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    10 January 2023, Volume 42 Issue 1
    Physiological responses of seedlings of Ping’ou hybrid hazelnuts to salt stress and their evaluation of salt tolerance.
    LUO Da, SHI Yan-jiang, SONG Feng-hui
    2023, 42(1):  1-8.  doi:10.13292/j.1000-4890.202212.015
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    Understanding the physiological responses of Ping’ou hybrid hazelnut to salt stress and the variations of salt tolerance of different varieties can provide scientific reference for the breeding of salt-tolerant varieties and their rational utilization in saline-alkali soil. The seedlings of three Ping’ou hybrid hazelnut varieties (Dawei, Liaozhen 7, and Yuzhui) were treated with control, mild, moderate and severe salt stress (0, 50, 100, and 200 mmol·L-1 NaCl, respectively) in a pot experiment. Leaf physiological indices related to salt tolerance were measured. The results showed that salt stress did not affect leaf relative water content of Dawei, while significantly reduced that of Liaozhen 7 and Yuzhui by 12.5% and 27.9%, respectively, under severe salt stress. With increasing salt stress, leaf soluble sugar and soluble protein increased first and then decreased. The proline content increased continuously, with an increment of 19.6%, 35.3%, and 96.9% under mild, moderate, and severe stress, respectively. The relative electrical conductivity, malondialdehyde and catalase activity in leaves increased with increasing salt stress. The superoxide dismutase activity in leaves increased first and then decreased, while peroxidase activity decreased first and then increased. With increasing salt stress, leaf Na+ and Cl- contents increased. The K+ content increased first and then decreased, and significantly increased by 43.6% and decreased by 28.3% under the moderate and severe stress, respectively. The K+/Na+ ratio decreased, with a significant decrease of 69.5% under severe stress. Our results suggested that Ping’ou hybrid hazelnut positively responded to mild and moderate salt stress through accumulating leaf osmotic adjustment substances, improving antioxidant enzyme activity, maintaining ion balance, which could help to reduce the damage of reactive oxygen under stress and protect the structure and function of membrane system. Plants suffered from severe stress that exceeded the threshold of normal physiological activities of Ping’ou hybrid hazelnut. Liaozhen 7 showed the strongest tolerance to salt stress through physiological regulation, followed by Yuzhui and Dawei.

    Rhizome growth characteristics of different potted Phyllostachys praecox ‘Prevernalis’ seedlings.
    GAO Gui-bin, ZHANG Xiao-ping, WEN Xing, ZHONG Hao, PAN Yan-hong, YANG Jin-lai, WU Zhi-zhuang
    2023, 42(1):  9-17.  doi:10.13292/j.1000-4890.202212.016
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    This study was aimed to clarify the mechanisms underlying the construction and maintenance of bamboo population, explore the process of bamboo population construction from a single mother bamboo to ramet system, and then construct bamboo population. We analyzed the growth characteristics of rhizome morphology, biomass and bud bank of bamboo seedlings in a pot experiment with mother bamboo (Phyllostachys praecox C. D. Chu et C. S. Chao ‘Prevernalis’, a bamboo species for small-diameter shoots) at different ages and mulching bamboo forest soils. The average rhizome length (666.58±111.75 cm·pot-1) and the average number of rhizome internode (342±44 ind·pot-1) in 2-year-old mother bamboo seedlings were significantly higher than those in 1-year-old mother bamboo seedlings (354.25±136.64 cm·pot-1 and 216±88 ind·pot-1), while average rhizome diameter (0.77±0.07 cm) was lower than that of the 1-year-old mother bamboo seedlings (1.07±0.12 cm). For the rhizome biomass accumulation, 1-year-old mother bamboo seedlings allocated more biomass to rhizome, while 2-year-old mother bamboo seedlings allocated more to root. The number of bud bank of 2-year-old mother bamboo seedlings was higher than that of 1-year-old mother bamboo seedlings. The number of total buds and dormant buds reached 342±43 and 277±42 ind·pot-1 respectively, while the number of 1-year-old mother bamboo seedlings was only 216±80 and 187±69 ind·pot-1. Those results indicated that the thicker the bamboo rhizome, the less differentiation of rhizome bud, and that the greater the number of rhizome internode, the higher the rhizome biomass. The rhizome bud bank mainly consisted of dormant buds. The lateral buds of slender bamboo rhizome with many rhizome internodes had larger bud reserves. The lateral bud germination was mainly rhizome buds, and the quantitative characteristics of shoot bud differentiation did not show obvious regular changes. As a single ramet, mother bamboo was efficient in rhizome regeneration by expanding and propagating into ramet system, increased the number of lateral buds which differentiated into rhizome buds, and achieved a rapid growth of rhizome length. Such characteristics were also good for total bud amounts of bud bank, especially the large-capacity reserve of dormant buds, providing good basis for the further propagation of the ramet system.

    Effects of drought and salt stresses on seed germination of Rheum officinale Baill. at different elevations, growth years and storage periods.
    XIE Feng-pu, WANG Nan, GAO Jing, ZHANG Gang, GE Tian-tian, ZHANG Ya-li, CHENG Shi-qiang, SONG Zhong-xing, TANG Zhi-shu
    2023, 42(1):  18-28.  doi:10.13292/j.1000-4890.202212.012
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    We explored the effects of drought and salt stresses on seed germination and seedling growth of Rheum officinale Baill. at different altitudes, growth years and storage periods, with seeds collected from Zhenba County, Shaanxi Province. PEG and NaCl treatments with two osmotic potential levels (-0.3 and -0.5 MPa) were used to simulate drought stress and salt stress, respectively. The number of seed germination was recorded daily and the growth of seedlings was observed. The results showed that the germination rate of seeds collected at the middle altitude of 1650 m was higher than that of seeds collected at the low and high altitudes. Seeds collected at the altitudes of 1650 and 1300 m were more tolerant to drought and salt stresses. With the increases of stress concentration, the inhibitory effect of drought stress on seedling growth was extremely significant. All seedlings died under -0.5 MPa PEG treatment. There was no significant difference in the endogenous GA3 content of seeds collected at different altitudes, growth years and storage periods. Seed vigor and endogenous GA3 concentration increased significantly after gibberellin soaking. The germination rate, vigor, and salt tolerance of seeds stored for one year at room temperature were significantly lower than that of newly collected seeds, while the germination rate, vigor, and salt tolerance of seeds from three-year-old plants were higher than those from two-year-old plants. Drought tolerance of seeds from three-year-old plants was stronger. In summary, R. officinale seeds are not suitable for long-term storage at room temperature. Medium altitude and mild salt stress are beneficial to seed germination and seedling growth of R. officinale. Seed quality of three-year-old plants is higher than that of two-year-old plants.

