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    10 September 2021, Volume 40 Issue 9
    Quantitative classification and phylogenetic structure of vegetation in valley of the middle and upper reaches of Lancang River.
    ZUO Yan-jie, SHU Guo-biao, WANG Chong-yun, PENG Ming-chun, XIE Ying-xu, ZHANG Qiu-yuan, LI Fu-li
    2021, 40(9):  2665-2677.  doi:10.13292/j.1000-4890.202109.020
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    Lancang River valley, with unique history of geological evolution and the longitudinal change of ecological environment, provides an ideal place for understanding the differentiation and assembling process of plant communities. In this study, we comprehensively used the methods of TWINSPAN quantitative classification, community ordination, and phylogenetic structure analysis to elucidate the community characteristics and maintenance mechanisms of the valley vegetation in the middle and upper reaches of Lancang River. The results showed that: (1) According to TWINSPAN classification, plant communities in the middle and upper Lancang River valley were divided into 28 types. The result of the classification was similar to the DCA twodimensional ranking map. CCA and DCCA ordination showed that elevation was the major environmental factor affecting vegetation distribution. (2) Among the 28 community types, the average net relatedness index (NRI) value of 19 communities was greater than 0. The environmental filtering effect of river valley habitat was obvious. The phylogenetic structure of the plant communities generally showed an aggregation pattern. (3) Dryhot scrubs and drywarm scrubs had a narrow range in the river valley, including Ass. Buddleja crispa,Ass. Sageretia horrida+Sophora davidii,Ass. Elsholtzia capituligera +Caryopteris forrestii,Ass.Osteomeles schwerinaeGramineae sp., Ass. Elsholtzia fruticose +Artemisia gyitangensis,Ass. Vitex negundo f. laxipaniculata+Pistacia weinmannifolia. Community phylogenetic structure generally had a significant aggregation pattern (P<0.05). The phylogenetic structure of widespread plant communities, including Ass. Cyclobalanopsis glaucoides, Ass. Pinus yunnanensis, Ass.Picea likiangensisvar. rubescens, and Ass.Betula platyphylla, showed a significant divergent pattern (P<0.05). (4) Ass. Castanopsis delavayi+Quercus variabilis had the highest average of phylogenetic diversity (PD), but species abundance was not the highest. (5) Ten climatic and topographic factors could explain 40.8%, 38.59%, and 9.97% of the variation of species richness, PD and NRI, respectively. Environmental differentiation in the Lancang River valley was illustrated by numerical classification and ordination analysis of plant communities. Combined with the analysis of the phylogenetic structure, the environmental factors that lead to ecological differentiation of river valley vegetation were revealed, reflecting the diversity and complexity of the river valley habitats.
    Effects of Yellow River Diversion Project on vegetation in the northern margin of Kubuqi Desert.
    GU Xi-ling, GUO En-liang, YIN Shan, WANG Yong-fang, WAN Zhi-qiang, WANG Jun
    2021, 40(9):  2678-2688.  doi:10.13292/j.1000-4890.202109.037
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    Water diversion project is one of the effective ecological projects to alleviate desertification, reduce ice flood, and promote vegetation growth. In order to understand the impacts of water diversion project on vegetation in the northern edge of the Kubuqi Desert, based on Landsat 7/8, GF1/2, project water diversion amount and temperature and precipitation data, we analyzed the land cover types and vegetation spatiotemporal variations of the northern edge of the Kubuqi Desert with and without water diversion engineering measures using Sen’s slope, residual analysis, and two sample T test. We further discussed the contribution of temperature, precipitation and water diversion projects to NDVI changes. The results showed that annual maximum value of NDVI increased in the past 10 years. The NDVI value of 55% of the pixels showed an upward trend before 2015, while the number of pixels that showed an upward trend after 2015increased to 73%. After the implementation of water diversion project in 2015, grassland area increased from 25 km2 to 41.31 km2, and sandy land area reduced from 65.95 km2 to 17.73 km2. Results of the residual analysis showed that the area where human activities promoted NDVI accounted for 52.92%. The area with significant NDVI changes after human activities accounted for 78.00%. Precipitation before 2015 was the main driving force of NDVI changes, whereas water diversion projects were the dominant factor driving NDVI changes after 2015.
    Niche and interspecific association of the main tree species in Vatica mangachapoi communities in Ganshiling, Hainan Island, China.
    SHU Qi, XU Rui-jing, HU Xuan, SHANG Ze-an, QI Liang-hua
    2021, 40(9):  2689-2697.  doi:10.13292/j.1000-4890.202109.040
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    Vatica mangachapoiis a key species in the tropical rainforest of Hainan Island, playing an important role in the restoration and development of lowland rainforest in Ganshiling, Hainan Island, China. In order to elucidate the structural characteristics of Vatica mangachapoi community and reveal its restoration status, we examined the niche characteristics and interspecific association of 20 main tree species (as indicated by importance value). The results showed that the niche breadths of Vatica mangachapoi and Hopea reticulata were significantly wider than others. They were the constructive species in Ganshiling, Hainan Island. Only 71.05% of 190 pairs of main tree species had niche overlap. Their resource utilization was not adequate, which was conducive to the growth and development of other species and the restoration of species diversity. There was no significant correlation among main tree species, indicating that the interspecific competition tended to be gentle and that the community was at a stable and rapid recovery period. Resource utilization and the growth and development of Vatica mangachapoi in the community was the best. During community development and succession, Vatica mangachapoi would threaten the growth and development of H. reticulata, displaying a tendency to replace H. reticulata in the community. H. reticulata is an endemic species and also an important component in Ganshiling. To ensure the restoration of biodiversity, human disturbance should be properly applied during community restoration, and the genetic resources of species at a disadvantage in competition should be preserved in time. Our results provide theoretical basis for scientific conservation and rational utilization of tropical rainforest resources.
    Distribution characteristics and influencing factors of glomalin-related soil protein in the rhizosphere of common tree species in evergreen broadleaved forest of Lushan.
    2021, 40(9):  2698-2708.  doi:10.13292/j.1000-4890.202109.009
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    Forests in Lushan show obvious latitudinal zonality. The evergreen broad-leaved forest and evergreen and deciduous broad-leaved mixed forest are widespread in the central region of Lushan, with great significance in biodiversity and ecological services of Lushan. The dynamic of glomalinrelated soil protein (GRSP) is one of the important indices to evaluate and indicate soil quality. Exploring the distribution characteristics and influencing factors of GRSP would be helpful for the improvement of forest soil quality in Lushan. We collected rhizosphere soils of nine dominant tree species (Rhododendron simsii, Corylopsis sinensis, Lindera reflexa, Ligustrum lucidum, Ulmus pumila, Symplocos stellaris, Loropetalum chinense, Lindera glauca, Camellia cuspidate) on the north and south slopes of evergreen broad-leaved forest and evergreen and deciduous broad-leaved mixed forest in Lushan Nature Reserve. The colonization rate of arbuscular mycorrhizal (AM) fungi, spore density, total GRSP (T-GRSP) and easily extractable GRSP (EE-GRSP) contents were measured, and their relationships with soil physicochemical properties were analyzed. GRSP contents in rhizosphere were different among various dominant tree species. EE-GRSP (1.5 mg·g-1) and T-GRSP (5.45 mg·g-1) contents ofCorylopsis sinensis were the highest, while those (1.12 and 4.07 mg·g-1) of Symplocos stellaris were the lowest. However, there was no difference in the ratio between EE-GRSP and T-GRSP among all the examined tree species. T-GRSP content of the same tree species was significantly higher in the north slope than in the south slope (P<0.05). The ratios of T-GRSP and EE-GRSP to soil organic carbon were 13.08% and 3.62%, respectively. Such values for Corylopsis sinensis and Lindera reflexainin the south slope were significantly higher than that in the north slope (P<0.05). Moreover, the average colonization rate and spore density of AM fungi were 35.43% and 117.2 ind·10 g-1 (dry soil), respectively. In addition, GRSP contents were significantly positively correlated with total nitrogen, soil organic carbon, soil moisture, and colonization rate of AM fungi (P<0.01). The AM fungi colonization and GRSP distribution were detected in all the nine dominant tree species in Lushan. Moreover, GRSP content was closely related to multiple soil factors. These results indicate that GRSP can be used as an effective indicator to reflect forest soil quality in Lushan. Our findings supplement and improve the evaluation index system of forest soil in Lushan.
    Root exudation rate and rhizosphere effect of different mycorrhizal associations of tree species in typical black soil area.
