 1.07, indicating that the communities were at a relatively stable and the late succession stage. The χ² test and Spearman rank correlation test for tree dominant species showed that 65.3% species pairs were not significantly associated with each other, indicating a weak interspecific association. Both association coefficient (AC) and Spearman rank correlation coefficient showed significantly positive correlations with the corresponding niche overlap index. The species pairs of Q. glaucoides-Rhamnella martini, Viburnum propinquum-Zanthoxylum myriacanthum, Cladrastis delavayi-Carrierea calycina, Z. myriacanthum-C. delavayi had strong interspecific associations and wide ecological niches, thus may have potential application value in ecological restoration of karst region in eastern Yunnan and the vicinity areas.

Differences in ecological resilience of radial growth between Larix principis-rupprechtii and Picea meyeri after drought

XIE Pingping, ZHANG Boyi, DONG Yibo, LYU Pengcheng, DU Mingchao, ZHANG Xianliang

2023, 34(7):  1779-1786.  doi:10.13287/j.1001-9332.202307.007

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To understand the responses of radial growth to climatic factors and the differences in ecological resilience to drought between a heliophilous species Larix principis-rupprechtii and a shade species Picea meyeri in mixed forests, we developed the tree-ring width chronologies of L. principis-rupprechtii and P. meyeri in three mixed forests based on the samples collected from Toudaogou of Saihanba in Hebei, Ningwu County and Kelan County in Shanxi Province. We analyzed the correlation between climatic factors and various chronologies and examined the differences in resistance (R_c), recovery (R_t), and resilience (R_s) of L. principis-rupprechtii and P. meyeri in response to drought stress. The results showed that the radial growth of L. principis-rupprechtii and P. meyeri was negatively correlated with the mean and maximum air temperature from May to July in three mixed forests, and was positively correlated with the Palmer drought index (PDSI) from May to September. Radial growth decline in trees due to drought stress was significantly different between the two species among the three sites, indicating different physiological and ecological regulation strategies. The resistance of P. meyeri was stronger than that of L. principis-rupprechtii at the three study sites, with stronger resilience and resilient elasticity of L. principis-rupprechtii than P. meyeri. As a result, P. meyeri exhibited greater drought resistance than L. principis-rupprechtii. Under global warming condition, L. principis-rupprechtii might be at greater risk of growth decline than P. meyeri in this region.

Elevational patterns of seed plants and the driving mechanisms in the Himalaya

LU Zixin, YANG Man, LI Bin, HU Junjie, YU Haibin

2023, 34(7):  1787-1796.  doi:10.13287/j.1001-9332.202307.008

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The Himalaya is an important biodiversity hotspot on earth, which is of great significance to study the elevational gradients in plant diversity and its influencing factors for further revealing the formation of biodiversity and conservation. In this study, we measured the elevational range of 11886 seed plant species and different growth-forms (7918 herbaceous species, 2587 shrub species, and 1388 tree species) in the Himalaya. Using the optimal fitted regression models, we found that species richness and phylogenetic diversity of seed plants in the Himalaya mainly showed unimodal curves with the increases of elevation. The species richness and phylogenetic diversity of all species, trees, shrubs and herbaceous species reached the maximum value at the elevation of about 2000, 1000, 1600 and 3000 m, respectively. The results of partial regression and hierarchical partitioning analysis showed that climate and topography together drove the elevational gradient in plant diversity. Among these, mean annual temperature and annual precipitation contributed greatly to the elevational pattern, while surface area ratio and topographic heterogeneity had little influence. Compared with all species and herbaceous species, the elevational gradients of trees and shrubs plants were affected to a greater extent by the interaction between climate and topography.

Provenance variation of root C, N, P, and K stoichiometric characteristics under different diameter classes of Larix gmelinii

LIU Yixiao, WANG Chuankuan, SHANGGUAN Hongyu, ZANG Miaohan, LIANG Yixian, QUAN Xiankui

2023, 34(7):  1797-1805.  doi:10.13287/j.1001-9332.202307.005

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For exploring the difference of root stoichiometric characteristics among diameter classes and provenances, we examined the contents and stoichiometric ratios of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) in three diameter classes of roots (0-1, 1-2 and 2-5 mm, respectively) of 39-year-old Larix gmelinii grown in a common garden. The results showed that root element contents and their stoichiometric ratios had significant difference among three diameter classes of roots. C content, C:N, C:P, C:K were the lowest, and N, P, K contents, N:P, and N:K were the highest in 0-1 mm diameter class roots. Compared with the 1-2 and 2-5 mm diameter class roots, 0-1 mm diameter class roots had different seasonal dynamics, which might be caused by the fact that 0-1 mm diameter class roots are absorptive roots and the other diameter class roots are transport roots. There was no provenance difference in C content among all diameter class roots, while significant provenance differences were found in N, K contents, C:N, and C:K in 0-1 mm diameter class roots, and great provenance differences for in P content, C:P, N:P, and N:K in 0-1 and 1-2 mm diameter class roots. N content, K content, C:P, N:P, and N:K in 0-1 mm diameter class roots had positive correlation with the aridity index of seed-source sites, while the P content, C:N and C:K had negative correlations. The stoichiometric characteristics were related with the diameter (or function) of roots, and had significant provenance differences in 0-1 mm (absorptive root) and 1-2 mm diameter class roots, which might be attributed to their genotypic adaptation to the environment of seed-source sites.

