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    10 May 2023, Volume 42 Issue 5
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    Spatial-temporal variations in methane flux and quantification of the influencing factors in different alpine ecosystems.
    GUAN Chongfan, HE Fangjie, HAN Huibang, ZHANG Lanxiao, LI Yajing, ZHENG Jingsheng, ZHANG Jinsong, SUN Shoujia
    2023, 42(5):  1025-1034.  doi:10.13292/j.1000-4890.202305.001
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    We carried out in situ monitoring of methane (CH4) fluxes of four ecosystems, alpine marsh, alpine meadow, alpine steppe, and alpine desert, in the Yushu Tibetan Autonomous Prefecture and Maduo County, with a portable greenhouse gas analyzer. Biomass, microorganism abundance, nutrients, soil moisture and temperature in each ecosystem were measured. These parameters were investigated to describe spatial-temporal variations in CH4 flux and quantify the key influencing factors in all the ecosystems. The results showed that alpine marsh and alpine meadow were CH4 sources, with the maximum flux in August. Alpine steppe and alpine desert were CH4 sinks, with a minimum in August. During the growing season, there were significant differences in CH4 flux among the four ecosystems (P<0.05). The abundance of mcrA gene in alpine marsh was highest, followed by alpine meadow, while the abundance of pmoA gene was highest in alpine meadow, followed by alpine marsh. The lowest abundances of mcrA and pmoA genes were found in alpine desert. There were significant differences in mcrA and pmoA among the four ecosystems (P<0.05). CH4 flux in alpine marsh and alpine meadow was significantly positively correlated with soil temperature and mcrA (P<0.05), whereas CH4 flux in alpine steppe and alpine desert was significantly negatively correlated with soil temperature and pmoA (P<0.05). Across all the ecosystems, CH4 flux was significantly correlated with soil moisture, organic carbon, total nitrogen, biomass, mcrA and pmoA (P<0.05). Results of path analysis showed that soil organic carbon and the abundance of mcrA and pmoA had significant direct effects on CH4 emissions, while soil temperature and water content indirectly affected it by changing soil microorganism abundances. Among all these key factors influencing CH4 flux, the relative contribution of mcrA abundance was the highest (up to 30.53%), followed by organic carbon and biomass. The results indicated that variations in CH4 flux among the different ecosystems were caused by differences in microorganism abundance, organic carbon, and biomass. It is therefore important to consider the heterogeneity of CH4 emissions among different ecosystems when modeling and estimating CH4 fluxes in alpine areas.

    Characteristics of bryophyte associations and their relationships with ecological factors in alpine grassland of Tibet.
    TIAN Yue, LIU Yan
    2023, 42(5):  1035-1042.  doi:10.13292/j.1000-4890.202305.006
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    The unique morphological structure and physiological characteristics of bryophytes enable them to grow in the harsh habitat with extreme drought and cold climate. As one component of alpine grassland on the Qinghai-Tibet Plateau, bryophytes play an important ecological role. The present study aimed to describe the characteristics of bryophyte associations in the alpine grassland of Tibet and explore their environmental driving factors. Forty plots were set up across the alpine grassland of Tibet. Bryophytes were collected and recorded from quadrats. Quantitative classification and ordination of the bryophyte associations were analyzed by two-way indicator species analysis (TWINSPAN) and canonical correspondence analysis (CCA), based on species and ecological data. A total of 36 species belonging to 18 genera and 9 families were recorded, all of which were mosses. The most species-rich family is Pottiaceae. The species number of genera Didymodon and Bryum accounted for one-third of the total species. The dominant species were Didymodon tectorus, Barbula gracilenta, Didymodon fallax, and Didymodon michiganensis. The dominant life form is turf, accounting for 83.33% of the total species. Two-way indicator species analysis divided the bryophyte associations into eight types (i.e. Bryum uliginosum association, Didymodon fallax + Anomobryum auratum association, Didymodon tectorus + Didymodon fallax association, Didymodon tectorus + Didymodon tophaceus + Didymodon fallax association, Didymodon michiganensis + Didymodon tectorus + Barbula gracilenta association, Barbula gracilenta +Didymodon tophaceus association, Didymodon constrictus + Didymodon ditrichoides + Didymodon rivicola association, Distichium brevisetum association). Some of the plots were clustered on the CCA ordination graph, which indicated the continuity of the associations and the complexity of the relationships between bryophytes and the environment. The CCA results showed that mean annual precipitation was the primary factor affecting the distribution of bryophyte associations in the alpine grassland of Tibet, followed by soil pH, silt fraction, NDVI, altitude, mean annual wind speed, and mean annual temperature.

    Effects of canopy structure on natural regeneration of Picea asperata secondary forest in Guandi Mountain.
    ZHANG Zhi, ZHANG Mengtao, SHEN Huanhuan, ZHANG Yuyuan
    2023, 42(5):  1043-1048.  doi:10.13292/j.1000-4890.202305.019
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    Canopy structure and understory light environment play an important role in the distribution and growth of naturally regenerated seedlings. Here, we analyzed the effects of canopy structure on naturally regenerated seedlings of Picea asperata secondary forest in Guandi Mountain by one-way ANOVA and Poisson correlation test. The number of naturally regenerated trees was the largest when the canopy openness (CO) was 19.5%-24.5% and the transmitted diffuse solar radiation index was 4-5. The optimum CO, transmitted direct solar radiation, and transmitted total solar radiation of seedlings were higher than those of saplings, while the optimal leaf area index (LAI) was lower than that of the saplings. Canopy structure and understory light were not significantly related to the growth of seedlings. Seedlings and saplings had different adaptation ranges to the understory light environment. There were significant differences in LAI and light intensity among the plots with different densities of regenerated seedlings. Our results provide a theoretical basis for understanding the natural regeneration of forests in this area.

