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    10 August 2023, Volume 42 Issue 8
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    Responses of photosynthetic traits and adaptive mechanisms of Rhododendron pulchrum Sweet to different light environments.
    LENG Hanbing, SU Ming, ZHANG Chunying
    2023, 42(8):  1793-1801.  doi:DOI:10.13292/j.1000-4890.202308.016
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    The aim of this study was to explore leaf photosynthetic and biochemical characteristics and adaptive mechanisms of Rhododendron pulchrum Sweet under different light environments, including full light (FL, 100% natural sunlight), slight shading (LS, 82.01% full light), moderate shading (MS, 50.13% full light), and severe shading (SS, 15.80% full light). The results showed that leaf area and the contents of photosynthetic pigments and total nitrogen increased with decreasing light intensity, while specific leaf mass, total carbon content and carbon/nitrogen ratio decreased, and chlorophyll a/b decreased firstly and then increased. Maximum quantum photochemical efficiency and non-photochemical quenching coefficient were significantly higher under MS and FL treatments than that under the other treatments, respectively. The actual quantum photochemical efficiency, photochemical quenching coefficient, and quantum yield of quenching under SS treatment were significantly lower than that under the other three treatments. Dark respiration rate and light compensation point decreased with decreasing light intensity, while the maximum values in apparent quantum efficiency, maximum net photosynthetic rate and light saturation point) were detected under MS treatment, suggesting the strongest photosynthetic capacity. R. pulchrum under FL treatment had lower net photosynthetic rate (Pn) accompanied with lower stomatal conductance and higher stomatal limitation value. Such decrease in Pn under FL treatment was mainly due to stomatal limitation. In comparison, Pn under SS treatment was inhibited mainly due to the reduction in photochemical efficiency and imbalance in fraction of incident light in photosystem Ⅱ. Our results suggested that R. pulchrum had good performance in tolerance range of light intensities, and that moderate shading (i.e., 50% full light) was optimal for its growth. Consequently, proper shading or community configuration under deciduous forest with sparse canopy should be employed regarding its cultivation or application in gardens.

    Effects of elevated CO2 and O3 concentrations on emission of isoprene and monoterpenes in Phoebe bournei.
    MA Fangyuan, ZHANG Li, WENG Zishan, LAI Jinmei, LIU Guizhen, GUO Hao, YI Zhigang
    2023, 42(8):  1802-1810.  doi:10.13292/j.1000-4890.202308.034
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    Elevated CO2 and O3 concentrations could affect ecosystem carbon (C) cycling. Isoprene (ISO) and monoterpenes (MTs) are the intermediate products in plant C metabolism, the synthesis and release of which are important pathways of ecosystem C cycling. We conducted a 4-month fumigation experiment with two-year-old Phoebe bournei seedlings. Four treatments, namely the control (CK), elevated CO2 concentration (EC), elevated O3 concentration (EO) and simultaneously elevated CO2 and O3 (EC+EO), were set up to examine the effects of elevated CO2 and O3 concentrations on ISO and MTs release and photosynthetic parameters in P. bournei. The results showed that after one month fumigation, a significant increase in MTs fluxes (P<0.05) and a 5.6% decrease in ISO flux were observed with the EC treatment compared with CK. After 4 months’ fumigation, the ISO and MTs fluxes decreased under EC, EO, and EC+EO treatments. The reduction was the strongest under EC+EO treatment, with the ISO and MTs fluxes being reduced by 76.4% and 89.6%, respectively. The decrease of fluxes might be attributed to the changes of net photosynthetic rate by changing the content of photosynthetic pigments and adjusting stomatal conductance under different treatments, which directly affects C source of ISO and MTs metabolism. The main components of MTs were α-pinene and limonene. Under elevated CO2 and O3 concentrations, net photosynthetic rate gradually decreased with fumigation duration. The effects of independently and simultaneously elevated CO2 and O3 concentrations on ISO and MTs fluxes differed. When we investigated the effects of elevated CO2 and O3 concentrations on ecosystem C cycling, compound factor interaction experiments should be taken into consideration, to provide more reliable data support for understanding the responses of ecosystem C cycling to global climate change.

    Effects of different ratios of  nitrogen and phosphorus addition on the relationship between relative growth rate and fine root traits of Machilus pauhoi seedlings.
    CHENG Jieru, ZHONG Quanlin, ZOU Yuxing, CHANG Yunni, LIAO Penghui
    2023, 42(8):  1811-1819.  doi:10.13292/j.1000-4890.202308.011
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    Nitrogen (N) and phosphorus (P) are important nutrients affecting plant growth. Fine root is an important organ to absorb nutrients and water. Here, we analyzed the effects of different N and P application ratios (15∶1, 12∶1, 10∶1, 8∶1) on the growth and fine root traits of 1-year-old Machilus pauhoi seedlings in a pot experiment. The results showed that: (1) All the N and P addition treatments significantly increased leaf biomass, total biomass, and leaf mass fraction, but decreased root-shoot ratio, especially at the treatments with N/P ratios of 10∶1 and 8∶1. (2) Combined applications of N and P significantly increased relative growth rates of both total biomass and biomass of each organ, with a strongest effect under N/P ratio of 10∶1. (3) Combined applications of N and P significantly increased N and P concentrations in fine roots (P<0.05), with no difference among treatments. Fine root N concentration was the highest in the treatments with N/P ratios of 15∶1 and 10∶1. Fine root P concentration was the highest in the treatment with N/P ratio of 10∶1. Combined applications of N and P reduced the average diameter of each fine root order and specific surface area (SRA) of the 1st-2nd order roots, but increased specific root length (SRL) of the 2nd-4th order roots and SRA of the 3rd-4th order roots. The changes of root tissue density (RTD) of each order was opposite to that of SRA. (4) The relative growth rates of total biomass and biomass of each organ were significantly positively correlated with RTD but negatively correlated with SRL and SRA after combined N and P application. The results indicated that application of different N/P ratios affected biomass allocation pattern, relative growth rate, and the relationship between relative growth rate and some fine root traits of M. pauhoi seedlings. The most suitable ratio of N/P for the growth of M. pauhoi seedlings was 10∶1. Our results provide an important reference for the development of precise nutrient management and efficient cultivation of M. pauhoi seedlings.