Estimation of forest canopy closure in northwest Yunnan based on multi-source remote sensing data colla-boration

ZHOU Wenwu, SHU Qingtai, WANG Shuwei, YANG Zhengdao, LUO Shaolong, XU Li, XIAO Jinnan

2023, 34(7):  1806-1816.  doi:10.13287/j.1001-9332.202307.021

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Forest canopy closure (FCC) is an important parameter to evaluate forest resources and biodiversity. Using multi-source remote sensing collaborative means to achieve regional forest canopy closure inversion with low cost and high-precision is a research hotspot. Taking ICESat-2/ATLAS data as the main information source and combined with data of 54 measured plots, we estimated FCC value by the Bayesian optimization (BO) algorithm improved random forest (RF), K-nearest neighbor (KNN), and gradient boosting regression tree (GBRT) model at footprint-scale. Combined with multi-source remote sensing image Sentinel-1/2 and terrain factors, we estimated the regional-scale FCC value of Shangri-La in the northwest Yunnan based on deep neural network (DNN) optimized by BO algorithm. The results showed that six characteristic parameters (percentage of tree canopy, standard deviation of relative height of photons at the top of the canopy, minimum canopy height, difference between 98% canopy height and median canopy height in the segment, number of top canopy photons, apparent surface reflectance) out of the 50 parameters that were extracted from ATLAS lidar footprint had higher contribution rate after RF characteristic variable optimization, which could be used as model variable for footprint-scale remote sensing estimation. Among BO-RF, BO-KNN, and BO-GBRT models, the FCC results estimated by the BO-GBRT model were the best at footprint-scale. The coefficient of determination (R²) was 0.65, the root mean square error (RMSE) was 0.10, the mean absolute residual (RS) was 0.079, and the prediction accuracy (P) was 0.792 for leave-one-out cross validation. It could be used as the FCC estimation model of 74808 ATLAS footprints for forest in the study area. We used the ATLAS footprint-scale FCC value of forest as the large sample data of the regional-scale BO-DNN model and combined with multi-source remote sensing factors to estimate FCC in the study area, the accuracy of the 10-fold cross-validation BO-DNN model was R²=0.47, RMSE=0.22, P=0.558. The mean values of FCC in the study area estimated by BO-DNN model and ordinary Kriging (OK) interpolation were 0.46 and 0.52, respectively, and the values mainly distributed in 0.3-0.6, accounting for 77.8% and 81.4%, respectively. The FCC efficiency obtained directly by the OK interpolation method was higher (R²=0.26), but the prediction accuracy was significantly lower than the BO-DNN model (R²=0.49). The FCC high value was distributed from northwest to southeast in the study area, and the northern and southeastern regions were the main distribution areas of high and low FCC values, respectively. It had certain advantages to estimate mountain area FCC based on ICESat-2/ATLAS high-density footprint, and the estimation results of small sample data at footprint-scale could be used as large sample data of deep learning model at region-scale, which would provide a reference for the low-cost and high-precision to FCC estimation on the footprint-scale up to the extrapolated regional-scale.

Effects of mixed substrates of different agricultural and forestry residues on the cutting seedlings of Thuja sutchuenensis

MA Fanqiang, JIAN Zunji, GUO Quanshui, QIN Aili, PEI Shunxiang, ZHANG Guangjian, HUANG Jilan, ZHOU Liping

2023, 34(7):  1817-1824.  doi:10.13287/j.1001-9332.202307.014

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To screen environment-friendly seedling cultivation substrates which could replace peat and with less cost, we compared the effects of different agricultural and forestry residue mixed substrates on cutting propagation of Thuja sutchuenensis, in an experiment following randomized block design. There were five types of mixed substrates, including peat + vermiculite + perlite (T₁), edible mushroom residue (EMR) + vermiculite + perlite (T₂), carbo-nized rice husk (CRH) + vermiculite + perlite (T₃), EMR + slag + sawdust (T₄) and CRH + EMR + slag (T₅). The results showed that the bulk density of T₃ was the lowest, followed by T₂, which significantly differed from other mixed substrates. The non-capillary porosity of T₂ was significantly greater than that of T₁, while the capillary porosity and the total porosity of T₂ was lower than T₁ and T₃, respectively. T₂ had the highest contents of total nitrogen, total phosphorus, total potassium, alkali-hydrolyzed nitrogen, available phosphorus, substrate moisture and the highest pH, which differed significantly from other mixed substrates in most chemical indicators. The membership function values of rooting rate and growth indicators of cuttings with different mixed substrates were in order of T₂ > T₃ > T₁> T₅ > T₄. Most indicators with larger grey relation values were physical indicators. The top five indicators were capillary water capacity, total potassium, field water capacity, maximum water capacity, and total porosity, with both capillary water capacity and total potassium content ranking first. In general, the physicochemical properties, rooting rate, and growth characteristics of cuttings under T₂ were better than those of other mixed substrates. The capillary water capacity and total potassium were the main factors affecting rooting and growth of cuttings. At the early stage of cutting, the physical properties of mixed substrate had greater effect on rooting rate and growth of cuttings than the chemical properties. Overall, our results suggested that T₂ should be preferred in the cutting propagation of T. sutchuenensis.

Responses of photosynthetic characteristics of Phragmites australis to simulated warming in salt marshes of the Yellow Sea and Bohai Sea, China

YUAN Shuyu, XIE Liujuan, YE Siyuan, ZHOU Pan, PEI Lixin, DING Xigui, YUAN Hongming, GAO Zongjun

2023, 34(7):  1825-1833.  doi:10.13287/j.1001-9332.202307.001

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Coastal wetlands are highly efficient in blue carbon sequestration. The impacts of climate warming on photosynthetic rates and light response characteristics of wetland plants would change the magnitude of carbon sequestration in coastal wetlands. We constructed warming observation stations in Phragmites australis (Phragmites) wetlands located in the Yellow River Delta in Dongying with dry climate, and in Yancheng by the Yellow Sea with wet climate. By using a Li-6800 photosynthesis system, we investigated the responses of simulated warming on photosynthetic characteristics of Phragmites in both wetlands, and compared the difference between months (June and August) in Dongying wetland. The results showed the photosynthetic rates of Phragmites were higher in June than in August. Warming increased net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (g_s) and intercellular carbon dioxide concentration (C_i) in the two months, but the variability of P_n to warming was lower in August. The P_n and water use efficiency (WUE) of Phragmites in the Yancheng wetland were higher than Dongying wetland, and the maximum net photosynthetic rate (P_{n max}), light saturation point (LSP), apparent quantum efficiency (AQY), and dark respiration rate (R_d) of the former responded more positively to warming. The values of AQY, LSP and P_{n max} of Phragmites in the Yancheng wetlands were increased by 16.7%, 53.6% and 30.3%, respectively, in the warming plots. Our results suggested that warming could improve the utilization efficiency of weak light, the adaptability to strong light and photosynthetic potential of Phragmites under rainy and humid conditions. This study is of importance for accurately quantifying carbon sequestration of coastal wetlands at the regional and seasonal scales in the context of climate warming.