    The physiological and ecological responses of two species of ectomycorrhizal fungi to Cd stress.
    YANG Zhi-hui, ZHU Yi-dan, YANG Bao-shan, WANG Hui, LI Feng, JIAO Ke-qin, QIN Guang-hua
    2023, 42(1):  29-38.  doi:10.13292/j.1000-4890.202301.006
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    To explore Cd tolerance mechanism and Cd accumulation characteristics of two ectomycorrhizal fungi \[ECMF; Pisolithus tinctorius(Pt) and Suillus luteus (Sl)\], we examined the physiological and ecological changes including cell morphology, extracellular secretion and antioxidant substances of Pt and Sl under three Cd2+ concentrations (0.1, 1.0, and 10.0 mg·L-1). The results showed that cell wall of Pt was significantly thickened and the plasmolysis occurred. The cells of Pt were seriously deformed and a great amount of inclusions were exuded. Both Sl and Pt secreted siderophores of hydroxamic acid type which chelate Cd2+. The secreted quantities of different organic acids varied with different strains, with succinic acid being the main organic acid secreted by both ECMF species. In addition, the activities of antioxidant enzymes and the content of non-enzymatic antioxidant substances in Pt and Sl varied with different strains. With the increases of Cd2+ concentration, ascorbate peroxidase (APX) activity and ascorbic acid (AsA) content in Pt and Sl increased obviously. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and the content of reduced glutathione (GSH) were different. GSH content and GR activity showed an opposite trend in Pt. Under low Cd concentration, SOD activity increased significantly in Pt and Sl. For Pt, CAT activity decreased first and then increased. In all, Pt and Sl showed different physiological and ecological responses to Cd2+ stress. They could resist Cd stress by enhancing the activities of SOD, CAT, APX, increasing the content of AsA, secreting organic acid and siderophores. In addition, cell wall thickening and chelation of GSH are important mechanisms underlying the tolerance of Sl to Cd stress.

    Effects of irrigation on the population development and accumulation of dry matter at post-anthesis and starch in grains of winter wheat.
    ZHANG Xiao-qi, LI Hong-yu, YANG Si, YANG Zhen-ping, GAO Zhi-qiang
    2023, 42(1):  39-48.  doi:10.13292/j.1000-4890.202301.021
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    To optimize water-saving irrigation regimes for late-maturing winter wheat region in North China, we conducted a field experiment in consecutive seasons of 2018-2020 to investigate the population development, post anthesis dry matter accumulation in wheat and starch accumulation in grains under different irrigation treatments. In the first year, there were eight treatments, including non-irrigation as control (CK), irrigation at overwintering stage (W), jointing stage (J) and booting stage (B), irrigation at overwintering and jointing stages (WJ), irrigation at overwintering and booting stages (WB), irrigation at jointing and booting stages (JB), and irrigation at overwintering, jointing and booting stages (WJB). The latter is the common practice in the local region. According to the results of the first season, four treatments were chosen in the second year, including CK, W, B, and WB. Treatment W had stronger positive effects on the stem number of winter wheat population. Compared with CK, irrigation treatments significantly improved dry matter accumulation at the stages of fore and post-anthesis. Irrigation at early stage (e.g. W) was beneficial to increase the transportation of pre-anthesis storage assimilates to grains, while irrigation at late stage (e.g. treatment B) was beneficial to increase the allocation of post-anthesis accumulated assimilates into grains. The contribution rates of pre-anthesis stored assimilates and post-anthesis accumulated assimilates to grains varied with precipitation of fallow summer period. With increasing irrigation frequency and amount, the contribution rate of post-anthesis assimilates to grains increased significantly. Dry matter content and proportion in different organs of winter wheat at the maturity was in the order of grain (about 50%)>stem sheath+leaf (about 33%)>glume+spike-stalk (about 17%). Irrigation increased the contents of starch and its components, but decreased the ratio of amylose to amylopectin. Total starch amount and its components were higher in treatments W and B, but the ratio of amylose/amylopectin was lower. With increasing irrigation frequency and total amount, total starch amount and its components increased first and then decreased, while the ratio of amylose/amylopectin decreased. The contents of total starch and amylose in grains were in the order of JB>WJB>WB>WJ>W>B>J>CK and without significant differences between the treatments with two and three irrigation times. Synthetically considering the factors including the population development and post-anthesis dry matter accumulation in plants and starch in grains of winter wheat, and water save, irrigation at overwintering and booting stages (WB) had the best performance. Our results could provide theoretical basis for water conservation and achieving stable yield in winter wheat production in the study area.

    Effects of post-anthesis drought on photosynthesis, antioxidant properties, and C4 photosynthetic enzyme activity in winter wheat.
    LI Jun-yan, YAO De-xiu, GUO Xiao-lei, WANG Zhi-min, ZHANG Ying-hua
    2023, 42(1):  49-57.  doi:10.13292/j.1000-4890.202301.010
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    Drought is one of the most important abiotic stresses limiting wheat yield. To clarify the responses of different winter wheat varieties to post-anthesis drought, we investigated changes of flag leaf photosynthetic characteristics, malondialdehyde content, activities of antioxidant enzymes, content of osmotic adjustment substances, and activities of C4 photosynthetic enzymes in various organs of two winter wheat cultivars, “Jingdong 18” (drought-sensitive) and “Nongda 211” (drought-resistant), under drought and rewatering treatments. The results showed that post-anthesis drought significantly reduced the 1000-grain weight of “Jingdong 18”, but did not affect that of “Nongda 211”. Compared with “Jingdong 18”, SPAD value and net photosynthetic rate in flag leaves of “Nongda 211” were higher, the Fv/Fm  value was more stable, the increment of malondialdehyde content was smaller, and the increment of SOD and POD activities and soluble protein and proline content was greater. The activities of C4 photosynthetic enzymes (PEPC, NADP-ME and PPDK) in spikes (glumes and grains) were higher than those in flag leaves, which were enhanced under drought stress. After rewatering, various indices were restored to some extent. The results of correlation analysis showed that the increment of C4 photosynthetic enzyme activities in spikes was significantly positively correlated to the increment of proline content and antioxidant enzyme activity in flag leaves under post-anthesis drought. In conclusion, post-anthesis drought reduced photosynthetic capacity of wheat flag leaves, accelerated membrane lipid peroxidation and chlorophyll degradation, and finally affected wheat yield. Cultivars with strong drought-resistance maintained grain weight and slowed yield decline by enhancing C4 photosynthetic enzyme activities in spikes, osmotic regulation and antioxidant capacity in flag leaves under drought stress.