    The niche of dominant plant species in the karst soil nutrient resource axis around FAST.
    ZHANG Ting, ZHANG Jianli, ZHANG Chen, YANG Tao, PU Lihua, ZHAO Weiquan, CHEN Pengli
    2023, 42(8):  1820-1828.  doi:10.13292/j.1000-4890.202308.014
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    To understand the niche characteristics of plants along soil nutrient resource axis in the karst peak-cluster depression, we analyzed the niche characteristics of dominant plant species in forests around the Five-hundred-meter Aperture Spherical radio Telescope (FAST) on soil nutrient resource axis using canonical correspondence analysis, Levins niche breadth, and Pianka niche overlap index. The results showed that total soil phosphorus, available nitrogen, and organic carbon had significant effects on the distribution of dominant species (P<0.05). The niche breadths of Quercus acutissima, Ficus tikoua, and Rhus chinensis on the soil nutrient resource axis were higher and more suitable for the habitat of the study area. Quercus fabri, Inula cappa, and Litsea coreana had lower niche breadth on the soil nutrient resource axis, with lower resource utilization efficiency. The niche breadth was influenced by the species’ importance value, in that species with higher niche breadth had higher importance values. The species with higher niche overlap index did not occupy higher niche breadth but were in the middle and lower values. The species with niche overlap greater than 0.5 accounted for 50% of the total species number when considering the soil nutrient resource axis. In conclusion, vegetation around FAST was relatively stable, and total phosphorus, available nitrogen, and organic carbon were important soil nutrient factors affecting the distribution of dominant species around FAST.

    Responses of plant community structure and stability to artificial disturbance in urban remnant mountains.
    SUN Yuzhen, WANG Zhitai, BAO Yu, LIU Shuping
    2023, 42(8):  1829-1840.  doi:10.13292/j.1000-4890.202308.010
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    To explore the responses of plant community of urban remnant mountains to artificial disturbance, plant community structure and stability of urban remnant mountains under different artificial disturbance ways and intensities were analyzed using the theories and methods of community ecology and quantitative ecology. The results showed that: (1) Vertical structure integrity of plant community under different intensities of human disturbance declined with increasing disturbance density. Reclamation, excavation, and construction had significant negative effects on trees and shrubs, while park utilization was beneficial to the integrity of community vertical structure. (2) The diameter class structure of trees exhibited an inverted “J” type distribution under different disturbance intensities. Small diameter trees (DBH<10 cm) accounted for 53%, 58% and 48% of the total individual numbers in the plots under light, moderate and heavy disturbances, respectively. The regeneration potential of tree layer was high. The diameter class structure of tree changed abnormally under reclamation and excavation disturbance ways. (3) Based on the coefficient of variation of community density and the Godron stability index, community stability decreased with human disturbance intensities. Plant communities under the disturbances of trample and park utilization were relatively stable, while those with the reclamation and engineering excavation were most unstable.

    Allocation of nonstructural carbohydrates in trunks of three main afforestation tree species in Horqin Sandy Land.
    WANG Kai, SHI Liang
    2023, 42(8):  1841-1850.  doi:10.13292/j.1000-4890.202308.009
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    Trunk is the main organ for storing non-structural carbohydrate (NSC) in trees. NSC allocation patterns in trunk can reflect carbon storage strategy and adaptability of trees. We measured the concentrations of soluble sugar, starch and NSC in trunks of three main afforestation conifer species (Pinus sylvestris var. mongolica, P. densiflora, and P. tabuliformis) in Horqin Sandy Land, the radial and vertical variations in trunks, and compared the interspecific variations in allocation patterns. The results showed that, at the middle and base of crown heights of trunks, concentrations of soluble sugar and NSC of the three species decreased with increasing radial depth. At breast and stump heights of trunks, soluble sugar concentrations and the ratios of sugar to starch gradually decreased, starch concentrations gradually increased, and NSC concentrations remained unchanged with increasing radial depth. NSC concentrations were higher at the middle of crown height than  at crown base, breast and stump heights of P. sylvestris var. mongolica, while they were higher at the middle and base of crown heights than at breast and stump heights of P. densiflora. There were no differences in NSC concentrations at different heights of trunks of P. tabuliformis. NSC concentrations in trunks of P. densiflora were higher than those of P. sylvestris var. mongolica and P. tabuliformis. Therefore, trunk is important pool for starch reserves for all the three conifer species, which is conducive to adapt to the environment of Horqin Sandy Land. The trunks of P. densiflora stored more carbohydrates, which may facilitate its resistance to adverse environments.