Short-term legacy effects of long-term nitrogen and water addition on soil chemical properties and micro-bial characteristics in a temperate grassland

DAI Zecheng, LIU Yuexiu, DANG Ning, WANG Zhirui, CAI Jiangping, ZHANG Yuge, SONG Yongbo, LI Hui, JIANG Yong

2023, 34(7):  1834-1844.  doi:10.13287/j.1001-9332.202307.016

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Nitrogen deposition and summer precipitation in eastern Inner Mongolia are predicted to increase in recent decades. However, such increases in nitrogen inputs and precipitation may not be continuous under the future new patterns of global change, with the direction and magnitude of which may change or weaken. The legacy effects of nitrogen and water addition after cessation on ecosystems are still unclear. Based on a 13-year nitrogen and water addition experiment in temperate grassland of northern China, we examined the short-term (2 years) legacy effects of historical nitrogen and water addition on soil physicochemical properties and microbial properties after the cessation of nitrogen and water addition in the 14th year. The results showed that the positive effects of historical nitrogen addition on most of soil nutrient variables diminished after two years of cessation, including ammonium nitrogen, nitrate nitrogen, dissolved organic carbon and nitrogen, and Olsen-P concentrations. In contrast, there were legacy effects on soil microbial characteristics. For example, the historical nitrogen input of 15 g N·m^-2·a^-1 reduced microbial biomass carbon, respiration, and alkaline phosphomonoesterase activity by 73.3%, 81.9%, and 70.3% respectively. It implied that microbial parameters restored slowly in comparison with soil nutrients, showing a hysteresis effect. Results of Pearson’s correlation and redundancy analysis showed that the legacy effects of historical nitrogen addition on microbial parameters could be attributed to the negative effects of nitrogen addition on soil pH. Historical water addition showed significant legacy effects on soil pH, ammonium nitrogen, dissolved organic carbon and nitrogen, respiration, and soil enzyme activities, which significantly interacted with historical nitrogen addition. These results are of great significance to predict the changes in grassland ecosystem functions and services under the local environmental improvement conditions, and to reveal the restoration mechanism of degraded grassland.

Contribution of microbial necromass to soil organic carbon formation during litter decomposition under incubation conditions

XUE Zhijing, QU Tingting, LIU Chunhui, LIU Xiaokang, WANG Rui, WANG Ning, ZHOU Zhengchao, DONG Zhibao

2023, 34(7):  1845-1852.  doi:10.13287/j.1001-9332.202307.004

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We conducted a 512-day incubation experiment to study the dynamics of microbial necromass and soil carbon fraction in the ‘litter-soil’ transformation interface soil layer (TIS) during litter decomposition, using a perennial C3 herb, Stipa bungeana, in the loess hills. The results showed that soil microbial necromass was dominated by fungi in the early and middle stages, and by bacteria in the late stage. The contribution of fungal necromass C to mineral-associated organic C (MAOC) was significantly higher (38.7%-75.8%) than that of bacteria (9.2%-22.5%) and 2-3 times more than the contribution rate of bacterial necromass. Soil organic C (SOC) content was decreasing during litter decomposition. The input of plant C resources stimulated microbial utilization of soil C fractions. The continuous decrease in particulate organic C during the early and late stages of decomposition was directly responsible for the decrease in SOC content. In contrast, the fluctuating changes in microbial necromass C and MAOC played an indirect role in the reduction of SOC. The increase in soil microbial necromass C caused by a single exogenous addition of litter did not directly contribute to SOC accumulation.

Effects of long-term tillage practices on the stability of soil aggregates and organic carbon in black soil farmland

SUI Pengxiang, LUO Yang, ZHENG Hongbing, LI Ruiping, WANG Hao, YUAN Ye, ZHENG Jinyu, LIU Wuren

2023, 34(7):  1853-1861.  doi:10.13287/j.1001-9332.202307.027

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We examined the effects of different tillage practices on plough layer soil structure and organic carbon stabilization in black soil farmland with a long-term positioning platform. The wet-sieving method and infrared spectroscopy method were used to investigate the impacts of conventional tillage (CT), no-tillage (NT), sub-soiling tillage (ST), and moldboard plowing tillage (MP) on soil aggregates distribution and organic carbon characteristics in 0-40 cm soil layers. Compared to CT, both NT and ST treatments significantly increased the proportion of large macroaggregates (>2 mm) in the topsoil layer (0-20 cm)and that of small macroaggregates (0.25-2 mm) in the subsoil layer (20-40 cm) for NT, ST, and MP. NT, ST, and MP treatments resulted in higher mean weight dia-meter (MWD) and mean geometric diameter (GMD) of soil aggregates in both the topsoil and subsoil layers. NT treatment improved organic carbon contents in bulk soil and large macroaggregates in the topsoil layer, while ST and MP enhanced organic carbon contents in bulk soil and large macroaggregates in the subsoil layer. The contribution rate of small macroaggregates organic carbon content to the total was between 68.9% and 83.4%. Furthermore, the organic carbon chemical stabilization of soil body and aggregates increased in the topsoil and subsoil layers under NT treatment compared to others. The MWD had a positive correlation with the organic carbon content and chemical stability of soil body and small macroaggregates. These findings offered a theoretical basis for understanding the impacts of different tillage practices on the stability of soil aggregate and organic carbon in black soil region.