    Effects of altitude and stand density on understory plant diversity in tropical rainforests.
    JIANG Zuyang, QIN Yehui, LIU Ji, WEN Zhi, ZHENG Hua, OUYANG Zhiyun
    2023, 42(5):  1049-1055.  doi:10.13292/j.1000-4890.202305.023
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    Altitude and stand density are important factors affecting biodiversity, but the compound effects and pathways of altitude and stand density affecting understory plant diversity in tropical rainforests are largely unknown. In this study, we set up 32 plots based on elevation and stand density gradients in tropical rainforests located in Hainan Island, China. We surveyed plant species diversity in each plot and analyzed the influence of altitude and stand density on understory plant diversity (species richness, Shannon diversity index, Simpson dominance index, and species evenness). The pathways by which altitude and stand density affect understory plant diversity directly or indirectly through overstory plant diversity and environmental factors (canopy closure, litter, soil C/N, soil N/P, and soil pH) were explored. The results showed that altitude had limited effect on understory species richness, Simpson dominance index, and species evenness, but significantly reduced Shannon diversity index indirectly via overstory Shannon diversity and canopy density. Compared with altitude, increases of stand density significantly reduced the understory species richness, directly and indirectly by increasing canopy density and soil N/P. Our results highlight the difference in the effects of altitude and stand density on understory plant diversity, and show that canopy density is an important factor for the combined effects on understory plant diversity. Our findings deepen the understanding of the formation mechanism of understory plant diversity in tropical rainforests.

    Flammability characteristics and fire resistance of common landscape shrub species in Beijing.
    SONG Linshu, WANG Zheng, LIU Yan, GAO Jianzhou, LI Bingling
    2023, 42(5):  1056-1063.  doi:10.13292/j.1000-4890.202305.033
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    Studies on the fire resistance of small and medium-sized shrubs in landscape plant community can guide the evidence-based landscape design and fire prevention when managing and constructing urban green spaces. In this study, four components of plant flammability of 10 landscape shrub species in Beijing were measured under varying moisture conditions in both winter and spring. We used principal component analysis combined with a comprehensive evaluation based on the entropy weight method to measure fire resistance under assumed heat radiation conditions. The canopy structure of individual species was taken into account. There was a significant correlation between the canopy fire resistance rank and twig fire resistance rank across the 10 shrub species, with a correlation coefficient of 0.867, predominantly related to combustibility. Among the four components of plant flammability, there was a significant correlation between the ranks of ignitability-fire resistance and consumability-fire resistance, with a correlation coefficient of -0.794. The relative fire resistances of the 10 shrub species in a descending order were: Cotoneaster horizontalis > Syringa oblata > Lonicera maackii > Weigela florida > Kerria japonica > Hibiscus syriacus > Forsythia suspense > Lagerstroemia indica > Kolkwitzia amabilis > Jasminum nudiflorum. Our results demonstrated that Cotoneaster horizontalis and Syringa oblata were the most suitable species among the 10 examined species for fire prevention when planning the construction and management of urban green spaces. City planners should be aware of the relatively poor fire resistance and low ignition threshold of Lagerstroemia indica.

    Classification and ordination of herbaceous flower communities in riparian zone of the Outer Qinhuai River, Nanjing.
    LI Yuhan, DING Yanfen, ZHANG Changwei, ZHANG Qiang
    2023, 42(5):  1064-1073.  doi:10.13292/j.1000-4890.202304.030
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    We examined the community types and distribution of herbaceous flower species along the riparian zone of the Nanjing Outer Qinhuai River, and explored the main driving environmental factors, aiming to provide scientific basis for improving ecological restoration and constructing river ecological corridor of the Qinhuai River. Based on the survey data, cluster analysis was performed by the unweighted pair-group method with arithmetic means (UPGMA). The plant diversity of different community types was quantified by α diversity indices. The distribution of sampling sites was explored by the DCA, while species and sampling sites were ordinated by the CCA. The results showed that: (1) four different communities of herbaceous flower were identified in riparian zone of the Outer Qinhuai River according to the UPGMA, which was consistent with the results of DCA ordination. (2) Among the four communities, species richness index, Simpson index, Shannon index, Pielou evenness index of the communities Ⅳ, Ⅲ and Ⅱ were higher than those of the community Ⅰ. (3) The first ordination axis showed the strongest correlation with litter thickness, while the second ordination axis was significantly correlated with slope. (4) Distributions of herbaceous flowers and communities in the Outer Qinhuai River were affected by environmental factors.

    Leaf anatomical structure and physiological characteristics of wild and cultivated tea trees in Qianjiazhai.
    HOU Mengyue, WANG Fei, CHEN Ming, CHENG Xiaomao, LUO Wen, HUANG Xiaoxia
    2023, 42(5):  1074-1082.  doi:10.13292/j.1000-4890.202305.011
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    We compared the differences of leaf anatomical structure, physiological index, nutrient concentrations, and nutrient stoichiometry among wild ancient tea tree (Camellia taliensis) in Qianjiazhai Nature Reserve, cultivated ancient tea tree (C. sinensis var.assamica)  and cultivated tableland tea tree (C. sinensis var. assamica) in Zhen-yuan County, Yunnan Province. The results showed that leaf thickness, mesophyll thickness, epidermis thickness, cuticle thickness, sponge tissue thickness, photosynthetic pigment content, antioxidant enzyme activity, and carbon content in wild ancient tea tree were higher than those in the two cultivated tea trees. The contents of nitrogen and phosphorus were higher in cultivated ancient tea tree, and there were no differences in leaf thickness and mesophyll thickness compared with wild ancient tea tree. The anatomical indices and nutrient contents of two types of ancient tea trees showed great plasticity and variation. The transportation ability of water and photosynthetic products in leaves of tableland tea tree was stronger, indicated by the higher values of palisade tissue, main vein thickness, and main vein protuberance. The wild and cultivated ancient tea plants had strong adaptability to environmental changes. The thicker leaves, mesophyll and spongy tissue suggested that leaves of ancient tea had abundant components, which is more conducive to the twisted integrity and brewing resistance of tea products and more suitable for the production of high-quality Pu’er tea. The leaves of tableland tea were thin and grew fast, which is more conducive to high and prosperous yield, and suitable for producing bulk tea products. Our results provide a theoretical basis for analyzing the differences of tea quality between cultivated ancient tea and tableland tea trees, and the conservation of wild ancient tea trees.

