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    15 September 2021, Volume 32 Issue 9
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    Opinion of the Editor-in-Chief
    Multi-disciplinary knowledge integration and its technical approaches in the integrated ecology of macroecosystem science
    YU Gui-rui, REN Xiao-li, YANG Meng, CHEN Zhi
    2021, 32(9):  3031-3044.  doi:10.13287/j.1001-9332.202109.040
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    The development of contemporary macroecosystem sciences requires to comprehensively understand the process mechanism and model mechanism of large-scale macroecosystem structure and function, spatial variation, and dynamic evolution, to realize quantitative simulation, scientific assessment, prediction and early warning of ecosystem change and its impacts on human well-being, and to serve the utilization, protection, regulation, and management of ecosystems. Therefore, a new research field of large-scale integrated ecology of macroecosystem science (IEMES) is emerging. Based on the systematic analysis of the basic theories, approaches and key technologies of integrated ecology of macroecosystem science, the following basic understandings have been formed: 1) IEMES takes macroecosystem at regional, continental, and global scales as the research object, and adopts the methods and technologies of multidisciplinary knowledge integration. It is aimed to solve the major resource and environmental problems during the development of human society, such as food security, resource security, ecological security, and environmental security. 2) The basic scientific and technological tasks of IEMES are to understand the basic structural and functional properties of macroecosystem, monitor the changes of ecosystem state, explain the spatiotemporal evolution of ecosystem, uncover the mechanism of ecosystem operation and maintenance process, quantitatively evaluate the functional state and service capacity of ecosystem, predict the dynamic evolution and geographical pattern of ecosystem, provide early warning of ecosystem changes and ecological environmental disasters. 3) It is needed to reconstruct the theory and methodology system of “multi-source data analysis, multi-model simulation, multi-disciplinary knowledge fusion” and develop key technology of multi-disciplinary knowledge fusion of “multi-scale observation, multi-method verification, multi-process fusion, and cross-scale simulation” for IEMES. 4) The continental scale multi-spatiotemporal ecosystem observation and experiment network is the basic scientific and technological facility to carry out deep integration of multi-disciplinary knowledge. It is necessary to develop key technology of multi-disciplinary ecological knowledge integration of multi-factor, multi-process, multi-interface, multi-medium, multi-scale, and multi-method around the regional, continental, and global scale macroecosystem science issues.
    Original Articles
    Soil enzyme activities and their stoichiometry at different altitudes in Helan Mountains, Northwest China
    WAN Hong-yun, CHEN Lin, PANG Dan-bo, MA Jin-peng, CHEN Gao-lu, LI Xue-bin
    2021, 32(9):  3045-3052.  doi:10.13287/j.1001-9332.202109.021
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    Understanding altitudinal variation characteristics and driving mechanism of soil enzyme activities and their stoichiometry is of great significance for studying nutrient cycling in fragile mountain forest ecosystems. In this study, we collected soil samples from different altitudes (1380-2438 m) in Helan Mountains to analyze the altitudinal changes in soil physicochemical properties, soil enzyme activities and their stoichiometry and its influencing factors. The results showed that the activities of β-glucosidase (βG) and β-N-acetylglucosaminidase (NAG) and the enzyme activities ratios of soil C/N and soil C/P firstly increased and then decreased with increasing altitude, which all peaked at 2139 m. Alkaline phosphatase (AKP) activities increased with the increases of altitude, with the maximum being found at 2438 m. However, L-leucine aminopeptidase (LAP) activities and soil N/P enzyme activities ratios did not change with increasing altitude. Compared with the soil enzyme stoichiometry in other regions of the world, Helan Mountains showed a certain degree of N limitation. Except for LAP, the activities of the other three enzymes were significantly positively correlated with the ratios of soil organic carbon/total nitrogen, soil organic carbon/total phosphorus, and total nitrogen/total phosphorus, and negatively correlated with pH. The LAP, soil C/P enzyme activities ratios and soil N/P enzyme activities ratios showed significant negative correlation with TP. In addition, AKP was significantly negatively correlated with soil bulk density.
    Fine root biomass, production, and turnover rate in a temperate deciduous broadleaved forest in the Maoer Mountain, China
    ZHANG Yun-yu, SUN Xiao-feng, ZHANG Lin-feng, LI Ying-chi, WANG Chuan-kuan, WANG Xing-chang
    2021, 32(9):  3053-3060.  doi:10.13287/j.1001-9332.202109.001
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    Fine roots play an important role in energy flow and substance cycling in forests. How-ever, the estimates of biomass, production and turnover of fine roots remain large uncertainties, and the mechanism underlying local-scale spatial variation in fine roots is still unclear. In a temperate secondary forest in the Maoer Mountain in Northeast China, we investigated the vertical distribution of fine root biomass and necromass at the 0-100 cm profile and the dynamics, production and turnover rate of fine root in 0-20 cm soil layer. The sequential coring (including the Decision Matrix and the Maximum-Minimum formula) and the ingrowth core (3 cm diameter and 5 cm diameter) were compared in estimating production and turnover rate of fine roots. Forest stand variables that might affect fine roots were also explored. The results showed that 76.8% of fine root biomass and 62.9% of necromass concentrated in the 0-20 cm soil layer, and that both decreased exponentially with increa-sing soil depth. The seasonal variation in both fine root biomass and necromass was not significant in 0-20 cm soil layer, which might be related to the negligible snowfall in winter and the extremely high precipitation in summer. There was no significant difference in the results of the estimated fine root production between two diameter ingrowth cores. After log-transformed, fine root production and turnover rate estimated by the Decision Matrix, the Maximum-Minimum formula and ingrowth cores were significantly different among methods. With the increases of soil nutrient concentrations, fine root biomass/fine root necromass ratio significantly increased, fine root necromass significantly decreased, whereas fine root biomass, productivity, and turnover rate were not related to soil nutrient. There was a significant positive correlation between fine root production and aboveground woody biomass increment in the previous-year but not current-year.
    Quantitative characteristics and distribution pattern of living and dead standing trees of secon-dary Picea forest in Guandi Mountain, northern China
    ZHOU Duo-duo, YAN Hai-bing, LI Jing, CHEN Song, YANG Xiu-qing
    2021, 32(9):  3061-3069.  doi:10.13287/j.1001-9332.202109.003
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    Based on the survey data from a 4 hm2 secondary Picea forest plot in the Pangquangou Nature Reserve, Guandi Mountain, Shanxi Province in 2010 and 2015, we analyzed the quantitative characteristics, distribution pattern, and correlation of living and dead standing trees during five years from four aspects, including species composition, diameter class structure, spatial pattern, spatial correlation between different diameter classes of living standing trees and dead standing trees, and intercorrelation between different diameter classes of dead standing trees. The results showed that there were 25811 living standing trees with DBH≥1 cm in the plot in 2010, belonging to 30 species, 22 genera, and 11 families. The distribution of individual diameter class was an inverted “L” type, and the number of individuals decreased in a fracture pattern with the increases of diameter class. During the five years (2010-2015), a total of 2145 dead standing trees were formed, involving 12 species, 10 genera, and 5 families. Most of the dead standing trees were distributed in diameter of 5-10 cm. At the scale of 0-50 m, the spatial distribution of living and dead standing trees was generally similar, indicating that the spatial pattern of dead standing trees was limited by that of living standing trees to some extent. The spatial correlation analysis of each diameter class of dead standing trees and living standing trees showed that with the increases of individual diameter class of trees, the intensified competition for space resources might be the main reason for the generation of dead standing trees. With the increases of diameter class of dead standing trees, the spatial correlation between living and dead standing trees was weakened to varying degrees, indicating that environment might be the key factor for the formation of large diameter class of dead standing trees. For the the dead standing trees, there was an obvious positive correlation between 5 cm≤DBH<20 cm dead standing trees and DBH<5 cm dead standing trees, between 10 cm≤DBH<20 cm dead standing trees and 5 cm≤DBH<10 cm dead standing trees, and between DBH≥20 cm dead standing trees and 5 cm≤DBH<20 cm dead standing trees. Our results indicated that dead standing trees would impact the subsequent dying of living standing trees.