Infiltration and shear strength characteristics of gully heads soil of typical vegetation on the gullied Loess Plateau, Northwest China

YANG Hao, WANG Wenlong, LOU Yibao, FENG Lanqian, ZHU Ya’nan

2023, 34(7):  1862-1870.  doi:10.13287/j.1001-9332.202307.020

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Gully head is the main active part of gully erosion, which seriously affects the occurrence of gully headcut erosion. To investigate root distribution and soil physical and mechanical characteristics of typical vegetation gully head, we analyzed the infiltration, root distribution, physical and mechanical properties of soil-root complex of soil in different layers (0-1 m) in natural restoration gully head and artificial restoration gully head. The results showed that the variability of soil bulk and total porosity among different vegetation gully heads was low, with bulk density ranging from 1.10 to 1.37 g·cm^-3 and total porosity ranging from 48.3% to 58.4%. Infiltration index of different vegetation gully heads generally decreased with increasing soil depth. The infiltration rate of different soil layers in natural restoration gully head tended to stabilize in 20-30 min, while that of artificial restoration gully head tended to stabilize in 40 min. The infiltration capacity and average infiltration rate of artificial restoration gully head were generally higher than those of natural restoration gully head in all soil layers. Root length density, root surface area density, and average diameter all tended to decrease with increasing soil depth. Except for the 20-40 cm soil layer, root length density, root surface area density and average diameter of natural restoration gully head were all lower than those of artificial restoration gully head. Root system of both vegetation gully heads mainly consisted of 0-0.5 mm roots, accounting for 84.2%-93.6% of the total root length. In the vertical depth, with the increases of water content, the cohesion force decreased linearly with the deepening of soil layer, ranging from 0.42 to 22.67 kPa. The average cohesion force of artificial restoration gully head was higher than natural restoration gully head at each level of water content. The study revealed the effects of vegetation on the gully head cut erosion, which could provide scientific basis for the effective prevention and control of soil erosion in the region.

Effects of groundwater depth on groundwater recharge and soybean growth dynamics in Northeast China Plain

ZHU Zhenchuang, SUN Shijun, ZHU Miaomiao, LI Dongyi, WANG Zhe, SHEN Ruxuan, CHEN Wei

2023, 34(7):  1871-1882.  doi:10.13287/j.1001-9332.202307.015

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To explore the groundwater recharge rate and soybean growth dynamics under different groundwater depths, we conducted a field experiment with four groundwater depth treatments (1 m, D₁; 2 m, D₂; 3 m, D₃; 4 m, D₄) through the groundwater simulation system in 2021 and 2022 and explored the relationships between groundwater depth and groundwater recharge, irrigation, growth dynamics of soybean plants, and yield. We used the Logistic regression model to simulate the dynamics of soybean growth indices, including plant height, leaf area index, and dry matter accumulation. The results showed that compared with D₁ treatment, the amount of groundwater recharge under D₂, D₃, and D₄ treatments decreased by 81.1%, 96.8%, 97.5% and 80.7%, 96.7%, 97.3% in the two years, respectively. The groundwater in D₁ treatment could meet water needs of soybean throughout the whole growth period, except that irrigation was needed in the sowing stage. The amount of irrigation under D₁ treatment was decreased by 91.7%, 93.0%, 94.2%, and 90.9%, 92.9%, 94.0% in the two years, respectively, compared with D₂, D₃, D₄ treatments. Among the four treatments, D₁ treatment took the shortest time for entering the rapid growth stage and reach the maximum growth rate, which had the highest maximum growth rate. At the mature stage of soybean, the dry matter distribution ratio of stem in D₁ treatment was the highest. D₁ treatment promoted the translocation of post-flowering assimilates in soybean, and its post-flowering assimilate contribution to seeds increased by 15.5%, 16.2%, 32.6% and 45.5%, 48.7%, 63.3% in the two years, respectively, compared with D₂, D₃, D₄ treatments. D₁ treatment had the highest plant height, leaf area index, and dry matter accumulation, follo-wed by D₄ treatment, while D₃ treatment had the lowest. Soybean yield, number of pods per plant, number of grains per plant, and 100-grain weight all decreased and then increased with increasing groundwater depth, following an order of D₁>D₄>D₂>D₃. Soybean yield was significantly positively correlated with groundwater recharge, which was positively correlated with plant height, leaf area index, and dry matter accumulation. Our results indicated that the D₁ treatment with adequate groundwater recharge increased plant height, leaf area index, and dry matter accumulation, coordinated the distribution and translocation of dry matter among all plant parts in the late soybean growth period, and ultimately achieved the highest yield. When groundwater depth was deep (D₄), groundwater recharge was small. In such case, the growth and development status and yield of soybean could also reach a high level if there was sufficient water supply.

Ecosystem service value of conservation tillage with cover crop-maize intercropping in the black soil region of Northeast China

BA Xiaobo, SUI Xin, LIU Mingda, XIE Hongtu, LIANG Chao, BAO Xuelian

2023, 34(7):  1883-1891.  doi:10.13287/j.1001-9332.202307.012

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Scientific evaluating ecosystem service value (ESV) of cover crop cultivation system can provide important guidance for the construction of conservation tillage pattern in Northeast China. Based on empirical analysis and the theory of ecosystem service value, we calculated the ESVs of intercropping maize with gramineous cover crop ryegrass and with leguminous cover crops, alfalfa and hairy vetch, with maize monoculture as the control. The ESVs included product supply, gas regulation, nutrient cycling, and soil and water conservation. Results showed that ESVs of cover crop-maize intercropping were higher than those of maize monoculture. Nutrient cycling value was the highest, followed by product supply value, accounting for 67.3% and 29.3% of total ESV, respectively. The nutrient cycling value of cover crop-maize intercropping was higher than that of maize monoculture. The product supply value of alfalfa-maize and hairy vetch-maize were 18.7% and 21.0% higher than that of ryegrass-maize, respectively. Cover crops had the potential to increase the value of gas regulation services, but had little impact on the value of soil and water conservation. Considering the ESVs, intercropping maize with leguminous cover crops would have the greatest benefits.

