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    15 June 2023, Volume 34 Issue 6
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    Special Features of Regional Ecology
    Carbon emission reduction potential assessment in food transportation by urban agriculture: A case study of main urban area of Nanjing, China
    SUN Yibing, SU Jie, YIN Haiwei, SUN Hui, KONG Fanhua
    2023, 34(6):  1441-1449.  doi:10.13287/j.1001-9332.202306.021
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    As an emerging urban green infrastructure and continuous productive urban landscape, urban agriculture can increase the resilience of urban food systems and reduce carbon emission in food transportation. However, there are few studies in China on the potential of urban agriculture and its role in carbon emission reduction. With semantic segmentation and spatial analysis method to identify urban agricultural potential spaces on the ground and rooftops based on satellite images and Lidar point cloud data in the main urban area of Nanjing, we estimated their potential in vegetable production and the CO2 emission reduction effect in food transportation. The results showed that there were 2904.39 hm2 of ground and 2976.96 hm2 of rooftops in the study area with the potential to be used for urban agriculture. Under a scenario with 80% potential space utilization, it could produce approximately 225000 t of vegetables per year, which equated to 43.6% of annual vegetable consumption in the study area. Meanwhile, it would reduce CO2 emission in long distance food transportation by 63700 t per year.
    Carbon neutral contribution and regional differences of clean energy based on life cycle assessment
    HUANG Hongjun, SUN Ranhao, LI Jialei, XIANG Junyong
    2023, 34(6):  1450-1458.  doi:10.13287/j.1001-9332.202306.022
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    Developing clean energy is an important strategy to achieve global carbon neutrality. In the entire life cycle industrial chain of clean energy systems, fossil energy was directly or indirectly consumed during the processes from raw material production to waste disposal stages. The energy consumed by clean energy construction differed across regions, resulting in various carbon neutrality contributions of clean energy in different regions. We used bibliometrics to sort out the energy consumption of clean energy construction in different regions, including photovoltaic power generation, wind power, hydropower, and other clean energy sources. By combining the loss of land to decrease carbon pool during the operation of clean energy, we analyzed the current research hotspots, development status and trends, and difference in carbon emissions, and summarized the carbon neutral contributions of different regions. The intensity of clean energy carbon emission in China was significantly lower than global mean value. The average intensity of carbon emission in China in the four fields of onshore wind power, offshore wind power, hydropower, and photovoltaic power was 28.8%, 18.2%, 10.1%, and 16.7% lower than global average, respectively. For further research on carbon neutrality of clean energy, it is important to establish a unified life cycle assessment system, put forward construction strategies according to geographical differences, carry out ecological benefit evaluation for clean energy, and establish a clean energy transmission network system.
    Connotation of urban ecological quality and the construction of its core index system
    YAN Ming, CHEN Liding, SUN Ranhao
    2023, 34(6):  1459-1466.  doi:10.13287/j.1001-9332.202306.019
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    Urban ecological quality is a necessary attribute for a healthy urban ecological state. In the period of urban development from large-scale incremental construction to stock improvement and quality transformation and incremental structural adjustment, there are many gaps between urban ecological quality construction and the requirements of the new stage. There is an urgent need to understand and integrate multiple needs, and construct an indicator system to promote the balance between supply and demand of ecological resources and efficient use to enhance urban ecological quality. We used the analysis methods of CiteSpace literature analysis, relevant policy collation and questionnaire survey to systematically sort out the key points of concern and differences in understanding among the three perspectives of science, government, and the public. The results showed that all the three perspectives, i.e., science, government, and public, were more concerned with indicators related to urban green space, gray infrastructure, and policy control. The concerns of science and public addressed indicators related to urban green space the most, while government being most concerned with indicators related to gray infrastructure. Based on those findings, we developed a core urban ecological quality index system with a total of 25 indicators, covering 10 major types of urban green space, environmental quality, gray infrastructure, and so on.
    Temporal and spatial patterns of habitat of Nipponia nippon in China under the background of climate change
    XIA Zhuoyi, SU Jie, YIN Haiwei, KONG Fanhua
    2023, 34(6):  1467-1473.  doi:10.13287/j.1001-9332.202306.008
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    Crested ibis (Nipponia nippon) is one of the endangered species in the International Union for Conservation of Nature. It is of great significance to pay attention to the changes of its suitable habitat in the context of climate change. Based on the geographical distribution data of crested ibis, the MaxEnt model was used to predict the suitable habitat of crested ibis under current scenario and future climate change. The results showed that the prediction accuracy of MaxEnt model was high, with an AUC value of 0.989. The minimum temperature of the coldest month, the mean temperature of the coldest quarter, and the mean annual rainfall were the dominant environmental factors affecting the habitat of crested ibis. Under current climate scenario, the area of moderately and highly suitable area of Chinese crested ibis was 10.65×104 km2, mainly distributed in Shaanxi, Sichuan, Hubei, Henan, and Gansu. In the future, the suitable habitat area of crested ibis would increase significantly under climate change, mainly distributed in Anhui, Chongqing, Guizhou, Jiangsu, Hunan, Shandong, Shaanxi, Jiangxi, Taiwan, Yunnan, Liaoning, and Fujian. In the SSP126 scenario from 2041 to 2060, the suitable habitat area of crested ibis would reach the maximum, being 139.53×104 km2 higher than that of the current climate scenario, accounting for 19.6% of the land area. This study could provide a basis for policy making on the conservation of crested ibis under global climate change.
    Construction and optimization of ecological networks based on future scenario simulation in Qianshan City, Anhui Province
    LI Jiulin, HU Dawei, CHU Jinlong, YIN Haiwei
    2023, 34(6):  1474-1482.  doi:10.13287/j.1001-9332.202306.026
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    The rapid urbanization adversely affects landscape pattern of mountainous cities. It is of great practical significance to explore the spatial and temporal evolution of ecological networks in mountainous areas to achieve regional ecological security. Taking Qianshan City in Anhui Province as an example, based on the land use data in 2012 and 2020, we simulated the land use situation in 2036 with PLUS model, and constructed the ecological networks in 2020 and 2036, respectively. We further analyzed its spatial and temporal evolution characteristics and explored the optimization path of ecological network. The results showed that the scale of various land use types in Qianshan City would change little from 2020 to 2036. The construction land would be centered on the built-up area, expanding in a point and block shape to the surrounding area. The ecological space would be continuously squeezed and encroached. The overall complexity and connectivity of ecological networks in Qianshan City would increase. The number and area of ecological source sites would increase, expanding spatially to the southwest and northeast. The overall density and number of ecological corridors would increase, with a lack of ecological corridor connections in the east-west direction, which need urgent improvement. The stability of ecological networks could be improved through three major measures, including protection and restoration of source sites, optimization and cultivation of corridors, and zoning control.