    Soil denitrifying enzyme activity and its influencing factors in a bamboo forest riparian zone in the upper reaches of the Taihu Lake Basin, China
    ZHOU Zhong-yu, ZHANG Hai-kuo, LIANG Jia-hui, ZHANG Bao-gang, JIANG Wen-ting, TIAN Lin-lin, LI Yan, CAI Yan-jiang
    2021, 32(9):  3070-3078.  doi:10.13287/j.1001-9332.202109.008
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    Soil denitrifying enzyme activity (DEA) was measured by acetylene inhibition technique, along with exploration of factors influencing DEA in a bamboo forest riparian zone in the upper reaches of the Taihu Lake Basin during summer. Our aim was to provide important insights into the assessment of ecological functions of bamboo forest riparian zone on reducing nitrogen pollution in rivers. The results showed that the riparian soil DEA ranged from 6.32 to 23.22 μg N·kg-1·h-1, with a mean value of 14.65 μg N·kg-1·h-1. The vertical distribution (0-40 cm soil profile) of DEA was affected by several factors, such as soil organic carbon (SOC), total nitrogen (TN), nitrate nitrogen (NO3--N), soil water content, and activity of carbon and nitrogen hydrolase, which resulted in decreased DEA with increasing soil depth. The horizontal changes in DEA (at the same soil depth but at different distances from river) was mainly governed by the variation in SOC concentration. In this area, the concentration of soil dissolved organic carbon was relatively low, which might inhibit the soil DEA during summer.
    Effects of nitrogen deposition and biochar application on soil N2O fluxes in a Moso bamboo plantation
    HUANG Kai-ping, LI Yong-fu, SONG Cheng-fang, QU Tian-hua, LIU Bo, LUO Hai-yan, LI Yong-chun, CAI Yan-jiang
    2021, 32(9):  3079-3088.  doi:10.13287/j.1001-9332.202109.027
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    In July 2019-July 2020, we conducted a field trial to examine the effects of nitrogen addition (60 kg N·hm-2·a-1), biochar application (10 t·hm-2), and their combination on soil N2O emission and the relationship between soil N2O emission and environmental factors in a typical Moso bamboo (Phyllostachys edulis) plantation in Hangzhou City of Zhejiang Province. Soil N2O flux of Moso bamboo plantation was measured by the static chamber-gas chromatography technique. The results showed that nitrogen addition treatment increased the annual cumulative N2O emission by 14.6%, while biochar application and the combination treatment reduced it by 20.8% and 10.6%, respectively. Soil N2O flux rate was significantly correlated with soil temperature, NO3--N concentration, urease and protease activities, and soil NH4+-N concentration across all treatments. In conclusion, under the background of nitrogen deposition, the application of biochar would have a significant reduction effect on soil N2O fluxes in Moso bamboo plantations.
    Effects of understory removal on soil microbial community composition in subtropical Phyllostachys edulis plantations
    XIAO Yi, CHEN Hui-xian, QIU Li-jun, ZHANG Yang, WAN Song-ze
    2021, 32(9):  3089-3096.  doi:10.13287/j.1001-9332.202109.034
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    We investigated the effects of understory removal on soil microbial community and soil physicochemical properties in a field experiment following random block design in subtropical moso bamboo (Phyllostachys edulis) plantations, which were widely contributed in middle subtropical area, aiming to assess the regulation mechanism of understory plants on soil microbial community. The results showed that understory removal significantly increased the contents of soil N, NO3--N, and soil available phosphorus, but decreased soil pH and the contents of soil NH4+-N and soil phosphorus (TP). Moreover, understory removal decreased total and bacterial PLFAs (B) and increasing soil fungal PLFAs (F), resulting in a higher F/B ratio. Redundancy analysis showed that changes in fungal PLFAs caused by understory removal were mainly attributed to soil acidification, while changes in bacterial PLFAs caused by understory removal were mainly due to the decreases in soil TP and pH. Furthermore, i14:0、i15:0 and i16:0 contributed to the decreases in bacterial biomass. Our results suggested that understory removal might not be suitable for the management of subtropical P. edulis plantations, as it would alter microbial community composition. The shift of soil microbial community from bacteria to fungi could inhibit microbial decomposition function.
    Community characteristics and functions of phosphate-solubilizing bacteria in rhizosphere soil of natural and planted Pinus tabuliformis forests on the Loess Plateau, Northwest China
    ZHU Ying, KU Yong-li, LIU Jin-liang, Le Thi Hien, ZHAO Zhong
    2021, 32(9):  3097-3106.  doi:10.13287/j.1001-9332.202109.006
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    To investigate the interaction between Pinus tabuliformis and root microorganisms and its effects on the stability of P. tabuliformis forests, we collected rhizosphere and non-rhizosphere soil from natural and planted P. tabuliformis forests in Huanglong County of Shaanxi Province. The non-rhizosphere soil was used to analyze chemical properties, while the rhizosphere soil was used to isolate and purify phosphorus-solubilizing (organic and inorganic phosphorus) bacteria. We mea-sured the phosphate-solubilizing ability and identified those bacteria using DNA genes sequencing. The results showed that soil total carbon concentration (TC), total nitrogen concentration (TN), carbon:nitrogen (C/N), and nitrogen:phosphorus (N/P) were significantly higher in natural forest than those in the plantation. A total of 20 genera and 65 species of phosphate-solubilizing bacteria were identified in those two forests, with Bacillus, Streptomyces and Pseudomonas as the dominant group. The diversity, richness, and evenness of phosphate-solubilizing bacteria in the natural forest were higher than that in the planted forest, but dominance was lower. Streptomyces was positively correlated with soil TC, TN, C/N and N/P ratios, while Bacillus and Pseudomonas were positively correlated with soil nitrate (NO3-), ammonium (NH4+), available phosphorus (AP), and total phosphorus (TP). The solubilizing ability of phosphate-solubilizing bacteria was different between two forest types, indicating that Pseudomonas sp.34-5 shared in two forests had the strongest phosphate-solubilizing ability for calcium phosphate with 11.40 μg·mL-1 and Bacillus mycoides BF1-5 exclusive to natural forest had the strongest phosphate-solubilizing ability for lecithin with 4.58 μg·mL-1. The composition and structure of phosphorus-solubilizing bacterial community were different in two forest types, with higher diversity, richness and phosphate-solubilizing ability in natural forest than that in plantation.
    Differences of bacterial and fungal communities in the tree and rhizosphere of the healthy and twig blight-diseased bayberry
    REN Hai-ying, XU Qiao, QI Xing-jiang, YU Zhe-ping, ZHENG Xi-liang, ZHANG Shu-wen, WANG Zhen-shuo
    2021, 32(9):  3107-3118.  doi:10.13287/j.1001-9332.202109.005
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    Twig blight is a serious disease of bayberry, which limits bayberry production. In order to prevent and manage the disease, we used high-throughput sequencing technology to analyze bacterial and fungal community richness and diversity in various organs of the tree, bulk and rhizosphere soil of healthy and diseased bayberry. The results showed significant differences in richness and diversity of bacteria and fungi in bulk soil, rhizosphere soil, roots, trunks, barks, and leaves between twig blight diseased trees and healthy trees. In bulk soil, the richness and diversity of bacteria significantly decreased, while that of fungi significantly increased. In barks of diseased trees, the richness and diversity of bacteria significantly increased, and those of fungi significantly decreased. The relative abundance of dominant bacteria and fungi in various organs, bulk soil, and root surface soil changed significantly at phylum, class, and genus levels in the diseased trees. The relative abundance of Pseudomonas sp. on the trunks, roots, and root surface soils of diseased trees significantly decreased, and Fusarium sp. of the diseased root surface and bulk soils also significantly decreased, while the relative abundance of Penicillium sp. on the diseased root surface and bulk soils significantly increased. Pestalotiopsis sp., from the same genus as the twig blight pathogen, was less abundant in the roots but more abundant in the leaves, trunks, barks as well as root surface soils and bulk soils of the diseased bayberry trees than those of the health trees. The relative abundance of Pestalotiopsis sp. was positively correlated with those of most of the fungi. Our results might provide useful theoretical basis for the development of ecological improvement and healthy-tree cultivation technology, and biological control of bayberry twig blight disease.