    The effects of forest management on species diversity and soil physicochemical property of poplar plantations along the expressway areas around Chengdu.
    SU Tian-cheng, XIANG Lin, CHEN Cong-lin, YU Jing, ZHANG Han-wen, LI Jing, WANG Qin, WANG Fang, HAO Jian-feng
    2023, 42(1):  58-66.  doi:10.13292/j.1000-4890.202212.017
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    With the reform of forest rights system in Sichuan Province, the management mode of forest plantations in expressway area has become diversified. We investigated the effects of different forest managements (UP: understory planting; PT: plow tillage; MO: mowing; AC: abandoned cultivation; CK: control, no management activity) on poplar plantations along expressway areas around Chengdu, aiming at providing theoretical reference for scientific forest management. The field survey was conducted in midJuly 2020, using typical plot sampling method. We measured each tree in the sampling plots, recorded understory species composition, calculated α diversity, and measured several soil characteristics, including soil water content, soil bulk density, total potassium, available potassium, total nitrogen, total phosphorus, available phosphorus, organic matter, soil pH. The treatments of UP, MO and AC significantly reduced species diversity of shrub layer, while PT increased species diversity of herb layer. There was no difference in soil bulk density, total potassium, and total phosphorus across different forest management modes. UP, PT, MO, and AC significantly reduced the concentrations of available phosphorus, total nitrogen and available potassium. UP and MO evidently increased soil pH. UP, PT, and AC decreased soil water content, while MO reduced organic matter content. Moreover, available phosphorus, soil water content, soil pH, total nitrogen and available potassium significantly affected species diversity of herb layer, while available phosphorus, available potassium and total nitrogen affected species diversity of shrub layer. Our results demonstrate that ecological effects differed among forest management modes of poplar plantations. Except CK, all forest management modes significantly reduced the contents of soil available phosphorus, total nitrogen, and available potassium. The change of understory species diversity in poplar plantations could be explained by the change of soil available phosphorus, total nitrogen, and available potassium.

    Variations of NDVI during main growing season in the Loess Plateau under climate change.
    WANG Jing-shu, BI Ru-tian, HE Peng, XU Li-shuai, LIU Zheng-chun, CAO Chen-bin
    2023, 42(1):  67-76.  doi:10.13292/j.1000-4890.202301.014
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    Understanding the responses of vegetation to climate change is crucial for predicting changes in ecosystem processes and developing adaptive strategy. In this study, we analyzed the spatial variations of normalized difference vegetation index (NDVI) of different vegetation types in the Loess Plateau in the main growing season from April to October of 2002 to 2019 and its relationship with meteorological factors using geographical detector model and geographically weighted regression. Affected by the fulfillment of “Grain for Green Program”, vegetation coverage on the Loess Plateau had been significantly improved, but the NDVI of steppe and desert were unstable due to their high sensitivity to environmental changes, especially in the summer. Increased sunshine duration indirectly led to the decrease of precipitation, which had a strong photoinhibition effect. The coefficient of variation of sunshine duration had the greatest explanatory power (0.124) for the spatial variation of vegetation NDVI in the Loess Plateau. Deserts in the northwest arid area of the Loess Plateau were affected by altitude, with low air pressure and large water vapor evaporation, which inhibited plant photosynthesis and was positively correlated with the variation of vegetation. In summer, precipitation increased sharply in desert, and the response of vegetation to temperature change slowed down, showing the hysteresis of NDVI change in response to the changes of temperature. From August to October, the sensitivity of high vegetation coverage of broadleaved forests to water stress decreased, resulting in a time lag in the responses to precipitation.

    Calcium carbonate content in the constructive plant species at different succession stages in steppe-desert ecotone of Ningxiang.
    ZHANG Jia-yue, HE Xing-dong, XIE Shu-qing
    2023, 42(1):  77-82.  doi:10.13292/j.1000-4890.202301.016
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    Amorphous calcium carbonate is of importance to plant growth. The characteristics of amorphous calcium carbonate content in the main constructive plant species in the steppe-desert ecotone are not clear. In this study, we measured the contents of calcium carbonate in leaves of constructive species in Ningxia Habahu National Nature Reserve and Hongsipu District of Wuzhong City of Ningxia. The results showed that the contents of calcium carbonate significantly varied across different herbaceous species, but not among shrub species. As for the herbaceous species, the content of calcium carbonate decreased gradually with succession stages, from the early successional species (Agriophyllum squarrosum and Salsola collina), to the middle successional species (Aneurolepidium dasystachys and Pennisetum centrasiaticum), and to the late successional species (Stipa bungeana and Cleistogenes squarrosa). The content of calcium carbonate in the constructive species at the late succession stage of typical steppe was significantly higher than that in the late succession stage of desert steppe. The content of calcium carbonate in the leaves of Artemisia ordosica at the young stage was significantly higher than that at the adult and old stages. There was no significant difference in calcium carbonate content in the leaves of different canopy positions for three leguminous shrub species, Ammopiptanthus mongolicus, Caragana microphylla, and Amorpha fruticose. We conclude that the significant change of calcium carbonate content in herbaceous species at different succession stages in steppe-desert ecotone is the result of long-term adaptation to the environment.

    Selection of greening plant species in the South Mountains of Lanzhou based on hydrogen and oxygen stable isotopes: A case study of Caragana.
    YANG Ye, ZHANG Ming-jun, ZHANG Yu, QU De-ye, WANG Jia-xin, XIAO Han-yu, YAO Xu-yang, TIAN Yuan-yuan
    2023, 42(1):  83-90.  doi:10.13292/j.1000-4890.202301.017
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    The ecological restoration applicability of plant species is of great significance to the selection of greening species. Based on hydrogen and oxygen stable isotope technique, we qualitatively analyzed the differences of water sources in growing season between two Caragana species (C. stenophylla and C. korshinskii) in similar habitats in the South Mountains of Lanzhou by using direct comparison method and Bayesian mixing models (MixSIAR). The results showed that the two species of Caragana have multiple water-absorbing layers and are non-single water source plants. The main water absorbing layer of C. stenophylla varied across different months in growing season. Except for September, the main water source of C. korshinskii was the medium-deep aquifers (70-130 cm), which contributed to more than 80%. C. stenophylla preferred to use surface soil water (0-30 cm) after rainfall, but C. korshinskii was not sensitive to rainfall. The main water absorbing layer of C. korshinskii was relatively stable. C. stenophylla can change the main absorbent layer in response to drought stress, indicating a more flexible strategy and strong ability to adapt to drought. Therefore, C. stenophylla has better applicability for ecological restoration.