    Original Articles
    Trade-offs between leaf stoichiometric characteristics and photosynthetic traits of Larix gmelinii and its differences among provenances
    SHANGGUAN Hongyu, WANG Chuankuan, QUAN Xiankui
    2023, 34(6):  1483-1490.  doi:10.13287/j.1001-9332.202306.005
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    Variations and trade-offs between leaf stoichiometric characteristics and photosynthetic traits are indicative of ecological adaptation strategies of plants and their responses to environment changes. In a common garden of Maoershan, we measured leaf stoichiometric characteristics (carbon content (C), nitrogen content (N), phosphorus content (P), C/N, C/P, N/P) and photosynthetic traits (maximum net photosynthetic rate (Amax), maximum electron transport rate (Jmax), maximum carboxylation rate (Vmax)) of Larix gmelinii from 17 geographical provenances. We examined the provenance differences in stoichiometric characteristics and photosynthetic traits, and analyzed their trade-offs and influencing factors. The results showed leaf stoichiometric characteristics and photosynthetic traits significantly differed among provenances. The climatic factors of seed-source sites explained 54.8% and 67.2% of the variation in stoichiometric characteristics and photosynthetic traits, respectively. Aridity index (AI) of seed-source sites was positively correlated with C, N, P, Amax, Jmax, Vmax, but negatively with C/N, C/P, and N/P. Results of redundancy analysis showed that stoichiometric characteristics accounted for 75.0% of the variation in photosynthetic traits. Amax, Jmax, Vmax were positively correlated with C, N, P, and negatively correlated with C/N, C/P, N/P. The provenance differences in stoichiometric characteristics, photosynthetic traits, and their synergistic relationship suggested the long-term adaptation of trees to the climate of seed-source sites. These findings were of great significance for understanding ecological adaptation strategies of trees in response to climate change.
    Spatial distribution pattern and correlation of dominant species in the arbor layer at a 25 hm2 forest plot in Lushan Mountain, China
    WANG Jingxuan, ZHANG Jiaxin, XIANG Zeyu, ZHANG Zhaochen, XI Dan, WAN Huilin, PENG Yansong, ZHOU Saixia
    2023, 34(6):  1491-1499.  doi:10.13287/j.1001-9332.202306.001
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    To explore the spatial pattern of zonal tree species in the subtropical subalpine mountain area on Lushan Mountain, a 25 hm2 forest plot was established in Yangtianping area of Lushan Mountain following the technical specification of CTFS in 2021. We classified these species into evergreen conifer species, deciduous broad-leaved species and evergreen broad-leaved species based on their leaf shape and deciduous or not to analyze the spatial pattern of dominant species of different types by spatial point pattern method. The results showed that Pinus taiwanensis, Cornus kousa subsp. chinensis, Platycarya strobilacea, Castanea henryi, Quercus serrata, Cornus controversa, Eurya muricata, Litsea elongata, and Eurya hebeclados were dominant species. Among these species, P. taiwanensis was the constructive one. The spatial pattern of dominant species was clustered at a certain scale, and gradually became to randomly distribution with the increases of scales. Evergreen conifer species was independent with deci-duous broad-leaved species and evergreen broad-leaved species at small scales, but was negatively correlated with them at large scales. Deciduous broad-leaved species and evergreen broad-leaved species were obviously negatively correlated with each other. Deciduous broad-leaved species were positively correlated or independent with each other at small scales, but were negatively correlated with each other at large scales. Evergreen broad-leaved species were positively correlated at small scales, independent at medium scales, and negatively correlated with each other at large scales.
    Responses of soil bacterial and fungal communities to altered precipitation in a desert steppe
    GUO Rong, WU Xudong, WANG Zhanjun, JIANG Qi, YU Hongqian, HE Jing, LIU Wenjuan, MA Kun
    2023, 34(6):  1500-1508.  doi:10.13287/j.1001-9332.202306.012
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    To investigate the response mechanisms of soil bacterial and fungal communities to the changes of preci-pitation in a desert steppe of Ningxia, we conducted a three-year precipitation control experiment following completely randomized design. There were five treatments, natural precipitation (T0), 50% less in precipitation (T1), 25% less in precipitation (T2), 25% more in precipitation (T3) and 50% more in precipitation (T4). By using Illumina high-throughput sequencing and bioinformatics analysis, we investigated the effects of increased and decreased precipitation on soil bacterial and fungal communities, and examined the correlations between soil physicochemical properties, plant communities and soil bacterial and fungal communities. The result showed that the richness of soil bacteria and fungi was highest in the T4 treatment. In addition, the relative abundance of Chloroflexi, the predominant phyla of soil bacteria was more sensitive to precipitation change. However, the relative abundance of only Ascomycota, a rare fungal taxon, responded to precipitation changes. Results of redundancy analysis showed that the first two axes accounted for 92.8% and 87.4% of the total variance for soil bacterial and fungal community composition, respectively. Precipitation and soil pH were the most important environmental factors driving changes in soil bacterial diversity and community composition. On the one hand, precipitation had a direct positive effect on bacterial diversity and community composition. On the other hand, precipitation changed pH by affecting soil moisture, which in turn had a significant indirect effect on bacterial diversity and community composition. Plant community biomass, plant species richness, and soil pH were the most influential environmental factors affecting fungal diversity and community composition. Precipitation had no direct effect on soil fungal community, but had a significant indirect effect by changing plant community richness and soil pH. The response mechanisms of bacterial and fungal communities in soil differed significantly under different precipitation regimes in the desert grasslands of Ningxia.
    Characteristics of net ecosystem exchange and source distribution of Xilinhot grassland, China
    CHEN Yang, LI Huirong, LI Dongnan, SUN Pengfei, SU Jianghua
    2023, 34(6):  1509-1516.  doi:10.13287/j.1001-9332.202306.006
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    To understand carbon sequestration capacity of grasslands, the changes of CO2 flux in Xilinhot grasslands and the influence of environmental factors were analyzed by using the eddy data of Xilinhot National Climate Observatory in 2018-2021, and the distribution of flux source areas was analyzed. The results showed that the southwest wind prevailed in the study area throughout the year, the source area in the growing season was larger than that in the non-growing season, and the source area under stable atmospheric conditions was larger than that under unstable conditions. The maximum length of source region with a contribution rate of 90% was close to 400 m, which was consistent with the length estimated by the classical law. The net ecosystem exchange (NEE) of Xilinhot grasslands had obvious diurnal and seasonal dynamics, which was manifested as a carbon sink in the daytime and a carbon source at night during the growing season and weak carbon source in the non-growing season. From 2018 to 2021, the annual total NEE were -15.59, -46.28, -41.94, and -78.14 g C·m-2·a-1, respectively, with an average value of -45.49 g C·m-2·a-1, indicating that Xilinhot grassland had strong carbon sequestration capacity. Vapor pressure deficit and photosynthetically active radiation helped grasslands absorb atmospheric CO2. At night, when temperature was above 0 ℃, the increases in air and soil temperature promoted vegetation respiration to release CO2.