    Effects of exogenous plant hormones on the accumulation of selenium and cadmium and physiological attributes of pak choi (Brassica chinensis L.).
    CHEN Jinping, HUANG Taiqing, XING Ying, ZENG Chengcheng, LIAO Qing, PAN Liping, LIANG Panxia, LIU Yongxian
    2023, 42(5):  1083-1089.  doi:10.13292/j.1000-4890.202304.029
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    Enhancing the enrichment capacity of selenium (Se) in crops is of great significance to improve soil Se utilization efficiency and optimize the production of Se-enriched crops. We conducted a pot experiment to examine the role of exogenous plant hormones (jasmonic acid, JA; salicylic acid, SA) in enhancing Se enrichment capacity of pak choi (Brassica chinensis L.). There were five treatments: control (CK), 50 μmol·L-1 JA (JA50), 100 μmol·L-1 JA (JA100), 50 μmol·L-1 SA (SA50), and 100 μmol·L-1 SA (SA100). We measured Se content, cadmium (Cd) content, biomass, chlorophyll fluorescence, MDA content, and antioxidant enzymatic activities of pak choi after harvest. We found that shoot Se content and root Se content under plant hormone treatments increased by 54.7%-229.1% and 175.0%-276.8% relative to CK, respectively, and that shoot Se content and accumulation were significantly higher in JA treatment groups than that in SA treatment groups. The shoot Cd content and accumulation under plant hormone treatments decreased by 26.3%-63.2% and 38.5%-72.1% relative to CK, respectively. Shoot Cd content and accumulation of the JA treatment groups were much lower than that of the SA treatment groups. With regard to fluorescence, Fv′/Fm′, ΦPSII, and qP were significantly lower, whereas NPQ was significantly higher in plant hormone treatments compared with that in CK, indicating that plant hormone treatments significantly decreased the activity of PSII. Plant hormone treatments significantly increased leaf MDA content, causing heavy lipid peroxidation. In summary, foliar spraying of 50 or 100 μmol·L-1 JA or SA can effectively enhance the enrichment capacity of pak choi to soil Se and reduce shoot Cd accumulation. These ameliorative effects of JA are greater than that of SA.

    Effects of deep-till-rototill rotation and organic fertilizer application on enzyme activity in aggregates of black soil cropland.
    HE Wanying, GU Siyu, GU Shaochen, CHE Yanjing, WANG Ziying, YUAN Wangbo, YANG Jiayu
    2023, 42(5):  1090-1098.  doi:10.13292/j.1000-4890.202303.031
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    The use of single tillage methods and excessive application of chemical fertilizer on the black soil of northeast China have resulted in poor soil structure, hardening of the plow base layer, and decline of soil fertility. We investigated the effects of deep-till-rototill rotation on soil structure and enzyme activity in the black soil area of Songnen Plain. With full straw returning in black soil, we carried out an experiment with two tillage treatments (continuous rotary tillage and deeptillrototill rotation) and two fertilization treatments (chemical fertilizer and chemical fertilizer+organic fertilizer). Soil samples from the 0-20 cm layer were air-dried, sieved, and divided into 2-5, 1-2, 0.5-1, 0.25-0.5, and <0.25 mm particle size aggregates. The activities of peroxidase, sucrase, urease, and acid phosphatase were measured for each aggregate size. The results showed that soil aggregates in the two fertilization treatments under deep-till-rototill rotation were mainly in the 2-5 mm particle sizes, which accounted for 26.8%-31.3% of the total mass and significantly higher than other particle sizes. The proportion of aggregates of 2-5, 1-2, and 0.5-1 mm in the deep-till-rototill rotation treatment was significantly higher than that in the conti-nuous rotary tillage treatment. The activities of catalase, urease, and acid phosphatase were higher under the deep-till-rototill rotation treatment than the continuous rotary tillage treatment. The application of organic fertilizer had a positive effect on the enzyme activity of large-sized aggregates. The activities of catalase, urease, and sucrase increased with particle size, with the highest activity of urease and sucrase in 2-5 mm aggregates. The activity of acid phosphatase increased with the decreases of particle size, being highest in <0.25 mm aggregates. In conclusion, combining deep-till-rototill rotation with the application of organic fertilizer benefits the coalescence and formation of soil macroaggregates in the 0-20 cm soil layer and has a significant effect on the improvement of enzyme activities in all aggregate sizes.

    Isolation and identification of rhizobia from rocky desertification area and the drought resistance effect in pot experiments.
    HE Yating, YAO Li, LIU Zichang, YANG Ziyun, WANG Jinhua
    2023, 42(5):  1099-1106.  doi:10.13292/j.1000-4890.202305.002
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    In this study, three bacterial strains were isolated from the root nodules of Sophora davidii, Indigofera tinctoria, and Trifolium repens in the peak cluster-depression rocky desertification areas of Wenshan, Yunnan Province, which were coded as SWFU-B1, SWFU-B2, and SWFU-B3, respectively. By testing the morphological characters, physiological and biochemical properties and sequence analysis of 16S rDNA of the three strains, the similarities between the three strains and Rhizobium leguminosarum, R. anhuiense, R. oryzihabitans were 100%, 99.93%, and 99.78%, respectively. With a pot experiment, the three rhizobia strains were inoculated on faba bean under different drought stresses (normal moisture, mild drought, and moderate drought). There were four inoculation treatments: uninoculated (T0), inoculated with SWFU-B1 (T1), inoculated with SWFU-B2 (T2), and inoculated with SWFU-B3 (T3). The effects of inoculation with three rhizobia strains on faba bean were quantified by measuring several variables, including plant height, stem diameter, nodule number, leaf area, antioxidant enzyme activity, osmotic adjustment substances and malondialdehyde content. With the severity of drought, the growth of faba bean slowed down, and the number of root nodules decreased significantly. Compared with no inoculation, under the same soil water content, the growth index of faba bean inoculated with rhizobia was better, showing a significant growth-promoting effect. Under moderate drought, plant height in T2 was 68.10% higher than that in T0, and the number of root nodules was 23.53% higher than that in T0. Under the same drought stress, compared with the T0 treatment, there were higher antioxidant enzyme activity and osmotic adjustment substance content in inoculated faba bean. The SOD activity of T1 reached 123.44 U·g-1·min-1, being 50.83% higher than T0. The proline content was 20.54 μg·g-1, being 72.32% higher than T0. Those results indicate that inoculating rhizobium can improve drought resistance of faba bean. Under the same drought stress, the malondialdehyde content of faba bean inoculated with rhizobium was significantly lower than that of no inoculation. In moderate drought, the malondialdehyde content of T1 was 33.33% lower than that of T0, indicating that the inoculation of rhizobium reduced the damage of drought to cell membrane of faba bean. The drought resistance of faba bean in the experimental groups was T1>T2>T3. The faba bean inoculated with strain SWFU-B1 showed the best drought resistance. In conclusion, under drought stress, inoculating rhizobium can significantly promote the growth and drought resistance of faba bean. This study provided a reference for restoration method and high quality strains for vegetation restoration in rocky desertification area.