    Climatic suitability regionalization of fruit apricot in Chinese mainland based on the MaxEnt model.
    ZHU Jing-yi, WANG Pei-juan, JIANG Hui-fei, TANG Jun-xian, E You-hao, YANG Jian-ying, HUO Zhi-guo
    2023, 42(1):  91-98.  doi:10.13292/j.1000-4890.202212.013
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    To identify the dominant environmental factors affecting the potential distribution of fruit apricot cultivation, we collected the distribution data of fruit apricot cultivation in Chinese mainland and daily weather data from 2303 weather stations from 1981 to 2020. We selected several natural factors affecting the potential distribution of fruit apricot cultivation, including heat condition, water supply condition, sunshine duration condition, tolerance to extreme weather/disaster, and topographic condition. The Maximum Entropy (MaxEnt) model and GIS technology were jointly used. By using natural break point classification method, the suitability of climate regions for fruit apricot cultivation was divided into four grades: unsuitable, subsuitable, suitable, and optimal. The threshold values of dominant environmental factors for each suitability grade were determined. The results showed that annual precipitation, altitude, probability of spring frost, and mean temperature of the coldest month were the dominant environmental factors affecting the potential distribution of fruit apricot cultivation in Chinese mainland. The suitable areas for fruit apricot planting were mainly concentrated in North China, Loess Plateau, Northwest China, and Southwest China, which is consistent with current geographical locations with successful fruit apricot cultivation. The optimal areas for fruit apricot cultivation were mainly distributed in the Loess Plateau, along the Ancient Yellow River Course, and the Bohai Bay area. Our results can provide a scientific basis for rational apricot cultivation planning in China.

    Effects of organic substitution of chemical fertilizers on soil organic carbon and microbial community in continuous cropping peanut fields. 
    GAO Xin, ZHAO Xue-song, ZHAO Feng-yan, GAO Chuan-jun, FENG Liang-shan
    2023, 42(1):  99-107.  doi:10.13292/j.1000-4890.202212.008
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    To reveal the microbial mechanisms of soil organic carbon (SOC) accumulation in continuous peanut cropping fields under organic substitution of chemical fertilizers, we carried out a five-year experiment with the treatments of vermicompost combined with chemical fertilizer (VM), bio-organic fertilizer combined with chemical fertilizer (BF), total-chemical fertilizer (CF) and no-fertilizer control (CK) in a continuous peanut cropping field. The composition and diversity of soil microbial community were tested by the phospholipid fatty acid method (PLFA). The contents of SOC and its components, peanut yields as well as the relationships between organic substitution, SOC and soil microbial community were analyzed. The results showed that the continuous peanut cropping seriously deteriorated soil environment and peanut yield, whereas the partial replacement of chemical fertilizers with organic fertilizers significantly increased the contents of SOC and its components and soil microbial biomass, changed the composition and diversity of soil microbial community, and enhanced peanut yield, with the most significant effect in the VM treatment (P<0.05). Compared with CK, the peanut yield of VM treatment increased by 56%, the SOC content and the total PLFA content increased by 11.4% and 149.4%, respectively. The results of redundancy analysis and stepwise regression analysis showed that VM and BF treatments were positively associated with the contents of SOC and its components and the PLFA contents of various soil microbial groups, especially in the VM treatment (P<0.05). The CK and CF treatments were negatively associated with all response variables except G+/G- ratio. The contents of SOC components were significantly correlated with the PLFA contents of various soil microbial groups. In conclusion, the organic substitution of chemical fertilizers induced increase of exogenous organic carbon and subsequent changes in soil microbial community which were the driving factors for SOC accumulation, and soil microbial activity was the key factor affecting SOC accumulation. Partial replacement of chemical fertilizers by organic fertilizers, especially vermicompost, is an effective strategy to improve soil quality in continuous peanut cropping fields and alleviate the obstacles in continuous cropping.

    Effects of Ulva prolifera outbreak on diversity of phosphate-solubilizing bacteria in rhizosphere of Suaeda salsa in intertidal zone.
    GAO Meng, GUO Xiao-hong, CONG Yong-ping, LI Shu-rong, WANG Yan, LI Ya-ting, WU Nan
    2023, 42(1):  108-114.  doi:10.13292/j.1000-4890.202212.003
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    We investigated the effects of Ulva prolifera outbreak on growth characteristics of Suaeda salsa in Weihai, Shandong during the extinction period of U. prolifera in October 2019. We analyzed diversity of phosphate-solubilizing bacteria community in rhizosphere soil of S. salsa by Illumina Miseq high-throughput sequencing. The results showed that after the outbreak of U. prolifera, water content and electrical conductivity of S. salsa rhizosphere soil covered by U. prolifera were significantly higher than those of uncovered by U. prolifera. Plant height and root length of S. salsa covered by U. prolifera were significantly lower than those of uncovered. The outbreak of U. prolifera did not affect richness of phosphate-solubilizing bacteria community of S. salsa rhizosphere, but affected its evenness and increased the community diversity. Compared with normally growing S. salsa, the abundance of phosphate-solubilizing bacteria including Proteobacteria, Actinobacteria, Labrenzia, Mesorhizobium, Pseudomonas, Rhodobacter,Xanthomonas and Streptomyces were all different in the rhizosphere soil of S. salsa covered by U. prolifera. Available potassium, available phosphate and alkali-hydrolyzed nitrogen were significantly positively correlated with the diversity of phosphate-solubilizing bacteria. Our results provided a basis for revealing the mechanism for driving the effect of U. prolifera outbreak on rhizosphere functional microbial diversity of dominant halophytes in coastal wetlands.

    Soil geochemistry characteristics and ecological risks in critical zones of different lithologic backgrounds.
    ZHANG Qian, HAH Gui-lin
    2023, 42(1):  115-122.  doi:10.13292/j.1000-4890.202212.004
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    We compared the distribution and influencing factors of heavy metals and rare earth elements in soils of Chenqi catchment in Puding, Guizhou and Jiulong River catchment in Fujian, China, and investigated the geochemical cycling processes and environmental effects of soil elements in both Earth’s critical zones. The results showed that Cr, Zn, Ni, Cu, and Pb contents in topsoils from Puding were higher than that from Jiulong River catchment, which were mainly associated with the leaching and geological background of the catchments. The contents of most heavy metals in cropland, shrub land, and abandoned cropland were higher than that in grassland and secondary forest in Puding, while the contents of some heavy metals in abandoned tea plantation were higher than that in forest in Jiulong River catchment. This may be related to atmospheric deposition and agricultural activities. The contents of rare earth elements in Puding soils (145-248 mg·kg-1) were higher than that in Jiulong River catchment (51-173 mg·kg-1), which was attributed to the formation process of karst soil in Puding and parent rock in Jiulong River catchment. Results of the ecological risk analyses showed low ecological risk in Puding soils and forest soils in Jiulong River catchment, while moderate ecological risk occurred in abandoned tea plantation in Jiulong River catchment, with a high ecological risk of Cd.