    Effects of strip cutting width on the concentrations and stoichiometry of soil C, N, and P in Phyllostachys edulis forests.
    SHEN Jingxin, FAN Shaohui, LIU Guanglu, WEI Songpo
    2023, 42(8):  1851-1857.  doi:10.13292/j.1000-4890.202308.013
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    Strip cutting of moso bamboo forests is a new strategy proposed in recent years to adapt to mechanized operation. Understanding the effects of strip cutting width on soil nutrient contents and stoichiometric ratios is of great significance for selecting reasonable cutting width and realizing sustainable management of moso bamboo forests. In this study, we compared the effects of different cutting widths (3, 6, 9, and 12 m) on the contents and ratios of soil C, N, P, with moso bamboo forest under traditional selective cutting as the control (CK). The results showed that with the increasing cutting width, the contents of soil C, N and P increased at first and then decreased. The contents of soil C, N, and P were the highest at 6 m and the lowest at 12 m. Soil C/P and N/P increased first and then decreased with increasing cutting width, whereas C/N was relatively stable. The cutting width of 6 m had significantly greater soil C/P than the cutting width of 12 m, while the cutting width of 3 m and 6 m had significantly greater soil N/P than the cutting width of 12 m. In conclusion, the cutting width of 6 m was most beneficial to the accumulation of soil C and N, with higher C/N, C/P, N/P, and more balanced nutrient ratios. Moreover, moso bamboo forest was influenced by the dual constraints of N and P contents, and soil P was more deficient. It is necessary to ensure soil nutrient balance through P fertilizer application and promote the rapid recovery of moso bamboo forest in strip cutting areas in the short term.

    Characteristics and influencing factors of crop water demand and yield in Shache irrigation area of Xinjiang.
    2023, 42(8):  1858-1868.  doi:10.13292/j.1000-4890.202307.017
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    The Shache irrigation area is an important area for agricultural planting in Xinjiang. To establish effective agricultural planting management and water resource allocation strategy, we analyzed water demands of three main crops (wheat, corn, and cotton) during the whole growing season in Shache irrigation area and their relationship with meteorological factors by using PenmanMonteith model and path analysis, based on the meteorological data of Shache County from 1990 to 2019. We further estimated crop yield through water demand-yield model, and analyzed the meteorological conditions in high-yield years to obtain important factors affecting crop yield. The results showed that water demands of wheat, corn, and cotton showed a slight upward trend from 1990 to 2019. Water demands of the crops in irrigated areas were affected by a variety of meteorological factors, with wind speed as the most important one. The meteorological conditions in the simulated high-yield years were different during different growing periods of the three crops. Temperature was one of the key factors leading to the fluctuation of crop yield. This study provides an effective reference for agricultural production and sustainable development in arid irrigated areas.

    Habitat variations of typical soil arthropods community structure in Hani peatland.
    LIN Yiling, SUN Xin, LIU Dong, DAI Guanhua, LIU Jiping, WU Haitao
    2023, 42(8):  1869-1879.  doi:10.13292/j.1000-4890.202308.003
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    Peatlands are characterized by low nutrient availability, high environmental gradient complexity, and high microhabitat variability. We investigated soil fauna in Hani peatlands of Changbai Mountain in October 2019 and September 2020 to explore the effects of environmental gradient and microhabitat heterogeneity on typical soil arthropods community structure. A total of 71454 soil springtails and mites were collected. At the spatial scale, there were substantial variations in density, richness, dominant species, endemic species, and diversity index of soil springtails and mites among different peatland habitats. At the temporal scale, community structure of soil arthropods varied greatly between 2019 and 2020, while the community structure of soil arthropods in the moss hummock microhabitats remained relatively stable. Among different microhabitats, soil arthropods density, species richness, and diversity index were significantly higher in moss hummock microhabitats than those in surrounding Carex miyabei community microhabitats. There was no significant difference in soil arthropod diversity among moss hummock microhabitats formed by different moss species. Fourteen indicator species of soil arthropods were recorded in moss hummock microhabitats. Results of redundancy analysis showed that water table depth and total organic carbon content of mosses were the key environmental factors influencing soil arthropods community in moss hummock microhabitats.