    JIANG Zhi-yan, ZOU Qing-qin, YANG Liu, LI Wen-zhuo, ZHANG He-dong, CHEN Xiang-wei, WANG Xiu-wei
    2021, 40(9):  2709-2718.  doi:10.13292/j.1000-4890.202109.001
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    We examined root exudation rate and rhizosphere effect of four arbuscular mycorrhizal (AM;Amygdalus triloba, Acer negundo, Viburnum opulus subsp. calvescens, and Armeniaca sibirica) and three ectomycorrhizal tree species (ECM; Picea koraiensis, Betula platyphylla, and Pinus sylvestris var.mongolica), to determine the differences of different mycorrhizal associations of tree species and to evaluate their improvement on soil quality in the black soil at Keshan Farm in Heilongjiang, China. The results showed that root exudation rate of the seven tree species was significantly different (P<0.05), with that of the ECM tree species being significantly higher than that of AM tree species (P<0.05). The pH of Viburnum sargenti, Armeniaca sibirica andAcer negundo rhizosphere soil was 0.3%-5.9% higher than the bulk soil. In contrary, it was1.9%-5.1% lower in Amygdalus triloba, Picea koraiensis, Betula platyphylla, and Pinus sylvestris var.mongolica rhizosphere soil. Rhizosphere effects on soil total organic carbon (TOC), total nitrogen (TN), alkalihydrolyzed nitrogen (AHN), total phosphorus (TP), and available phosphorus (AP) in the rhizosphere soil of the seven tree species were 22.1%-250.4%, 9.9%-146.9%, 5.5%-23.8%, 3.8%-48.8% and 23.6%-189.1% higher compared to bulk soil, respectively. The rhizosphere effects of the ECM tree species on TOC, TN, and AHN were greater than that of the AM tree species, while that on soil TP and AP was lower than the AM tree species. Compared to the bulk soil, the abundance of bacteria and actinomycetes in the rhizosphere soil of the seven tree species was increased by 42.9%-309.6% and 13.3%-134.7%, respectively. The abundance of fungi in the rhizosphere soil of Armeniaca sibirica and Amygdalus triloba was decreased by 21.6% and 8.6%, respectively, but increased by 43.5%-215.4% in the rhizosphere soil of other tree species. The rhizosphere effect on the abundance of bacteria and fungi in the ECM tree species was greater than that of the AM tree species (P<0.05), while the rhizosphere effect on actinomycetes was not different between the AM and ECM species (P>0.05). The correlation among root exudation rates, microbial quantity, and soil chemical properties in AM species was significantly greater than that in the ECM species. The effect of ECM tree species on soil improvement was stronger than that of AM tree species.
    Effects of ectomycorrhizal fungi inoculation on growth and photosynthetic characteristics of Broussonetia papyrifera seedlings under drought stress.
    2021, 40(9):  2719-2726.  doi:10.13292/j.1000-4890.202109.005
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    Drought stress restricts plant growth in the Karst area of Guizhou. Ectomycorrhizal fungi can form mutualistic symbionts with the roots of most woody species, which can improve their drought tolerance. In this study, a pot experiment was conducted to evaluate the effects of ectomycorrhizal fungi inoculation on growth and photosynthetic characteristics of 1-year-old Broussonetia papyrifera seedlings under drought stress. There were six treatments, including singleinoculated with Pisolithus tinctorius (Pt), single-inoculated with Scleroderma polyrizum (Sp), single-inoculated with Pseudomonas fluorescens (Pf), mixed-inoculated with P. tinctorius and Pseudomonas fluorescens (Pt+Pf), mixed-inoculated with S. polyrizum and P. fluorescens (Sp+Pf), and non-inoculated (CK). B. papyrifera seedlings were subjected to three water treatments: normal water, moderate drought, and severe drought. Six months later after incubation, the growth and photosynthetic indices (including root infection rate, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, aboveground and belowground biomass) of B. papyrifera seedlings were measured. Results showed that root infection rate and root/shoot ratio increased significantly with decreasing water supply level, while net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate and plant biomass decreased significantly (P<0.05). The inoculation significantly affected infection rate, photosynthetic parameters, aboveground and underground biomass of B. papyrifera seedlings (P<0.05), but there were obvious differences among different inoculation methods. Compared with CK, single and mixed-inoculation treatments significantly promoted the symbiotic relationship between B. papyrifera and ectomycorrhizal fungi. The root infection rates of Pt+Pf and Sp+Pf were 9.7 and 5.9 times higher than that of CK, respectively. Mycorrhizal helper bacteria (Pf) showed a significant promoting effect on the colonization of Pt at root tips ofB. papyrifera. Compared with CK, shoot and root biomass of Pt+Pf, Sp+Pf and Pt increased significantly, and the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and transpiration rate of Pt+Pf and Sp+Pf also increased significantly. Inoculation of ectomycorrhizal fungi could therefore alleviate the impacts of drought stress on the growth and photosynthetic parameters of B. papyrifera seedlings, and mixed inoculation of ectomycorrhizal fungi and mycorrhizal helper bacteria could achieve stronger promotion effect than singleinoculation of ectomycorrhizal fungi.
    Characteristics of leaf litter decomposition of Ginkgo biloba L. exposed to elevated O3 concentration.
    WANG Nan, WANG Yi-jing, PING Qin, XU Sheng, LI Yan, HE Xing-yuan, CHEN Wei
    2021, 40(9):  2727-2736.  doi:10.13292/j.1000-4890.202109.010
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    To clarify the effects of elevated ozone (O3) concentration on leaf litter decomposition, we carried out a litterbag experiment and examined the decomposition rate and nutrient release of leaf litter of G. biloba L. exposed to ambient air (about 40 nmol·mol-1) and elevated O3 concentration (160 nmol·mol-1) using open-top chambers (OTCs). Leaf litter from 10-year-old G. biloba incubated under ambient air (about 40 nmol·mol-1) and elevated O3 concentration (160 nmol·mol-1) for one growing season was collected. There were four treatments: decomposing under ambient air for those incubated under ambient air (AA, control); decomposing under elevated O3 concentration for those incubated under ambient air (AE); decomposing under ambient air for those incubated under elevated O3 concentration (EA); decomposing under elevated O3 concentration for those incubated under elevated O3 concentration (EE). Compared with leaf litter incubated under ambient air, the contents of K, Mg, P, Ca, Mn, condensed tannins, lignin, and total phenols of litter incubated under elevated O3 concentration significantly decreased (P<0.05), while N content increased by 15.87% (P<0.01). After 195 days decomposition, compared with AA group, the decomposition of lignin was lower in AE group (P<0.05), while the release of C and N was higher, especially for those incubated under elevated O3 concentration (P<0.05). The remaining rates of lignin, C, and N in group AA were 25.22%, 41.29% and 75.68%, while those in group AE were 29.89%, 36.61% and 70.17%, respectively. Our results suggest that increasing atmospheric O3 concentration can indirectly affect carbon and nitrogen cycling of urban forest ecosystems by altering litter decomposition of main tree species.
    Radial growth characteristics of dioecious Populus purdomii at the high and low altitudes of Gongga Mountain.
    XIA Hong-xia, ZHANG Yue, FAN Yan-xin, DU Liu-shan, LEI Yan-bao
    2021, 40(9):  2737-2744.  doi:10.13292/j.1000-4890.202109.019
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    Populus purdomii, a typical dioecious plant species, is often used as a pioneer species in vegetation succession and ecosystem restoration. It is important to understand the response and adaptation characteristics of dioecious species to environmental changes under the background of global climate change. In this study, we examined the differences of radial growth of tree rings between male and female P. purdomii at high (2600 m, malebiased ratio) and low altitude (2000 m, balanced sex ratio) in Gongga Mountain, and analyzed the correlations between radial growth and climatic factors. The results showed that: (1) There was no significant difference in average annual radial growth and basal area increment (BAI) between male and female P. purdomii at 2000 m, whereas male P. purdomiiexhibited higher radial growth than female at 2600 m. (2) At low altitude, the BAI of male and female P. purdomii was positively correlated with the highest temperature in last October and February and the average temperature in current February, while negatively correlated with precipitation in current February. The negative correlation between BAI and relative humidity in different months was more frequently found in male P. purdomii than in female. (3) At high altitude, there were significantly positive correlations between BAI and average temperature in last December and current May to July in both genders, while no significant correlations of BAI with precipitation and Palmer drought severity index (PDSI) were found. Therefore, the gender specific radial growth of P. purdomiicould partly explain the skewed sex ratio pattern at different altitudes. This study provides a theoretical reference for predicting the dynamics of population size and spatial characteristics of dioecious plants under future climate change.