    Response of root dynamics to nitrogen addition and the influencing factors in a Tibetan alpine steppe, China
    LIU Yang, PENG Yun-feng, MEN Ming-xin, PENG Zheng-ping, YANG Yuan-he
    2021, 32(9):  3119-3126.  doi:10.13287/j.1001-9332.202109.002
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    A field manipulative experiment was carried out during 2015 and 2016 to examine the changes and influencing factors of root production, turnover rate, and standing crop under different nitrogen (N) addition levels, i.e., 0, 1, 2, 4, 8 and 16 g N·m-2·a-1, in a Tibetan alpine steppe. The results showed that root production and standing crop decreased linearly or exponentially with increasing N addition rates. Compared with control, 16 g N·m-2·a-1 significantly reduced the two-year average root production and standing crop by 43.0% and 45.7%, respectively. Root turnover rate increased first and then decreased along the N addition gradient, with the maximum appearing under 2 and 4 g N·m-2·a-1 treatments for 2015 and 2016, respectively. Results from linear mixed-effects models showed that root starch content was the main factor modulating the N-induced changes in root production and turnover rate, explaining 21.7% and 25.4% of their variations. Root protein content mainly contributed to the variations in standing crop, with an explanation of 20.8% of its variance. Overall, N addition had negative effect on root production and standing crop, and low N promoted while high N inhibited root turnover rate. Root metabolic parameters were the main factors modulating the N-induced changes in root dynamics.
    Potential impacts of climate change on suitable habitats of Marco Polo sheep in China
    WANG Mu-yang, ZHANG Chu-jie, MI Chun-rong, HAN Lei, LI Mei-ling, XU Wen-xuan, YANG Wei-kang
    2021, 32(9):  3127-3135.  doi:10.13287/j.1001-9332.202109.020
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    Climate change may lead to biodiversity loss and species extinction. Understanding the impacts of climate change on the distribution pattern of endangered species is of great value to the identification of priority reserves and the formulation of relevant conservation strategies. Based on the distribution data of Marco Polo sheep (Ovis ammon polii) obtained from the field survey in Taxkorgan Nature Reserve (TNR) in Xinjiang during 2017-2018, the maximum entropy (MaxEnt) model was used to predict the distribution pattern of its suitable habitat under climate change. The results showed that the suitable habitat of Marco Polo sheep was mainly distributed in the northwest of the TNR, with temperature as the key factor affecting its suitable habitat distribution. Under the medium and high emission concentration (RCP4.5 and RCP8.5), the suitable habitat area of Marco Polo sheep would decrease in the next two periods (2050s and 2070s), with the loss rate of suitable habitat being as high as 40.5%. The loss of suitable habitat was mainly located in the low-altitude area, while the area of suitable habitat increased correspondingly in the high-altitude area. The area of suitable habitat from low elevation to high elevation increased with the increases of greenhouse gas emission concentration. According to the results of centroid transfer, the suitable habitat was mainly moved to the west, namely Tajikistan, the main distribution country of Marco Polo sheep.
    Resident breeding bird responses to wind turbines: A functional and phylogenetic perspective
    DING Zhi-feng, LIANG Jian-chao, CAI Jian, WEI Long
    2021, 32(9):  3136-3144.  doi:10.13287/j.1001-9332.202109.037
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    As a clean and green renewable energy source, wind power attracts more and more attention globally, and rapidly expands its use scale. There are conflicts between wind power development and bird protection. The impacts of wind farms on birds is a hot topic for ecologists and conservationists. To estimate the effects of wind turbines on avian species diversity and their functional and phylogenetic diversity, we conducted line transect surveys in January, March, April and May 2019. Thirty-two line transects were divided into four gradients according to the distance from the wind turbines, i.e., 100-300 m (6 transects), 300-500 m (13 transects), 500-700 m (8 transects), >700 m (5 transects). The results showed that a total of 76 resident breeding birds were recorded, belonging to 11 orders and 31 families. Passeriformes and Timaliidae had the highest species richness (53 and 12 species, respectively). Bird species richness, functional richness (FRic), and phylogenetic diversity (Faith's PD) were increased with increasing distance from the wind turbines. Specifically, bird richness, FRic and phylogenetic diversity increased little within 500 m of the wind turbines, whereas a significant increase occurred over 500 m from wind turbines. The community-weighted mean of dispersal ability showed an increasing trend with distance from the wind turbines. The standardized effect size of both mean pairwise functional/phylogenetic distance (SES.MFD and SES.MPD) were less than 0 in all transects, with about half of which being significantly lower than expected at random. This finding suggested that the impacts of wind farms on bird species, functional and phylogenetic diversity occurred within 500 meters from wind turbines, with a pattern of functional and phylogenetic clustering. The impacts of wind turbines on birds were multi-dimensional. It is therefore difficult to provide complete perspective on assessing the impacts of wind farms on birds when only considering species diversity.
    Effects of different interstocks on the growth, yield, and fruit quality of Hanfu apple
    YUAN Ji-cun, CHENG Cun-gang, ZHAO De-ying, LIU Shang-tao, LI En-mao
    2021, 32(9):  3145-3151.  doi:10.13287/j.1001-9332.202109.009
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    A field experiment was conducted using Hanfu apple grafted on 10 dwarfing interstocks to evaluate plant growth, yield, and fruit quality of different apple-interstock combinations in Hulu-dao, Liaoning Province, in order to select the most suitable apple-interstock combinations in the study area. The results showed that tree vigor, yield, and fruit quality were largely affected by the interstocks. Among the interstocks evaluated here, plant height, branch numbers, leaf fresh weight, branch fresh weight, root fresh weight, total root volume, average root diameter and total root tip numbers were the largest on GM256, while the highest trunk diameter, branch length, total root length and total root surface area were observed on CX5, the highest fruit firmness, soluble solids and soluble sugar contents were observed on M26, and the highest fruit vertical diameter, transverse diameter and single fruit weight were observed on GM256. The fuzzy evaluation results showed that the comprehensive character scores decreased in order of GM256, CX5, B9, JM7, CG80, Liaozhen 2, M26, Qingzhen 3, SH38 and MD001. Our results indicated that interstock GM256 and CX5 was better for the cold climate region.
    Effects of plastic film mulching on soil quality, growth of Angelica sinensis, and weed occurrence in cold and humid areas
    MI Yong-wei, GONG Cheng-wen, SHAO Wu-ping, DUN Zhi-heng
    2021, 32(9):  3152-3158.  doi:10.13287/j.1001-9332.202109.026
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    We analyzed the growth dynamic and bolting rate of Angelica sinensis, soil quality and enzyme activities and weed density and control effect in a field experiment under different mulching patterns, to provide theoretical basis for the application of plastic film in genuine producing area of A. sinensis. The planting patterns were conducted as hole seeding under ridging with plastic-film mulching (LS), trenching and slant planting under film-side cultivation (MC) and trenching and slant planting in open field (LD). Our results showed that, 1) compared with LD, soil organic matter content in top layer under the treatments of LS and MC was increased by 4.4% and 14.3%, respectively, with that under MC being statistically significant. Soil bulk density was significantly decreased by 11.6% and 8.5%, while pH was significantly decreased by 4.6% and 1.7%. The activities of soil sucrase, phosphatase and urease were significantly increased by the two mulching methods, but that of catalase was inhibited to a certain extent. 2) Mulching film improved the speed of returning green after transplanting, the early bolting rate, and the individual medicinal quality of A. sinensis. MC showed the fastest, the most uniform, and the highest greening rate. LS bolting rate was the highest, and the fresh mass of MC and LS was significantly increased by 20.4% and 58.4%, respectively. 3) Weed density under the treatment of MC and LS was significantly reduced by 34.0% and 25.8%. Compared with LS, MC significantly increased the control effect of plant and fresh mass by 21.7% and 63.4%, respectively. In conclusion, film cultivation methods could improve the environment for root growth, reduce weed density, improve weed control effect, and promote growth process and substance accumulation, but could promote the bolting of A. sinensis in early phase.
    Distribution characteristics of soil water and nutrients in pear orchard and their relationship with yields in loess hilly region
    CHEN Wei, WANG Hong-yang, WANG Zhi-jian, WANG Jia, LI Ya-xin, SUN Cong-jian
    2021, 32(9):  3159-3166.  doi:10.13287/j.1001-9332.202109.028
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    We analyzed soil water, nutrients, and yields in three different slope sites in the sloping farmland under Yuluxiang pear planted in the loess hilly region of Western Shanxi, across the growth periods and different soil depths. The results showed that: 1) The yield of pear was in the order of high slope site > middle slope site > low slope site. In high slope site, the yield was significantly correlated with soil water content (SWC), soil organic matter (SOM), available potassium (AK), with AK showing the most significant effect. The yield of pear in middle and low slope sites was significantly correlated with SWC, SOM, and total nitrogen (TN), with SWC having the most significant effect on yield. The contents of SWC, SOM, available phosphorus (AP) and TN in high slope site were higher than in middle and low slope sites, while AK was the highest in middle slope site. 2) Among different soil depths, soil nutrient contents were the highest within 0-20 cm soil layer, but the lowest within 20-40 cm soil layer. The SWC was significantly lower within 0-20 cm than the other soil layers and was the highest within 20-40 cm soil layer. 3) Among different growth periods, the contents of SOM, AP, and TN were the highest in flowering period, the SWC was the highest in fruiting period, and AK content was the highest in maturing period. It was suggested that in the future management of pear water and fertilizer in the region, more K fertilizer should be applied in the high slope sites in the flowering period, while N and P compound fertilizer should be applied in the fruiting period, to enhance irrigation in middle and low slope sites to decrease the limitation of water with 300 m3·hm-2. Our results could provide theoretical support and data refe-rence for planting precision irrigation and scientific fertilization of pear planted in loess hilly areas.