Three-dimensional model construction and wind simulation of different tree species in farmland shelter

JIA Xiaoxiao, XIAO Huijie, XIN Zhiming, FAN Guangpeng, LI Junran, YANG Yuli, WANG Litao

2023, 34(7):  1892-1900.  doi:10.13287/j.1001-9332.202307.025

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Protective forests are the ecological barriers of oases in arid sand areas and can effectively prevent and control wind and sand hazards. The structural characteristics of individual trees, as the basic unit of protective forests, are the key factors affecting the protective benefits. With the typical leafless tree species of Ulan Buh Desert oasis, i.e., Populus alba var. pyramidalis, Populus nigra var. thevestina, and Populus popularis, as the research objects, and by using the ground-based LiDAR and through computational fluid dynamics (CFD), we fully explored the structural characteristics of individual trees and their surrounding aerodynamic characteristics on the basis of real 3D models. We further established the relationship between structural parameters of individual trees and wind field index. The results showed that combining AdQSM and MeshLab to build tree models had high accuracy. The wind field around the individual trees could be roughly divided into six regions, including the attenuation zone of the windward side of the plant, the acceleration zone at the top of the plant, the eddy zone, the calm zone, the transition zone, and the recovery zone of leeward side of the plant. The pressure field around individual trees showed a gradual change of high pressure on the windward side to low pressure on the leeward side. Horizontally, in the range of 20% to 50% reduction in relative wind speed, the effective protection distances were 0.21H-1.51H, 0.20H-0.91H, and 0.25H-1.64H (H was the corresponding tree height) for P. alba var. pyramidalis, P. nigra var. thevestina, and P. popularis, corresponding to effective protection areas of 18-294, 15-227, and 18-261 m², respectively. The maximum wind speed decay rate in the vertical direction was at 0.3H height for P. alba var. pyramidalis and P. popularis, and was reflected at 0.5H height for P. nigra var. thevestina. The correlation and stepwise regression analysis of the single tree structure parameters with the wind field indicators clearly indicated that optical porosity and volume porosity dominated the protection effect. Among the wind field factors, the best regression models related to the porous coefficient were screened for three factors, including diameter at breast height, tree surface area, and optical porosity. The regression variables screened for effective protection distance and effective protection area differed among the classes.

Land use function change and its driving force of the “production-living-ecological” space in Fenhe River Basin from 1980 to 2020

FU Jianxin

2023, 34(7):  1901-1911.  doi:10.13287/j.1001-9332.202307.022

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It is of importance to analyze land use function change and driving factors of the production-living-ecological space of national territory to realize the coordinated development. Based on land use remote sensing data in 1980, 1990, 2000, 2010, and 2020, we used the methods of land use dynamics, transfer matrix, center of gravity shift and geographic detector to analyze the pattern of production-living-ecological space in Fenhe River Basin and explore the influencing factors. The results showed that the area proportion of production-living-ecological space in the basin was ecological space > production space > living space from 1980 to 2020. The ecological space and agricultural production land showed a decreasing trend, with a decrease of 72441.19 and 105882.96 hm², respectively. The living space and industrial production land showed an upward trend, with an increase of 119503.02 and 58821.13 hm², respectively. There was significant difference in the land use function change of production-living-ecological space. Agricultural production land had the largest transferred area, accounting for 47.9% of the total. The largest transfer area of industrial land was agricultural land, which accounted for 61.3% of the total from 2000 to 2010. The occupation of agricultural land by urban living land was mainly distributed in the marginal area of various urban areas of Taiyuan Basin. Among them, the increasing area of urban living land in Taiyuan City showed a trend of gradual southward expansion. The center of gravity migration of urban land for living and industrial production land was the most obvious, and that for living showed the trend of first moving south and then moving north, while industrial production land moved northward significantly. The influence of social-economic factors on the land use change was obviously stronger than that of natural factors, while the interaction between social-economic factors had a stronger explanatory power. The results would provide reference for clarifying the relationship between land function transformation and optimizing land use function of production-living-ecological space.

Comparison of ecosystem health in different geomorphic regions of Chishui River Basin, Southwest China

CHEN Honglian, LI Rui, ZHANG Yushan, WU Qinglin, YUAN Jiang, GAO Jiayong

2023, 34(7):  1912-1922.  doi:10.13287/j.1001-9332.202307.024

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Ecosystem health of the Chishui River Basin (CRB, a crucial ecological barrier in the upper reaches of the Yangtze River) is vital for the ecological security and sustainability of the Yangtze River Basin. We used RUSLE model, SWAT model, Fragstats and geographic detectors to construct a theoretical framework of ecosystem health assessment for CRB, and examined the spatiotemporal variations and driving factors of ecosystem health in CRB under ecological restoration from 2010 to 2020. The results showed that ecosystem service in the CRB decreased and then increased during 2010-2020 and the overall trend was downward. The overall ecosystem service function was higher in the Danxia (non-karst) area than that in the karst area. The ecosystem health was generally subhealthy, with the Danxia area being mostly extremely healthy and healthy, whereas the karst area mostly subhealthy and unhealthy. There were differences in the dominant drivers of ecosystem health between karst and Danxia areas. Vegetation, precipitation, and bedrock bareness rate were the dominant drivers in the karst area, while vegetation, land use, and precipitation were the dominant factors in Danxia area. After interaction detection, the explanatory power of impact factors increased, and the dominant interaction factor combinations in different geomorphological type regions had shown great differences. Among them, precipitation∩normalized difference vegetation index (NDVI), precipitation∩digital elevation model (DEM) and precipitation ∩ bedrock bareness rate were the dominant interaction factor combinations in the karst area, and NDVI∩precipitation, NDVI∩land use and NDVI∩DEM were the dominant interaction factor combinations in Danxia area. These results would provide scientific support for health maintenance and conservation of CRB ecosystem.