    Cadmium accumulation in different rice varieties based on quantitative evaluation method.
    CHEN Zhi-qin, LIU Qi-zhen, ZHANG Shi-jun, LU Li-min, LU Ping, JIN Hai-yang, HUANG Lu-lu, YANG Xiao-e
    2023, 42(1):  123-130.  doi:10.13292/j.1000-4890.202212.005
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    The high-yielding and Cd resistant cultivars have great implications for ensuring food security. In this study, the screening process on eighteen rice cultivars were carried out in the moderately and slightly Cd-contaminated field through a comprehensive quantitative evaluation (CQE) method. We considered differences in yield, Cd uptake, transfer factor (TF), and accumulation in cultivars with different weights for these evaluation indices. The results showed that JR-9 (Hu Xiangjing 106), JR-2 (Hu Zaoxiang Ruan-1), JR-7 (8333), JR-15 (Baonong 34) and JR-8 (Nan Jing 9108) exhibited high-yield and low-Cd-accumulation as assessed by the CQE method. JR-8 showed the maximum yield, followed by JR-9, JR-7, and JR-15 compared to the other cultivars. The Cd contents varied in different rice cultivars, with lower contents in the JR-9, JR-15 and JR-7 than the other cultivars. JR-2 showed the lowest TF value and the highest straw Cd accumulation, thus representing high-yield and low-Cd-accumulation rice cultivar. The CQE method can scientifically evaluate high-yield and low-Cd-accumulation rice cultivars. The five rice cultivars screened out in this study can be recommended as low Cd accumulation cultivars for moderately and slightly Cd contaminated croplands to fulfill the national food safety limit standard for Cd contents in rice.

    Succession characteristics of phytoplankton functional groups and water quality evaluation in Wuchang Lake.
    LIU Lu, LI Xue-mei, MENG Zi-hao, CHEN Kang, HU Fei-fei, ZHU Yong-jiu, YANG De-guo
    2023, 42(1):  131-139.  doi:10.13292/j.1000-4890.202301.011
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    To explore the characteristics of phytoplankton functional groups and assess their influencing factors in Wuchang Lake, water samples were quarterly collected from December 2019 to October 2020. The composition and succession characteristics of phytoplankton functional groups were analyzed. Canonical correspondence analysis (CCA) and variance partitioning analysis were used to assess the key driving environmental factors. Water quality was evaluated by assemblage index (Q) and trophic level index (TLI). The results showed that 343 phytoplankton species from nine phyla were detected in Wuchang Lake. According to the functional group classification, phytoplankton could be divided into 25 functional groups, among which 18 (A, B, D, P, MP, T, TB, S1, SN, X3, Y, E, H1, J, LO, M, W1 and W2) were the dominant functional groups. The seasonal succession of dominant functional groups was P, E (winter) → W1, MP (spring) → D, LO (summer) → D (autumn). CCA results showed that environmental variables played an important role in the succession of phytoplankton functional groups. Depth, water temperature, electrical conductivity, transparency, total nitrogen, ammonium nitrogen, nitrate nitrogen and nitrite nitrogen were the main environmental factors. The Q value of different seasons was summer (2.28) < spring (2.30) < autumn (2.67) < winter (3.02), indicating lake water quality was in a mediumgood range. The TLI value of different seasons was winter (59.85) < autumn (59.91) < summer (62.12) < spring (65.74), indicating the lake was at a state of light-moderate eutrophication. The two evaluation results showed that water quality was better in winter. The changes in phytoplankton functional groups could reveal the succession characteristics of phytoplankton community and reflect the state of water environment in Wuchang Lake, which will be instructive for lake water quality evaluation and ecological protection.

    Differences in muscle nutrients between wild and cultured populations of Brachymystax lenok tsinlingensis.
    LI Ping, QI Xi-rong, XIA Ji-gang, CAO Su-jie, SHEN Hong-bao, LIU Qi-gen
    2023, 42(1):  140-145.  doi:10.13292/j.1000-4890.202212.021
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    Brachymystax lenok tsinlingensis (wild population) is one of the national class Ⅱ protected aquatic wild animals. To understand the differences of traits between wild and cultured populations and distinguish wild population from the cultured population, we investigated the differences in muscle nutritive components between wild and cultured populations. The results showed that there were significant differences in muscle general nutrient composition, fatty acid composition and content, mineral and micronutrient contents between both populations, but no difference in the composition and content of amino acids. Water, crude protein, and crude ash contents in the muscle of the wild population were significantly higher than those of the cultured population (P<0.05), while crude fat content in the cultured population was significantly higher than that in the wild population (P<0.05). C12:0 was detected only in the wild population. The contents of saturated fatty acid, monounsaturated fatty acids and polyunsaturated fatty acids were significantly lower in the wild population than in the cultured populations (P<0.05). The contents of K, Na, Ca, Mg, P, and Zn were significantly higher in the wild population than in the cultured population (P<0.05). In conclusion, the composition and content of fatty acids, minerals, and micronutrients in muscle were significantly different between the wild and cultured populations, which could be used as a basis for identification of wild and cultured populations, and provide a reference for the conservation and management of B. lenok tsinlingensis.

    Changes of physiological metabolism and enzyme activities of Crassostrea sikamea under long-term starvation.
    WANG Jie, LI Xue-ying, CHEN Qi-yi, ZHANG Yang, TANG Bao-jun
    2023, 42(1):  146-151.  doi:10.13292/j.1000-4890.202301.007
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    To clarify the physiological and metabolic responses of Crassostrea sikamea under long-term starvation stress, we measured oxygen consumption rate, ammonia excretion rate and activities of lactate dehydrogenase, succinate dehydrogenase, pyruvate kinase, superoxide dismutase, alkaline phosphatase and lysozyme in hepatopancreas after long-term starvation (0-80 d) and refeeding (90-118 d). The results showed that oxygen consumption and ammonia excretion rate of C. sikamea decreased significantly under long-term starvation (P<0.01). With the prolongation of starvation, the activities of lactate dehydrogenase, succinate dehydrogenase, pyruvate kinase, superoxide dismutase, and alkaline phosphatase in C. sikamea showed a trend of fluctuating decline, while lysozyme activity showed a trend of fluctuating rise. After refeeding, oxygen consumption and ammonia excretion rate of C. sikamea significantly increased (P<0.01). Long-term starvation may damage the metabolism and immune functions of C. sikamea, and C. sikamea, and they respond to long-term starvation stress by reducing metabolic rate and metabolic enzyme activities. Our results provide a reference for the study of metabolic regulation mechanism of marine shellfish under starvation stress.