    Potential suitable area and niche shift of different ploidy kiwifruit
    LIU Cai-yan, LI Da-wei, YANG Shi-jian, PAN Zhi-li, JIN Ruo-han, CHEN Fang, GUO Wen
    2021, 32(9):  3167-3176.  doi:10.13287/j.1001-9332.202109.014
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    Niche shift between polyploid and diploid plants is an important requirement for the success of polyploid. Diploid, tetraploid, and hexaploid of kiwifruit distribute in different areas. Whether there is obvious niche differentiation and the major environmental factors which could influence the ecological niche of different ploidy kiwifruits are still unknown. Based on the natural distribution information collected from literature and by field works, the maximum entropy model (MaxEnt) was used to predict the potentially suitable ranges and the major climatic factors affecting distribution of different ploidy kiwifruits. Niche divergence between different ploidy kiwifruits was quantified by niche identity test. The results showed that there were obvious differences in the potential suitable areas of different ploidy kiwifruits. Diploid occurred in lower altitude Hunan foothills. Tetraploid nearly overlapped with diploid but tended to northern Guizhou and eastern Chongqing. Hexaploid were centered in Guizhou Plateau, northwestern Hunan, southwestern Hubei and southern Shanxi. Hexaploid kiwifruits preferred higher altitudes and latitudes. In addition, the hexaploid had wider highly suitable areas. Results of niche identity test showed overlapped niches between diploid and tetraploid, and different niches between diploid/tetraploid and hexaploid kiwifruits. Minimum temperature of the coldest month (Bio6) and precipitation of the driest month (Bio14) were key environmental factors driving the niche shift of ploidy kiwifruits. Polyploid kiwifruits could maintain a higher probability of existence under lower Bio6 and Bio14, which indicated more extreme niche in cold and arid mountains for polyploids.
    Ecological security characteristics of main irrigated agricultural areas on the Loess Plateau based on remote sensing information
    LI Xiao-ming, SUN Cong-jian, SUN Jiu-lin, CHEN Wei, LI Xin-gong
    2021, 32(9):  3177-3184.  doi:10.13287/j.1001-9332.202109.012
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    Ecological security is an important guarantee for the sustainable development of regional economy and society. We analyzed the change characteristics of fraction vegetation coverage (FVC) and remote sensing ecological index (RSEI) of four irrigated agriculture regions of the Loess Plateau (Yinchuan Plain, Hetao Plain, Fenhe River Valley and Weihe River Plain) based on the remote sensing data from 2000 to 2018. The results showed that the FVC decreased in the study area from 2000 to 2018. The variation trend of FVC differed among the four irrigated agricultural distribution areas. The RSEI of the whole area showed an overall downward trend, the RSEI of Yinchuan Plain (down 0.06) and Weihe River Plain (down 0.07) decreased significantly, and the RSEI of Hetao Plain remained stable. The RSEI of Fenhe River Valley showed an increased trend. The ecological stability of Yinchuan Plain and Fenhe River Valley was relatively low, the ecological environment of Hetao Plain was relatively stable, and the ecological environment of Weihe River Plain continued to degrade. The results were important for regional ecological environment protection and agricultural sustainable development.
    Spatio-temporal evolution of climate-induced reduction risk for winter wheat in Anhui Pro-vince based on principal component analysis
    HUANG Jin, CHEN Jin-hua, ZHANG Fang-min
    2021, 32(9):  3185-3194.  doi:10.13287/j.1001-9332.202109.016
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    Winter wheat is one of the main crops in Anhui Province, to analyze the spatial-temporal variations of climate-induced reduction risk is of great significance to ensure regional food security. Based on the data of winter wheat yield from 1973 to 2014 in 74 districts and counties, nine risk assessment indicators were extracted from annual series of climate-induced reduction rate, and the spatial-temporal variations of climate-induced reduction risk for winter wheat in Anhui was analyzed by using principal component analysis. The results showed that north Anhui, especially the region along Huaihe River, was the higher-risk area for climate-induced yield loss. Results of the barycenter migration model showed that the high value regions of climate-induced reduction rate of winter wheat in Anhui Province had a significant tendency of moving from north to south. In the whole province, climate-induced reduction risk of winter wheat presented a significant interdecadal variation. Furthermore, the number of districts and counties with moderate or more reduction intensity was significantly reducing since the 2000s. Results from S-mode principal component analysis and climate-induced reduction rate series showed that the climate-induced reduction risk for winter wheat in north Anhui had a downward trend and that in southern Anhui had an upward trend. Climate-induced reduction risk of winter wheat in Anhui had notable temporal and spatial variations, the interdecadal fluctuation and north-south regional difference of which should draw our attention.
    Spatial variability of soil properties in fixed sand dunes of the Eastern Ningxia Province
    ZHAN Xiu-li, XU Yi-xin, WANG Hong, GAO Ying, HAN Lei
    2021, 32(9):  3195-3203.  doi:10.13287/j.1001-9332.202109.030
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    As sand dunes gradually become fixed, soil particle size, soil organic carbon (SOC) and total nitrogen (TN) contents vary across different locations of the dunes. To investigate the spatial variation of soil particle size distribution and soil nutrition in the fixed sand dunes, we examined particle composition, SOC and TC features in different locations of dunes in the Eastern Ningxia. The results showed that the particle sizes of each soil layer were mainly characterized by medium and coarse sands. The SOC and TN contents were higher in surface soil layers, with a maximum of 5.781 and 0.412 g·kg-1, respectively, which were observed in interdune lands and dune ridges, while the leeward slope of the dunes showed the least. The SOC content of both the leeward and windward slope gradually decreased with increasing soil depth along the dune. By contrast, that of the interdune lands decreased first and then increased. At small scale, both the SOC and TN contents showed a clear spatial heterogeneity. There was a positive correlation between soil nutrition contents (SOC and TN) and silt and very fine sand contents in the fixed sand dunes, and a negative correlation with medium and coarse sand contents. Our results implied that soil particle size composition influenced SOC and TN contents. The contents of soil nutrition increased with increa-sing contribution of fine particles, highlighting the role of fine particles in adhesion and accumulation of organic matter.
    N2O and N2 emission characteristics from maize and greenhouse vegetable soils in Northern China
    ZHAO Xing-han, LIU Dong, HUANG Kai, QUAN Zhi, HUANG Bin, FANG Yun-ting, CHEN Xin
    2021, 32(9):  3204-3212.  doi:10.13287/j.1001-9332.202109.007
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    To explore N2O and N2 emissions from upland soils after nitrogen fertilizer application, a 60-day aerobic incubation experiment (25 ℃,80% water-filled pore space) using the 15N tracing method was conducted to quantify the N transformation, N2O and N2 emissions from maize soils from four sites (Harbin, Shenyang, Luancheng and Shouguang) and vegetable soils from two sites (Shen-yang and Shouguang), with urea being applied at 167 mg N·kg-1 to simulate the field application rate of 200 kg N·hm-2. The results showed that for the four sites with maize soils, the cumulative emission of N2O was in the order of Shouguang (20 mg N·kg-1) > Luancheng (14 mg N·kg-1) > Shenyang (5 mg N·kg-1) > Harbin (0.5 mg N·kg-1) and the cumulative N2 emission was in the order of Luancheng (176 mg N·kg-1) > Shenyang (106 mg N·kg-1) > Shouguang (75 mg N·kg-1) > Harbin (12 mg N·kg-1). For vegetable soils, the cumulative N2O emission of Shouguang (21 mg N·kg-1) was 10 times of that of Shenyang (2 mg N·kg-1), but without differences in cumulative N2 emissions (28 and 24 mg N·kg-1, respectively). The N2O/(N2O+N2) of the six soils ranged from 5% to 40%. The N2O/(N2O+N2) of the two soils from Shouguang (30%-40%) was significantly higher than other four soils (1%-10%). Soil bulk N pool contributes to 56% of total N2O emission and 61% of total N2 emission, which was higher than the contribution of fertilizer. The cumulative N2O emission was positively correlated with soil background pH, which indicated that soil background pH might be an important factor regulating N2O and N2 emission from upland soils. In the alkaline soil regions of North China Plain (such as Luancheng and Shouguang), mea-sures to reduce soil pH might have great impact on reducing N gaseous emission.