    Blooming characteristics and breeding system of an invasive plant Gaura parviflora
    GUO Yuying, LIU Longchang, MENG Wei, WANG Xinye, YAO Hairui, LI Longji
    2023, 34(6):  1517-1524.  doi:10.13287/j.1001-9332.202306.003
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    The invasiveness and dissemination of exotic species are strongly influenced by its sexual reproduction characteristics, including blooming characteristics and breeding system. Exploring the association of these sexual reproductive traits with invasiveness would be helpful for revealing the mechanism of its successful invasion. We examined the blooming characteristics and breeding system of Gaura parviflora based on field observations, out-crossing index (OCI) estimation, and hand-pollination experiments. The results showed flowering duration of the G. parviflora population (flowering period) was short (more than 3 months). The life span of single flower (floral longevity) was 40.46 h. Its flower diameter was 3.99 mm. Over seven flowers in bloom per inflorescence and most individuals often bloomed synchronously, which showed a ‘mass-flowering pattern’. The changing trend of pollen and stigma vitality was relatively similar, but the duration of stigma vitality was 2 h longer than that of pollen. The stigma and the anthers were close to each other at the initial flowering stage, but the stigma removed from the anthers at the full-blooming stage with the style curving downwards. Many pollinators visited flowers in late full-blooming stage, which were mainly Apis mellifera and Syrphidae spp. Their average visiting frequency was 9.8 times·m-2·h-1. The fruit set in natural pollination after emasculation treatment (insect or wind pollination) was signi-ficantly higher than that in bagged and emasculation treatment, and the treatment of emasculated and bagged with nylon net (excluding insect pollination) could also bear fruits, indicating possible existence of ambophily in G. parviflora. The results of pollen ovule ratio (P/O) mensuration, OCI estimation and hand-pollination experiments showed that its mating system type belonged to additive mixed mating system. So, its characteristics, such as smaller flower size, shorter floral longevity and flowering period, were conducive to allocating more resources to plant growth and seed development, which would help improve its total fitness. The changes of spatial position of male and female organs not only avoided interference between male and female functions, but also created opportunities for stigmas to receive outcross pollen. In addition, the ‘mass-flowering pattern’ was conducive to attracting pollinators. The pollination mechanism of ambophily was helpful to ensure cross-pollination. The additive mixed mating system could provide double reproductive assurance for this species. These reproductive characteristics were significant for the successful invasion and expansion of G. parviflora.
    Effects of vegetation and soil changes on microbial biomass carbon and nitrogen in the Napahai meadow under N deposition
    LYU Jinghua, ZHAO Xuyan, LU Mei, LI Cong, YANG Zhidong, LIU Pan, CHEN Zhiming, FENG Jun
    2023, 34(6):  1525-1532.  doi:10.13287/j.1001-9332.202306.004
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    To explore the responses of soil microorganisms to short-term nitrogen deposition in alpine meadow, we set three treatments of low nitrogen (5 g N·m-2·a-1), medium nitrogen (10 g N·m-2·a-1), and high nitrogen (15 g N·m-2·a-1) addition to investigate the effects of nitrogen-deposition induced alterations in plant diversity and soil physicochemical properties on microbial biomass carbon (MBC) and nitrogen (MBN) in a typical alpine meadow community of Carex nubigena in Napahai. The results showed that nitrogen addition significantly increased soil MBC, MBN, and their quotients, with the increases of MBC being as high as 139.3% under medium nitrogen treatment. Both MBC and MBN showed significant decreases along the soil layer, with a reduction of 24.1% to 75.1%. Nitrogen addition significantly increased aboveground biomass and reduced Shannon and Simpson indices by 6.6%-65.4%. Nitrogen addition significantly decreased soil pH, increased the contents of organic matter, total nitrogen, ammonium nitrogen and nitrate nitrogen, with the highest reduction (7.0%-511.1%) being observed in medium nitrogen treatment. Soil pH increased while other physical and chemical indicators significantly decreased with the increases of soil layer, with a variation range of 19.5%-91.2%. Results of structural equation model showed that microbial biomass was significantly positively correlated with ammonium nitrogen, nitrate nitrogen and organic matter, but negatively correlated with pH and Shannon index. The interaction of plant and soil physicochemical properties explained 55%-77% of the variations in MBC, MBN and their quotient. Soil physicochemical properties had the highest effect value (0.56-0.95) on MBC, MBN and their quotients, followed by plant diversity and aboveground biomass. Therefore, nitrogen deposition increased soil MBC and MBN and their quotient, primarily through improving soil nutrient availability and plant aboveground biomass, whereas MBC and MBN and their quotient were suppressed by high-level nitrogen deposition due to soil acidification and plant diversity losses.
    Spatiotemporal variation of drought in the Western Sichuan Plateau based on standardized precipitation evapotranspiration index
    LAN Haochen, LIU Yanyan, ZHANG Yufang, KANG Yang
    2023, 34(6):  1533-1540.  doi:10.13287/j.1001-9332.202306.025
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    Drought is a destructive natural disaster in the Western Sichuan Plateau. Understanding its spatiotemporal variations has important practical significance for drought prevention, ensuring agricultural production safety, and maintaining ecosystem health in the region. Based on the daily meteorological data from 48 meteorological stations in the Western Sichuan Plateau from 1980 to 2020, we used the Penman-Monteith model to calculate potential evapotranspiration and standardized precipitation evapotranspiration index (SPEI). The temporal and spatial variations of drought in the Western Sichuan Plateau were analyzed using linear trend analysis and drought characteristics analysis methods. The results showed that the annual and spring SPEI of the Western Sichuan Plateau showed a weak wetting trend from 1980 to 2020, while summer, autumn, and winter showed a drought trend. The southwest mountains and northeast grasslands in the study region were prone to drought. The range of interannual drought impact in the study area was weakly increasing, with a decreasing trend in spring and an increasing trend in summer, autumn, and winter. The overall drought frequency in the whole region was relatively high. The areas drought of low-frequency were mainly located in parts of west and northeast of the Western Sichuan Plateau, while the rest were high frequency areas.
    Characteristics and risk assessment of chilling injury on Morchella esculenta in Western Sichuan Plateau, China
    WANG Qingli, ZHANG Liping, HAN Lu, WANG Mingtian, TANG Mingxian, CHEN Hui, RAN Wangqun, LI Zhengrong
    2023, 34(6):  1541-1546.  doi:10.13287/j.1001-9332.202306.027
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    The development of precise climate risk zoning for chilling injury of Morchella esculenta can provide scientific basis for agricultural cultivation planning, dynamic assessment of chilling injury, and disaster prevention strategies. Based on meteorological data from 17 counties (cities) that located below the altitude of 3000 m in the Western Sichuan Plateau from 2011 to 2020, we analyzed the critical meteorological conditions for M. esculenta disasters in typical years. With the average yearly cold accumulation and cold injury frequency during the first day when the temperature remained stable between 5 ℃ and 10 ℃ during mushroom emergence as zoning indicators, we established a geographical spatial distribution model of the cold injury index, and then divided the risk level of M. esculenta cold injury in the Western Sichuan Plateau, evaluated the risk of cold injury. The results showed that the temperature index for chilling injury risk of M. esculenta in the study area was the daily minimum temperature ≤2.0 ℃. The daily average temperature <6.0 ℃ would cause slow growth or the cessation of growth, which was set as a warning indicator for chilling injury risk. Along the Dadu River and Minjiang River basins, the frequency of chilling injury on M. esculenta increased from south to north. Wenchuan, Maoxian, and Lixian had the fewest overall chilling injuries during the study period, whereas Jiulong, Yajiang, and Batang had the most. The duration for cold injury was mainly 1-3 d, followed by 4-5 d, and rarely for >5 d. The frequency of chilling injury lasting for more than 5 d in Xiangcheng, Batang, Jiulong, Yajiang, and Xiaojin was more than that lasting for 4-5 d. The annual average days of chilling injury of was 3.0-27.4 d, the daily average minimum temperature was -0.84-1.36 ℃, the extreme lowest temperature was -5.8-0.1 ℃, and the average accumulated cold was 0.16-9.64 ℃·d during the period of chilling injury. With the increases of elevation and latitude, the average days of chilling injury and the average accumulated cold increased. The largest duration of chilling injury was 3-20 d, the maximum accumulated cold was 0.44-13.34 ℃·d. The risk of chilling injury to M. esculenta increased from south to north and from low elevation to high elevation. The suitable planting areas were distributed in strips and branches along the direction of mountains and rivers, mainly in the flat areas of low mountains and valleys below the altitude of 2200 m, including Kangding, Luding, Danba, Wenchuan, Lixian, Maoxian, Jiuzhaigou, and Songpan.