    Occurrence of dominant pests on chrysanthemum seedlings in Kunming.
    PENG Xiao-qin, WANG Yue, TU Yan-fang, LI Yi-ru, PU Xiao-mei, CHEN Guo-hua, CHEN Zhi-xing, ZHANG Xiao-ming
    2023, 42(1):  152-159.  doi:10.13292/j.1000-4890.202212.006
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    To clarify the occurrence pattern and seasonal dynamics of dominant pest insects, a five-point sampling method was used to investigate the dominant pests on chrysanthemum seedlings in greenhouse from 2018 to 2020 by using sticky board. The main occurrence periods of chrysanthemum pest insects were divided by quartile method. Meanwhile, the occurrence pattern, seasonal dynamics and temporal niche of the dominant pest insects were also analyzed. The results showed that Frankliniella occidentalis damaged chrysanthemum seedlings for most of the year. The main occurrence period was from April to August and peaked in May, June and July. Population size of  F. occidentalis  was 636, 1411, and 256 individuals per sticky board  in main occurrence period, respectively. The niche width of F. occidentalis decreased with the year. The ecological niche width of Phytomyza syngenesiae was relatively small, the damage mainly occurred from January to June, and the main occurrence period was from March to June. The occurrence peaked in March during the three years, with the population size of P. syngenesiae being 256, 239, and 124 individuals per sticky board, respectively. The niche width of Myzus persicae and Trialeurodes vaporariorum was larger than that of F. occidentalis and P. syngenesiae in the three years, indicating that M. persicae and T. vaporariorum could hold longer occurrence time than other pests; the main occurrence period was from February to April, and the peak occurrence date was not fixed throughout the year. The similarity of niche overlap indices among the four species of pests indicated that they were similar and competitive in the temporal dimension of their occurrence. Therefore, the control of dominant pest insects on chrysanthemum seedlings should be focused on F. occidentalis from March to October and P. syngenesiae from January to June.


    Heat island characteristics and influencing factors of urban agglomerations in the Yangtze River Economic Zone based on GEE.
    YIN Yu-xin, ZHANG Hua, AN Hui-min, LEI Jin-ping, LI Ming, SONG Jin-yue, HAN Wu-hong
    2023, 42(1):  160-169.  doi:10.13292/j.1000-4890.202212.009
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    Remote sensing technology can objectively and quantitatively evaluate the spatial and temporal variations of surface urban heat island intensity. Analyzing the influencing factors of urban heat islands could provide effective scientific references for urban ecological construction. Based on the GEE (Google Earth Engine) platform, we estimated the surface urban heat island intensity in the Yangtze River Economic Zone from 2003 to 2019 using long time series of MODIS satellite data. We evaluated the ecological environment using urban thermal field variance index, and analyzed the causes of urban heat islands using geographical detectors. The results showed that mean annual temperature of the five urban agglomerations in the Yangtze River Economic Zone during 2003-2019 was 22.78 ℃, with 23.91 ℃ on daytime, 7.59 ℃ at nighttime, and an overall increasing trend of 0.02, 0.02 and 0.006 ℃·a-1, respectively. The five urban agglomerations in the Yangtze River Economic Belt had the highest proportion of heat island free during 2003-2019, followed by weak heat islands and weak cold islands, and the lowest proportion of strong heat islands. The urban heat island effect showed a decreasing trend throughout the year, during the day, and at night. The overall environmental quality of the Yangtze River Economic Zone was excellent. Geographic detector for factor detection showed that DEM, land-cover type, and O3 were the main drivers for surface urban heat island effect in the Yangtze River Delta urban agglomeration. Evapotranspiration, ultraviolet aerosol index, and population density were the main controlling factors of surface urban heat island effect in the middle reaches of the Yangtze River urban agglomeration. Normalized difference vegetation index, nighttime light index, and land-cover type were the main controlling factors for surface urban heat island effect in the Chengdu-Chongqing urban agglomeration. Normalized difference vegetation index, DEM, and CO were the main controlling factors of surface urban heat island effect in the central Guizhou urban agglomeration. Evapotranspiration, O3 and normalized difference vegetation index were the main controlling factors of surface urban heat island effect in the central Yunnan urban agglomeration.

    Temporal variation of PM2.5 and air anion concentration in urban park greenspace of  arid and semi-arid area.
    BAO Hong-guang, YAN Xiao-yun, HOU Xiu-juan, WANG Bo
    2023, 42(1):  170-179.  doi:10.13292/j.1000-4890.202212.007
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    We observed PM2.5 and negative air ion concentration in five different vegetation configuration structures and the entrance to the west side of the park (hard pavement, control site (CK)) in Chilechuan Park, Hohhot City. The observation was carried out at 07:00-19:00 across different seasons from 2020 to 2021, under sunny and partly cloudy weather conditions. We analyzed the change characteristics, influencing factors and interactive effects of pollution and negative air ions in the park. The results showed that PM2.5 concentration of different configuration structures was the highest in autumn and the lowest in summer. The diurnal variation curve in spring showed a downward trend, with a “double peak and double valley” pattern in summer and winter, and a “single peak and single valley” pattern in autumn. In different seasons in the park, the daily variation of PM2.5 concentration in sites of different vegetation configuration structures could reach or surpass the ambient air quality level II standard. Except for spring, the concentration of negative air ions at different sites with different vegetation configuration structures in various seasons was higher than that of the CK. The daily change of negative air ion concentration in spring and summer was roughly in a pattern of “low at noon, high in the morning and evening”, but a fluctuating trend in autumn and winter. The air ion evaluation index (CI) values of different seasons in the park were summer>autumn>winter>spring. The mean evaluation grades were all within the range of moderate (III) and allowable (IV) concentrations. The CI value of sites with multi-layer configuration structure was higher in different seasons. The correlation between negative air ion and PM2.5 concentrations was different among seasons. The concentration of PM2.5 was most significantly affected by air pressure, followed by temperature and relative humidity. The concentration of negative air ions was affected by wind speed, temperature, relative humidity and PM2.5 concentration in different seasons, respectively.