    Continuous-rain hazard of transplanting and direct-sowing rice in Sichuan Basin, China
    GUO Xiang, ZHAO Jin-peng, WANG Ru-lin, LI Xu-yi, WANG Ming-tian
    2021, 32(9):  3213-3222.  doi:10.13287/j.1001-9332.202109.013
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    Continuous rain disaster is a kind of complex disaster with high frequency in the Basin area of Sichuan Province. Continuous rainy weather may appear in every growing stage of rice, with consequences on the yield and quality. Based on the meteorological data of 105 meteorological stations between 1981 and 2019, combining the observation data of rise production, agricultural statistics and the basic geographic information, we quantitatively evaluated and compared the continuous-rain disasters in the whole growth period and the four growth stages (sowing-jointing, jointing-booting, booting-early filling, mid-late filling-maturity) between transplanted rice and direct-seeded rice in the basin area of Sichuan Province. The results showed that the disaster index of continuous-rain for rice was higher in the sowing-jointing stage and the mid-late filling-maturity stage, higher in the northern and southwest edges of the basin, and lower in the middle, western and southern basin. The area with high-risk was relatively limited, which concentrated in the northern edge of the basin and scattered in the southern region of the basin. The low-risk area was the most widely distributed, which concentrated in the western and central parts of the basin. The total area of high-disaster areas for transplanted rice was 2.4 times as large as that for direct-seeded rice.
    Root morphological changes in maize and soybean intercropping system under different phosphorus levels
    QIN Xiao-min, PAN Hao-nan, XIAO Jing-xiu, TANG Li, ZHENG Yi
    2021, 32(9):  3223-3230.  doi:10.13287/j.1001-9332.202109.023
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    A pot experiment was conducted to investigate the changes of root morphology and its relationship with P uptake under different P levels (0, 50 and 100 mg P2O5·kg-1, represented by P0, P50 and P100, respectively). The results showed that intercropping significantly changed root morphological parameters of both maize and soybean, and increased the root:shoot ratio in soybean under different P levels. Intercropping significantly increased root length, root surface area, root volume, and root dry weight of maize and soybean by 25.6%, 22.0%, 39.2%, 34.3% and 28.1%, 29.7%, 37.3%, 62.3%, respectively, but significantly decreased the average root diameter by 15.2% and 11.7% compared to corresponding monoculture. The phosphorus uptake equivalent ratio (LERP) was >1, showing P uptake advantage of intercropping and that the LERP were unaffected by P levels. The root morphological changes induced by intercropping were closely related to P uptake improvement. The increases of maize root surface area and soybean root length were the main mechanisms driving efficient P uptake in maize and soybean intercropping. Based on the regression equation, 10% increase of maize root surface area or soybean root length caused 5%-10% increase of phosphorus uptake. P uptake of intercropped maize was not declined under P50 level compared to that of monoculture supplied with P100 level. In conclusion, maize and soybean intercropping has the potential to maintain crop P uptake when reducing application of phosphate fertilizer.
    Effects of organic fertilizer application on crop yield and soil properties in rice-wheat rotation system: A meta-analysis
    LI Yuan-bin, LI Peng, WANG Shu-hua, XU Lu-yao, DENG Jian-jun, JIAO Jia-guo
    2021, 32(9):  3231-3239.  doi:10.13287/j.1001-9332.202109.024
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    To clarify the effects of organic fertilizer application on crop yield and soil properties in rice-wheat rotation system in China, we carried out a meta-analysis to quantitatively evaluate the effects of organic fertilizer types (ordinary organic fertilizer, biochar, and straw), fertilization regimes (organic fertilizer alone, organic fertilizer + partial chemical fertilizer, and organic fertilizer + full amount of chemical fertilizer), and experiment duration (short term, medium term, and long term) on soil properties and the yield of rice and wheat, as well as their responses to soil conditions (acid, neutral, basic). Results showed that the application of organic fertilizer had similar yield-increase effect on rice yield (3.1%) and wheat yield (3.0%) compared to chemical fertilizer application alone. The effect of organic fertilizer application on soil quality was more obvious, significantly reducing soil bulk density by 5.7%, and increasing the concentrations of soil organic matter, total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen, available phosphorus, available potassium, microbial biomass carbon, and microbial biomass nitrogen by 11.7%-38.4%. Among different types of organic fertilizer, the effects of ordinary organic fertilizer and biochar on soil properties improvement were better than straw. Compared to the organic fertilizer application alone, the effects of organic fertilizer combined with chemical fertilizer on crop yield was better, but poorer on soil property improvement. With the increasing duration of organic fertilizer application, crop yield and soil fertility gradually increased. Under the condition of acid soil, the effect of organic fertilizer application on crop yield was the best. The annual yield of rice and wheat showed significant negative correlation with soil bulk density, but a significant positive correlation with the concentrations of soil total nitrogen, available phosphorus, available potassium, and microbial biomass nitrogen.
    Effects of addition of sorghum stubble rhizosphere soil on growth and rhizosphere microbes of continuous cropping cucumber
    ZHANG Lei, ZHOU Zhe-zhe, WANG Xue-xia, WANG Jia-chen, WANG Dian-wu, CHEN Yan-hua
    2021, 32(9):  3240-3248.  doi:10.13287/j.1001-9332.202109.032
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    We explored the effects of addition of sorghum stubble rhizosphere soil on the growth of continuous cropping cucumber and rhizosphere microbial community in a pot experiment. The diffe-rences in soil bacterial and fungal community composition were analyzed with fluorescence quantitative PCR and high-throughput sequencing technology. There were four treatments: CK (no fertilization), T1(fertilizer only), T2(optimized fertilization), and T3(optimized fertilization + rhizosphere soil of sorghum stubble). The results showed that compared with other treatments, T3 promoted the growth and development of cucumber, and increased the abundance of 16S rRNA and ITS rRNA genes in soil. Compared with the T1 treatment, T2 and T3 significantly increased the richness and diversity of bacterial communities. There was no significant difference in fungal community richness and diversity among different treatments. Adding rhizosphere soil of sorghum stubble changed the composition of bacterial and fungal communities at both phylum and genus levels. For bacteria, it increased the abundances of Acidobacteria and Bacteroides, but decreased that of Proteobacteria, Firmicutes, Nitrospira and Bacillus. For fungi, it increased the abundance of Basidiomycota, Trichoderma and Pseudurotium, but decreased that of Fusarium and Metarhizium. Results of redundancy analysis showed that soil nitrate and organic matter were the key factors affecting the difference of bacterial and fungal community composition, respectively. In conclusion, addition of sorghum stubble rhizosphere soil improved the total abundance of soil microorganisms and bacterial diversity for continuous cropping cucumber. It increased the abundance of beneficial bacteria Trichoderma, reduced that of pathogenic Fusarium, and maintained the survival rate of cucumber, thus provided a feasible solution for alleviating the barriers for the continuous cropping of cucumber.