    The relationship between leaf dry mass and leaf area, leaf thickness of Hippophae rhamnoides under different light conditions in Taohe River riparian forest.
    TANG Yu-rui, ZHAO Cheng-zhang, ZHAO Hui, HOU Gang, MA Min, ZHAO Ting-ting, WANG Yu-fang, ZENG Hong-xia
    2021, 40(9):  2745-2753.  doi:10.13292/j.1000-4890.202109.014
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    The relationship among plant functional traits is a habitat adaptation strategy that can affect their ability to use space resource, reflecting pathways and mechanisms of plant adaptation. Using the method of standardized major axis (SMA) estimation, we examined the relationship between leaf dry mass and leaf area, leaf thickness of Hippophae rhamnoidesunder three natural habitat conditions in Taohe River riparian forest: full sun (I), gap (II), under canopy (III). The results showed that soil moisture gradually increased, and the photosynthetically available radiation (PAR) displayed decreasing trends with decreasing light availability. Population height, canopy closure, leaf area (LA), leaf thickness (LT), leaf dry weight (LDW), transpiration rate (Tr), and stomatal conductance (Gs) gradually increased, while specific leaf area (SLA) decreased with increasing shading. There were significant different growth relationships of leaf area, leaf thickness, and leaf dry mass of H. rhamnoides among three habitats (P<0.05). There was an allometric relationship between LDW and LT, but an isometric relationship between LDW and LA at habitat I. The increasing speed of LDW was greater than that of LT. The LDW was isometrically related to LA and LT at habitat Ⅱ. At habitat Ⅲ, there was a clear allometric relationship between LDW and LA and an isometric relationship between LDW and LT, with the growth rate of LA being greater than that of LDW. H. rhamnoides grown in the full sun habitat and under canopy habitat generally had small and thin, big and thick leaves respectively, reflecting an investment trade off among plant leaf functional traits in adapting to heterogeneous light environment.
    Comparison of cold resistance in root collar and different parts of root of Cabernet Sauvignon.
    CHEN Ren-wei, ZHANG Xiao-yu, YANG Yu, LI Fang-hong, FENG Rui, LI Hong-ying, WANG Jing, SU Yu-xian, DING Yong-ping
    2021, 40(9):  2754-2762.  doi:10.13292/j.1000-4890.202109.03
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    Winter freezing injury is one of main limiting factors restricting the development of wine grape cultivation in northern China, which seriously affects the growth, development, yield, and quality formation of wine grape in the northwest inland with soil buried for winter protection. As the necessary channel for exchanges of nutrient and water, root collar is located at the junction between aboveground and underground, as well as that of soil and atmosphere. Root collar is sensitive to environmental changes because it suffers drastic changes of temperature. In this study, we examined the cold resistance of the wine grape tree ‘Cabernet Sauvignon’ planted in the eastern foothills of Helan Mountain in Ningxia. Root collar, primary lateral root, secondary lateral root and fibrous root of wine grape tree were divided into upper, middle and lower parts, respectively. The supercooling point, freezing point, relative electrical conductivity and water content of roots were measured in the process of simulated natural low temperature freezing. The cold resistance of wine grape root neck and different parts of roots were evaluated by fuzzy membership function method and cluster analysis. There were significant differences in cold resistance among different parts. The cold resistance of root collar was the strongest. The cold resistance of upper part of the primary lateral root was stronger than that of the secondary lateral root. The cold resistance of the middle and lower part of the primary lateral root was similar to that of the corresponding part of the secondary lateral root. The cold resistance of fibrous root was the weakest. The upper part in root collar, primary lateral root, secondary lateral root and fibrous root showed the strongest cold resistance, followed by the middle part and the lower part. The results of cluster analysis showed that the tested roots could be divided into three categories: (1) the upper and middle part of the primary lateral root with strong cold resistance; (2) the lower part of the primary lateral root, the upper and middle part of the seco〖HJ*4〗nd lateral root, the upper and middle part of the fibrous root with moderate cold resistance; and (3) the lower part of the fibrous root with weak cold resistance. Our results are of great significance for monitoring, early warning anddefense of root collar and root winter freezing injury in wine grape.
    Seed germination characteristics of Spartina alterniflora from high and low latitude populations in relation to temperature
    WANG Xiu-yan, ZHOU Yu-peng, XUE Yu-fei, CHENG Jing-yang, LIU Wen-wen, ZHANG Yi-hui
    2021, 40(9):  2763-2772.  doi:10.13292/j.1000-4890.202109.007
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    Spartina alterniflora is distributed over 20 degrees (20°N to 39°N) of latitude after 40 years of deliberate planting and natural dispersal, which poses a serious threat to coastal and wetland ecosystems in China. Seed germination, a critical stage determining the invasion of S. alterniflora into different latitudes, is affected by temperature. Seed germination characteristics of S. alterniflora would be different at the high latitude and low latitude regions. We explored the response of seed germination of S. alterniflorapopulations from high and low latitude to temperature, with seeds from highlatitude provenance at Dongying (38.0°N) and low-latitude provenance at Leizhou (20.9°N). We measured the germination percentage, germination index, and mean germination time of S. alterniflora seeds under different temperatures (5, 15, 25 ℃). The results showed that: (1) Provenances significantly affected germination percentage and germination time (P<0.0001). Seeds from highlatitudinal provenance had higher germination percentage and longer mean germination time than of those from low-latitudinal provenance. (2) Within 5-25 ℃, rising temperature significantly promoted germination percentage and germination index (P<0.0001), shortened the mean germination time, and advanced the germination peak. (3) Temperature and provenance significantly interacted to affect germination percentage (P<0.001). The effect of temperature on germination characteristics might be due to the enhanced enzyme activity at higher temperature, which accelerated the germination process and altered germination characteristics. The difference of seed germination characteristics between highand low-latitudinal provenances indicated that S. alterniflora adapted to local climate of different geographical areas. Our results suggest that the risk of invasion and diffusion of S. alternifloraat high latitude is higher than that at low latitude.
    Effects of salt stress on root respiratory metabolism, antioxidant enzyme activities, and yield of oats.
    CHEN Xiao-jing, XU Zhong-shan, ZHAO Bao-ping, MI Jun-zhen, YAN Wei-kai, LIU Jing-hui
    2021, 40(9):  2773-2782.  doi:10.13292/j.1000-4890.202109.036
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    A field experiment was carried out in typical saline-alkali soils to examine the effects of salt stress on root growth, antioxidant enzyme activity, respiration metabolism at different growth stages and yield of oats of salt-tolerant cultivar “Bai 2” and salt-sensitive cultivar “Bai 5”. The results showed that under salt stress, total root respiration rate of Bai 2 and Bai 5 decreased first and then increased across the growth period. The respiratory rate of EMP pathway in Bai 5 was higher than that in Bai 2, and increased by 83.3%, 120.3%, 3.3% and 63.9% in tillering, jointing, heading and filling stage, respectively. TCA pathway respiration rate of Bai 2 was significantly increased by 88.9% compared with Bai 5 at heading stage, while PPP pathway respiration rate of Bai 2 was significantly increased by 48.1% compared with Bai 5 at tillering stage. SOD enzyme activity of Bai 2 was significantly higher than that of Bai 5 at the tillering stage, jointing stage and heading stage, being 2.2, 1.5 and 1.6 times, respectively. SOD enzyme activity of Bai 5 was significantly increased by 1.8 times compared with Bai 2 at the filling stage. POD enzyme activity showed a similar pattern of SOD. The dry weight, total root length, surface area, volume, and average diameter of Bai 2 were higher than those of Bai 5 at different growth stages. Under salt stress, the number of harvested ears of Bai 2 was significantly increased by 96.6% compared with Bai 5, the number of grains per ear was significantly increased by 21.6%, 1000grain weight was significantly increased by 9.6%, and grain yield was increased by 24.7% (P<0.05). In summary, the transformation of EMP-TCA pathway to PPP pathway of Bai 2 in the early stage of growth enhances its adaptability to salt stress. Compared with Bai 2, all the examined parameters of Bai 5 were much lower, resulting in lower yield.
    Effects of mixed cropping of rice cultivars on occurrence of Cnaphalocrocis medinalis and rice growth under different rice cropping patterns.