    Responses of root-associated fungal community structure of mycorrhizal plants to nitrogen and/or phosphorus addition in a subtropical forest
    LIU Shanshan, WANG Quancheng, SHI Jiamian, LIU Zikai, SHEN Jupei, HE Jizheng, ZHENG Yong
    2023, 34(6):  1547-1554.  doi:10.13287/j.1001-9332.202306.017
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    Root-associated fungi play a vital role in maintaining nutrient absorption and health of host plants. To compare the responses of root-associated fungal community structures to nitrogen (N) and/or phosphorus (P) additions across differential mycorrhizal types, we collected roots of nine plant species belonging to three mycorrhizal types (arbuscular mycorrhiza, ectomycorrhiza, and ericoid mycorrhiza) under control and N and/or P addition treatments from a subtropical forest, and detected the diversity and community composition of fungi inhabiting roots through the high-throughput sequencing technique. The results showed that root-associated fungal communities of all nine plant species were mainly composed of Basidiomycota and Ascomycota. The relative abundance of Ascomycota and Basidiomycota was significantly lower and higher under the P addition than that under control, respectively. The relative abundance of Ascomycota of ericoid mycorrhizal trees was significantly higher than those of arbuscular mycorrhizal and ectomycorrhizal trees, while the relative abundance of Basidiomycota was significantly lower than the other two mycorrhizal types. Compared with the control, P addition significantly reduced the α-diversity and changed community composition of root-associated fungi across different mycorrhizal plant types, while no effect of N addition or mycorrhizal type was observed. Compared with the control and N addition treatments, NP addition caused root-associated fungal communities of all plants becoming integrally divergent. In addition, the fungal communities of ectomycorrhizal mycorrhizal trees became apparently convergent in comparison with those of arbuscular and ericoid mycorrhizal trees under the NP addition. Collectively, our results highlighted that P was a critical factor influencing community structures of tree root-associated fungi in subtropical forest soils. This study would enhance our understanding of the responses and maintenance mechanisms of plant root-associated fungal diversity under global environmental changes in the subtropical region.
    Effects of grazing on soil water recharge of rehabilitated grassland under natural rainfall on the Loess Pla-teau, Northwest China
    MING Jiao, YANG Guang, ZHAO Yunge, MA Xinxin, SUN Hui, QIAO Yu
    2023, 34(6):  1555-1562.  doi:10.13287/j.1001-9332.202306.011
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    Rainfall is critical to the regulation of slope runoff and soil water recharge. Grazing affects land cover and soil structure, with consequence on slope runoff generation and soil water recharge. Little attention has been paid to the effects of rainfall on soil water recharge caused by grazing. In this study, we examined land covers and soil water contents under different grazing intensities (G1-G5: 2.2, 3.0, 4.2, 6.7, 16.7 sheep·hm-2) and no grazing sites (NG), aiming to analyze soil water recharge under natural rainfall conditions after grazing. The results showed that grazing exerted significant effects on vegetation and biocrust coverage. The vegetation coverage was decreased by 8.3%-16.4% under G1-G5 grazing, while the biocrust coverage was increased by 106.9% under G2 grazing compared to NG. The soil surface roughness under G1-G5 grazing was increased by 53.1%-152.5%, and the thickness of biocrust was decreased by 24.1% under G5. Soil wetting front velocity decreased with increasing rainfall intensity, and that of 0-5 cm layer under the G2 grazing intensity decreased by 60.0% to 83.3% under rainfall between 18.0 mm and 70.3 mm compared to NG. The effect of grazing on soil wetting front velocity was significantly related to biocrust coverage and soil bulk density of 0-5 cm soil layer. Generally, grazing did not affect soil water recharge rates of the slope grassland on the Loess Plateau. G2 grazing may prolong the migration time of soil water in the surface layer by increasing the coverage of cyanobacteria biocrusts, which may be beneficial to the restoration of soil microenvironment. Our results provided scientific basis for water management in the enclosure grassland of the Loess Plateau in the “post-conversion era”.
    Response of rice resistance based on the validation of rice blast to elevated CO2 concentration and temperature
    WEI Zhaowei, CHEN Ruogu, YIN Nan, KE Haonan, SHA Yaqing, ZHAO Junchi, LI Qi, HU Zhenghua
    2023, 34(6):  1563-1571.  doi:10.13287/j.1001-9332.202306.014
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    Rice (Oryza sativa) resistance is its ability to resist various stresses, the changes of which have important impacts on O. sativa yield security. However, the responses of O. sativa stress resistance to elevated atmospheric CO2 concentration and temperature are poorly understood. We conducted a field open top-chamber experiment with O. sativa (Nanjing 9108 and Jinxiangyu I) based on the CO2 and temperature automatic control platform. The experimental treatments included ambient CO2 concentration and temperature treatment (CK, control), elevated CO2 concentration treatment (C, CO2 concentration increase of 200 μmol·mol-1 above CK), elevated temperature treatment (T, temperature increase of 2 ℃ above CK) and elevated CO2 concentration and temperature (CT, CO2 concentration increase of 200 μmol·mol-1 and temperature increase of 2 ℃ above CK). At the critical growth stages of O. sativa, we measured superoxide dismutase activity, silica content, total flavanol content, malondialdehyde content, soluble sugar content, proline content, and soluble protein content by cutting the uppermost functional leaves. We obtained the rice stress resistance index (RSRI) by principal component analysis to analyze the differences in the composition of stress resistance indicators under different treatments. Considering the disease resistance of O. sativa, the spike neck blast disease was counted to verify the expression level of RSRI for O. sativa stress resistance at maturity stage. Results showed that at the elongation-booting stage, C and CT treatments significantly reduced the RSRI of Jinxiangyu I by 36.5% and 41.1%, respectively, compared with CK. T treatment significantly decreased the RSRI of the two varieties by 44.9% and 33.8%, respectively. The RSRI explained 71.9%-74.3% of the variation in the spike neck blast disease. Overall, the stress resistance of two O. sativa varieties were adversely affected by elevated temperature at the elongation-booting stage. There was an interactive effect of CO2 concentration and temperature on O. sativa stress resistance. Compared with Nanjing 9108, the stress resistance of Jinxiangyu I was more sensitive to elevated CO2 concentration.