Differences in the evolution of urban and rural surface thermal environment and their responses to urban renewal in Shanghai, China

ZHAO Chengyu, ZHANG Shuyi, ZHU Hongkai, GU Xuan, LIU Min

2023, 34(7):  1923-1931.  doi:10.13287/j.1001-9332.202307.023

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The rapid and extensive urbanization has profound impacts on urban thermal environment. It is of great significance to comprehensively understand how urbanization affects the evolution of urban thermal environment for urban ecological safety, environmental quality, and residents’ health. Based on daily land surface temperature (LST) products of MODIS Aqua satellite in the summer of 2002-2020, we investigated the evolution of urban-rural differences in surface summer thermal environment in Shanghai during 2002-2020 and its response to urban spatial renewal. We used normalized land surface temperature (NLST) and urban heat island ratio index (URI) as the surface thermal environment measurement indicators, by combining vegetation index and impervious surface cove-rage, and used M-K trend analysis and interpretation analysis. The results showed that the linear growth rate of LST in Shanghai was 0.09 ℃·a^-1 (2002-2020), and that URI showed a trend of first increasing (2002-2010) and then decreasing (2010-2020). The mean summer LST was generally in the order of urban core>suburban>rural. 1.6% of the areas showed a significant cooling trend, of which 54.0% were distributed in the urban core. 39.5% of the regions showed a significant warming trend, of which 77.6% were distributed in the suburban. In general, there were concentrated significant cooling areas in the highly urbanized urban areas, while there was a significant warming trend in the suburban. The transformation from urban expansion to urban renewal was the main reason for the emergence of concentrated and significant cooling areas in the urban. Nearly 20% of the urban area showed a signi-ficant increase of vegetation coverage. Urban renewal projects such as gathering vegetation or dispersing impervious surfaces in highly urbanized areas are important ways to effectively improve the urban residential thermal environment.

Influence of green biomass composition on the urban thermal environment in hot summer and warm winter regions: The example of Fuzhou residential area

QIU Yao, LUO Tao, WANG Qiong, JIANG Siyu

2023, 34(7):  1932-1940.  doi:10.13287/j.1001-9332.202307.026

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The aim of this study was to investigate the relationship between green biomass composition and thermal environment, as well as their optimal composition pattern. We decomposed total green biomass in a certain spatial range into two categories: trees and shrubs-grasses, with urban residential areas as sampling sites and based on aerial photography and field research data of green biomass and optimized green biomass measurement method. We analyzed the correlation between the green biomass composition indicators (shrub and grass biomass, tree canopy biomass, green biomass, mean tree canopy biomass, number of trees) and ambient temperature and humidity in different spatial ranges. The results showed that the most significant cooling and humidifying effect of different green biomass composition indicators was at 50 m below the building scale. The mean tree canopy biomass and tree canopy biomass were the key factors affecting ambient temperature and humidity, respectively, in different time periods during the day. With an average canopy biomass of about 211 m³ and 62 trees in a 50 m space, the regulation effects of trees on ambient temperature and humidity were closer to the thermal comfort requirements of human body.

Effects of bacteria on early-stage litter decomposition in Wudalianchi volcanic forest

HUANG Qingyang, XIE Lihong, CAO Hongjie, WANG Limin, YANG Fan, WANG Jifeng, LIU Yingnan, NI Hongwei

2023, 34(7):  1941-1948.  doi:10.13287/j.1001-9332.202307.002

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To understand the role of microorganisms in litter decomposition and nutrient cycling in volcanic forest ecosystem, we conducted in-situ litterbag decomposition experiment and used Illumina MiSeq high-throughput sequencing to analyze the response of bacterial community structure and diversity during the decomposition of litters from Larix gmelinii, Betula platyphylla and Populus davidiana, the dominant tree species in volcanic lava plateau of Wudalianchi. The results showed that mass remaining percentage of litters of three species after 18-month decomposition was 63.9%-68.1%. Litter of B. platyphylla decomposed the fastest, with significant difference in N, C:N, and N:P before and after decomposition. The richness of bacterial species and diversity index differed significantly among the three litters. Proteobacteria, Actinomycetes, and Bacteroidetes were the dominant bacterial groups at the phylum level, while Rhizobium, Sphingomonas, and Pseudomonas were the dominant groups at the genus level, with significant difference among the three litters. After 18 months, the dominant bacterial groups in litter tended to be consistent with those in volcanic lava platform soil. In the volcanic forest ecosystem, bacterial diversity and community structure were mainly affected by P, C:N, and N:P in the litter.

Effects of long-term fertilization patterns on bacterial community structure and soil nutrients in dryland of yellow soil

XIONG Han, LIU Yanling, LI Yu, ZHANG Yarong, HUANG Xingcheng, YANG Yehua, ZHU Huaqing, JIANG Taiming

2023, 34(7):  1949-1956.  doi:10.13287/j.1001-9332.202307.011

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Understanding the responses of soil bacterial community to long-term fertilization in dryland of yellow soil could provide theoretical basis for establishing scientific fertilization system and cultivating healthy soil. Based on a 25-year long-term fertilization experiment on yellow soil, we collected soil samples from 0-20 cm layer under different fertilization treatments: no fertilization (CK), balanced application of N, P and K fertilizers (NPK), single application of organic fertilizer (M), combined application of constant organic and inorganic fertilizer (MNPK), and 1/2 organic fertilizer instead of 1/2 chemical fertilizer (MNP). Illumina MiSeq high-throughput sequencing technology was used to examine the effects of different fertilization patterns on soil bacterial community structure and soil nutrient content. The main driving factors of soil bacterial community were explored. The results showed that soil pH and organic matter content under treatments with organic fertilizer increased by 11.4%-13.5% and 28.8%-52.0%, respectively, compared to that under NPK treatment. Long-term fertilization did not affect soil bacterial α diversity, but significantly affected soil bacterial β diversity. Compared with CK and NPK treatment, treatments of M, MNP, and MNPK significantly changed soil bacterial community structure, and increased the relative abundance of Fusobacteria and Anaerobes. Four fertilization treatments increased the relative abundance of Bacteroidetes, and decreased the relative abundance of Actinomyces and Campylobacter, compared to CK. Soil pH was the most important factor affecting soil bacterial community structure. Fertilization-stimulated rare microbial taxa (Pumilomyces and Anaerobes) were more sensitive to changes in different environmental factors and were the main drivers of the formation of community versatility. In conclusion, organic fertilizer improved soil properties and fertility and changed soil bacterial community structure, which are conducive to cultivating healthy soil.