    Effects of sweet corn-soybean intercropping and nitrogen application on weed communities in upland red soil.
    XU Gang, CHEN Zhongping, YU Xia, XIAO Shihao, CAI Rushen, PAN Yuzhuo, LU Meijuan, YANG Wenting
    2023, 42(8):  1880-1889.  doi:10.13292/j.1000-4890.202306.026
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    Biodiversity is one of the important measures for ecological control of weeds. In this study, a two-year (2019-2020) field experiment was conducted to explore the effects of cropping systems (sweet corn-soybean, CS; sweet corn monocropping, MC; and soybean monocropping, MS) and nitrogen application rates (0 kg·hm-2, N0; 150 kg·hm-2, N1; 300 kg·hm-2, N2) on weed populations and community structure. The species number and density of weeds were counted in sweet corn seedling, booting and harvest stages during spring and autumn sweet corn cropping season. The results showed that a total of 34 weed species from 15 families were recorded in the two years. Crabgrass (Digitaria sanguinalis) was the dominant species in all treatments and accounted for 34.60%-54.95% of total weed density in different planting patterns. Barnyard grass (Echinochloa crusgalli) was the dominant species in CSN0, which accounted for 24.52% of total weed density. Melochia (Melochia corchorifolia) was the dominant species in MCN1, accounting for 13.96% of total weed density. Green bristlegrass (Setaria viridis) was the dominant species in CSN1, MCN0 and MCN2, accounting for 11.26%, 13.76% and 17.27% of total weed density in each planting pattern, respectively. Goose grass (Eleusine indica) was the dominant species in CSN2, MCN1, and MCN2, accounting for 10.72%, 10.81%, and 16.40% of total weed density, respectively. Compared to the treatment without nitrogen application, nitrogen application significantly reduced the average weed density in the CS in spring and in the MC in spring and autumn in 2019. The results of multivariate analysis of variance showed that the growth period of sweet corn had a significant impact on the average density of weeds in two years, the species number in 2020, the density-species index in 2019, and Simpson index, Shannon index and Margalef richness index of weed in 2020. Nitrogen application significantly affected the weed density-species index in 2019. Results of the detrended correspondence analysis showed that the changes of weed community composition were closely related to growing season and growth period of sweet corn, and that cropping system and nitrogen application did not have consistent effects on weed community composition. In conclusion, nitrogen application reduced weed density, while intercropping system could partially inhibit weed species richness in crop seedling stage. Sweet corn-soybean intercropping system under nitrogen application is beneficial to weed control.

    Temporal and spatial distribution characteristics of drought during winter wheat growth stages in Jiangsu Province.
    REN Yifang, ZHANG Lei, LI Yutao, LING Fenghua
    2023, 42(8):  1890-1901.  doi:10.13292/j.1000-4890.202306.017
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    Jiangsu Province is a key region for wheat planting in southern China, where droughts occur frequently during the growing season of winter wheat under the background of climate warming. Understanding the regularity of drought occurrence, especially the characteristics of drought in different growth stages of winter wheat, is crucial to avoid the risks to winter wheat yield. Based on data of weather, soil moisture and winter wheat phenology observations, drought indices were established by considering the effects of soil moisture and water demand at each growth stage of winter wheat. Furthermore, based on the relationships between drought index and soil relative moisture in the 0-10 cm layer, drought levels in different growth stages of winter wheat were determined. The spatial and temporal distributions of winter wheat drought in different growth stages in different regions of Jiangsu Province during 1981-2020 were then analyzed using regression and empirical orthogonal function (EOF) methods. The results showed that there were obvious temporal and spatial variations of winter wheat droughts in different growth stages. Spatially, drought intensity was stronger in north region and weaker in south region, and the frequency was higher in north region and lower in south region. Moderate and severe droughts mostly occurred in north and central Jiangsu, while mild drought mainly occurred in south Jiangsu. Temporally, the most severe and frequent droughts occurred in the emergence-overwintering periods. Compared with 1981-2000, the occurrence period with frequent droughts during 2001-2020 gradually shifted from emergence-overwintering stage to heading-maturity stage. In practice, special attention should be paid on the regions with severe drought and the periods with frequent occurrence, in order to reduce the potential losses caused by drought in a scientific and comprehensive way and to transfer the risk reasonably.

    Surface pollen assemblages and their ecological significance on the south slope of Bogda Mountain, Xinjiang, China.
    2023, 42(8):  1902-1910.  doi:10.13292/j.1000-4890.202308.002
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    Based on 57 topsoil pollen samples collected from the south slope of Bogda Mountain, we analyzed the relationship between pollen assemblages and modern vegetation by means of quantitative ecology and discussed its ecological implications. According to principal component analysis (PCA) and cluster analysis (CA), the pollen samples were divided into five vegetation zones along the elevation, including shrub desert, semi-shrub desert, mountain steppe, mountain meadow steppe, and alpine meadow. The pollen assemblages differed significantly among vegetation zones, with Ephedra-Chenopodiaceae-Nitraria, Chenopodiaceae-Artemisia, Gramineae-Chenopodiaceae-Artemisia, Gramineae-Chenopodiaceae-Artemisia-Compositae-Cyperaceae, and Cyperaceae-Chenopodiaceae-Poaceae-Compositae-Rosaceae pollen assemblages dominating corresponding vegetation zones. By weakening the influence of Chenopodiaceae and Artemisia on other vegetation zones, topsoil pollen assemblages responded well to modern vegetation distribution. Pollen assemblage indicated the dry and wet conditions of soil and environment based on PCA. Cheno podiaceae, Gramineae, Artemisia, Cyperaceae, Ephedra, Compositae, Rosaceae, and Nitraria were the main pollen types, with high content and large variation, which could be used as important references for the reconstruction of paleoenvironment. Ephedra and Cyperaceae were well represented. Chenopodiaceae and Artemisia were super representatives, which interfered with the discrimination of the quantitative relationship between pollen content and modern vegetation in other zones. The content of Gramineae was reflected in the pollen spectrum of topsoil, but it was still less representative than that of grasses in modern vegetation. Shrubs, subshrubs, and upland herbs in arid habitats had obvious advantages in the simplified pollen spectrum of topsoil, revealing the aridity of natural environment and the sensitivity and fragility of ecosystems on the south slope of Bogda Mountain.