    Effects of sowing patterns on nitrogen utilization and yield formation of winter wheat in the western Huang-Huai-Hai region
    YANG Yixuan, CHEN Yingzhi, TANG Peng, LIN Wen, SUN Min, GAO Zhiqiang
    2023, 34(6):  1572-1582.  doi:10.13287/j.1001-9332.202306.016
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    To examine the differences of three improved sowing methods in winter wheat yield and nitrogen efficiency and reveal the characteristics responsible for such differences, we conducted field experiments in the Jinnan area of the western Huang-Huai-Hai wheat region for three consecutive seasons from 2016 to 2019. The three improved sowing methods were wide space sowing (WSS), furrow sowing in moisture soil (FS), and three-dimensional uniform sowing (TDUS), with conventional drilling sowing (CDS) as the control. The results showed that meteorological factors such as accumulated temperature, solar radiation, and precipitation in the growing seasons from 2016 to 2019 showed great intra- and inter-annual variations. Compared with CDS, the improved sowing methods (WSS, FS, and TDUS) enhanced spike number per unit area and increased grain yield in three growing seasons by 18.3%-55.5%, 8.6%-22.2%, and 10.9%-39.5%, respectively. The three methods increased nitrogen uptake efficiency (NEup) by 5.8%-57.1%, pre-flowering nitrogen transfer ratio (Np/Nt) by 3.0%-15.3%, and nitrogen efficiency by 7.9%-35.7%, respectively. We developed a structural equation model (SEM) by integrating meteorological factors and experimental variables. The results showed that the three improved sowing methods could reduce the effects of extreme low temperature on wheat plant population, increase NEup and Np/Nt, and provide sufficient nitrogen supply to the grains of high-spike number wheat population for high yield and high nitrogen efficiency. In summary, our results demonstrated that WSS, FS, and TDUS all improved NEup and Np/Nt in the 2016-2017 season when meteorological conditions were favorable for wheat growth, and enhanced yield components with high SN, leading to high yield and high nitrogen efficiency. In contrast, in both 2017-2018 and 2018-2019 seasons with extremely low temperature and uneven distribution of meteorological conditions, WSS had a higher number of tillers at the jointing stage and enhanced pre-flowering nitrogen uptake and translocation, whereas TDUS had a relatively stable nitrogen uptake rate, leading to a stable grain yield.
    Safety profile evaluation of different herbicides used on peach rootstock seedlings
    HUANG Chenyan, GUO Lei, SONG Hongfeng, SHEN Zhijun, ZHANG Binbin, MA Ruijuan, YU Mingliang
    2023, 34(6):  1583-1591.  doi:10.13287/j.1001-9332.202306.010
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    To screen out suitable herbicides for peach nurseries, we treated the potted seedlings of the peach rootstock ‘Nemaguard’ with eleven herbicides under recommended doses to investigate the changes of physiological indices and comprehensively evaluate the safety of different herbicides using principal component analysis (PCA). The results showed that soil application of quizalofop-p exhibited no detectable phytotoxicity on rootstock seedlings, while the remaining herbicides generated multiple symptoms, including green loss, wilting, spot, and withering. Starane caused rapid wilting and death, with a 100.0% phytotoxicity index (PI). Soil application of n-(phosphonomethyl)glycine, glufosinate-ammonium, acetochlor, and MCPA-Na showed a PI＞65.0%. As compared with the control, all herbicides inhibited leaf area growth to varying degrees, with a 10.0%-56.2% and 5.8%-44.4% reduction in young leaf area and mature leaf area, respectively. All herbicides, except quizalofop-p, increased the electrolyte permeability of leaf and root tip cells by 21.2%-145.0% and 36.9%-291.4%, respectively, and significantly inhibited root growth. The total root length, root surface area, root volume, and the number of root tips significantly decreased by 37.3%-75.3%, 35.7%-83.0%, 44.3%-89.9%, and 42.6%-73.7%, respectively. Although net photosynthetic rate (Pn) and transpiration rate (Tr) of leaves were not significantly affected by quizalofop-p, mesotrione-atrazine, MCPA-Na·bentazone, bensulfuron-methyl·quinclorac, and bensulfuron-methyl·acetochlor, there was significant reduction of 29.6%, 28.9%, 28.4% and 27.9% in Pn and 21.9%, 29.2%, 26.4%, and 19.7% in Tr post soil application of n-(phosphonomethyl)glycine, glufosinate-ammonium, acetochlor, and MCPA-Na. The overall safety ranking of the 11 examined herbicides is as follows: quizalofop-p>bensulfuron-methyl·acetochlor>bensulfuron-methyl·quinclorac>esotrione·atrazine> auizalofop-p·fluoroglycofen>acetochlor>MCPA-Na·bentazone>MCPA-Na>n-(phosphonomethyl)glycine>glufosinate-ammonium>sterane.
    Alleviation effect of GR24, a strigolactone analogue, on low-nitrogen stress in Malus baccata seedlings
    ZHANG Xin, MA Yingjie, QI Bianbin, YU Bo, LYU Deguo, QIN Sijun
    2023, 34(6):  1592-1600.  doi:10.13287/j.1001-9332.202306.015
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    To investigate the efficacy of foliar application of GR24, a strigolactone analogue, in alleviating low-nitrogen stress in Malus baccata, we applied GR24 with different concentrations (0, 1, 5, 10, and 20 μmol·L-1) to leaves of plants under low nitrogen stress. We evaluated the changes in photosynthetic characteristics of leaves, reactive oxygen metabolism, and nitrogen assimilation in roots. The results showed that shoot biomass of seedling significantly decreased and root-shoot ratio increased under low-nitrogen stress. The chlorophyll contents decreased, the carotenoid content increased, and the photosynthetic activity decreased. The activities of superoxide dismutase and catalase enzymes in roots changed little, while the activities of peroxidase and ascorbic acid peroxidase enzymes, along with the levels of soluble sugar, free proline, and reactive oxygen species showed a significant increase, and the soluble protein content decreased. The NO3- content in roots decreased, the NH4+ content increased, while activities of nitrate reductase and glutamine synthase decreased. Compared to the control group without GR24 application, foliar sprays of 10 and 20 μmol·L-1 GR24 under both normal and low-nitrogen increased biomass and root-shoot ratio to varying degrees. Additionally, GR24 application increased chlorophyll content, photosynthesis indices (net photosynthetic rate, transpiration rate and stomatal conductance), and fluorescence (maximum photochemical efficiency of PSⅡ and quantum yield of electron transfer per unit area) performance parameters, as well as the contents of osmotic regulation substances (soluble protein, soluble sugar, and free proline) and glutamine synthase activity. Application of 10 and 20 μmol·L-1 GR24 under low-nitrogen stress decreased carotenoid, reactive oxygen species, and NH4+ contents, while increased the activities of antioxidases and key enzymes in nitrogen metabolism (nitrate reductase and glutamine synthase) and NO3- content. The 10 μmol·L-1 GR24 treatment was the most effective in alleviating low nitrogen stress, which has potential for application in apple orchards with low nitrogen soil.
    Spatio-temporal dynamics and sensitive distance of nighttime light environment in Pearl River Delta Protected Areas, China
    JIANG Benyan, ZHANG Yuli, LI Shan, LI Jianjun, ZHENG Zihao, WANG Hongguang
    2023, 34(6):  1601-1609.  doi:10.13287/j.1001-9332.202306.020
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    Protected areas (PAs) are important barriers to ensure the ecological security of territory. Light pollution is a threat to PAs, which is particularly obvious in the urban agglomeration environment. We used multi-source big data (satellite remote sensing light data, land cover types and points of interest) to quantitatively analyze the temporal and spatial dynamics of nighttime light in the PAs of the Pearl River Delta (PRD) urban agglomeration from 2000 to 2018, the correlation between the night light environment within the PAs and human activity intensity outside, as well as the sensitive distance of the PAs to artificial light interference. The results showed that the total value of nighttime light data of PAs in the PRD increased from 71107 nanoW·cm-2·sr-1 to 127682 nanoW·cm-2·sr-1 from 2000 to 2018, the mean value per pixel increased from 15.3 nanoW·cm-2·sr-1 to 23.7 nanoW·cm-2·sr-1, and the lighted ratio increased from 73.3% to 86.4%, indicating that the nighttime light environment of PAs in the region were facing cumulative deterioration risks and serious challenges. The nighttime light intensity of the PAs in the core area of the PRD was much higher than that in the peripheral areas such as Zhaoqing and Huizhou, whereas the expansion degree of the PAs in the peripheral areas was higher than that in the core area. The nighttime light environment inside the PAs was positively correlated with the intensity of human activities around it. The most sensitive distance of the PAs to the artificial light interference around it was 10 km, and the interference degree tended to be stable after 30 km. We proposed that 0-10 km area outside the boundary of the PAs should be the light control core zone and 10-20 km area as the control buffer zone.