    ZHANG Hai-wei, JIANG Shuo-chen, KONG Pan, DU Bin, ZHU Jian-qiang
    2021, 40(9):  2783-2792.  doi:10.13292/j.1000-4890.202109.033
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    Cnaphalocrocic medinalis is one of the main pests in rice producing areas in China, and chemical control is usually used in practice. Chemical residues would have environmental consequences, particularly in the rice-crayfish symbiotic mode where chemical control increases the risk of healthy crayfish farming. It is necessary to explore and utilize biodiversity to control rice diseases and insect pests. Based on the rice-crayfish symbiosis mode and the traditional one-season medium rice mode, we conducted a field experiment of mixed cropping of different rice cultivars. During the experiment, we recorded the occurrence of Cnapalocrocis medinalis under single cropping of four rice cultivars (Y Liangyou 911, Huanghuazhan, Meixiangzhan 2 and Xiangyaxiangzhan) and mixed cropping of two rice cultivars (Y Liangyou 911 + Meixiangzhan 2, Meixiangzhan 2 + Xiangyaxiangzhan), and measured main indices of rice growth and metabolism. Compared with the rice-crayfish symbiotic mode, leaf rolling rate of rice was increased by 173.93% under the traditional medium rice mode. Plant height, tiller number, leaf area index (LAI), and aboveground dry matter weight (DW) were increased by 5.82%, 16.44%, 19.51% and 15.84%, respectively. Wax content, SPAD, and net photosynthetic rate (Pn) of leaves were increased by 11.09%, 3.36% and 6.50%, respectively. Effective panicle and rice yield were increased by 17.58% and 20.69%, respectively. Compared with rice monoculture, mixed cropping decreased leaf rolling rate, and increased tiller number, LAI, and DW. In mixed cropping of two rice cultivars that have great difference in silicon content, wax content, and Pn of the leaves, the aforementioned index values of the two mixed cropping cultivars were between their monoculture, but the SPAD value was usually lower than that of their monoculture. Under mixed cropping, the effective panicle number and grain number per panicle were between those of the two mixed cropping cultivars, but seed setting rate and 1000grain weight showed no difference. The effect of mixed cropping on yield varied with cultivar and environment. Our results suggested that mixed cropping of rice cultivars can be used as an effective means for green controlling of Cnaphalocrocis medinalis.
    Effects of mycotoxins ofUstilaginoidea virens on physiological-biochemical characteristics of different resistant rice varieties.
    FU Rong-tao, WANG Jian, CHEN Cheng, ZHAO Li-yu, CHEN Xue-juan, LU Dai-hua
    2021, 40(9):  2793-2801.  doi:10.13292/j.1000-4890.202109.021
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    To clarify the effects of the mycotoxins of Ustilaginoidea virenson physiological0biochemical characteristics of different resistant rice varieties, the susceptible variety 9311 and the resistant variety IR28 were treated with the crude toxin ofU. virens. The effects of toxin on the growth of radicle, germ, seedling stem and leaf, hypersensitive reaction of leaves, defense enzyme activity, soluble protein (SP) and esterase (EST) isozyme of seedling were analyzed. The results showed that the crude toxin of U. virens inhibited the growth of radicle, germ, seedling stem and leaf of resistant and susceptible varieties, with higher inhibitory effect of toxin on susceptible cultivar 9311 than cultivar IR28. The toxin caused hypersensitive reaction in leaves and disease symptom. Under the stress of toxin, the enzyme activities of SOD, POD, PAL and PPO of resistant and susceptible varieties increased by different magnitude compared with the control, and the peak value increased by 8.79%-34.29%. The activities of POD and PAL increased slowly at first, reached the peak along with the extension of toxin treatment time, and then decreased gradually. The activities of SOD and PPO decreased sharply at first and then increased slowly, reached the peak, and then decreased gradually. The activities of four enzyme of the resistant cultivar IR28 were higher than that of the susceptible cultivar 9311, with peak values being 17.85% to 58.30% higher. After treated with mycotoxins, the content of SP in rice seedlings decreased to some extent. The content of SP in cultivar IR28 was higher than that in cultivar 9311, and reached the highest at the fifth day, which was 51.37% higher in cultivar IR28 than cultivar 9311, and the color of SP band of IR28 was darker than that of cultivar 9311. In addition, the EST isozyme bands of the two cultivars became lighter along with the prolongation of treatment time, but the EST isozyme bands of cultivar IR28 were darker than those of cultivar 9311. This study provided scientific basis for the application of mycotoxins ofU. virens in identification and breeding for disease resistance cultivar.
    Effects of dry-farming rice on bacterial community diversity and the abundance of microsclerotia of Verticillium dahliae in soil of cotton fields
    LIU Hai-yang, NUERZIYA Ya-li-mai-mai-ti, WU Li-li, ZHANG Ren-fu, WANG Wei, YAO Ju
    2021, 40(9):  2802-2811.  doi:10.13292/j.1000-4890.202109.003
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    Clarifying the effects of dry farming of rice on bacterial community diversity and structure, and microsclerotia of Verticillium dahliae in the soil of cotton fields is of great significance to the improvement of ecological prevention and control technology of cotton Verticillium wilt in Xinjiang. The Illumina Miseq highthroughput sequencing platform was used to analyze bacterial diversity and community composition of rhizosphere soils, which were sampled from the cotton fields in July and October. The selective medium method was used to detect the changes in the abundance of microsclerotia of Verticillium dahliae in soil. The results showed that, at the 97% similarity level, ACE index, Chao1 index and OTU quantity of bacteria in rhizosphere soil-between dry-farming rice and cotton were more different in October than in July, but without statistical significance. The abundance and composition of the top 20 bacterial populations ranked by abundance changed greatly between July and October. The abundance of Rhizobium in rhizosphere soil of dry-farming rice (2.15%) was 10.8 times of that in cotton field (0.20%). Results of cluster analysis showed that the difference in bacterial community structure between the dry-farming rice and cotton rhizosphere soil became larger in October. According to LEfSe (LDA Effect Size) analysis, the rhizosphere soil of dry-farming rice was rich in three beneficial bacterial populations: Pseudonocardiaceae, Chryseobacterium, and Ensifer.The abundances of beneficial Pseudomonas, Lysobacter, and Rhizobium in the rhizosphere soil of dry-farming rice increased by 38.7%, 96.8%, and 1433% respectively in October than in July, while the abundances of Pseudomonas, Lysobacter, Bacillus, and Streptomyces in the rhizosphere soil of cotton decreased by 43.3%, 26.3%, 31.3%, and 32.0%, respectively. The relative abundance ratios of Pseudomonas, Lysobacter and Rhizobium in dry-farming rice and cotton rhizosphere soil significantly increased by 157.1%, 177.8%, and 881.8%, respectively, in October than in July. The abundance of microsclerotia of Verticillium dahliae in dry-farming rice and cotton rhizosphere soil was 59.2 and 124.2 ind·g-1 in July, respectively. By contrast, the abundance was 92.5 and 98.3 ind·g-1 in October respectively, without significant difference. Our results suggest that, with the extension of growth period, dry-farming rice has a significant effect on soil bacterial community composition in cotton fields, and can obviously enrich beneficial bacterial populations, but has a negative effect on the microsclerotia of Verticillium dahliae.
    Effects of bamboo charcoal application on quality of Andrographis paniculata and bacterial community structure in continuous cropping soil.
    HONG Biao, LI Ming, XU You-yang, ZHOU Jie, DUAN Shu-lei, ZHENG Yang-bo, ZHANG Hui-ye, ZOU Jiang-lin
    2021, 40(9):  2812-2821.  doi:10.13292/j.1000-4890.202109.028
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    Andrographis paniculata(Burm. F.) Nees has many functions, including antibacterial, anti-inflammatory, and antiviral. However, the continuous cropping obstacles in planting and production have adverse effects on the yield and quality of A. paniculata. In this study, a field experiment was conducted with two levels of bamboo charcoal addition \[1.2 kg·m-2 (C1) and 2.4 kg·m-2 (C2)\] in continuous cropping systems of A. paniculata for five years, with no bamboo charcoal addition as the control (C0). The agronomic traits were measured during the picking period, and the rhizosphere bacterial community structure, abundance, and diversity were examined using the Illumina Miseq high-throughput sequencing methods. The results showed that the application of bamboo charcoal was beneficial to the growth of A. paniculata in continuous cropping soil, with plant height, root length, stem thickness, chlorophyll content, fresh weight per plant, and andrographolide and dehydrated andrographolide contents being significantly higher than those without bamboo charcoal. Moreover, the promotion effect of high-level application of bamboo charcoal on the growth of A. paniculata was greater than that of low-level application. The application of bamboo charcoal increased bacterial diversity in the rhizosphere soil of the continuous cropping of A. paniculata, altered bacterial community structure, and increased the abundance of bacteria (Nitrospira, Bradyrhizobium) that are beneficial to nitrogen uptake. UPGMA clustering and PCoA β-diversity analysis showed that the composition of soil bacterial community was closely related to the level of bamboo charcoal application. In addition, RDA analysis showed that the abundance of three genera (Nitrospira, Bradyrhizobium and Candidatus_Solibacter) in the rhizosphere of A. paniculata was significantly positively correlated with many growth indices. The functional prediction of Tax4Fun showed that the application of bamboo charcoal could promote the upregulation of metabolicsrelated genes of soil bacteria and amino acid metabolism, nucleotide metabolism, and secondary metabolites. The application of bamboo charcoal in field cultivation of A. paniculata can improve its agronomic characteristics and promote the accumulation of active ingredients, and affect soil bacterial community structure and abundance, which facilitates the growth of beneficial bacterial populations and may play an important role in alleviating the continuous cropping obstacles of A. paniculata.