    Effects of no-tillage sowing with crop stubbles on seeding emergence and yield of spring wheat in Hexi Oasis Irrigated Area, Northwest China
    LU Bing-lin, CHE Zong-xian, BAO Xing-guo, ZHANG Jiu-dong, WU Ke-sheng, CUI Heng, YANG Rui-ju
    2021, 32(9):  3249-3256.  doi:10.13287/j.1001-9332.202109.025
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    We examined the effects of long-term no-tillage sowing with crop stubbles on seedling emergence quality and yield of spring wheat under the three typical spring wheat planting modes of single wheat, wheat-corn intercropping and wheat-soybean intercropping in a long-term field experiment in Hexi oasis irrigated area, aiming to provide theoretical support for the efficient and sustai-nable production of spring wheat. The results showed that, compared with traditional tillage, no-tillage sowing with crop stubbles significantly decreased seedling emergence rate and emergence evenness of spring wheat in wheat-corn intercropping and wheat-soybean intercropping by 3.3%-8.6%, 9.6%-20.5%, 2.9%-8.8%, and 10.7%-61.7%, respectively. Emergence evenness was significantly increased by 14.9% in 2019, while seedling emergence rate was significantly decreased by 4.2% in 2020 under the mode of single wheat compared with traditional tillage. Seedling uniformity of spring wheat seedling stage were reduced under the three typical planting modes, including single wheat, wheat-corn intercropping and wheat-soybean intercropping. Spike number of spring wheat were equal to that of traditional tillage at harvest under the three planting modes of no-tillage sowing with crop stubbles, and the differences were not significant. Effects of seedling emergence rate of spring wheat on yield was weakened by increasing grain number per spike and 1000-grain weight of spring wheat under the three planting modes. Grain yield was significantly increased by 10.3%-12.9% (single wheat), 10.5%-11.9% (wheat-corn intercropping), and 10.3%-22.5% (wheat-soybean intercropping) at harvest, respectively. Our results indicated that no-tillage sowing with crop stubbles was the feasible tillage mode in the production process of spring wheat in Hexi oasis irrigation area with extremely serious farmland wind erosion degradation.
    Effects of long-term straw returning on distribution of aggregates and nitrogen, phosphorus, and potassium in paddy
    LI Xin-yue, LI Bing, MO Tai-xiang, WANG Chang-quan, WAN Yi-yuan, CHEN Xie-chang, LI He-ming
    2021, 32(9):  3257-3266.  doi:10.13287/j.1001-9332.202109.022
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    In order to understand the composition and stability of soil aggregate in paddy filed, as well as the changes of soil aggregate-associated nitrogen (N), phosphorus (P) and potassium (K) after straw addition combined with chemical fertilization, soil samples were collected from a 34-year positioning experiment with three treatments, including no chemical fertilizer (CK), chemical fertilizer only (NPK), and straw addition plus chemical fertilizer (NPKS). The composition of water-stable aggregates at the soil layers of 0-20 cm and 20-40 cm were analyzed with the wet sieving method, as well as the distribution characteristics, contribution rate and activation rate of soil aggregate-associated N, P, and K. Results showed that the fractions of >2 mm and 0.25-1 mm aggregates dominated the soil water-stable aggregates in paddy field, while the contribution of <0.053 mm aggregates was lowest. Compared with CK, NPKS treatment increased the contents of >2 mm and 1-2 mm aggregates at the layers of 0-20 and 20-40 cm, and reduced the contents of 0.053-0.25 mm and <0.053 mm. Similar result in NPK treatment was observed at the layer of 0-20 cm. Compared with tat under the NPK treatment, mean weight diameter (MWD) and geometric mean diameter (GMD) increased by 3.9%-15.5% and 6.3%-41.7% in NPKS treatment, respectively. However, the unstable aggregate index (ELT) reduced by 5.7%-28.7% in the NPKS treatment. NPKS significantly increased the contents of total N (TN), available P (AP), and available K (AK) in soil aggregates, especially in the >0.25 mm aggregates. There were no significant diffe-rences about alkali-hydrolysable N (AN) and total K (TK) between NPK and NPKS treatments. The nutrient contribution of soil aggregates in paddy field was affected by aggregate composition. NPKS significantly increased the contribution of AN, AP, and AK within >1 mm aggregates. In all, straw addition combined with chemical fertilizer could increase the stability of soil aggregates at the layers of 0-20 cm and 20-40 cm, and increase the contents of soil aggregate-associated N, P and K, especially for the >1 mm aggregates. Our results provided insights into ensuring soil quality and sustainable development of resources in paddy field by adjusting the ratio of soil C to N.
    A model for the evaluation of groundwater ecological compensation budget
    ZHAO Wen-yi, HE Li, CHEN Bai-xue, YE Wei
    2021, 32(9):  3267-3276.  doi:10.13287/j.1001-9332.202109.015
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    Groundwater, one of the important water resources, plays an important role in maintaining sustainable social and economic development. The ecological compensation of groundwater is a beneficial tool for guaranteeing reasonable exploitation and utilization of groundwater resources. However, there is a lack of associated studies, especially compensation budget. We proposed an integrated groundwater compensation standard model, which consisted of four components: base, stimulus and punishment, research and development, and potential risk. The priority level of compensation was estimated by considering regional climate and economic conditions comprehensively. The model was applied to a total of 11 cities in Shanxi Province to calculate the groundwater ecolo-gical compensation standard. The results showed that the base compensation accounted for the largest proportion in the total compensation, with the non-market value contributing more than 60%. Our results indicated that groundwater had a high regulated service value. From 2008 to 2017, the development coefficient of each city had significantly increased, suggesting the improved regional economic level and enhanced compensation capacity. Compensation priority was affected by the non-market value of groundwater and economic level, and obvious difference in the compensation priority existed in all the cities, implying the requirement for the implement of groundwater ecological compensation. Meanwhile, we suggested that groundwater risk compensation system should be improved, special funds should be set up for supporting research projects on groundwater ecological compensation, and long-term effective compensation mechanisms should be established.
    Temporal-spatial and non-stationarity characteristics of extreme precipitation in the Poyang Lake Basin, China
    LEI Xiang-yong, GAO Lu, MA Miao-miao, DANG Hao-fei, GAO Jian-yun
    2021, 32(9):  3277-3287.  doi:10.13287/j.1001-9332.202109.017
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    Extreme weather/climate events increased significantly because of global warming. Based on daily records from 16 meteorological stations in the Poyang Lake Basin (PLB) from 1959 to 2019, we comprehensively investigated the temporal-spatial and non-stationarity characteristics of extreme precipitation from three dimensions (intensity, frequency and duration) using PreWhite-ning Mann-Kendall (PWMK), extreme-point symmetric mode decomposition method (ESMD) and the generalized additive models for location, scale and shape (GAMLSS). The results showed that the intensity and frequency of extreme precipitation increased significantly in the PLB, while the duration of extreme precipitation decreased from 1959 to 2019. The extreme precipitation had features of high intensity, high frequency, and short duration in the PLB. There was a clear distinction between flood season and non-flood season for extreme precipitation. Extreme precipitation was concentrated in the northern and central PLB during the flood season and in the central PLB during the non-flood season. The increasing trend of extreme precipitation amount was 2.10 mm·a-1 in the Xinjiang basin, which had the largest increment over the PLB. In the flood season, the extreme precipitation had longer duration but weaker intensity and smaller range, contrasting with the status during the non-flood season. The intensity and frequency of extreme precipitation showed stationarity characteristics in the PLB. However, the duration of extreme precipitation showed non-stationarity characteristics. With the continuous increase of extreme precipitation amount, the risk of related disasters would increase.
    Ecological network construction and optimization in Foshan City, China
    SHEN Qin-wei, LIN Mei-ling, MO Hui-ping, HUANG Yu-bin, HU Xin-yu, WEI Ling-wei, ZHENG Yu-shan, LU Dong-fang
    2021, 32(9):  3288-3298.  doi:10.13287/j.1001-9332.202109.019
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    Under the background of rapid urbanization, the problem of fragmented habitat patches in economically developed areas is particularly prominent, where biodiversity is seriously threa-tened. Therefore, the construction of ecological network is an important measure to connect habitat patches and protect biological habitats. We extracted ecological source areas of Foshan City by using the connectivity index and morphological spatial pattern analysis (MSPA). Potential ecological corridors were identified based on InVEST model and minimal cumulative resistance (MCR). Combining the radiation channels extracted from hydrological analysis to build an ecological network in Foshan City. The ecological network was optimized by adding ecological source areas, stepping stones, and identifying fracture points. Finally, the network before and after optimization was evalua-ted from the aspects of both structure and function based on network analysis method and circuit theory. The results showed that ecological network in Foshan City was composed of 10 ecological source areas, 8 important corridors, 37 general corridors, and 11 radiation channels. After optimization, 7 new ecological source areas, 17 planning corridors, 13 stepping stones, and 80 fracture points were added. After optimization, the ecological network closure, the line rate index and the connection degree index were 0.59, 1.94, and 0.73, respectively. The maximum current density increased from 1.39 to 9.66 after optimization, indicating that the optimized ecological network structure was more perfect and highly connective.