    Potential ecological risks of heavy metals in soil along an urbanization gradient.
    Nazupar SIDEKJAN, Mamattursun EZIZ, LI Xinguo, YANG Xiuyun
    2023, 42(5):  1107-1114.  doi:10.13292/j.1000-4890.202305.004
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    To identify the influences of urbanization on the environmental safety of urban soil, a total of 77 topsoil samples were collected along an urban-suburban-rural gradient in Urumqi City, Xinjiang, northwest China. The concentrations of nine trace elements were measured, including As, Cd, Ni, Pb, Hg, Cu, Zn, V, and Co. We used the potential ecological risk index and the environmental risk early warning index to compare the ecological risks of heavy metals in soil along the urbanization gradient. The average concentrations of Hg in urban, suburban, and rural soils were higher than the background value of soil in Urumqi. The average concentrations of As in soils in urban and suburban zones were higher than the corresponding background. The average concentrations of Zn and Pb in the soils in urban zone exceeded the corresponding background values. The average concentrations of other elements were lower than the corresponding background value. The concentrations of all heavy metals in urban soils were higher than that in rural soils. The Hg element in all the sites presented a very strong ecological risk situation, whereas other eight elements showed a slight ecological risk situation. The ecological risk early warning index of Hg showed a heavy, medium and heavy warning situation in urban, suburban, and rural zones, respectively. As showed early ecological warning situation in urban and suburban zones. Zn showed early ecological warning situation in urban soils, while the other elements showed no ecological warning situation. On the whole, the concentrations and potential ecological risk of heavy metals in topsoil showed an obvious decreasing trend along the urban-suburban-rural gradient. Hg was the main ecological risk factor in the topsoil of each zone in the study area, and thus the potential ecological risk of Hg should be cautious.

    Effects of different kinds of organic matter on the adsorption process of arsenic on goethite.
    SUN Meiling, YE Yufang, ZHAO Zhixi, MA Xiaoyan, XIE Qingqing
    2023, 42(5):  1115-1122.  doi:10.13292/j.1000-4890.202305.008
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    Arsenic is listed as one of the most important poisons in the environment. The influence of organic matter on the environmental geochemical behavior of arsenic has attracted more and more attention. Aiming to understand the influence of different active functional groups of organic matter on arsenic adsorption, a batch experimental method was used to explore the adsorption isotherm and adsorption kinetics of arsenic on goethite with the coexistence of different organic matters. The influence of different organic matters on arsenic adsorption was explored by Zeta potential and infrared spectrum. The results showed that the addition of carboxymethyl cellulose, tannic acid, p-benzoquinone and dodecylbenzene sulfonic acid inhibited the adsorption of arsenic on goethite, and the adsorption of which was fit well with the Freundlich adsorption isotherm model. When the four kinds of organic matter were added respectively, the adsorption of arsenic on the surface of goethite was well described by pseudosecondorder kinetic model. Moreover, with the changes of pH, organic matter with different functional groups had different effects on the adsorption rate of arsenic. The arsenic adsorption rate constants of tannic acid, dodecyl benzenesulfonic acid, carboxymethyl cellulose and pbenzoquinone were 0.37, 0.03, 0.02, and 0.01 mg·g-1·h-1, respectively. Ta〖HJ*4〗nnic acid can significantly increase the adsorption rate of arsenic, while p-benzoquinone can effectively reduce the adsorption rate of arsenic, probably due to the different modes of interaction between their functional groups and arsenic. The results of Zeta potential measurement showed that the ternary complexes were formed among arsenic, tannic acid, and goethite. The results of infrared spectrum also evidenced the formation of ternary complexes.

    Characteristics of plankton community structure and its relation to environmental factors in Kizil River, Xinjiang, China.
    ZHAO He, ZHAO Nianhua, LI Li, QIANG Zhuang, WEI Jie, NIE Zhulan, SHEN Jianzhong
    2023, 42(5):  1123-1131.  doi:10.13292/j.1000-4890.202305.014
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    To evaluate the plankton community structure and ecological environment in Kizil River, we investigated the plankton and water physicochemical factors in the upper, middle and lower reaches of the Kizil River during the high-water period in May and the low-water period in September of 2020. The results showed that there were 28 species and 4 phyla in the phytoplankton community, in which diatoms and green algae were dominant, with a contribution of 71.43% and 14.29%, respectively. There were 14 species and 3 phyla in zooplankton community, including seven species of rotifiers, four species of protozoans and three species of copedods. In May, the month within abundant water season, the dominant species in the Kizil River were Spirogyra communis, Arcella sp. and Rotaria tardigrada, while Spirogyra communis, Navicula oblonga, Navicula simplex, Nebela barbata and Arcella sp. were dominated in September, a month of drought season. Meanwhile, the mean density and biomass of these two plankton communities in the dry season were higher and richer than those in the wet season. The species of both communities, however, were less diversified. The values of Shannon Diversity Index of plankton in May and December were 1.83 and 2.27, indicating a status of moderate and mild pollution, respectively. The results of redundancy analysis showed that pH, transparency, and the load of ammonia were the important environmental factors affecting plankton community structure, while pH, total phosphorus, and total nitrogen were the key factors affecting zooplankton community structure. This study can provide basic data for the protection of water resources in the Kizil River.