    Community structure of fungi in different tissues and rhizosphere soil of Sorghum bicolor in cold region.
    HAN Yi-qiang, LI Xin, LI Ming-yang, SUN Dong-mei, XIAO Cui-hong, WANG Yan-jie, WANG Wei-dong, GAO Ya-mei
    2021, 40(9):  2822-2831. 
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    To understand the beneficial fungal resources of sorghum, ITS high-throughput sequencing was used to examine the fungal community structure in different tissues and rhizosphere〖JP〗 soil of mature sorghum in cold region. The results showed that a total of 238 OTUs were obtained, with 88 shared OTUs. Ascomycota and Basidiomycota were the dominant groups of fungi in all the tissues and rhizosphere soil of sorghum. Results of principal coordinate analysis (PCoA) showed that fungi community structure was significantly different among sorghum tissues, while the structure of fungal community in rhizosphere soil was more similar to that in sorghum roots. The richness and diversity of fungal community in rhizosphere soil were significantly higher than those in sorghum tissues. Plant pathogen, wood saprotroph and dung saprotroph were the dominant functional groups in sorghum tissues and rhizosphere soil. Our results provide a basis for further isolation of fungi in sorghum and exploration of the underlying mechanism of fungal community structure in sorghum.
    Deciphering hosts of antibiotic resistance genes by metagenomic binning approaches in Union Glacier, Antarctica.
    LI Yi, XIA Cheng-qiang, FENG Yan, LI Hong, ZHANG Feng, GUAN Li, DONG Kai-shi, SHEN Shao-fei
    2021, 40(9):  2832-2841.  doi:10.13292/j.1000-4890.202109.038
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    Antimicrobial resistance (AMR), caused by antibiotic resistance genes (ARGs), is a growing threat to human health. Deciphering of ARG hosts is crucial for assessing the risk of AMR transmission from environment to human pathogens. Currently, ARG hosts in remote and pristine areas are poorly understood. Here, based on metagenomic data from Antarctic Union Glacier areas, the distribution pattern, resistance mechanism, and migration potential of ARG hosts were investigated by using metagenomic assembly and binning methods. A total of 80 MAGs (metagenomeassembled genomes) were constructed in the Antarctic Union Glacial soils, of which 18 MAGs could carry 86 ARGs (13 ARG types). The most commonly detected ARG types were related to multidrug, aminocoumarin, rifampicin, glycopeptide, and bata-lactams. Different ARGs present different host association resistance patterns. In the ARG hosts, 21 ACCs (ARG-carrying contigs) were found to carry MGEs (mobile genetic elements). Among those MDEs, translocase is the most common one, followed by transposase, integrase, conjugated transfer protein and recombinase. The MGEs and ARGs formed certain ARG-MGE co-existence patterns to promote the spread of AMR. In addition, due to carrying multiple ARGs, Escherichia, Burkholderiaceae, and Nocardioides members were important ARG repositories in Union Glacier soils. Together, these results provided basis for the risk assessment and control of environmental antibiotic resistance.
    Bacterial community structure and diversity in different habitats of Xiangshan Bay.
    YU Jia-yue, JIANG Ya-zhou, SUN Peng, ZHANG Hui, LING Jian-zhong
    2021, 40(9):  2842-2849.  doi:10.13292/j.1000-4890.202109.031
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    Microbial community structure and diversity in marine environment are important indicators for assessing structure and function of marine ecosystems. To understand the characteristics of bacterioplankton communities in Xiangshan Bay, to compare the bacterial composition and structure in different habitats, and to assess the causes of community differences in different habitats, 16S rRNA gene high-throughput sequencing was employed to evaluate the bacterial structure and diversity in marine water samples collected from artificial reef area (AR), natural control area (NC), oyster culture area (OC), and cage culture area (CC) of Xiangshan Bay. Results showed that a total of 46 phyla were detected, including Proteobacteria (50.74%), cyanobacteria (13.80%), actinobacteria (13.51%), Firmicutes (10.02%), and Bacteroidetes (9.63%). Among all the habitat types, the dominant bacterial community composition of seawater samples from the AR, NC and OC habitat was similar, but a great difference was found between them and samples from the CC habitat (P<0.05). The abundance and diversity of bacterial community were higher in the AR habitat, but lower in the OC and CC habitat (the lowest in the CC habitat). Marine environment of the OC was relatively stable, without significant change in microbial community structure and diversity. The deployment of artificial reef improved the marine ecological environment, which was beneficial to the diversity and stability of bacterial structure in the corresponding area, while the cage culture in offshore area caused the change of bacterial community to an unstable structure with reduction in diversity.
    Seasonal variations and driving factors of phytoplankton functional groups in the Longfeng wetland, Daqing City.
    LI Lei, ZHANG Ying, CHEN Ning, QI Qing-song, LU Xin-xin, LIU Yan, FAN Ya-wen
    2021, 40(9):  2850-2859.  doi:10.13292/j.1000-4890.202109.027
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    To understand the temporal and spatial distribution of phytoplankton functional groups in Daqing Longfeng wetland, we collected the samples in the spring, summer, and autumn of 2019. A total of 200 taxa of phytoplankton were identified, belonging to 7 phyla, 10 classes, 18 orders, 35 families, and 75 genera. Among them, Chlorophyta (41.5%) and Bacillariophyta (30%) were the dominant groups, followed by Cyanophyta (12.5%) and Euglena (12%), while the abundance of Cryptophyta, Dinophyta, and Chrysophyta were relatively low (together accounting for 4%). The composition of phytoplankton in the Longfeng wetland changed obviously among different seasons, with the abundance of phytoplankton following a seasonal trend of summer < spring < autumn. The phytoplankton community could be divided into 22 functional groups, with 15 of which being representative functional groups. The representative functional groups had obvious succession among seasons (P<0.05), and the community structure had significant differences (P<0.05). Results of SIMPER analysis showed that five of the 15 representative functional groups were the main contributors to the variations of the phytoplankton community structure in the Longfeng wetland among three seasons. Redundancy analysis (RDA) of functional groups and nine water variables was performed to explore the relationship between environmental variables and the seasonal variations of functional groups. RDA results showed that electrical conductivity and water temperature were the main factors driving the seasonal variations of phytoplankton functional groups in the Longfeng wetland.
    Distribution characteristics and influencing factors of microplastics in intertidal zone sediments of the Yangtze Estuary.
    LONG Ji-yi, TONG Chun-fu, WANG Tao, WU Feng-run, LIU Mao-ya
    2021, 40(9):  2860-2871.  doi:10.13292/j.1000-4890.202109.006
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    As a transition zone between land and ocean, estuarine intertidal zone has become a hotspot in studies on microplastics. We investigated the composition and distribution characteristics of microplastics in the sediments in a typical estuarine intertidal zone of China, the intertidal zones of the Yangtze Estuary. In April 2019, sediments in eight fixed sampling sites in the vegetated areas of the intertidal zones around the Chongming Island, Changxing Island, and Hengsha Island were sampled and analyzed. The results showed that average abundance of microplastics in the sediment was 0.015±0.002 n·g-1. The average size of microplastics ranged from 204.4 to 546.4 μm. According to the shape, fibers and fragments were the dominant components, accounting for 59.8% and 29.9% of the total, respectively. As for the color, the transparent, blue, and white were the main colors. The most popular material types of microplastics were polypropylene (PP), ethylene-propylene copolymer (EPM), polyethylene (PE), and polyethylene terephthalate (PET). There were significant differences in the abundance and size of microplastics among different sites, but without vertical variation in the sediments. In some sites, the abundance and size of microplastics were significantly correlated with the median particle size, TOC content, water content, and bulk density of the sediments. We concluded that the composition and distribution characteristics of microplastics in the intertidal zone sediments of the YangtzeEstuary differed significantly between the mud flat and the vegetated area, which were affected by the land ocean interactions, human activities, intertidal vegetation, physical and chemical characteristics of the sediments.