    Habitat characteristics of rodents in desert steppe in the middle part of northern piedmont of Qilian Mountains.
    MA Yijie, WANG Jun, QU Yong, CHU Bin, TANG Zhuangsheng, BAO Daerhan, HUA Rui, HUA Limin
    2023, 42(8):  1911-1919.  doi:10.13292/j.1000-4890.202308.008
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    Rodent damage is becoming increasingly serious across desert steppe in the middle region of the northern piedmont of Qilian Mountains, which threatens local animal husbandry and grassland ecological protection. It is therefore of great significance to identify the characteristics of local rodent habitats for precise control over rodents. In this study, we investigated the geographical distribution of rodents in this region as well as soil physical characteristics and plant community structure in the main distribution areas, aiming to reveal the habitat characteristics of rodents at three aspects of vegetation landscape, soil, and plants. Results showed that desert steppe was the main distribution area of rodents in the study area. The density of rodent holes was significantly correlated with soil compactness and soil moisture of the 0-30 cm layer (R2>0.32, P<0.05). Vegetation coverage, plant biomass, Patrick index and Pielou index were significantly correlated with rat hole density (R2>0.31, P<0.05), while the frequency of Salsola passerina was significantly negatively correlated with rodent hole density (P<0.05). The results of redundancy analysis showed that soil compactness of 0-30 cm layer significantly affected the habitat selection of rodents (P<0.01). Our results demonstrate that soil compactness of 0-30 cm layer is the main environmental factor affecting habitat selection of rodents in the study area.

    Effects of water depth on phytoplankton community structure in rice-Procambarus clarkii cultivation model.
    ZHANG Lu, LI Tao, ZHANG Yefei, WANG Haiyan, XI Xiaojie, ZHU Jianqiang, YANG Jun
    2023, 42(8):  1920-1927.  doi:10.13292/j.1000-4890.202307.023
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    We investigated the effects of water depths (0.6 m (D1), 0.9 m (D2), 1.2 m (D3) and 1.5 m (D4)) on phytoplankton community structure in paddy fields with Procambarus clarkii from April to May 2021 in the Agricultural Science and Technology Park of Yangtze University in Jingzhou, Hubei Province. The results showed that a total of 106 phytoplankton species belonging to 8 phyla were identified across the four treatments. Chlorophyta was the most dominant group, which accounted for 50.67%, 46.83%, 46.91% and 46.38% of total phytoplankton species in D1, D2, D3, and D4 treatments, respectively. Schroederia nitzschioides, Chlorella sp., and Chroomonas caudata were the dominant species. The total phytoplankton abundance and biomass in the four treatments ranged from 0.82×106 to 99.74×106 cells·L-1 and 0.77 to 27.21 mg·L-1, respectively. The total phytoplankton abundance and biomass was lower in D1 than in other treatments, with the highest phytoplankton abundance in D4 treatment and biomass in D2 treatment. The Margalef, Pielou, and Shannon indices were higher in D1 treatment than in other treatments. Based on the phytoplankton diversity indices, water quality in paddy fields was at light to medium pollution level. Results of redundancy analysis showed that dissolved oxygen and water temperature greatly impacted dominant phytoplankton species in paddy fields of different water depths. Therefore, keeping shallow water is beneficial to phytoplankton growth and increase phytoplankton standing stocks in paddy fields.

    Effects of organic fertilizer application combined with bacterial agent on the growth and nutrient contents of reclaimed plants in mining area.
    WANG Dongli, ZHENG Xiaoying, LIU Yang, ZHAO Xiaoliang, LIAN Zhao, WANG Dong, XIE Wei, GUO Jianjun
    2023, 42(8):  1928-1935.  doi:10.13292/j.1000-4890.202306.031
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    Plant growth is restricted in the reclaimed waste dumps due to the harsh habitat. In this study, a field experiment was conducted to explore whether the addition of a mixed microbial agent would have synergistic effects with organic fertilizer on reclaiming plants, Sophora flavescens. The mixed microbial agent was composed of three strains at dosages of 3.6, 10.8 and 18 g·m-2 (T1, T2 and T3) applied in combination with organic fertilizer, while no microbial agent addition as control (CK). The growth characteristics of Sophora flavescens and the contents of C, N and P in stems, leaves and roots were examined to reveal the synergistic effects and mechanisms of combined application of microbial agent and organic fertilizer. The results showed that: (1) The combined application could promote plant growth. T2 treatment significantly increased plant root diameter, root fresh weight, root dry weight and bud number (P<0.05) by 26.49%, 122.76%, 109.84% and 21.41% respectively. The comprehensive growth characteristics of plants were in the order of T2>T1>T3>CK, suggesting that moderate dosage was more conducive to plant growth. (2) The combined application had different effects on plant nutrient contents, and significantly improved the total nitrogen content of stems and leaves, with T3 treatment having the most significant effect (an increase of 29.22%). However, it did not affect organic carbon content in stems, leaves and roots and total nitrogen and total phosphorus contents in roots, and was unfavorable to the improvement of total phosphorus content in stems and leaves (P<0.05). Plants were always limited by P during their growth. (3) The contents of organic carbon, total nitrogen and total phosphorus were higher in stems and leaves than those in roots. (4) The application of bacterial agent combined with organic fertilizer could increase C/P and N/P in stems and leaves (P<0.05), but did not affect C/N in stems and leaves, the C/P, N/P and C/N in roots. Our results indicated that medium dosage of microbial agent combined with organic fertilizer (T2) is more conducive to the growth of S. flavescens in the study area, but phosphorus fertilizer should be supplemented in time.