    Spatiotemporal variations and scenario simulation of habitat quality in a typical basin of the Three Gorges Reservoir Area.
    GOU Meng-meng, LIU Chang-fu, LI Le, XIAO Wen-fa, OUYANG Shuai, WANG Na, HU Jian-wen
    2023, 42(1):  180-189.  doi:10.13292/j.1000-4890.202301.013
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    Rapid socioeconomic development has greatly altered regional land use patterns, habitat quality, and biodiversity. Accurately assessing and predicting spatiotemporal variations and future development trends of habitat quality is therefore essential for regional biodiversity protection and sustainability. Based on land use data of 2000, 2010, and 2018, we analyzed spatiotemporal variations of land use and habitat quality in the Daning River Basin of the Three Gorges Reservoir Area. We further simulated the patterns of land use and habitat quality in 2034 under three scenarios (natural development, economic priority, and ecology protection) by applying a land use simulation model. The results showed that the area of paddy field, dryland, and grassland had decreased from 2000 to 2018, while that of forest, urban land, rural residential area, and other construction land displayed an increasing trend, indicating a pattern of land use change with the coexistence of urban construction and ecological restoration. Habitat quality showed a trend of decreasing first and then increasing. The entire pattern was relatively stable from 2000 to 2018, but habitat quality for the local areas tended to be decreased and a polarization trend was obvious. In the future scenarios, habitat quality in 2034 would vary in the following order: ecology protection>natural development>economic priority. In the ecology protection scenario, both the local and entire habitat quality would be significantly improved. Thus, future biodiversity protection and regional sustainability planning should pay more attention to coordinating the relationship between economic development and ecological protection.

    Spatial and temporal characteristics and ecological impacts of nitrogen dry deposition in the Danjiangkou Reservoir.
    WU Li, SONG Bai-hui, LI Xiao-lin, WANG Hai-po, ZHAO Tong-qian, WANG Zu-heng
    2023, 42(1):  190-197.  doi:10.13292/j.1000-4890.202301.008
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    Nitrogen deposition is a vital pathway for the input of exogenous nitrogen into reservoir waters, which has a direct effect on aquatic ecosystems. By collecting 162 atmospheric nitrogen dry deposition samples from the Xichuan area of the Danjiangkou Reservoir, we analyzed the characteristics of nitrogen dry deposition fluxes, the contribution of typical agricultural periods to nitrogen deposition, and potential ecological impacts. The results showed that the nitrogen dry deposition flux was 22.60 kg N·hm-2·a-1 and that organic nitrogen deposition accounted for approximately 50.8% of the total nitrogen deposition fluxes. The dry deposition was dominated by organic nitrogen deposition. The nitrogen dry deposition fluxes were higher in the northeast and southwest regions than that in the north and southwest regions of the reservoir. Fluxes of total nitrogen, organic nitrogen, and urea deposition were higher in spring and autumn than in summer and winter. Seasonal characteristics were related to nitrogen source, agricultural production activities, and meteorological factors. The mean value of monthly nitrogen dry deposition during the typical agricultural period was 1.75 times higher than that during the atypical agricultural period. The contribution of agricultural activities to the total deposition could not be ignored. Atmospheric nitrogen dry deposition flux was 2.26 times that of the critical load of total nitrogen deposition from nutrients in lakes in China and was associated with the potential risk of water eutrophication. Given that agricultural activities significantly affect nitrogen deposition, attention should be paid to the effects of typical agricultural activity periods on aquatic ecosystems.

    Temporal and spatial distribution of forest fire and the dynamics of fire danger period in southern and northern China: A case study in Heilongjiang and Jiangxi provinces.
    ZHU He, ZHANG Zhen, YANG Song, ZHU Zhong-pan, ZENG Ai-cong, GUO Fu-tao
    2023, 42(1):  198-207.  doi:10.13292/j.1000-4890.202301.015
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    Fire is a critical disturbance factor in forests, with consequences on ecosystem structure and function. Based on the satellite fire point data in Heilongjiang and Jiangxi provinces of China from 2005 to 2017, we analyzed the spatial-temporal variations of fire occurrences and fire risk period using Mann-Kendall test and sliding test methods. The annual variation of forest fire occurrences in both provinces showed a trend of first rising and then falling. The mutation year of forest fire occurrences in Heilongjiang was around 2011 and that in Jiangxi was around 2016. The statutory fire risk period in Jiangxi was more reasonable than that in Heilongjiang. Forest fire in Heilongjiang mainly occurred in spring and autumn. The occurrence period of forest fire in spring shifted to early spring, and the occurrence period of forest fire in autumn shifted to summer and extended, the mutation years of spring, summer, and autumn were 2010, 2014, and 2011 respectively, and there was no mutation year in winter. Forest fire in Jiangxi mainly occurred in winter, the occurrence period of forest fire tended to shift to winter and shortened, and the mutation years of spring, summer, autumn and winter were around 2010, 2015, 2014 and 2016, respectively. The density of forest fires in both provinces showed an opposite increasing trend in the spatial perspective. In Heilongjiang, the density of forest fires increased from southeast to northwest, dominantly distributed in Heihe (a northern city of the province) and Daxinganling (a northwest part of the province). In contrast, the density of forest fires increased from northeast to southwest in Jiangxi, concentrated in Ganzhou (a southern city of the province) and Ji’an (a southwest city of the province). The overall number of forest fires showed a downward trend in both provinces. The number of forest fires in Daqing, Jiamusi and Daxing’an Mountains in Heilongjiang had a significant downward trend, while the number of forest fires in Yichun and Jixi during the statutory fire danger period was on the rise. This study demonstrated the temporal and spatial variations of forest fires in two provinces located in north and south China and the shifts of fire risk period in both provinces. These findings can provide support for revealing forest fire impacts on regional environment and effective management of forest fires.

    Research progress of vegetation status, adaptive strategies and ecological restoration in the water-level fluctuation zone of the Three Gorges Reservoir.
    DOU Wen-qing, JIA Wei-tao, ZHANG Jiu-hong, YI Xue-mei, WEN Zhao-fei, WU Sheng-jun, MA Mao-hua
    2023, 42(1):  208-218.  doi:10.13292/j.1000-4890.202301.018
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    Water-fluctuation zone of the Three Gorges Reservoir is a large area of “winter water and summer land” formed by the periodic submergence in the main and tributaries of the Yangtze River. Understanding the mechanisms underlying plant adaptation to flooding is important for restoration and protection of plant community in the water-level fluctuation zone of the Three Gorges Reservoir area. Here, we compare vegetation community changes before and after water fluctuation and summarized the mechanism of annual and perennial plants resisting submergence stress. Annual plants mainly rely on seed dormancy when they are exposed to submergence stress for a long time, while perennial plants may take the “static” strategy to reduce energy consumption and recover rapidly when water falls back. For perennial woody plants in the high altitude, a large number of adventitious roots emerge to alleviate root damage induced by the hypoxia stress in the case of semi-flooding. The research progress of vegetation restoration was summarized and the possible ways to reconstruct plant community of water-level fluctuation zone were discussed according to existing problems, which can provide reference for ecological restoration of vegetation in water-level fluctuation zone of the Three Gorges Reservoir.