    Impacts and prediction of land use change on ecosystem carbon sequestration in Zhejiang Province, China
    XU Caiyao, REN Yan, KONG Fanbin
    2023, 34(6):  1610-1620.  doi:10.13287/j.1001-9332.202306.024
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    It is crucial to clarify the impact of land use change on ecosystem carbon sequestration service for exploring natural-based carbon neutral solutions. We used InVEST and FLUS models to analyze land use change and its impacts on ecosystem carbon sequestration service in Zhejiang Province from 2000 to 2021, and predict ecosystem carbon sequestration service potential and its economic value of land use pattern in 2035 and 2050 under three scenarios of natural development, ecological protection, and cultivated land protection. The results showed that the area of cultivated land, forest, grassland, and water was continuously reducing and the area of construction land was continuously increasing from 2000 to 2021 in Zhejiang Province. The total amount of ecosystem carbon sequestration service decreased by 29.9658 million t, and the net income of carbon sequestrqtion service was -170.7184 million dollars. The distribution of ecosystem carbon sequestration services showed a spatial pattern of high in the southwest and low in the northeast. In the future, the total amount of ecosystem carbon sequestration services in Zhejiang Province would be the highest under the ecological protection scenario, followed by the cultivated land protection scenario, and the lowest under the natural development scenario. From 2021 to 2035 and 2050, ecosystem carbon sequestration services in Zhejiang Province would increase by 3.2326 million and 4.73 million t respectively under the ecological protection scenario, generating carbon sequestration service benefits of 77.0786 million and 111.8391 million dollars, respectively. Under the cultivated land protection scenario, it would be reduced by 10.1318 million and 16.1611 million t, and the net loss of carbon sequestration service value would be 241.3849 million and 381.9109 million dollars, respectively. Under the natural development scenario, it would be reduced by 11.6490 million and 16.1651 million t, resulting in a net loss of carbon sequestration service value of 277.5393 million and 382.0063 million dollars, respectively. In the context of actively addressing climate change and striving to achieve the goal of carbon neutrality, Zhejiang Province should focus on protecting ecological land such as woodlands, grasslands, and water, expand the scale of ecological land, optimize the spatial structure of ecological land, and continuously enhance carbon sequestration and sink enhancement functions of ecological land.
    Identification of bird conservation gaps of protected areas in high-intensity development area: A case study of Tianjin, China
    ZHANG Da, ZENG Jian, NAMAITI Aihemaiti
    2023, 34(6):  1621-1629.  doi:10.13287/j.1001-9332.202306.009
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    Due to the long-term disturbance of human activities, natural habitats in the high-intensity development areas have been seriously degraded, causing serious threat to local biodiversity. The conservation efficiency of natural reserves in these regions needs to be improved urgently. Scientific evaluation of conservation efficiency of nature reserves and identification of biodiversity conservation hotspots and conservation gaps in high-intensity development areas are of great significance to sustainable development of urbanization. With birds as the indicator group for biodiversity, we used MaxEnt and InVEST models to calculate the hot spots of bird diversity and habitat quality, and compared with current boundaries of protected areas in Tianjin to accurately identify the conservation gaps. The results showed that 228 bird species belonging to 54 families and 19 orders were recorded. All kinds of natural and artificial wetlands in the coastal area were the most suitable habitats for birds, accounting for 66.8% of bird diversity hotspots in Tianjin, and the artificial wetlands of reservoirs and fish ponds had high suitability as bird habitats due to sufficient food sources, which indicated that moderate anthropogenic interference would improve species diversity. The coverage rate of protected areas for bird diversity hotspots was only 37.7% in Tianjin, which indicated a serious conservation gap. The gaps mainly included wetlands in Dashentang and Lin’gang areas, the river junction and the estuary wetland, which should be planned as the key protected areas in the future. The method of collaborative analysis of the two models could improve the identification accuracy in detecting the conservation gaps and has certain universality for improving the efficiency of biodiversity conservation in high-intensity development areas.
    Spatio-temporal distribution and overlap of Naemorhedus griseus and Capricornis milneedwardsii in Gongga Mountain, Sichuan, China
    LIU Wei, LI Xuqin, LI Zhonglun, LI Ying, YOU Zhiyuan, JIANG Yong, RUAN Guanghua, LU Bigeng, YANG Nan
    2023, 34(6):  1630-1638.  doi:10.13287/j.1001-9332.202306.031
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    Clarifying the distribution pattern and overlapping relationship of sympatric relative species in the spatio-temporal niche is important for our understanding of the behavioral relationship between species and the integrated management of multi-species habitats. Based on the infrared camera monitoring data from 2012 to 2021, we investigted the spatio-temporal distribution characteristics of the national secondary-class key protected animals Naemorhedus griseus and Capricornis milneedwardsii in the Gongga Mountain National Nature Reserve, Sichuan Province. We analyzed the distribution of N. griseuss and C. milneedwardsiis in the reserve using the MaxEnt model, based on 72 and 108 occurrence data of the two species, respectively, obtained by infrared cameras from 2016 to 2021, combined with 12 environmental factors potentially affecting their spatial distribution. Then, based on 1312 occurrence data of N. griseus and 1889 occurrence data of C. milneedwardsii collected by infrared camera from 2012 to 2021, we estimated their daily activity rhythms by using the kernel density estimation to understand the distribution pattern and overlap of the two species in the temporal niche. The results showed that the area of suitable habitats for N. griseus and C. milneedwardsii was 731.95 km2 and 1220.46 km2, respectively. The overlapping area was 697.17 km2. The main environmental factors had similar effects on the habitat selection of the two species. The daily activity of both species peaked in the early morning and evening. The utilization of the interval and intensity of the morning and evening time periods were different for the two species. The morning and evening activity peaks of C. milneedwardsii were earlier and later, respectively, than that of N. griseus. C. milneedwardsii had a higher utilization intensity during the nocturnal period. In general, high degree of spatial overlap and low degree of overlap in the temporal niche dimension contribute to the long-term coexistence of the two species.