    The structural and functional characterization of bacterial community in sediments of diseased area of Apostichopus japonicus  culture pond.
    LIN Zhiping, ZHOU Yeqing, ZHANG Jingjing, WANG Luo, LIU Yanxia, DING Jun, CHANG Yaqing
    2023, 42(8):  1936-1943.  doi:10.13292/j.1000-4890.202308.017
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    To clarify the structure and function of sediment bacterial community in diseased areas of Apostichopus japonicus culture ponds, an experiment was conducted to examine the commonness and specificity of sediment bacterial community between diseased and normal areas in an A. japonicus culture pond by high-throughput sequencing. The results showed that there was no difference in the diversity of sediment bacterial community between diseased and normal areas, but richness was significantly lower in diseased areas (P<0.05). At the phylum level, Proteobacteria and Bacteroidetes were dominant bacteria in the sediments of the diseased and normal areas. The specific bacterial community in sediments of the diseased areas mainly belonged to Actinobacteria and Cyanobacteria, represented by Pseudoalteromonas, Vibrio, Staphylococcus, and Aliivibrio. The results of KEGG metabolic pathway annotation showed that there was significant difference for sediment bacterial communities in diseased and normal areas, with significant differences in 36 tertiary metabolic pathways (P<0.05), represented by significant upregulations in the pathways of glycosaminoglycan degradation, protein digestion and absorption, and various types of nitroglycan biosynthesis. Our results indicated that there were significant differences in the structure and function of sediment bacterial community in normal and diseased areas of A. japonicus  culture pond, and that the proliferation of opportunistic pathogens such as Vibrio, Pseudoalteromonas, and Staphylococcus increased the risk of A. japonicus suffering disease.

    Residue characteristics of petroleum hydrocarbon and the prediction of ecological environment risk in oil field soil.
    CHENG Zhigao, LI Gang, WU Bo, GUO Shuhai, LIU Dong, SHI Nan, LI Yang
    2023, 42(8):  1944-1952.  doi:10.13292/j.1000-4890.202308.005
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    Petroleum hydrocarbons (C10-C40) are composed of hydrocarbon compounds with different carbon numbers, which would have different degrees of ecological environmental risks. In this study, we analyzed the residual characteristics of petroleum hydrocarbons in each carbon segment in soils with different pollution histories in the oil exploitation area of Liaohe Oilfield. We evaluated and predicted the ecological environment risk of soil petroleum hydrocarbon pollution based on soil quality index and Monte Carlo simulation. The results showed that the content of residual petroleum hydrocarbons in the soil of oil field mining area varied greatly (17.8-2004.7 mg·kg-1), and that the proportion of each carbon segment was different as follows: C22-C40 (53.00%) > C13-C16 (31.81%) >C17-C21 (15.17%) > C10-C12 (0.02%). The natural decay rate constants (λ) of petroleum hydrocarbons in different carbon segments ranged from 0.0286 to 0.0395 a-1. The residue model and 95% confidence interval constructed based on λ reflected the accumulation and residue processes of petroleum hydrocarbons in each carbon segment. Risk assessment showed that short-term pollution (≤35 a) residual petroleum hydrocarbons led to low levels of ecological environment risks, while long-term pollution (>35 a) led to medium and low risks. Our results suggest that the overall ecological environment of oilfield area will be at a very high risk level for a long time under the condition of continuous pollution and no reasonable control.

    Temporal and spatial dynamics of MODIS fire points in Xishuangbanna, Yunnan during 2011 to 2020.
    REN Jing, SHEN Caiming, LIU Fang, YE Liaoyuan
    2023, 42(8):  1953-1962.  doi:10.13292/j.1000-4890.202308.015
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    Xishuangbanna is an important part of the ecological security barrier in southwest China and a key area for global biodiversity protection. We analyzed the spatiotemporal dynamics of MODIS fire points in Xishuangbanna from 2011 to 2020 using spatial correlation analysis and probability density estimation of fire points and natural and anthropogenic elements. The results showed that: (1) Global Moran’s index of the MODIS fire points in Xishuangbanna exceeded 0.94, with significant correlation in spatial distribution; (2) the temporal distribution of the MODIS fire points had an obvious seasonality, with fire points mainly occurring between February and April; (3) when the significance level was set at 0.01, the probability distributions of the fire points’ elevation, slope, distance from the water system, fractional vegetation coverage in winter and summer, precipitation, air temperature, wind speed, and humidity all followed Gamma distribution, indicating that these natural factors all contributed significantly to fire points; (4) the kernel density estimation results showed that MODIS fire points were mainly distributed in the forests within the distance of 5-8 km from the residential areas and within 2.5 km from the roads (accounting for 58.7%). Our results provided a scientific basis for understanding the pattern of fire occurrence, and a reference for fire prevention and control as well as ecological protection in tropical rainforest areas.