    Spatio-temporal evolution and driving mechanism of green economic efficiency at county level in the Yellow River Delta, China
    CAO Nai-gang, ZHAO Lin, GAO Xiao-tong
    2021, 32(9):  3299-3310.  doi:10.13287/j.1001-9332.202109.039
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    A comprehensive measurement of green economic efficiency in the Yellow River Delta region can provide a reference basis for achieving ecological protection and high-quality development. We constructed an evaluation system of green economic efficiency in counties based on multi-source remote sensing data. We adopted the Super-EBM model that considered non-expected output to make a comprehensive measurement of green economic efficiency in Yellow River Delta counties, used the kernel density function estimation method to portray the characteristics of spatial and temporal evolution, and finally used the system generalized moment estimation method to identify influen-cing factors. The results showed that the comprehensive efficiency and pure technical efficiency of the green economy in the Yellow River Delta counties showed a fluctuating upward trend from 2000 to 2015. The scale efficiency showed a rapid increase and then stayed stable in a ‘Γ' type trend, while the increase in comprehensive efficiency transformed from being driven by scale-technology to being led by technology. The comprehensive efficiency and pure technical efficiency of the green economy in the Yellow River Delta counties showed an evolutionary trend from ‘club convergence' to ‘overall convergence', with the low efficiency counties formed a ‘catch-up effect' on the high efficiency counties and the scale efficiency toward a balanced and smooth development. The comprehensive efficiency of green economy and its decomposition efficiency spatially formed a ‘mountain' pattern, which was high in the middle, low in the two wings, and the high value area concentrated in the headland of the Yellow River Delta and along the coast of Laizhou Bay. The high-value area showed the characteristics of a northwest-southeast shift, and the east and west wings of the Yellow River Delta formed low-value subsidence areas. Industrial structure, population concentration level, and fixed asset investment intensity had positive effects on green economic efficiency, while population urbanization rate had negative effects on green economic efficiency. There was an obvious ‘environmental Kuznets' effect between green economic efficiency and economic development level.
    Interaction between the characteristics of urban three-dimensional landscape pattern and social-environmental factors based on boosted regression tree
    DONG Qian-qian, LIU Yao-yi, ZENG Peng, SUN Feng-yun, ZHANG Ran, TIAN Tian, CHE Yue
    2021, 32(9):  3311-3320.  doi:10.13287/j.1001-9332.202109.011
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    Vertical expansion makes the structure and pattern of the city more complicated. Traditional two-dimensional landscape pattern cannot completely reflect the ecological structure and functional characteristics of urban landscape. In this study, we used the three-dimensional landscape pattern metrics to quantify the regional three-dimensional landscape pattern, and used boosted regression tree (BRT) machine learning algorithms to comprehensively analyze the interaction between social-environmental factors and urban landscape patterns in the central part of Shanghai. Results showed that high building ratio, mean architecture height, and architecture height standard deviation had higher values in the surrounding area of the inner ring. The number of buildings and landscape shape index were higher in the outer ring than those in other area. Building coverage ratio, floor area ratio and Shannon's diversity index had higher values in the central part, with the metrics of Puxi being generally higher than those of Pudong. Population density and normalized vegetation index (NDVI) interacted most significantly with the three-dimensional landscape pattern, with GDP as the least influential factor. Within a certain range, the three-dimensional landscape pattern metrics increased with larger population density in the social factors, and decreased with lower rate of NDVI and water surface ratio in the environmental factors. Our results demonstrated that the BRT method was effective in quantifying the interaction between landscape pattern and social-environmental factors. Our results help improve the understanding of the relationship between ecological environment and human well-being in the central part of Shanghai and provide a scientific basis for the urban three-dimensional expansion planning.
    Effects of two Streptomyces strains on growth and physiological properties of Gerbera jamesonii
    HU Xiao-jing, AO Fei-xiong, SHI Le-juan, PENG Qiang, LI Xin, ZHOU Xiao-hui, CHEN Xiao-yulong
    2021, 32(9):  3321-3326.  doi:10.13287/j.1001-9332.202109.029
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    We applied different concentrations of spore suspension of Streptomyces exfoliatus FT05W and S. cyaneus ZEA17I to inoculate Gerbera jamesonii to screen for the most effective application concentration. We aimed to explore the effects of two Streptomyces strains on growth and physiological properties of G. jamesonii, and to provide scientific evidence for the application of Streptomyces in G. jamesonii production. The results showed that different concentrations of S. exfoliatus FT05W and S. cyaneus ZEA17I spore suspension could effectively promote the growth of G. jamesonii. In general, S. exfoliatus FT05W performed better than S. cyaneus ZEA17I. S. exfoliatus FT05W (1×109 CFU·mL-1) could significantly increase the height and crown width of G. jamesonii respectively by 30.2% and 41.5%. Meanwhile, it increased the length and width of the stem. When treated by S. exfoliatus FT05W (1×109 CFU·mL-1), the content of chlorophyll in G. jamesonii was significantly increased by 65.2%, root activity was significantly increased by 103.3%, and the superoxide dismutase activity was increased by 84.4%. The malondialdehyde content in G. jamesonii was maintained at a low level when treated with the two Streptomyces strains. In summary, S. exfoliatus FT05W and S. cyaneus ZEA17I could effectively promote the growth and physiological properties of G. jamesonii, which could further contribute to its resistance to stress. Therefore, S. exfoliatus FT05W had the potential as a bio-fertilizer for G. jamesonii to solve cultivation obstacles.
    Toxic effects of sublethal acetochlor with sublethal doses on earthworms in soil using multi-endpoints system
    YANG Xiao-xia, GONG Jiu-ping, ZHANG Xue-mei, ZHANG Wei, LI Dian-yan, YANG Jun-ying, CHAI Yong, LIU Jian-fei
    2021, 32(9):  3327-3334.  doi:10.13287/j.1001-9332.202109.033
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    In this study, we examined the toxic effect of sublethal doses of acetochlor (1, 2, 4, 8 mg·kg-1) on earthworms by exogenous addition. The growth inhibition rate, cytochrome P450 isozymes (CYP1A2, 2C9 and 3A4) activities and the metabolomics were analyzed after seven days of exposure, to infer the toxicity threshold of acetochlor, screen the sensitive biomarkers from the levels of the individual, detoxified enzymes and small molecular metabolites, and elucidate the underlying toxicity mechanism. The results showed that CYP1A2, 2C9 and 3A4 activities were all significantly inhibited, and that the levels of ten metabolites (fructose-6-diphosphate, cytosine monophosphate, uridine monophosphate, adenosine monophosphate, adenosine, xanthine, fumaric acid, dihydroxyglutaric acid, ornithine and 16-hydroxyeicosatetraenoic acid) were significantly decreased by acetochlor exposure. The levels of six metabolites (adenosine succinic acid, succinic acid, arginine, tryptophan, asparagine and phenylalanine) were significantly increased when earthworms being exposed to 2-8 mg·kg-1 acetochlor. Acetochlor exposure caused oxidative damage to earthworms, weakened the glycolysis, disturbed the tricarboxylic acid cycle, disordered the purine and pyrimidine metabolism, and impaired the amino acids metabolism. Compared with the end point at individual level, the above 16 small molecule metabolites and CYP isozymes activities were more sensitive to acetochlor exposure. It was thus recommended that CYP isozymes (1A2, 2C9, and 3A4) activities and small molecular metabolites could be used as a set of biomarkers to diagnose the acetochlor pollution, given their high sensitivity and accuracy.
    Toxic effects of polystyrene and dibutyl phthalate on purple lettuce
    WANG Sheng-li, SONG Zheng-guo, WANG Cheng-wei, LIU Yu, GAO Min-ling
    2021, 32(9):  3335-3340.  doi:10.13287/j.1001-9332.202109.038
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    As a carrier of environmental pollutants, microplastics have received wide concerns in recent years. However, the direct and indirect effects of the coexistence of polystyrene particles (PS) and pollutants on vegetables are still unclear. Here, the combined effects of 0.25, 0.50, 1.0 mg·mL-1 PS and 5 mg·L-1 dibutyl phthalate (DBP) on the biomass and biochemical indices of purple lettuce were investigated in hydroponic experiments. The results showed that the presence of PS increased the inhibition of DBP on lettuce biomass and increased O2-· content in roots and leaves relative to the control group with DBP alone, with positive consequences on the activities of supero-xide dismutase, ascorbic acid peroxidase, dehydroascorbate reductase and monodehydroascorbate reductase. According to transmission electron microscope analysis, plasmolysis occurred in root cells under the treatment of DBP alone, cell wall was damaged in PS-only treatment, and the negative effect was enhanced when DBP and PS coexisted. Therefore, the combined pollution of PS and DBP aggravated the toxic effect on purple lettuce.