Soil microbial community characteristics and the influencing factors at different elevations on the eastern slope of Helan Mountain, Northwest China

PANG Danbo, WU Mengyao, ZHAO Yaru, YANG Juan, DONG Liguo, WU Xudong, CHEN Lin, LI Xuebin, NI Xilu, LI Jingyao, LIANG Yongliang

2023, 34(7):  1957-1967.  doi:10.13287/j.1001-9332.202307.031

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As an important bridge connecting aboveground communities and belowground biological processes, soil microorganisms play an important role in regulating belowground ecological processes. The altitudinal changes and driving factors of soil microbial community in mountain ecosystem in arid region are still unclear. We measured soil physicochemical properties at seven altitudes in the range of 1300-2800 m in Helan Mountains, and investigated the understory community composition, soil physicochemical properties, and soil microbial community. The driving factor for soil microbial community was explored by variance partitioning analysis and redundancy analysis. The results showed that the total amount of soil microorganisms and bacterial biomass first increased and then decreased with the increases of altitude, fungi, actinomyces, arbuscular mycorrhizal fungi, Gram-positive bacteria, and Gram-negative bacteria groups showed a gradual increase. The variation of fungal-to-bacterial ratio (F/B) along the altitude showed that the cumulative ability of soil bacteria was stronger than that of fungi at low altitudes, while the pattern is opposite at high altitudes. The ratio of Gram-positive bacteria to Gram-negative bacteria (GP/GN) showed an overall decreasing trend with the increases of altitude, indicating that soil bacteria and organic carbon availability changed from “oligotrophic” to “eutrophication” and from “low” to “high” transition as the altitude increased. Vegetation properties, soil physical and chemical properties jointly accounted for 95.7% of the variation in soil microbial community. Soil organic carbon (SOC), soil water content (SWC), and total nitrogen (TN) were significantly correlated with soil microbial community composition. Our results revealed the distribution pattern and driving factors of soil microbial communities at different elevations on the eastern slope of Helan Mountain, which would provide theoretical basis and data support for further understanding the interaction between plant-soil-microorganisms in arid areas.

Bacterial community structure of water, sediment and microplastics in Poyang Lake wetland

YU Jinli, CHEN Xu, ZHANG Ying, ZHU Yingting, ZHANG Wenhui, LUO Siqi, LIU Shuli

2023, 34(7):  1968-1974.  doi:10.13287/j.1001-9332.202307.028

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As a new type of pollutant, microplastics accumulate continuously in the environment. The environmental problems caused by microplastics have attracted wide attention. In this study, we collected water, sediment and four types of microplastics (film, foam, fiber and fragment) from wetland in East Lake area of Poyang Lake. We used high-throughput sequencing technology to analyze the bacterial diversity and community structure of water, sediment, and microplastics surface. The results showed that the bacterial richness and diversity of water and sediment were significantly higher than that on microplastics, and the bacterial richness of foaming microplastics was significantly lower than that of the other three types of microplastics. There were significant differences of bacterial communities between water, sediment, and microplastics. There were significant differences cross different types of microplastics. Proteobacteria, Bacteroidetes, and Actinobacteria were the main bacterial communities of water, sediment, and microplastics. The relative abundance of Bacteroidetes and Actinobacteria in water was higher than that in sediments and microplastics, while the relative abundance of Bacteroidetes and Actinobacteria in foaming microplastics was higher than that in other three types. At the genus level, the dominant ones included Massilia, Flavobacteria, and Pseudomonas. The relative abundance of Massilia and Pseudomonas in water and sediments was lower than that on microplastics, and the relative abundance of Flavobacteria was not different among water, sediment and microplastics. The relative abundance of Massilia in microplastics followed an order of fragment>fiber>film>foam, and that of Pseudomonas was film>fiber>foam>fragment. The results of metabolic pathway prediction analysis showed that except for foaming microplastics, the bacterial metabolic pathways on the surface of the other three types of microplastics were significantly different from those in water and sediment. The cellular processes, organismal systems, environmental information processing, and human diseases in bacterial metabolic pathways on microplastics surface were significantly higher than those in water and sediment. Our results suggested that microbial community structure on the surface of microplastics was significantly different from that in water and sediment, and that the morphology type of microplastics affected microbial community structure on the surface.

Effects of nitrogen inputs and mowing on the abundance and species richness of herbivorous insects in a meadow steppe

WU Yuanxiu, LIU Jingtong, DING Cong, ZHANG Bingchuan, LIANG Xiaosa, NING Yu, YIN Jiangxia, LV Xiaotao

2023, 34(7):  1975-1980.  doi:10.13287/j.1001-9332.202307.009

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To reveal the effects of nitrogen (N) inputs and mowing on the abundance and richness of insect community in meadow steppe, we investigated the abundance and diversity of herbivorous insects under four treatments in Inner Mongolia meadow steppe in August 2022, including control, N addition, mowing, and combined N addition and mowing. At a long-term control experimental platform, we collected insects using the vacuum sampling method. The results showed that N addition significantly increased the abundance of herbivorous insects, and mowing significantly decreased the abundance of herbivorous insects. Nitrogen addition significantly increased insect abundance in unmown condition but not in the mown condition. The responses of insect abundance at the community level to N addition were mainly driven by the dominant groups, Cicadellidae and Lygaeidae, which was affected by the abundance of Gramineae species. In contrast, their responses to mowing were the opposite. Both N addition and mowing did not affect the diversity of herbivorous insects. Our results indicated that the responses of herbivorous insect abundance to N inputs and mowing were directly regulated by food resources. With increasing food resource availability, the abundance but not the diversity of herbivorous insects increased, with stronger responses of dominant groups than subordinate ones.