    Evaluation of green and ecological integration development of heavy industrial region based on emergy analysis.
    ZHANG Zhibin, YU Xiaoman, LIU Mingda, LI Jinni
    2023, 42(8):  1963-1972.  doi:10.13292/j.1000-4890.202308.004
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    Heavy industrial regions are facing great challenges in excessive resource consumption and plenty of pollutant emission. How to balance ecological protection and economic development has attracted more and more attention. Taking Liaoning Province in 2017 as an example, emergy analysis was used to calculate natural capital stocks, ecosystem service values, resource consumption including environmental services and ecological economic losses due to large industrial pollutants discharged for heavy industrial region, and evaluate green and ecological integration development. The results showed that: (1) the total natural capital stock was 5.46E+25 sej, equivalent to emergy monetary value of 1.54E+13 Em$. Geological asset had the largest contribution, accounting for 48.90%; (2) the emergy monetary value of ecosystem services was 3.27E+11 Em$ and the corresponding market price was 5.80E+10 $. The emergy monetary values of aquatic products, mineral mining, and fossil fuel mining were much higher than their market prices; (3) the total amount of resource consumption was 1.54E+24 sej, including renewable resources (3.28E+21sej), nonrenewable resources (4.99E+23sej), and input resources (1.03E+24sej), indicating that economic growth in Liaoning mainly depended on local nonrenewable resources and input resources; (4) environmental services were 9.85E+21 sej, which was 1.73 times higher than ecosystem regulating services; ecological economic losses caused by industrial pollutants were 1.84E+22sej, indicating that pollutant emissions from economic activities inevitably caused ecological overload and ecological economic losses and that input of massive resources and energy are needed for artificial purification; (5) Based on the traditional emergy accounting method, environmental services and ecological economic loss, the emergy yield rate, environmental loading rate, and emergy sustainability index were 1.47, 476 and 0.0031 respectively, indicating that Liaoning was under great pressure on ecological and environmental protection, and that its economic development highly depended on local natural resources and ecological systems. It was in state of unsustainable development. There is still a certain gap with good green ecological integration development.

    Spatial and temporal evolution and drivers of eco-efficiency in the Pearl River Delta urban agglomeration.
    2023, 42(8):  1973-1981.  doi:10.13292/j.1000-4890.202308.033
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    Under the context of China’s carbon peak and carbon neutrality goals, improving urban eco-efficiency has become an important topic for green development. Based on panel data from nine cities in the Pearl River Delta urban agglomeration from 2011 to 2019, we used the Super-SBM model to quantitatively measure urban eco-efficiency. The spatio-temporal evolution pattern was revealed by combining kernel density estimation and trend surface analysis. Furthermore, the geographically and temporally weighted regression model (GTWR) was employed to explore the effects of the driving factors and their spatio-temporal differences from the temporal and spatial perspectives. The results showed that: (1) The overall eco-efficiency of the Pearl River Delta fluctuated and rose during the study period. From 2011 to 2014, the average eco-efficiency of the Pearl River Delta decreased from 0.61 to 0.44, with a rate of -27.93%. From 2015 to 2019, it increased from 0.57 to 0.71, with a growth rate of 23.18%. The kernel density curve showed a “catch-up effect” from low-efficiency cities to high-efficiency cities. (2) The eco-efficiency of the cities showed a spatial pattern of high in the middle and low in the two wings, with the Pearl River Estuary as the core. This pattern showed an “inverted U” shape in both east-west and north-south directions, which weakened over time and presented a trend differentiation of central part > eastern part > western and northern parts > southern part. (3) The driving factors of eco-efficiency in the cities exhibited spatio-temporal heterogeneity. Temporally, the positive driving effect of urbanization on eco-efficiency decreased with fluctuation over time, the inhibitory effect of environmental regulation weakened gradually, and the impact of industrial structure changed from positive to negative. Spatially, the impact coefficient of urbanization increased from southwest to northeast, the inhibitory effect of environmental regulation mainly occurred in the central cities such as Zhongshan and Guangzhou, and the impact coefficient of industrial structure presented a pattern of positive in the west and negative in the east. Our results provided spatial decision-making support for the green and low-carbon development of the Pearl River Delta urban agglomeration and offered important insights for ecosystem management and research of other large urban agglomerations.