    Suitable overwintering habitat simulation and the drivers of their population expansion for Siberian cranes (Grus leucogeranus) in China
    SHAO Mingqin, WANG Jianying, DING Hongxiu
    2023, 34(6):  1639-1648.  doi:10.13287/j.1001-9332.202306.023
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    To gain a more comprehensive understanding of habitat preferences, potential wintering area distribution and drivers of population expansion of Grus leucogeranus, we selected 70 geographical distribution points and 11 environmental variables in its wintering period from 2015-2022. We modeled suitable habitat patterns for G. leucogeranus in China using MaxEnt model, and analyzed the relationship between suitable habitat distribution and environmental factors. The results showed that the dominant factors affecting the overwintering distribution of G. leucogeranus were distance to mudflats, elevation, average precipitation in February, distance to water sources, minimum temperature in December, and land use type, with a cumulative contribution rate of 94.6%. The wintering ground of G. leucogeranus in China was mainly distributed in the middle and lower reaches of the Yangtze Plain and the Yellow River Delta of the North China Plain. In these regions, the area of high-, medium- and low-suitability habitat were 17685, 60787 and 60747 km2, respectively. A total of 40 protected areas had been established in the high-suitability wintering range of G. leucogeranus in China, whereas 12 high-suitability wetlands such as Qili Lake in Anhui, Liangzi Lake in Hubei and Chenjia Lake in Jiangxi were still unprotected. The wintering grounds had shown a trend of expansion to the northeast and southeast since 2015. Considering the large-scale habitat shifts of G. leucogeranus in recent years and the frequent new wintering records in various places, we suggested that the shortage of food resources in natural habitats was the main factor driving the expansion of G. leucogeranus’ wintering range. To protect G. leucogeranus more effectively, we should strengthen the restoration of natural habitats and the management of farmland habitats.
    Multidimensional climatic niche conservatism and invasion risk of Phenacoccus solenopsis
    ZHANG Huisheng, XU Lin, LYU Weiwei, ZHOU Yu, WANG Weifeng, GAO Ruihe, CUI Shaopeng, ZHANG Zhiwei
    2023, 34(6):  1649-1658.  doi:10.13287/j.1001-9332.202306.018
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    The cotton mealybug Phenacoccus solenopsis, a globally invasive insect, is listed as a national quarantine pest in agriculture and forestry, which seriously threatens biological safety of China. Niche conservatism is a key assumption of species distribution model. An evaluation of the applicability of using ecological niche models to assess the invasion risk of cotton mealybug, and further optimizing model complexity, are of both theoretical and practical significance. Based on 706 occurrence records and key bioclimatic variables, we used n-dimensional hypervolume niche analysis method to quantify the climatic niche hypervolumes of this pest in both native and invasive sites, and further tested the niche conservatism hypothesis. MaxEnt model parameters were optimized to predict the invasion risk of the mealybug under current and future climate scenarios in China. The results showed that four climatic variables (annual mean temperature, mean temperature of wettest quarter, mean temperature of warmest quarter, and precipitation of driest quarter) were the key climate factors affecting the distribution of cotton mealybug. Compared with native climatic niche (hypervolume volume, HV=40.43), the niche hypervolume of cotton mealybug in the invasive areas was significantly reduced (HV=6.04). Niche contraction (the net differences between the amount of space enclosed by each hypervolume was 0.84) explained 98.8% of niche differentiation, whereas niche shift (the replacement of space between hypervolumes was 0.01) contributed less than 2%. The direction of climatic niche contraction of the pest in different invasive areas was not exactly consistent. The default parameters of MaxEnt model were unreliable (ΔAICc=14.27), and the optimal parameter combination was obtained as follows: feature combination was linear-quadratic-hinge-product and regularization multiplier was 0.5. The most suitable habitats of cotton mealybug were concentrated in the south of Huaihe River-Qinling Mountains line, and the north-central provinces contained a large area of low suitable habitat. The increase of suitable habitat was not significant at the end of 21 century (SSP1-2.6: 1.7%, SSP5-8.5: 0.7%). The multidimensional climatic niche of P. solenopsis was highly conservative. The species distribution model was suitable for analyzing its invasion risk. The northward spread was obvious, and climate change had less impact on the pest.
    Shrimp community structure and influence of environmental variables in the East China Sea and Yellow Sea in spring
    LI Huiyu, JIN Yan, LING Jianzhong, LIU Zunlei, CHENG Jiahua
    2023, 34(6):  1659-1668.  doi:10.13287/j.1001-9332.202306.032
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    Based on data collected from research vessel cruises performed in May 2020 off the East China Sea (ECS) and the southern Yellow Sea (YS) (26°30′-35°00′ N, 120°30′-127°00′ E), we analyzed the shrimp community and its relationships with environmental variables by using index of relative importance, biodiversity indices, and multivariate techniques. A total of 29 species were recorded, belonging to 11 families and 19 genera. The dominant species were Metapenaeopsis longirostris, Leptochela gracilis, Solenocera melantho, Crangon hakodatei, Parapenaeus fissuroides, Plesionika izumiae, and Trachypenaeus curvirostris, which together accounted for 82.9% of the total biomass and 90.8% of the total abundance of shrimps. Results of Cluster and NMDS analyses showed that three groups were identified for the shrimp community in the ECS and YS in spring, including group A (inshore of northern ECS and YS group), group B (offshore of northern ECS group) and group C (southern ECS group). ANOSIM and SIMPER analysis showed significant differences between group A and B, gourp A and C, and group B and C, with the dissimilarity of 92.2%, 95.8% and 91.6%, respectively. The typical species were T. curvirostris, C. hakodatei, L. gracilis and Palaemon gravieri in group A, and S. melantho in group B, and M. longirostris, P. fissuroides, P. izumiae and Solenocera alticarinata in group C. Significant differences were also detected in biomass, diversity index, species richness index and evenness index among groups, with significantly greater values in group C than those in A and B. Environmental variables and the substrate also displayed significant differences among groups. Results of canonical correspondence analysis showed that bottom temperature, bottom salinity, depth, and the substrate were the main environmental variables affecting spatial structure of shrimp community. Water mass characteristics and substrate type had important influences on the distribution of shrimp community in the ECS and YS in spring.
    Characteristics of phytoplankton community and its influencing factors in the Yanhe River Basin, Northwest China
    LU Yue, HU En, DING Yitong, GUO Shansong, LI Gang, PAN Baozhu
    2023, 34(6):  1669-1679.  doi:10.13287/j.1001-9332.202306.030
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    Yanhe River is one of the important tributaries of the Yellow River, with a vital role in the maintenance of biodiversity and ecological conservation in the middle reaches of the Yellow River. In this study, we conducted a systematic aquatic ecological survey of the Yanhe River Basin in spring (April-May) and autumn (September-October) of 2021, with phytoplankton as indicator organism. A total of 33 sampling sections were selected in the mainstem, five first-class tributaries, and impounded water bodies (reservoir and check dam water bodies) of the Yanhe River Basin. The results showed that a total of 253 phytoplankton species, belonging to 7 phyla and 91 genera, were detected in the two surveys. Diatoms and green algae prevailed in spring (168 species), while diatoms and cyanobacteria dominated in autumn (179 species). The mean phytoplankton density and biomass were 316.07×104 cells·L-1 and 6.41 mg·L-1 in spring, and 69.56×104 cells·L-1 and 1.59 mg·L-1 in autumn, respectively. At the temporal scale, phytoplankton abundance in spring was higher than that in autumn. At the spatial scale, the phytoplankton abundance in the middle and lower reaches of the mainstream was higher than that in the upper reaches. Phytoplankton biomass in the impounded water bodies formed by dam interception was maintained at a high level, which was significantly higher than that in the mainstem and tributary water bodies in autumn. The phytoplankton diversity, as indicated by Shannon diversity index, Margalef richness index, and Pielou evenness index, in spring was greater than that in autumn. Phytoplankton diversity was greater in the trunk and tributary waters than that in impounded waters. The results of redundancy analysis showed that the key factors driving the phytoplankton community structure in spring were flow velocity, dissolved oxygen, nitrite nitrogen, and water depth. In contrast, the key driving factors in autumn were nitrate nitrogen, water depth, and dissolved oxygen.