    Identification and conservation assessment of priority conservation areas for terrestrial vertebrates in Yunnan.
    ZHOU Jian, YANG Fei-ling, WANG Jun-jun, WANG Yi-ting, ZHANG Chen, FENG Zhi-xue, WU Rui-dong
    2021, 40(9):  2872-2882.  doi:10.13292/j.1000-4890.202109.012
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    The systematic identification of priority conservation areas (PCAs) is one of the key and costeffective approaches for biodiversity conservation. Yunnan, as a global biodiversity hotspot, still lacks planning studies on PCAs for terrestrial vertebrates. Past studies only assessed the protection coverage of nature reserves, with less information on other categories of protected areas (PAs). Here, we first used protected species as surrogates and the models of species distribution and systematic conservation planning to identify PCAs for Yunnan’s terrestrial vertebrates. We examined the spatial distribution pattern of terrestrial vertebrate PCAs by comparing the results obtained with three portfolios of PCAs developed in previous studies. We finally assessed the protection coverage of PCAs provided by six different categories of PAs. The results showed that: (1) PCAs for terrestrial vertebrates based on both conservation targets of 17% and 31% Yunnan’s land were primarily distributed in northwestern, southwestern, southern, and northeastern Yunnan as well as regions nearby national borders. (2) PCAs under the 31% target had >44% of its total area overlapped with each of the three PCA datasets defined by previous studies. Meanwhile, terrestrial vertebrate PCAs also identified many new priority areas. (3) Under the 17% and 31% targets, the established nature reserves covered 14.11% and 11.39% for PCAs, respectively, whereas the coverage was increased to 24.01% and 20.95% when all six PA categories were considered. This result indicated that the remaining five sustainable use categories of PAs (i.e. Scenic Spots, Forest Parks, Wetland Parks, GeoParks, Drinking Water Source Conservation Areas) can greatly increase the protection coverage and fill the conservation gaps in Yunnan. This study could provide data and method support for the policy on establishing a new “PA System with National Parks as Its Mainstay” in Yunnan.
    A comparison of wetland landscape pattern changes of Yalu River Estuary between China and North Korea in recent 40 years.
    YAN Heng-qi, MAO De-hua, ZHU Wei-hong, WANG Zong-ming, LI Lan
    2021, 40(9):  2883-2894.  doi:10.13292/j.1000-4890.202109.016
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    The Yalu River Estuary is an important part of waterbird migration corridor in the Northeast Asia-Australasia Flyway. Based on Landsat MSS/TM/OLI remote sensing images, the land cover datasets of Yalu River Estuary in six periods from 1980 to 2020 were obtained by a combination of objectoriented and random forest classifications. By analyzing wetland area, landscape metrics, wetland centroid migration, we compared the differences between China and North Korea, by quantitatively comparing the impacts of human activities on wetland landscape change. Results showed that: (1) Over the past 40 years, total wetland area in the Yalu River Estuary experienced a decreasing trend, with a high wetland loss rate (15%) on the Chinese side and a low wetland loss rate on the North Korean side (12%). (2) The changes of landscape metrics suggested that wetlands in the Yalu River Estuary tended to be fragmented and the connectivity between landscapes decreased. (3) Consistent expansion of cultivated land and artificial surface was the main driving force for wetland loss. (4) During the four decades, the centroid of wetland landscape moved 1.4 km seaward. The conservation effectiveness of coastal wetlands over the Yalu River Estuary should be improved. Our findings could facilitate management, development and biodiversity conservation of estuarine wetland ecosystems.
    Characteristics and the driving mechanism of urban construction land expansion in mountainous areas of southwest China.
    WANG Xu-xi, PENG Li, LIU Shou-jiang, WEI Yun-yun
    2021, 40(9):  2895-2903.  doi:10.13292/j.1000-4890.202109.017
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    Clarifying the driving mechanism of urban construction land expansion is beneficial to restraining the disordered expansion. In this study, we analyzed the characteristics of urban construction land expansion of 410 counties (districts) in the mountainous areas of southwest China from 2000 to 2015. The driving factors and mechanism of urban construction land expansion were explored by multiple linear regression. The results showed that: (1) There were obvious differences in the intensity of urban construction land expansion among counties (districts), with a Gini coefficient of 0.385; (2) The expansion of construction land in the mountainous area of southwest China showed a agglomeration distribution. High-high and low-high types were mainly distributed in Sichuan and Yunnan, lowlow type was scattered in various provinces as a shape of cluster, and high-low type was scattered in Sichuan, Yunnan and Chongqing; (3) The intensity of urban construction land expansion was positively correlated with the change rates of population density, urbanization, and temperature, while negatively correlated with the change rates of precipitation and Normalized Difference Vegetation Index (NDVI), and the number of towns under its administration. The change rates of population density, urbanization, precipitation, temperature, and NDVI, and the number of towns under its administration were the key factors affecting the intensity of urban construction land expansion. The results will provide scientific references for the rational utilization and optimization of urban lands in mountainous areas of southwest China.
    Land use change and ecological environment effect of Danghe River source region.
    LI Xiao-ya, ZHAO Cheng-zhang, ZENG Hong-xia, SE Yong-jun, LI Qun, MA Min
    2021, 40(9):  2904-2913. 
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    Land use change affects ecosystem structure and function. Evaluating the ecological environment effect of land use change can provide a basis for regional ecological protection. We analyzed the land use change, ecological environmental effects, and influencing factors of Danghe River source region, with Landsat remote sensing images in 1987, 1994, 2000, 2006, 2011 and 2017 as the main data source, using the remote sensing ecological index (RSEI) and plant community survey methods. The results showed that from 1987 to 2017, the areas of natural pasture, marshland, and bare rock gravel land in Danghe River source region showed a decreasing trend, while the areas of marsh grassland, river surface, sandy land, glaciers and permanent snow exhibited an increasing trend. The area with excellent and good ecological grades increased by 14.26%, while the area with poor and inferior ecological grades decreased by 27.9%. The RSEI increased from 0.48 in 1987 to 0.57 in 2017. The 6-year average value of RSEI in natural pasture, marsh grassland, and marsh was higher than that in sandy land and bare rock gravel land. The RSEI value of natural pasture, marsh grassland, and sandy land showed an overall upward trend, while that of marsh showed an overall downward trend, and that of bare rock gravel land had no obvious trend. There was a significant positive correlation between precipitation and the RSEI value of marsh grassland, natural pasture, and marsh land (all P<0.05). There was no significant correlation between RSEI value of sandy land, bare rock gravel land and annual precipitation, mean annual temperature, livestock inventory (P>0.05). The superposition of climate warming, humidification and socio-economic factors promoted the evolution of landscape types and improved the quality of ecological environment in the Danghe River source region.
    Ecological security pattern construction in typical ecological shelter zone: A case study of Chengde.
    HU Qiu-hong, CONG Nan, YIN Guo-dong
    2021, 40(9):  2914-2926.  doi:10.13292/j.1000-4890.202109.018
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    Optimizing the spatial patterns of urban expansion and ecological space is an urgent need in toplevel design of land development. As a method for reconciling conflict between ecosystem conservation and urban exploitation, ecological security pattern (ESP) construction is important to improving the efficiency of land consolidation in ecological shelter zone, which is characterized by ecosystem diversity and ecosystem services. Chengde in Hebei Province is an ecological barrier area in the north of Beijing and Tianjin. According to the results of ecosystem services evaluation, we identified the most important zones of forest, shrubland, and grassland, and designated the ecological sources in combination with existing protection areas in Chengde. ESP was constructed based on minimal cumulative resistance (MCR) model. The area of identified ecological sources was 13200 km2, accounting for 34.22% of total area. The ecological corridors were 2160 km, including cluster corridors and landscape corridors, which were distributed in pattern of one horizontal direction (Wuling Mountain-Dushan Mountain) and three vertical directions (Liaohe headwaters-Maojing Dam, Baicao Depression-Yudao Pass, Baicao Depression-Luanhe headwaters). The corridors effectively linked up the ecological sources. In total, 22 ecological nodes were identified, which could be classified into two types as core nodes and stepping stone nodes. The areas of high and low-level ecosecurity buffer zones were 12550 and 11352 km2. Compared with the status and planning of land-use, most natural vegetation was effectively conserved, and the ESP was generally consistent with the pattern of Chengde’s environment protection and urban development strategies. The results indicated that the improved method reduced the uncertainty of ESP resulted from heterogeneous vegetation distribution and difference in net primary productivity among different vegetation types, and had well applicability in ecological shelter zone. Our results provide scientific guidance and technical support for territorial development and environment protection in ecological shelter zone.