    Zoobenthos community characteristics and ecological health assessment in river-lake ecotone: A case study in Nansi Lake.
    HAO Ziran, YU Lihua, KONG Fanlong, ZHANG Qian, LI Fanyi, YU Zhengda
    2023, 42(5):  1132-1141.  doi:10.13292/j.1000-4890.202305.003
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    To explore the characteristics of macrobenthic invertebrate community and ecosystem health status in river-lake intersection areas, we investigated water quality, sediment quality, and zoobenthos community in the intersection areas of 14 rivers entering Nansi Lake in September 2020 and April 2021. A total of 55 species were collected, belonging to 6 classes, 15 orders, and 39 families. Results of non-metric multi-dimensional scaling analysis showed that the similarity of zoobenthos community across all sampling sites in spring was higher than that in autumn. The community structure had high similarity among Xinxue River (S7), Panlong River (S9), and Beisha River (S11) in both seasons. Results of redundancy analysis showed that total phosphorus and CODCr in water and total carbon in sediment were the key factors affecting zoobenthos community. The scoring of biological monitoring working party (BMWP) index concluded the similar consequence with water quality characteristics, indicating that BMWP is a valid biological index for assessing the health status of the river-lake intersection areas in the Nansi Lake. The health status of major river-lake intersection areas in the Nansi Lake Basin was generally at the level of mild to moderate pollution. This study provides a basis for ecological restoration in river-lake intersection areas.

    Effects of fluorescent polystyrene microsphere on stress level and immune function in the tadpoles of Pelophylax nigromaculatus.
    DIAO Yingzhu, PEI Xinyi, WANG Ping, SHI Shuang, LI Wenhui, PENG Xiujuan, LI Ran, WU Liang, BAO Chuanhe, ZHANG Zhiqiang
    2023, 42(5):  1142-1149.  doi:10.13292/j.1000-4890.202305.015
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    To explore the effects of nano-scale microplastics on the health status of Gosner stage 37 tadpoles of Dark-spotted frogs, Pelophylax nigromaculatus, the tadpoles were exposed to low, moderate, or high concentration of fluorescent polystyrene microspheres (FPMs, 50 nm in diameter) solution for 7 days (day 7), then they were transferred to clear water and housed for 7 days (day 14) or 14 days (day 21). Clear water group was used as the control. The variations of the ratio of body mass to total body length, the ratio of neutrophils to lymphocytes (N/L ratio), and the responsiveness to phytohemagglutinin (PHA-P) were measured in multiple sampling time points for each group. On day 14, the ratio of body mass to total body length was significantly lower in control than that of any other FPMs groups. On day 21, the N/L ratio was significantly lower in control than that of any other FPMs groups, which was greatly increased from day 7 to day 21 for low, moderate or high concentration groups. The peak of the responsiveness to PHA-P for different concentration groups of FPMs on day 7 was observed after injection 3 h or 4 h, and occurred forwards after injection 2 h or 3 h on day 14, then gradually returned to that after injection 3 h or 4 h on day 21. On day 21, the peak of the responsiveness to PHA-P in high concentration group was higher than that of low and moderate concentration groups. Exposure and primary clearance of FPMs significantly promoted the growth and development of tadpoles of Dark-spotted pond frog, but such effect disappeared with increasing duration of treatments. Meanwhile, the stress level of the tadpoles responding to external stimuli was significantly increased, but not at the expense of suppressed immune function.

    Effects of exogenous melatonin on the growth and reproduction of Aphis craccivora.
    ZHANG Yuxia, ZHANG Tingwei, SHI Li, YUAN Yue, LIU Changzhong
    2023, 42(5):  1150-1154.  doi:10.13292/j.1000-4890.202304.028
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    To clarify the effects of different concentrations of exogenous melatonin on the biological characteristic of Aphis craccivora, we measured the developmental and reproductive indices of A. craccivora under different concentrations of exogenous melatonin by plant meditation in vitro. The results showed that feeding exogenous melatonin had a significant effect on the developmental duration, body size, fecundity and life-table parameters of A. craccivora, which was dose-dependent. With the increases of exogenous melatonin concentrations, the developmental duration of alfalfa aphid was significantly prolonged, the growth rate slowed down and the body size decreased. Meanwhile, the adult longevity and reproductive period were shortened gradually. The average fecundity and the average daily fecundity per female were decreased, and the number of embryos in ovariole tubes was decreased compared with the control. Under the high concentration (50 mg·L-1) treatment, A. craccivora had the longest developmental duration (11.14 d), the shortest adult longevity (19.85 d) and reproductive period (14.71 d). Body length (1.48 mm), hind food tibia length (0.77 mm), and body weight (0.63 mg) were the lowest. Furthermore, A. craccivora had the lowest average fecundity of per female (66.14 offsprings per female) because of the decreased number of embryos per ovariole in ovaries of A. craccivora. Our results suggested that feeding melatonin has a signi-ficant effect on the growth and reproduction of A. craccivora.

    Spatiotemporal variations of birds under COVID-19 pandemic and implications for urban ecological planning: A case study of Hong Kong.
    TIAN Beichen, NONG Yun, HUANG Xiao, XIE Yanhua
    2023, 42(5):  1155-1166.  doi:10.13292/j.1000-4890.202305.032
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    Birds are important indicator species that reflect urban ecological health status and effectiveness of ecological restoration. The current ecological planning and restoration for Pearl River Delta in China lacks supports from bird ecology related data, leading to the quantitative knowledge gap on birds’ habitat selection and movement mechanisms, thus posing challenges for the construction of bird-friendly cities. Taking Hong Kong as the study area, by analyzing eBird data before and during the COVID-19 pandemic, we revealed four major responding mechanisms of local birds when the dramatic pandemic-triggered decrease in human mobility occurred using Shannon index and maximum entropy model: (1) the standard deviation (25.68) of overall bird diversity during breeding season was apparently higher than performances throughout the whole year (15.25) and during overwintering season (12.43), which indicated a higher level of sensitivity to changes in human mobility; (2) the overall bird diversity was high and stable in northern districts, and medium and fluctuated seasonally in central and southern districts, low and fluctuated markedly in core urban districts; (3) the increases no less than 24% in distribution probabilities of the dominant land bird and waterbird species, compared with pre-pandemic situations, mainly occurred in land cover types including grassland, agricultural land, woodland, shrubland, and rural settlement; (4) agricultural land was the only land cover type whose area proportions within  500 m×500 m quadrats were positively correlated with averaged increases in distribution probabilities of the dominant land bird (r=0.25) and waterbird species (r=0.049). Based on the above results, we suggest cities within the Pearl River Delta to generate pertinent schemes for ecological planning and restoration by considering the characteristics of local bird ecology, including seasonal fluctuations, species compositions, and covers.