    Reviews
    Biogeochemical behavior and ecological environmental effects of fluoroquinolones
    WEN Lilian, SONG Jinming, LI Xuegang, MA Jun, DAI Jiajia, YUAN Huamao, DUAN Liqin, WANG Qidong
    2023, 34(6):  1680-1692.  doi:10.13287/j.1001-9332.202306.029
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    Synthetic fluoroquinolones (FQs) are the third most commonly used antibiotics in the world and play an extremely important role in antibacterial drugs. The excessive use and discharge will alter ecological environment, with consequence on human health and global sustainable development. It is therefore of great significance for scientific use and management of FQs to systematically understand their biogeochemical behavior and eco-environmental effects. After drug administration in humans and animals, only a small part of FQs are transformed in vivo. The main transformation processes include formylation, acetylation, oxidation and cleavage of piperazine ring, defluorination and decarboxylation of aromatic core ring, etc. About 70% of the original drug and a small amount of transformed products would be migrated to the environment through excretion. After entering the environment, FQs and their transformation products mainly exist in environmental media such as water, soil and sediment, and undergo migration and transformation processes such as adsorption, photolysis and biodegradation. Adsorption facilitates transfer of FQs from medium to another. The photolysis mainly affects the C7-amine substituents of FQs, whereas the core structure of FQs remains intact. Biodegradation mainly refers to the degradation of FQs by microorganisms and microalgae, including piperazine modification of the piperazine ring such as acetylation and formylation, partial or complete ring cleavage, core structure decarboxylation, defluorination and conjugation formation. The migration and transformation processes of FQs cannot completely eliminate them from the environment. Instead, they would become “pseudo-persistent” pollutants, which seriously affect the behavior, growth and reproduction of algae, crustaceans and fish, change biogeochemical cycle, destroy aquatic environment, and stimulate microbial resistance and the generation of resistance genes. In the future, more in-depth studies should be conducted on the environmental behavior of FQs and their impacts on ecological environment, the risk assessment of microbial resistance and resistance genes of FQs, and the mechanism and effect of micro-biodegradation of FQs.
    Effects of warming on fine root lifespan of forests: A review
    LIU Yuanhao, DU Xulong, HUANG Jinxue, XIONG Decheng
    2023, 34(6):  1693-1702.  doi:10.13287/j.1001-9332.202306.007
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    As an important parameter of forests growth, fine root lifespan plays an important role in plant water and nutrient absorption, and affects underground distribution of photosynthetic products and forest ecosystem carbon cycling. The impact of climate warming on fine root lifespan has become a hot issue under the context of global change. The responses of fine root lifespan to global warming will affect ecosystem carbon balance. We reviewed the research progress of the response characteristics and mechanism of fine root lifespan of trees to warming. Most stu-dies proposed that warming would affect fine root lifespan by changing rhizosphere soil environment, fine root morphology, and tree phenology. However, the growth and death of fine roots were affected by lots of factors, leading to differences in the research results on fine root lifespan due to natural environment of the study area, the way of warming, and the research objects. Therefore, it is of importance to comprehensively analyze the responses of fine root lifespan in forests under the background of climate warming to study the underground ecological process. In the future, the following research should be strengthened: 1) Combining multiple methods to warming underground and aboveground simutaneously, and explore more accurate and effective non-destructive observation methods. 2) Combining multiple observations to study the effects of warming on fine root lifespan. 3) Carrying out research on the effect of warming on fine root lifespan of different tree species, and deeply understand the response mechanism of fine root lifespan of different trees to warming. 4) A comprehensive analysis of the effects of warming on fine root lifespan from various perspectives, and an investigation into the mechanism of the combined effects of various factors on fine root lifespan. 5) The interaction between warming and other environmental factors fine root lifespan. 6) The effect of root architecture on the fine root lifespan after warming. 7) The effects of rhizosphere microorganisms (bacteria and fungi) on fine root lifespan after warming.
    Current situation of “non-grain production” of cultivated land in China and the research progress of re-tillage and fertilization technology
    LI Tingqiang, HAO Dian
    2023, 34(6):  1703-1712.  doi:10.13287/j.1001-9332.202306.013
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    In recent years, the influx of business capital to rural areas, land transfer and adjustment in planting structure have led to the widespread of “non-grain production” of cultivated land in China, which threatens the “1.8 billion mu of arable land protection red line” as well as national food security. Both tillage layer stripped and unstripped are examples of “non-grain production” of cultivated land, which are detrimental to long-term food security because they might reduce soil fertility to varied degrees. In the former case, the original topsoil has been destroyed and the tillage layer is gone. In the latter, there may be impediments such as acidification and salinization. Domestic and international scholars have conducted extensive research on the improvement of degraded soils, including measures with guest soil and soil replacement, the reduction of soil barrier factors, biological fertilization and other measures. There are no systematic research results on the remediation of “non-grain production” of cultivated land. Using data from the National Statistical Yearbook data and literature analysis, we systematically summarized current status of “non-grain production” of cultivated land and key technologies for land improvement, recultivation and fertilization in China, and put forward future directions in this area.
    Ecological causality between vegetation construction and habitat drought in arid areas
    YANG Xinguo, SONG Naiping, CHEN Lin, WANG Lei
    2023, 34(6):  1713-1720.  doi:10.13287/j.1001-9332.202306.002
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    The core of scientific greening in arid areas is ‘greening based on water’. One of its preconditions is the potential causal relationship between vegetation construction and habitat drought. However, the causal relationship between factors or processes in ecology is generally difficult to accurately define and describe, especially for complex ecosystems. To scientifically carry out ‘greening based on water’, it is necessary to clarify the relationship between vegetation construction and hydrological cycle in drylands, and clarify the basis and conditions for habitat drought. Taking the construction of scientific greening pilot demonstration province in Ningxia as an example, we started with the theoretical connotation and application model of ecological causality of ‘greening based on water’, and empirically analyzed the causal relationship between vegetation construction and habitat drought at the regional, landscape, and ecosystem scale, respectively. The contradictions and problems in relevant understanding and practice were pointed out, and the principles and suggestions of scientific practice of ‘greening based on water’ were put forward.
    Effects of “audience effects”on animal mate choice: A review
    GAO Qian, CHEN Guangyan, SUN Kaijie, JIN Taihua, WANG Zhennan, WEI Mingji
    2023, 34(6):  1721-1728.  doi:10.13287/j.1001-9332.202306.028
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    The information tranfered among individual animals can be shared by a network, which is consisted of the sender, the receiver, and the extra bystander of the communication signals. The bystanders can read and use the signal that is not sent directly to them and make use of it to interfere with the sender and the receiver, which is known as “audience effects” in the research area of animal behaviors. The processes of mate choice and mating of animals occur mainly in the network that is composed of the particular species. Increasing evidence show that the audience effects play an important role in regulating mating preference and mating strategy, resulting in changes in species evolution. Here, we review the role of audience effects on animal mate choice and evolution by clarifying the definition and functional explanations of audience effects, the factors contributing to audience effects, as well as the different impacts of audience effects on males and females. It would provide novel ideas to study the impacts of audience effects on mate choice and species evolution in the future.