    Ecological sensitivity evaluation of Longnan County based on AHP and MSE weighting method.
    HE Su-ling, ZOU Feng-qiong, WANG Jin-liang
    2021, 40(9):  2927-2935.  doi:10.13292/j.1000-4890.202109.022
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    Ecological sensitivity is one of the important indicators for regional ecological fragility, the evaluation results from which play an important guiding role in regional ecological protection and development planning. Seven sensitive factors were selected from two aspects of soil erosion and acid rain erosion. With the support of GIS, we evaluated the spatial and temporal variations of ecological sensitivity in Longnan County, Jiangxi Province from 2003 to 2018 by combining analytic hierarchy process (AHP) and mean square deviation (MSE) decision-making method. The results showed that: (1) From 2003 to 2018, the ecological sensitivity of Longnan County always showed a spatial pattern of high in the south and low in the north, and gradually decreased over time. (2) The ecological sensitivity had a positive spatial correlation, which showed temporal fluctuation. (3) Construction land and arable land were the land types with low ecological sensitivity, while woodland showed high ecological sensitivity. The degree of ecological sensitivity in the study area increased with increasing slope. Our results can provide scientific reference for ecological protection and territorial planning of Longnan County.
    Prediction of potentially suitable distribution area of Propomacrus davidi Deyrolle in China based on MaxEnt model.
    SHI Wen, ZHU En-jiao, WANG Yu-chen, MA Fang-zhou, HE Qiu-ju, YI Chuan-hui
    2021, 40(9):  2936-2944.  doi:10.13292/j.1000-4890.202109.024
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    To provide theoretical basis for the conservation and population restoration of the endangered species Propomacrus davidiDeyrolle, we simulated its contemporary and future (2050s, 2070s) suitable distribution areas in China under two climate scenarios (RCP2.6, RCP8.5) and screened out the dominant factors affecting the distribution, using the MaxEnt model with 18 effective distribution points and 19 environmental factors. Results showed that the MaxEnt model had a high accuracy in simulation prediction, with the AUC value above 0.966. Under current climatic conditions, the highly suitable areas of P. davidiare mainly distributed in the border area of northeast Jiangxi, Zhejiang, and Fujian, the border area between the south Jiangxi and Guangdong, and the northwest area of Taiwan. The moderately suitable areas are mainly distributed on the edge of those highly suitable areas. Under future climatic conditions, the overall pattern of the moderately-highly suitable areas of P. davidi will basically remain unchanged, but with a trend of spreading to Hunan Province and other places, and an increase of the total suitable area. The dominant factors affecting the potential geographic distribution of P. davidi are the mean rainfall in the coldest season, the rainfall in the wettest season, the mean temperature in the driest season, the mean temperature in the coldest season, and the rainfall in the driest month. In conclusion, the suitable distribution area of P. davidi will expand in the future.
    Variation of plant species richness in road area and its influencing factors based on meta-analysis.
    2021, 40(9):  2945-2953.  doi:10.13292/j.1000-4890.202109.026
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    Studying the variation pattern and its influencing factors of plant species richness in road area can provide references for the management of nature protected areas. Based on literature, we selected five influencing factors that have been most frequently studied, including road width, species attributes, vegetation types, plant growth forms, and latitude to which the road belongs. Their effects on plant species richness in road area were investigated by Meta-analysis. The results showed that, among those five factors, species attributes (native species or not) had the greatest effects on the variation range of plant species richness in road area. The species richness of alien species, native species and unclassified species (alien and native species were not classified) all increased significantly (ranges were 130.5%, 14.9%, and 27.0%, respectively), with the increment of alien plants significantly exceeding that of native plants. The variation range of plant species richness in road area did not show a regular trend as road width increased. The variation range of plant species richness in road area was significantly different above and below 4.5 m road width. Plant species richness in road area did not change significantly within 4.5 m road width, while that of roads between 4.5 m and 26 m increased significantly (the range was 42.1%). The variation range of plant species richness in road area did not change in grasslands, but increased significantly in forests. In coniferous forests, deciduous broad-leaved forests, and evergreen broad-leaved forests, the elevation range of plant species richness in road area decreased (76.7%, 38.0% and 20.3%, respectively). In coniferous forests, the variation range of plant species richness in road area was significantly different above and below 2.75 m road width. Plant species richness in road area within 2.75 m road width was significantly smaller than that for roads between 2.75 and 26 m (18.8%, 74.0%, respectively). In forest road area, the species richness of herb and shrub increased significantly (ranges were 16.2% and 37.6%, respectively), while that of tree species did not change. The latitude of roads did not affect the variation range of plant species richness in road area.
    Ecological compensation standard and its influencing factors of agricultural non-point source pollution control based on farmers’ willingness to accept compensation.
    LUAN Ruo-fang, WEN Gao-hui, HU Xian-hui
    2021, 40(9):  2954-2966.  doi:10.13292/j.1000-4890.202109.039
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    The key to control agricultural non-point source pollution is to effectively encourage farmers to reduce or not apply pesticides and fertilizers from the source. The compensation standards and influencing factors of agricultural non-point source pollution control are of great significance for the sustainable implementation of ecological compensation policy. Based on the survey data of farmers in the Dongting Lake Basin, we constructed a utility function based on utility theory and compensation principle to measure ecological compensation amount when farmers participate in agricultural non-point source pollution control to maximize their individual utility, and analyzed the influencing factors of farmers’ willingness to accept compensation using binary Logistic regression model. The results showed that: (1) About 77.3% of farmers in the survey area were willing to participate in agricultural nonpoint source pollution control and to protect agricultural ecological environment under the condition of giving certain ecological compensation. (2) When the application of chemical fertilizers and pesticides was reduced by 50%, the nonparame tric estimation result of ecological compensation standard of nonparametric agricultural non-point source pollution control without considering the objective factors was 2094.41 yuan·hm-2, while that of the parameter estimation model was 1640.21 yuan·hm-2, which can be used as the upper and lower limits of ecological compensation standards for agricultural non-point source pollution control in the Dongting Lake Basin. (3) Results of regression analysis showed that the farmers’ cognition level of policy is the direct key factor determining the acceptance of farmers to accept the ecological compensation for agricultural non-point source pollution control. The willingness of farmers to reduce pesticide and chemical fertilizer is the fundamental motivation for them to participate in agricultural non-point source pollution control. From the perspective of farmers’ willingness, related departments should improve the current compensation standards for agricultural non-point source pollution control, and explore ways to enhance farmers’ well-being.
    Dynamics of vegetation NDVI in Chengdu-Chongqing Economic Circle from 2000 to 2018.
    LI Xi-rong, YANG Dong, FENG Lei, HUANG Yue-yue, YI Wei
    2021, 40(9):  2967-2977.  doi:10.13292/j.1000-4890.202109.025
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    The status of vegetation coverage was analyzed using the MODIS NDVI remote sensing data of the Chengdu-Chongqing Economic Circle from 2000 to 2018. Combined with the climatic indices (temperature and precipitation) from the meteorological stations in the study area, the spatiotemporal variations of NDVI and the influence of climate on NDVI were analyzed. The results showed that the NDVI of vegetation in the Chengdu-Chongqing Economic Circle presented a significant enhancement from 2000 to 2018, with substantial spatial variations. The areas with vegetation degradation were mainly concentrated in the northwest and southeast of the Chengdu-Chongqing Economic Circle, and areas with improvement were mainly distributed in the south and east. The annual NDVI was negatively correlated with mean annual temperature and positively correlated with precipitation. The impact of human activities on vegetation coverage cannot be ignored. Human activities improved vegetation, and areas with improved vegetation accounted for 95.33% of the total area. However, 61.66% of the region would have a trend of vegetation degeneration from improvement in the future.
    Research advances in hydraulic redistribution of plant roots.