    Research on ecosystem services in national parks: A review and outlook.
    XIE Jia-qi, XU Man, WANG Wei-han, YU Yi-na
    2023, 42(1):  219-227.  doi:10.13292/j.1000-4890.202301.023
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    National parks are natural areas that are established and managed by states or countries, designed to conserve natural resources and to provide well-being. There are many studies on the conservation, management and utilization of national parks. Ecosystem services derived from natural resources comprise an important foundation for human well-being. The analysis of the research advances of ecosystem services in national parks could provide reference for the development of China at this field and provide a theoretical basis for the establishment and management of natural reserve systems, including national parks. Focusing on the ecosystem services in national parks, we mainly review research progresses in five aspects: its relationship to biodiversity, the impacts from land use patterns and the underlying mechanisms, its responses and feedbacks to global climate changes, the quantitative assessments, and the tradeoffs of ecosystem services. We highlight the comprehensive, complex and heterogeneous characters of ecosystem services in national parks, and thereby propose that future works should be based on ecological theory, integrate social science, and strengthen the application of machine learning and spatial tools in the frameworks, methods and models in ecosystem services assessment. In the future, researches on the mechanisms underlying ecosystem services and the optimization of system models should be intensified comprehensively and broadly. Special attention should also be paid continuously on the dependency between ecosystem services of national parks and human well-being.

    Analytical error correction and data normalization in the determination of δ13C in plant and soil.
    WANG Jing, FAN Chang-fu, ZHANG Lin, QU Dong-mei, TIAN You-rong, WEN Xue-fa
    2023, 42(1):  228-236.  doi:10.13292/j.1000-4890.202301.004
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    Stable isotopic composition of carbon (δ13C) in plants and soil can indicate, trace, and integrate key processes and functions of carbon cycling. Dual-inlet and continuous-flow isotope ratio mass spectrometry (IRMS) are two techniques for determining δ13C of carbon-containing compounds. The precision and accuracy of analyzed data depends on analytical error and data normalization method. Analytical errors include memory effect, time drift and signal intensity-dependence effect, etc. The easiest method to eliminate or minimize the memory effect is to set up a measurement sequence ranging from low to high isotopic composition of the actual samples, or increasing the flushing time of the tube. A sufficient number of identical standards should be included with the measurement sequence, and the function of measurement time and analysis error of identical standards are used to correct time drift. Signal intensity dependence can be corrected by considering the impacts of blank effect and nonlinear response of instrument separately, with the blank effect considered first, and the nonlinear response of the instrument second. Data normalization strategy includes the selection of standards and normalization methods. The δ13C of selected standards should bracket the range of δ13C of samples. Based on the principle of identical treatment, the selected standards should share similar physical and chemical properties with the samples, and undergo the same analytical procedure. The number of selected standards should be ≥4, or the number of repeated determinations for each standard should be ≥4. The same set of standard materials should always be used for a particular element and be specific to an analytical technique. The measurement sequence should add quality control standard material to monitor the long-term accuracy of the analytical results.

    Robustness analysis of wetland ecosystem network models.
    HU Zi-xuan, HUA Jing, LI Yi-min
    2023, 42(1):  237-247.  doi:10.13292/j.1000-4890.202301.002
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    With the intensification of human activities in recent years, the structure and function of wetlands have been strongly disturbed and damaged. Understanding the changes of structure of wetland ecosystems after disturbance is of great significance to the conservation, management, and restoration of wetlands. We construct a network model of wetland ecosystem based on complex network related theory and ecosystem characteristics, and propose an evolutionary model of wetland ecological network structure considering overload and underload states based on the Shelford’s law of tolerance of organisms and the self-regulation ability of the ecosystem. The evolutionary process of an attacked ecological network structure is described in terms of initial load, load capacity, load redundancy range, and load redistribution, while robustness indicators are used to reveal the impacts of species on the robustness of wetland ecosystem after disturbance. For the Teacapan wetland ecosystem, numerical simulations revealed that the extinction of keystone species at different trophic levels had different degrees of impacts on ecosystem structure and robustness. The loss of key species in the primary producers (mangrove debris and material in the water) led to a rapid collapse of the Teacapan wetland ecosystem network structure and a rapid decline in ecosystem robustness index to zero, while the loss of key species in the consumers had less impacts on the fluctuation of ecosystem network structure and system robustness, and the ecosystem could reach a secondary equilibrium within a certain period of time. At this time, wetland ecosystem still has some ability to resist external disturbances. The results demonstrate the importance of mangrove detritus as a major food source supporting food chain, and provide a scientific reference for the conservation and ecological reconstruction of wetland ecosystems.

    Assessment of light-temperature adaptation of sugar beet based on gas exchange and OJIP photochemical parameters and screening of its identification indicators.
    LI Si-zhong, ZHANG Li-ming, LIN Ming, GAO Wei-shi, BAI Xiao-shan, LIU Jun, DONG Xin-jiu, SHA Hong, CAO Yu
    2023, 42(1):  248-256.  doi:10.13292/j.1000-4890.202301.024
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    High temperature and intense light are the most common abiotic stresses in summer, seriously threatening crop yield and fruit quality. To provide a theoretical basis for stress tolerant variety breeding and high yield cultivation of sugar beet, we explored the photosynthetic performance of different varieties under compound environmental constraints of high temperature and intense light, to screen out resistance indicators. The leaf photosynthetic performance of eight sugar beet varieties under the compound stress of strong light and high temperature was evaluated at the tuber expansion stage. A total of 26 indicators, including gas exchange and chlorophyll fluorescence kinetic parameters of sugar beet leaves, were measured. The stress tolerance of sugar beet under combined environmental constraints was comprehensively evaluated. The results showed that different sugar beet varieties responded differently to combined stresses of high temperature and intense light. The 26 indicators were transformed into four independent composite indicators by principal component analysis, covering 95% of the total data information. The eight sugar beet varieties were classified into three categories by using the membership function and cluster analysis. An optimal evaluation mathematical model for sugar beet tolerance to combined stress of high temperature and intense light was established by using stepwise regression analysis: D=0.745φEo-0.320 (D, the value of comprehensive evaluation of stress resistance; φEo, the quantum yield of absorbed energy used for electron transfer). φEo can be used as an auxiliary index to identify the strength of sugar beet varieties to tolerate combined stress of high temperature and intense light. Sugar beet varieties with strong tolerance to combined stress of high temperature and intense light have higher energy connectivity between photosystem II (PSII) units, higher photosynthetic electron transfer capacity between PSII and photosystem I (PSI), less damage to the activity of the oxygen release complex, and higher stability of PSII.