    Altitudinal and seasonal variations of nutrients in edible plants of blue sheep (Pseudois nayaur) in the Helan Mountains.
    CUI Luyao, QIU Kaiyang, LI Jingyao, XIE Yingzhong, ZHAO Pengbo, LIU Wangsuo, HUANG Yeyun, YANG Yi, BAO Pingan, WANG Siyao
    2023, 42(5):  1167-1174. 
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    Changes in nutrients in edible plants of blue sheep (Pseudois nayaur) in the Helan Mountains are an important link to study of the distribution of their browsing areas, which has great significance for clarifying the relationship between blue sheep and natural environment. The spatial and temporal variations in edible plant nutrients of blue sheep along an altitudinal gradient (1100-2600 m above sea level) in the Helan Mountains across different seasons (June, August, and November) were analyzed. Results showed that plant nutritional value was the highest in August, and that each plant nutritional ingredient except for crude ash was significantly different among different seasons (P<0.05). In June, except ether extract, nutrient contents of edible plants significantly varied across different altitudes (P<0.05). In August, there were significant differences in the contents of all nutrients among altitudes (P<0.05). In November, the contents of all nutrients except crude protein were significantly different among different altitudes (P<0.05). There was an interactive effect of altitude and season on changes in the nutritional ingredient of edible plants (P<0.05). Considering altitudinal and temporal variations of plant nutritional value, it is suggested that the management and conservation strategy for blue sheep should be dependent on altitudes and seasons to promote the healthy and sustainable development of blue sheep population.

    Spatio-temporal variations of habitat quality and its underlying mechanism in the central region of Yangtze River Delta.
    CHEN Shi, JIN Yunxiang, HUANG Yinlan
    2023, 42(5):  1175-1185.  doi:10.13292/j.1000-4890.202305.022
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    Clarifying the spatial and temporal variations of habitat quality and its driving factors is important for regional ecological protection and restoration and integrated high-quality sustainable development under rapid urbanization. Based on the satellite-based land-use dataset from 1995 to 2020, we used the InVEST model to detect the spatio-temporal variations of habitat quality in the central region of the Yangtze River Delta, and assessed its driving force. Habitat quality in the central region of the Yangtze River Delta showed a trend of degradation. Heterogeneity across provinces (municipalities) increased mainly because of the increases of habitat area with poor and worst grades and little area change in other grades. The spatial changes of habitat quality mainly happened in the  exchange between poor grade and worst grade, better grade, best grade. There was a good balance between the area of habitat with upgraded quality and degraded quality in Nanjing, Changzhou, and Zhenjiang cities, and more potential for habitat restoration in Xuancheng, Chizhou, Zhoushan, and Anqing cities. The habitat management and improvement in Zhejiang Province were better than other provinces (municipalities) in the recent five years. The differences in habitat quality management and improvement between provinces (municipalities) highlight the importance of integrated management and development of ecological environment in this area in the future. The natural environment and social-economic development are the main reasons for the spatio-temporal variations of habitat quality in this area. Elevation and slope determined habitat quality, while the intensity of human activities drove the changes in habitat quality pattern.

    Spatial and temporal variations of landscape ecological risk in the mountainous region of southwestern Hubei Province based on the optimal scale.#br#
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    ZUO Qian, ZHOU Yong, LI Qing, WANG Li, LIU Jingyi, HE Nan
    2023, 42(5):  1186-1196.  doi:10.13292/j.1000-4890.202305.024
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    Investigation of landscape ecological risks is essential for optimizing landscape patterns and strengthening ecological management in ecologically fragile mountainous areas. Using multi-period land use data in the mountainous area of southwestern Hubei Province, we constructed an ecological risk assessment model based on landscape pattern index. We explored the spatial and temporal patterns and trends of mountain landscape ecological risks at optimal scales using methods such as geostatistics, spatial autocorrelation, and geoinformation mapping. The results showed that the most suitable scales for landscape ecological risk analysis in the mountainous area of southwestern Hubei Province were 50 m grain and 4 km grid. From 1990 to 2018, the structure of landscape types in the study area was more stable, mainly composed of forestland, cultivated land, and grassland. The area of construction land increased the most and continued to expand. The transfer-out of cultivated land and the interconversion between ecological lands were the main factors. The overall landscape ecological risk showed a downward trend, with the grades being mainly at  low and very low risk. There were interlacing distribution phenomenon between local high risk and low risk areas. The change of landscape ecological risk area mainly was the transfer between adjacent grades. The spatial distribution of landscape ecological risk in mountainous area showed significant positive correlation, mainly with high-value and low-value clustering patterns. The risk spatial clustering effect was substantial. The local spatial autocorrelation pattern did not change much, with strong stability of spatial distribution. Finally, we proposed suggestions for landscape ecological risk prevention and ecological environmental protection in the mountainous area of southwestern Hubei Province. This study provides data basis and theoretical support for decision-making on ecological security in mountainous areas.

    Identification and construction of county-level ecological security pattern integrating ecological space: A case study of Wuyishan City.
    WEN Hui, DENG Xipeng, LI Ying, WANG Chen, WANG Lirui, HE Dongjin, WU Liyun, YOU Weibin
    2023, 42(5):  1197-1204.  doi:10.13292/j.1000-4890.202305.017
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    The rational allocation of ecological space is one of the important bases for constructing ecological security. Taking Wuyishan City, a county-level city in Fujian Province, as the study area, we delimited the forbidden development zone, restricted development zone and general development zone based on ecosystem service importance assessment and ecological sensitivity assessment. The three types of zones covered 1079.71, 1267.22, and 375.35 km2 respectively, accounting for 39.7%, 46.6%, and 13.8% of the total area of the city, respectively. Integrating the results of spatial zoning, combined with the existing natural protection area in Wuyishan City, the Minimum Cumulative Resistance model was used to construct the ecological security pattern. The area of ecological sources was identified as 1322.22 km2, accounting for 47.3% of the total area of Wuyishan City. A total of 755 km ecological corridors and 55 ecological nodes were determined. Three ecological security level patterns were classified, which were 904.89, 511.09 and 1392.15 km2 respectively, accounting for 32.2%, 49.6% and 18.2% of the study area, respectively. Our results provide a basis for the rational control of territorial space of Wuyishan City.