Effect of low-temperature stress on the survival of Meloidogyne incognita and its application in greenhouse of northern China

WEI Peiyao, PAN Song, PENG Deliang, ZHANG Feng, CHEN Zhijie, ZHANG Shulian, LI Yingmei

2023, 34(7):  1981-1987.  doi:10.13287/j.1001-9332.202307.032

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We examined the effects of low temperature on egg hatching and killing rate of the 2nd instars of Meloi-dogyne incognita (J2) in the laboratory. We further evaluated the effects of two soil treatment methods on the survival rate of M. incognita in northern China in a field experiment. The results of laboratory experiment showed that survival rate of J2 was 0 after being subjected to -7 ℃ for 24 hours, and that egg hatching was completely inhibited 24 hours after being subjected to -9 ℃. The survival rate of J2 was 0 after being subjected to -1, -2, -3, and -4 ℃ for 8, 5, 3, and 1.5 d, respectively. Egg hatching was completely inhibited after being subjected to -2, -3, -4, and -5 ℃ for 9, 6, 4, and 1 d, respectively. Results of the fitting analysis showed that both the relationships between the temperature and the lethal time of J2 as well as the temperature and the non-hatching time of the eggs followed exponential functions. The results of field test showed that death rate of M. incognita in 0-50 cm soil layer after ridging treatment and 0-30 cm soil layer after leveling treatment could reach 100%, while the disease index of the former in 30-40 cm and 40-50 cm was 84.9% and 75.8%, respectively, which was lower than that in the greenhouse. Our results suggest that preventing and controlling M. incognita in greenhouses through low-tempe-rature in winter could achieve a better control effect in Yulin City and the northward region. The proposed technique is convenient and has high potential for popularization.

Growth, mortality, and resource utilization of Gymnocypris chui in Langcuo Lake of Tibetan Plateau, China

ZHANG Zepeng, JIN Hongyu, CHI Miao, SHAO Huili, LI Lei

2023, 34(7):  1988-1994.  doi:10.13287/j.1001-9332.202307.030

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To investigate the growth, mortality, and resource utilization of Gymnocypris chui in Langcuo Lake of Tibetan Plateau, we measured body length and body weight of 389 fish based on four sampling surveys from October 2018 to November 2019. We identified the ages through lapillus. Based on frequency distribution of body length, we estimated the growth and mortality coefficients of G. chui in Langcuo Lake and the utilization status of existing population resources according to the Beverton-Holt dynamic comprehensive model. The results showed that G. chui were mainly composed of individuals aged 2 to 19 years in Langcuo Lake, with a length-body weight relationship equation of W=0.0105L^3.042. The von Bertalanffy growth equation revealed that the fish had an asymptotic body length of L_∞=37.28 cm, growth coefficient of k=0.160, and theoretical growth starting age of t₀=-0.887 a. The total mortality coefficient Z was estimated as 0.48, based on the length-converted catch curve method. According to Pauly’s empirical formula, the natural mortality coefficient M was 0.34, fishing mortality coefficient F was 0.14, and exploitation rate E was 0.29, indicating that G. chui resources in Langcuo Lake were not over-exploited. Considering the growth and mortality of G. chui in Langcuo Lake, fishing is appropriate, with a recommended fishing length of L_c=22.37 cm.

Reviews

A review on light response model of photosynthesis under different environmental conditions

WANG Fubiao, YANG Xiaolong, KANG Huajing, YE Zipiao

2023, 34(7):  1995-2005.  doi:10.13287/j.1001-9332.202307.003

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Light response curve of photosynthesis (A_n-I curve) is a useful modeling tool to investigate how photosynthesis reacts with different abiotic factors, which would help quantify the response of photosynthetic rate to photosynthetically active radiation. Based on the mathematical characteristics of photosynthesis A_n-I models, we reviewed the advantages of using these model in practice and the potential caveats. We proposed the development of new mechanistic photosynthesis A_n-I models based on the primary light response and discussed its advantages in the field of plant ecology and physiology. Photosynthesis has three main steps, including the primary reaction, the assimilatory power forms, and the carbon assimilation. Changes in each step could directly affect the photochemical efficiency and carbon assimilation in photosynthesis. The primary reaction consists of a series of physical processes that are related to light energy absorption and utilization, including the absorption of light energy, the change of quantum state, and the transfer and de-excitation of exciton resonance of light-trapping pigment molecules. How-ever, the empirical photosynthesis A_n-I models can not explain some scenarios. For example, the non-photochemical quenching in plants increases with increasing light intensity in a non-linear manner. Further, the life-time of singlet chlorophyll molecules can be extended when plant light-harvesting pigment molecules absorb excessive light energy but would not be immediately used for the photochemical reaction. Meanwhile, the parameters obtained by fitting the mechanistic A_n-I curve model can not only reflect the primary photochemical reaction characteristics of plants, but also describe the physical characteristics of plant light harvesting pigment molecules, such as the number of light harvesting pigment molecules in the excited state (N_k) and effective light energy absorption cross-section (σ_ik′). This can be used to further investigate the physical characteristics of light harvesting pigment molecules, including the light-response of N_k and σ_ik′ and the average life time of light harvesting pigment molecules in the lowest exciting state (τ_min). In addition, it would be necessary to determine how to incorporate abiotic factors, such as temperature and CO₂ concentration, into the mechanistic A_n-I curve model, as well as to determine the association between the abiotic factors and light harvesting pigment molecules, such as N_k, σ_ik′, and τ_min.

Study on the equity of urban green space: Origin, progress, and enlightenment

CHEN Yang, JING Xin, MA Renfeng, WANG Xueqi, LI Guan

2023, 34(7):  2006-2016.  doi:10.13287/j.1001-9332.202307.019

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Urban green space equity focuses on whether different social groups can equally share the well-being from green space, which is an important issue in the realm of environmental justice. We systematically introduced the origin and development of green space equity, explored its multidimensional progress in conceptual connotation, measurement methodology, phenomenon, mechanism, and regulation, and proposed the enlightenment for deepening the related studies. The green space equity originated from environmental social movement and environmental justice studies, and experienced multilevel evolution in topic constriction and theoretical interpretation. Although the connotation of green space equity was interpreted from various perspectives, its core idea was distributional equality. There was a frequently-used framework for measurement methodology of green space equity, whose spatial scale issue was critical. Due to the differences of characteristics, developmental stages, and institutional backgrounds between Chinese and Western cities, the phenomena and driving mechanisms of green space equity were different. The regulation strategies of green space equity could be summarized into three types, including green distributional equitable strategy, social recognitional justice strategy, and procedural justice orientated strategy. Future studies should deepen the research from the hierarchical logics for practice management, the fine-scale measurement methodology, the interpretation of mechanism for green space inequity in Chinese context, and simulation of differentiated regulation strategies. Social development endows green space equity with more practical tasks and theoretical logics, which is urgent to clarify the research progress to support the future research.