    Effects of crude oil pollution on soil moisture infiltration with loessial soil and aeolian sandy soil
    WANG Li-jing, SHANG Zhen-kun, ZHANG Xing-chang, ZHEN Qing
    2021, 32(9):  3341-3348.  doi:10.13287/j.1001-9332.202109.035
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    Crude oil may block soil pores, affect soil water repellency, and change soil water movement. In this study, soil column simulation was used to study the effects of different crude oil pollution levels (0, 0.5%, 1%, 2%, 4%) on the water infiltration processes in loessial soil and aeolian sandy soil. The results showed that soil wetting front speed and infiltration rate of those two soils decreased with increasing crude oil content. The time needed for wetting front reaching the bottom of the soil column was the longest under 4% crude oil polluted soil, which was 4 times and 48 times longer than that of no crude oil polluted soil for loessial soil and aeolian sandy soil, respectively. The cumulative infiltration of loessial soil decreased with increasing crude oil content, while it increased to the max and then decreased as the crude oil content increased in aeolian sandy soil. The cumulative infiltration curves of aeolian sandy soil with high crude oil contents (2% and 4%) presented “up-tail” phenomenon. Kostiakov infiltration model and Philip infiltration model could better fit the infiltration process than Green-Ampt model for loessial soil with different crude oil content. However, the two models could only well fit the infiltration process for aeolian sandy soil with low crude oil content (0, 0.5%, 1%). Crude oil pollution could significantly affect soil water infiltration process, especiall in aeolian sandy soil.
    Population structure and resource change of Larimichthys polyactis in spring in Zhoushan fishery spawning ground protection area, China
    WANG Ya-li, HU Cui-lin, LI Zhen-hua, JIANG Ri-jin, ZHOU Yong-dong, ZHANG Lin-lin, ZHANG Hong-liang, XU Kai-da, XIONG Ying
    2021, 32(9):  3349-3356.  doi:10.13287/j.1001-9332.202109.036
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    We investigated population structure, resource density changes of Larimichthys polyactis and its relationship with environmental factors in spring, based on the survey data of bottom trawl in adjacent sea areas of Zhoushan fishery spawning ground protection area from 2014 to 2019. The results showed that the relationship between body length and body weight of Larimichthys polyactis was W=0.44×10-4×L2.78, and parameter b was less than 3, which indicated that L. polyactis had negative allometric growth in recent years. There was a negative correlation between fullness and body length, with body becoming slender. From 2014 to 2019, body length and weight of L. polyactis were the highest in 2014 and the lowest in 2019. Since 2014, population size of L. polyactis in Zhoushan fishery spawning ground protection area and adjacent sea area had gradually decreased, indicating that the miniaturization of L. polyactis had not altered in recent years. From the perspective of the annual change of resource density, resource density of L. polyactis was higher than that before the establishment of the reserve, indicating that the management and protection of the reserve area played a protective role in the recovery of L. polyactis resources. The fitting results of GAM model showed that water depth and bottom water temperature were the environmental factors closely related to the density distribution of L. polyactis resources. With increasing water depth, the resources showed a fluctuating upward trend and were the highest near the water depth of 60 m. In the range of 12-16 ℃ water temperature, the resources increased with the increases of bottom water temperature. When water temperature was above 16 ℃, resources decreased with the increases of bottom water temperature.
    Coexistence strategies of invaded gobies in the Dianchi Lake, Yunnan, China
    CHEN Li-juan, XIAO Qiao-zhi, QIU Yu-ping, CHEN Guo-zhu
    2021, 32(9):  3357-3369.  doi:10.13287/j.1001-9332.202109.004
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    Gobiids are widespread invasive species, with many species from this group usually invade into the same ecosystem simultaneously. Understanding the mechanisms underlying the coexi-stence of different gobiid species in the sympatric habitats is a key issue in fish invasion ecology. Incorporating morphological analyses, spatial distribution survey, and trophic analyses, we examined the coexistence strategy of Mugilogobius myxodermus and related species (the earlier invaders) in Dianchi Lake, Yunnan, China. Our results showed significant differences in morphology and spatial distribution among the four invasive gobies species (i.e., M. myxodermus, Micropercops swinhonis, Rhinogobius giurinus and Rhinogobius cliffordpopei). The spatial niche index of M. myxodermus was the highest. Food composition between M. myxodermus and other gobies was significantly different, with the former mainly feeding on Chydorus ovalis and Cypris sp. The trophic diversity index of M. myxodermus was the highest. Overall, we found that morphological differences, spatial niche diffe-rentiation, and trophic niche differentiation contributed to the coexistence of the gobies in Dianchi Lake, which could help M. myxodermus reduce interspecific competition. Importantly, the feeding strategy is the key factor determining population size and habitas of M. myxodermus during their competition with the other gobies, and finally contributing to the dominant position in the study area.
    Distribution of melanin in the larvae of Schizothorax o'connori
    TIAN Na-na, WANG Xian-xian, BIAN Fang-fang, ZENG Ben-he, LIU Hai-ping, YANG Rui-bin, YANG Xue-fen
    2021, 32(9):  3370-3376.  doi:10.13287/j.1001-9332.202109.031
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    We examined the distribution of melanin during the development of the larvae of Schizothorax o'connori except the eyes with histological method. The results showed that after hatching, the appearance sequence of melanin in different organs were following an order of the outer membrane of neurocranium, the pericardial cavity and the dorsal skin, and the peritoneum and the spinal cord. Specifically, melanin appeared in the outer membrane of neurocranium around 5 DAH (days after hatching), in the pericardial cavity and the back skin at 7 DAH, and in the peritoneum and the spinal cord at 10 DAH. Melanin was found in the skin and internal organs (the outer membrane of neurocranium, the pericardial cavity, the peritoneum, the spinal cord) of S. o'connori at 10 DAH, which was mainly distributed on the back. The appearance and distribution of melanin in the postembryonic development of S. o'connori might be related to the high ultraviolet radiation. Our results could provide reference for further research on the UV protection mechanism of melanin for fish and provide theoretical support for the optimization of rearing conditions for larvae in the plateau.
    Reviews
    Research progress on air pollutant distribution in urban street canyons
    MIAO Chun-ping, CHEN Wei, CUI Ai-wei, LI Ping-ping, HU Yuan-man, HE Xing-yuan
    2021, 32(9):  3377-3384.  doi:10.13287/j.1001-9332.202109.018
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    Urban street canyon is one of the most important characteristics and spatial forms of cities. It is one of the most frequently used public spaces in cities, with the most serious automobile exhaust pollution and the largest population density. The unreasonable space configuration and internal composition might decrease self-purification of urban ventilation but increase local air pollutant concentration. Here, we reviewed the impacts of street canyon morphology, street trees, vehicle flow and meteorological factors on the distribution of air pollutants in street canyons. We scrutinized the relevant methods of numerical simulation, wind tunnel experiments, and field monitoring on the distribution and diffusion of air pollutants in street canyons. We recommended that future research should concentrate on the impacts of various parameters on the distribution and diffusion of air pollutants based on the field monitoring data. Meanwhile, further research should develop optimization strategies for street canyon design which is conducive to the dispersion of air pollutants, and put forward scientific support and optimization scheme for the controlling of air pollutants from the perspective of urban planning and pattern optimization.
    Research progress on mechanism of arbuscular common mycorrhizal networks in plant-plant interactions
    CAO Ben-fu, JIANG Hai-xia, LIU Li, LU Yin-gang, WANG Mao-sheng
    2021, 32(9):  3385-3396.  doi:10.13287/j.1001-9332.202111.032
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    Plant-plant interactions is one of the key field in ecology, which is important for the efficient nutrient utilization, productivity improvement, and plant community assembly. Arbuscular mycorrhizal fungi are important plant mutualistic microorganisms that connect plant roots to form common mycelial networks (CMNs), which play major roles in transferring nutrients and water and regu-lating plant community dynamics. Recent studies demonstrated that these CMNs could act as conduits for transmitting disease and aphid-induced signals among plants, and activating chemical defence in uninfested neighboring plants. In this review, we introduced recent research advances on the contribution of CMNs on plant interaction, the main factors that influences the functions of CMNs, and the role of CMNs transfer and redistribute nutrients and water among plant. In addition, the mechanism underlying underground chemical signal communication, seedling establishment and plants community assembly were summarized. Finally, we proposed challenges facing CMNs in plant-plant interactions and the practical problems. It would provide reference for further understanding the ecological functions of CMNs in plant-plant interactions.