    Multi-objective optimization of land use based on ecosystem service bundle zoning: A case study of Bayannur City.
    LI Yunxia, WANG Chenxu, LIU Yanxu
    2023, 42(5):  1205-1213.  doi:10.13292/j.1000-4890.202305.020
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    Optimization in spatial structure of land use is an important way to effectively manage ecosystem services and coordinate the conflicts between human and land. Current available optimization programs are mostly from the perspective of whole region, ignoring the regional differentiation of ecosystem services, which would underestimate optimization benefits or be low in feasibility. Taking Bayannur City of Inner Mongolia Autonomous Region as an example, we used ecosystem service cluster and genetic algorithm to implement zoning land use optimization based on SAORES platform. The results showed that compared with current land use pattern, the overall optimization of land use layout functionally improved ecological benefits by 16.8% and reduced the service of food production by 6.4%. The zoning optimization of land use layout was more cost-effective, with 27.3% improvement in ecological benefits and only 5.6% reduction in food production service. The landscape disturbance in the pattern showed a general decrease after optimization. The edge effect was significantly reduced, with no significant difference between the overall and zoning optimization schemes. We proposed an optimized scheme for the spatial configuration of ecological reserves conforming to the long-term development of Bayannur City.

    A review of the impacts of climate change on agro-ecosystem services and adaptation measures.
    WANG Chunyi, ZHAO Mingyue, ZHAO Yuncheng, XU Yinlong
    2023, 42(5):  1214-1224.  doi:10.13292/j.1000-4890.202303.026
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    Due to the vulnerability of agro-ecosystems, climate change poses great challenges to the sustainable provision of agro-ecosystem services. Previous studies have analyzed the impacts of climate change on agroecosystems. However, integrative studies about the influences of climate change on agro-ecosystem services and relevant adaptation actions are still rare. In this paper, we reviewed the impact mechanisms of climate change on crop yield, stability of regulating services, and supply of cultural services, as well as the current adaptation measures from the perspective of agricultural landscape diversity. We proposed to deepen research on the comprehensive impacts of climate change on multiple ecosystem services, explore the adaptation mechanisms of agro-ecosystems to climate change, strengthen studies of model simulation, and strengthen the connection between adaptation measures and government decision-making. This review provides scientific evidence for national agricultural policy-making and action implementation on climate change in China.
    Application prospect of lure technology by robotic fish in fish collection process.
    SHI Xiaotao, ZHOU Liuqing, LIN Chenyu, CHEN Jun, LIU Zhenbiao, XIE Guangming
    2023, 42(5):  1225-1233.  doi:10.13292/j.1000-4890.202303.030
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    The use of biomimetic robotic fish to regulate fish behavior is of great significance in the conservation of fish resources, providing a new idea for the development of fish repellent technology. Based on the research status of robotic fish, we analyzed the visual luring mechanism, wake field luring mechanism, and electric signal luring mechanism of robotic fish lure technology. Moreover, we summarized the main factors affecting the fish luring technology of robotic fish and the relevant research achievements of foreign robotic fish regulating fish behavior, and discussed the application prospect of fish luring technology of robotic fish. This review would provide reference for the further development of fish luring technology of robotic fish in China.

    Current situation and the influencing factors of planting-breeding relationship for feces and sewage of livestock and poultry in Liaoning Province.
    ZHANG Yulan, SUN Caixia, QIANG Zhe, XIE Hongtu
    2023, 42(5):  1234-1242.  doi:10.13292/j.1000-4890.202305.005
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    Under the layout “from-south-to-north strategy of livestock and poultry breeding” in China, the quantities of livestock and poultry have increased rapidly in Liaoning Province, with nearly 70 million pigs equivalent in 2019 and nearly 100 million in 2020. With the rapid transformation of from traditional pattern to large-scale animal husbandry, the sharp increase in the quantities and concentration of livestock and poultry manure has brought huge pollution risks to the ecological environment of Liaoning Province. The imbalance and disconnection between crop planting and breeding is increasingly serious. There are many factors leading to the exacerbation of disconnection between crop planting and breeding. The inconsistency of the interests between the livestock and poultry breeding and crop planting is the primary cause. The rapid development of large-scale breeding makes the problem more and more serious. The regional planning of livestock and poultry breeding is unreasonable. The existing small and medium-sized farms in Liaoning Province have a lot of historical problems. Fecal sewage of smallholders in intensive breeding areas, especially liquid fecal sewage, is a big problem. The equipments for feces and fecal sewage treatments are outdated, the technologies are antiquated, and technical procedures are cumbersome. The non-standard technology has resulted in nutrient losses and land degradation. To promote the combination of planting and breeding in the utilization of livestock and poultry manure resources in Liaoning Province, we suggest that the preferred strategies are to coordinate the interests of planting and breeding, improve the manure reclamation technology and facilities, standardize the manure resource return technology, strengthen the promotion of research achievements and government guidance. This work would provide strategic supports for the integration of livestock and breeding industry and planting industry in Liaoning Province.