    LIN Fu-rong, GU Da-xing, HUANG Yu-qing, HE Cheng-xin, WEI Qi-sheng
    2021, 40(9):  2978-2986.  doi:10.13292/j.1000-4890.202109.013
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    Hydraulic redistribution (HR) in plant roots is a common phenomenon. The water magnitude of HR is related to measurement methods and influencing factors. The main methods for HR measurement include soil moisture dynamic method, isotope labeling method, sap flow method, and Ryel model method. Given that each method has its shortcomings, the result from single method should be treated carefully. Two conditions are needed for the occurrence of HR. First, soil water potential (ψs) is less than leaf water potential (ψl), with the cease of canopy transpiration. Second, there is obvious spatial heterogeneity of soil moisture in the rhizosphere. HR can relieve drought stress of plants and their neighboring plants, promote soil nutrient cycling, and then facilitate plant nutrient uptake (such as nitrogen and phosphorus). As a result, HR has great ecological significance in plant hydraulic safety, and ecosystem nutrient cycling and balance. Although there have been great progresses on plant HR, there are still deficiencies in the research methods and the accuracy evaluation of quantitative determination of HR. In addition, HR research on plants living in special habitats also needs to be strengthened. Future HR research should focus on the combination of multiple technologies, with the aim to comprehensively understand the generating mechanism and to quantify its magnitude.
    Effects of water depth and nitrogen addition on functional traits of wetland plants: A review.
    BAI Jiang-shan, TANG Hao-ran, LOU Yan-jing
    2021, 40(9):  2987-2995.  doi:10.13292/j.1000-4890.202109.002
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    Water depth and nitrogen nutrition are the key factors affecting the growth of wetland plants. Plant functional traits reflect plant adaptation strategies to environmental changes. Studies on the effects of water depth and nitrogen addition on the functional traits of wetland plants can help predict the growth and distribution of wetland plants under future environmental changes. Under the scenario with the impacts of global changes and human activities, the effects of changes in water depth and nitrogen enrichment on the functional traits of wetland plants can be more profound and complex. Here, we summarized the effects of water depth, nitrogen addition, and their interactions on growth-related traits, clonal reproductive traits, and biomass accumulation of wetland plants. In the future, we should pay more attention to strengthen the research in belowground and clonal reproductive traits of wetland plants, emphasize multi-scale and long-termseries research, and further explore the interactive effects of water depth and nitrogen addition on the functional traits of wetland plants.
    Research advances on coral reef fish biodiversity and conservation.
    DAI Xue-jiao, ZHANG Jun, CHEN Zuo-zhi
    2021, 40(9):  2996-3006.  doi:10.13292/j.1000-4890.202109.034
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    Coral reefs are among the biodiversity-richest marine ecosystems. Over the last several decades, global coral reefs are continuously decreasing, arousing widespread concern. Coral reef fish is an important ecological group with great economic and ecological values. Due to the joint disturbance of climate change and human activities, the diversity, trophic levels and productivity of coral reef fish have declined significantly. There are more and more concerns on how to protect coral reef fish resources and promote stability and sustainability of their ecological and economic functions. Here, we summarized the natural and anthropogenic threats to reef fish diversity and proposed methods for the scientific conservation and management of reef fish. Currently, the greatest threats to coral reef fish are overfishing and destructive fishing practices, while future threats would be large-scale coral bleaching caused by ocean acidification and global warming. Five measures should be implemented to restore reef fish diversity: (i) reducing and strictly controlling fishing intensity; (ii) strengthening the protection of herbivorous fish on coral reefs; (iii) improving dynamic monitoring of coral reefs; (iv) expanding coral reef ecological restoration; and (v) establishing coral reef protection areas.
    Simulation of vegetation distribution on natural grassland slopes around Shengli mining area and its application in reclamation.
    XIA Jia-nan, LI Heng, LEI Shao-gang, YANG Xing-chen, LIU Feng, WANG Wei-zhong, LI Juan
    2021, 40(9):  3007-3016.  doi:10.13292/j.1000-4890.202109.011
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    A large number of openpit coal mines are distributed in the grasslands of north China, where soil and water erosion of the mining slope is serious and the resistance of ecological restoration is relatively high. In order to design the slope of the dump in the mine which is in line with the layout of surrounding natural grassland vegetation, we proposed a method of near-nature planting based on object learning. Taking the typical natural grassland around Shengli mining area in Inner Mongolia as an example, combined with the CLiDE evolution model, we evaluated soil antierosion effects of slope samples under different plant arrangements. The results showed that: (1) In terms of visual effects, the near-natural simulation results of plant layout based on object learning were similar to natural grassland, and both had stripe distribution characteristics at the mesoscale and random distribution characteristics at the small scale. (2) The statistical results showed that the simulation results of the near-natural layout were highly consistent with natural grassland in the number of cluster centers, distribution form, and the characteristic parameters of plant strips. (3) Under the same plant density, natural grassland slope had the strongest resistance of soil erosion, and the near-natural plant placement method can achieve simulation results that were very similar to the natural grassland in the slope resistance to water erosion. Moreover, compared with the traditional “uniform grid” plant layout under the same plant layout density, the nearnatural plant layout can reduce soil and water erosion by 46.3%. (4) In the restoration of slope vegetation in the grassland mining area, it can be considered to imitate plant distribution pattern of the surrounding natural grassland slope to improve the slope resistance to water erosion after restoration.
    Estimation and validation of nitrogen nutrition of potato based on digital image processing technology.
    WEI Quan-quan, LI Fei, ZHANG Meng, CHEN Long, GOU Jiu-lan
    2021, 40(9):  3017-3024.  doi:10.13292/j.1000-4890.202109.030
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    A field experiment was conducted with potato under different nitrogen application levels (0, 120, 240, 300 and 360 kg·hm-2) in Weining County, Bijie City, Guizhou Province from 2018 to 2019. In 2018, the canopy images of potato were obtained by digital camera at both tuber initiation stage and tuber bulking stage. The nitrogen nutrition indices of plants were measured. We analyzed the correlation between canopy digital parameters and nitrogen nutrition indices, screened the optimal canopy digital parameters for estimating nitrogen nutrition indices, and constructed the estimation model of nitrogen nutrition indices. The accuracy of the above equation model was verified and a 1∶1 linear relationship was drawn by using an independent nitrogen level experiment in 2019. The results showed that the ratio of redness intensity to blueness intensity (R/B) was better than other canopy parameters in characterizing nitrogen nutrition status of potato attuber initiation stage. R/B, the ratio of greenness intensity to blueness intensity (G/B), and the normalized blueness intensity (NBI) could characterize the nitrogen status of potato at tuber bulking stage, with R/B being the best. The correlation values (R2) between measured and estimated biomass and between measured and estimated nitrogen accumulation were 0.911 and 0.888, with RMSE being 0.685 and 25.115, and RE being 12.92% and 23.41%, respectively. The digital image processing technology can be used to evaluate and estimate nitrogen nutrition of potato. The best estimated period is tuber initiation stage and tuber bulking stage, the best estimation parameter is R/B, and the best model is linear regression equation.
    Application of soundscape monitoring technology in bird diversity monitoring at the typical wetland of Poyang Lake.
    YOU Hai-lin, WU Yong-ming, XU Li-gang, CHENG Jun-xiang, LIU Li-zhen, YAO Zhong, XIN Zai-jun
    2021, 40(9):  3025-3032. 
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    Sound is a fundamental attribute of nature. Using the soundscape technology to monitor bird diversity and richness can effectively overcome the deficiency of traditional methods. The sound data of wetland birds at 00:00, 06:00, 12:00 and 18:00 of each day during April to June in 2020 were collected using Song Meter SM4, a professional collection instrument, in Fanglan Lake, a typical human-controlled lake in Poyang Lake. Using the professional sound processing packages (i.e. seewave, tuneR, and soundecology) in the statistical software R, all the collected sound data were analyzed and converted into bioacoustic index (BI). The main aims were to clarify the corresponding bird diversity and activity habits in the early morning, morning, noon and evening of each day during these three months, and to reveal the characteristics of bird diversity in a longtime sequence at the typical wetland of Poyang Lake. The MannKendall test method was used to analyze the trend and mutation of bird diversity characteristic sequence. The Morlet wavelet analysis method was applied to analyze its multitemporal scale characteristics. The results showed that: (1) The BI values at 00:00, 06:00, 12:00, and 18:00 within the three months were different, with ranges of 5.73-63.49, 5.76-67.00, 3.36-60.24, and 4.91-52.62, respectively. The BI values generally showed an increasing trend. (2) The Mann-Kendall mutation test indicated that all the BI sequences for three months had a sudden change around 06:00 on April 27 in 2020, which was mainly caused by human activities. (3) The evolution of daily average BI values showed three types of periodic change scales of 12-30, 10-18, and 4-9 days. The wavelet variance had three significant peaks, corresponding to the time scales of 24, 15, and 7 days. As an exploratory research, this study could provide a new technical approach for the research on bird population, behavior characteristic and its diversity, as well as the diversity monitoring research for other animals (amphibians, insects, etc.).