    Estimation of aboveground biomass dynamics of Pinus densata by considering topographic factors.
    LIAO Yi, ZHANG Jialong, BAO Rui, XU Dongfan, WANG Shuxian, HAN Dongyang
    2023, 42(5):  1243-1252.  doi:10.13292/j.1000-4890.202305.021
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    Estimation models of aboveground biomass change of Pinus densata in Shangri-La were established based on remote sensing. The estimation accuracy of the models with or without terrain factors being considered was compared. Based on the continuous inventory plots and the Landsat TM/OLI images during 1987 to 2017, the remote sensing factors were extracted, and the change rates of those remote sensing factors and aboveground biomass of the corresponding plots were calculated. Multiple linear regression (MLR), random forest (RF) and gradient boosting regression tree (GBRT) were then used in the modeling. Finally, the factors of elevation, slope and aspect were added to these three models and their modeling effects were compared. The change rate models constructed with the three methods varied a lot, with the fitted results of R2 being 0.457, 0.946 and 0.887, the RMSE being 2.431, 0.692 and 1.027 t·hm-2·a-1, the rRMSE of predicted effect being 56.66%, 33.17% and 35.30%, and the precision being 44.31%, 78.77% and 70.95%, respectively. The accuracy of the three models was improved, and the confidence intervals of RF and GBRT were narrowed after adding terrain factors. In all models, the result of RF model with slope aspect factor was best, the R2 was 0.976 (with an enhancement of 3.1%), the RMSE was 0.502 t·hm-2·a-1 (a reduction of 27.46%), the rRMSE was 31.50% (a reduction of 5.05%), the precision was 82.07%, (an increase of 4.18%). Adding terrain factor into the change rate model of RF can improve the accuracy of the model, and the aspect factor has the best performance on improving the model accuracy. Our results can provide a useful basis for accurate estimation of aboveground biomass of Pinus densata in Shangri-La.

    Simulating the long-term effects of planting Pinus sibirica on aboveground biomass of forests in the north-central Great Xing’an Mountains.#br#
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    HU Mengting, LUO Xu, ZHAO Xintian, LI Lu
    2023, 42(5):  1253-1263.  doi:10.13292/j.1000-4890.202305.018
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    Pinus sibirica is an important cold-temperate tree species introduced and planted in the Great Xing’an Mountains, which directly affects forest ecosystem structure and carbon sequestration. Analyzing the long-term effects of planting P. sibirica on aboveground biomass of forests has significant implications for clarifying regional carbon sinks and carbon neutrality. We assessed the dynamic changes in aboveground biomass of various native tree species based on field survey data and forest landscape model. The introduction and planting of P. sibirica played a positive effect on the forest aboveground biomass at landscape scale. P. sibirica should thus be introduced and planted at a large scale in the future. The increasing rates of aboveground biomass under different planting intensity scenarios were basically similar, with a maximum of 8.66 Mg·hm-2 in low-intensity planting scenario. The change rates in aboveground biomass differed significantly among major native tree species. The aboveground biomass increased by 0.19-8.88 Mg·hm-2 for Larix gmelinii and Picea koraiensis, while decreased by 0.42-12.86 Mg·hm-2 for Pinus sylvestris var. mongolica, Populus davidiana, and Betula platyphylla.

    Adaptability of DSSAT crop model to main crops in Lishu County, Jilin Province.
    LIU Tao, WAN Nenghan, ZHANG Zhentao, WANG Xiaoyu, SUN Shuang, LIU Zhijuan, ZHAO Jin, YANG Xiaoguang
    2023, 42(5):  1264-1272.  doi:10.13292/j.1000-4890.202305.010
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    Clarifying the applicability of DSSAT model to the growth and yield simulation of main crops in Northeast China is of great significance to further promote its application in Northeast China and ensure food security. An experiment was conducted based on four kinds of main crops in Lishu County, Jilin Province, including spring wheat, soybean, millet, and potato. The applicability of DSSAT model was evaluated systematically with three years data from field experiment. The results showed that the determination coefficients of simulated and measured values of growth period, leaf area index (LAI), aboveground biomass, stem biomass, leaf biomass, and yield of spring wheat, soybean, millet and potato in DSSAT model were 0.94-0.99, 0.92-0.99,  0.96-0.99, and 0.97-0.98, respectively. The normalized root mean square errors were 12.21%-26.01%, 1.67%-33.24%, 1%-15.34%,  and 3.2%-28.08%, respectively. D values were above 0.994. The fitting degree of growth period and yield for spring wheat was the highest, followed by LAI. The fitting degree of yield and LAI for soybean and millet was the highest, followed by growth period. The fitting degree of growth period and yield for potato was the highest, followed by LAI. The growth dynamic simulation of LAI, leaf biomass, stem biomass, and total aboveground biomass showed that the determination coefficients for spring wheat, soybean, millet and potato were more than 0.84, and the normalized root mean square errors were 24.5%-38.2%, 28.7%-47.4%, 9.2%-26.3%, and 28.7%-45.1%, respectively. The fitting degree of stem biomass for spring wheat was the highest, and that of LAI was the lowest. The fitting degree of LAI for soybean and potato was the highest, and that of leaf biomass was the lowest. The fitting effect of millet leaf biomass was the highest and that of stem biomass was the lowest. In general, the validated DSSAT model can better simulate the growth period, LAI, aboveground biomass and yield of the four kinds of crops. In the future, it can be used as an important tool in the related research about the growth simulation of major crops in Jilin Province.

    Spatial distribution of preferential flow in sugarcane field in Guangxi under radar detection.
    LIU Sijia, CHEN Xiaobing, LIU Junjie, QIN Zicheng, JIANG Bo, WU Han
    2023, 42(5):  1273-1280.  doi:10.13292/j.1000-4890.202305.007
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    Based on the combination of dye tracer and radar detection technology, the spatial distribution patterns and influencing factors of soil priority flow in sugarcane fields under ridge tillage and no-tillage treatments in Guangxi were examined by morphological analysis of dye image, interpretation of radar image information, and Logistic regression analysis. The results showed that soil dielectric constant and radar profile image amplitude showed a trend of first increasing and then decreasing with soil depth, and that the dielectric constant was significantly different among soil depths (P<0.05). Under no-tillage, the soil layer of 20-50 cm had a range of amplitude variation, with a variation range between -0.3×106 and 0.3×106, which indicated that water moved vertically. The fluctuation of electromagnetic wave amplitude in ridge-cultivated sugarcane fields was concentrated in the soil layer of 0-20 cm, and the preferential flow was mostly lateral movement. The change value between the peak and the nadir was 0.27 under ridge tillage, which was smaller than that under no-tillage (0.34) (P<0.05). Saturated hydraulic conductivity and organic matter content were the main factors affecting the development of preferential flow under radar detection. Radar detection can quantitatively characterize the spatial distribution of preferential flow in the soil. Ridge tillage can reduce the rapid migration of soil water in sugarcane fields to a certain extent, and enhance water retention and storage conditions in the fields.