    Topographic effect of county-level land-use landscape pattern in the dry-hot valley of Jinsha River, Yunnan Province.
    XU Yingjie, YANG Shaowei, ZHANG Junming, SUN Yongyu, YANG Xiubiao, OU Zhaorong
    2023, 42(8):  1982-1992.  doi:10.13292/j.1000-4890.202308.012
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    The dry-hot valley of Jinsha River region is one of the most ecologically fragile regions in China. Understanding land-use landscape patterns in this region has great significance for regional ecological and environmental regulation. Based on land-use data of four periods in 2005, 2010, 2015, and 2020, as well as the GIS spatial ana-lysis and landscape pattern analysis methods, we investigated the landscape pattern and topographic effect of land use with different elevation ranges, slope categories and topographic position indices. The aims of this study were to reveal the driving mechanisms of land-use landscape pattern change and provide a scientific basis for regional ecological regulation and control. The results showed that the degree of land-use landscape fragmentation was strengthened from 2005 to 2020, landscape heterogeneity was obvious, landscape diversity was increased, and landscape evenness was improved. Woodland, grassland and arable land were landscape substrates of the study area. The main landscape types of dry-hot zone were grassland and arable land, with a significant growth in area of waters and construction land. The main landscape types in the non-dry-hot zone were woodland and grassland, with a continuous decrease of arable land area and a constant increase of construction land area. The distribution trend of slope and topographic position of various land-use types were almost the same. Arable land, water area, and construction land were mainly distributed in low terrain, while woodland, grassland, and unused land were primarily distributed in middle and high terrain. There was an obvious topographic effect of land-use landscape patterns in the study area. Natural factors drove the basic pattern of land-use landscape in the study area. The impacts of human factors on regional land-use landscape pattern had been strengthened during the past 15 years, while the effects of human factors had become more obvious after 2015. In the future, more research about landscape pattern in the dry-hot valley of the Jinsha River should be done on the construction of regional landscape ecological security pattern and response characteristics and mechanism of regional land-use landscape pattern to global climate change.

    Review on the development of slope greening technology patents for  30 years in China.
    YANG Yuhe, LIAO Kewu, MA Jian, Lv Qing, XU Hui, XU Ligen
    2023, 42(8):  1993-2002.  doi:10.13292/j.1000-4890.202308.001
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    We reviewed the research and development of the slope greening technology in China in recent 30 years from a perspective of patent. The number, type, application time, and applicants for patents applied and issued in field of the slope greening in China during 1991-2020 were searched. The patents were classified into five types of technologies, including soil stabilization, vegetation reconstruction, maintenance, effect evaluation, and construction method. The R&D trend, categories, and key technologies of the slope greening in China were summarized. There were totally 2477 patents in the field of slope greening in China, half of which were invention patents and half were utility model patents. The research and develop in slope greening technologies in China has entered a rapid developing period since 2015. The number of the patents was 886 for soil stabilization, 846 for revegetation, 282 for maintenance, 19 for effect evaluation, and 444 for construction method, which accounted for 35.8%, 34.2%, 11.4%, 0.8%, and 17.9%, respectively. This result indicated that soil stabilization and vegetation reconstruction were the two technology hotspots in China, and that the evaluation technology attracted relatively less attention. In addition, the four key technologies of seed spraying, framing, grooving and bag pillowing have been becoming mature. Further research is needed in development of new materials and the application of special habitats. This paper provides a reference for the innovation and R&D of slope greening technology.

    Development of low-carbon community in China: Retrospect and prospect.
    CHEN Yixin, ZENG Hui
    2023, 42(8):  2003-2009.  doi:10.13292/j.1000-4890.202308.006
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    Carbon peak and carbon neutrality are important strategies for China’s future socioeconomic development. To achieve the goal of “dual-carbon” strategy, a national-level action plan is needed, as well as strong public participation. Developing a low-carbon community is an important strategy for public participation, materializing low-carbon economy and carbon neutrality. Here, we review the development of low-carbon community concept and analyze the characteristics of low-carbon communities. We examined the problems in low-carbon community deve-lopment in China, including the lack of detailed guidance in planning and construction, the lack of evaluation and supervision in community maintenance, and the lack of detailed guidance for public participation and behaviors in the collective action. Finally, we discussed the challenges and areas for future low-carbon community development in China from the perspectives of both government and public participation in order to achieve the “dual-carbon” strategy. We believe that the following two major areas should be focused during building low-carbon communities: to establish a low-carbon community development model under the government guidance and to quantitatively evaluate the carbon neutrality potential of low-carbon community construction and its contribution in carbon neutrality, thus to enhance the public’s sense of gaining in participating in the construction of low-carbon communities.

    Review on phytoplankton research during the frozen period in lakes.
    JIANG Mengyu, WANG Xiaodong, LIU Xiaohui, LIANG Pinwen, YUAN Yuxiang
    2023, 42(8):  2010-2019.  doi:10.13292/j.1000-4890.202308.019
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    More than half of global lakes are seasonally or annually frozen. Freeze is a special physical-hydrological process in frozen lakes, affecting physical and chemical variables of lake ecosystems. Many ecological issues caused by climate warming and lake eutrophication have attracted global attention, including the shortening frozen period, phytoplankton phenological shifts and earlier spring algal blooms. We reviewed the important progress of phytoplankton research during the frozen period in lakes from three aspects. First, we summarized recent progress in various environmental conditions and the variations of physicochemical factors in different stages of frozen period. We then synthesized the temporal and spatial variations of phytoplankton growth, species composition, and community structure under changing environment during the frozen period, as well as their response mechanism. Lastly, we introduced the research progress on phytoplankton during the frozen period in China. Accordingly, the future trends of phytoplankton research during the frozen period are prospected, especially biogeochemical processes, feedback mechanism among lake-atmosphere-land and climate, research methods, and the construction of theoretical models.

    Landscape ecological risk identification and optimization strategy in Xining City based on land use change.
    QIAO Bin, YAN Yuqian, ZHANG Tinghua, LI Xiuyang, ZHANG Rui, LI Xiaodong, LI Fu, LI Suyun, ZHU Cunxiong, ZHOU Bingrong
    2023, 42(8):  2020-2031.  doi:10.13292/j.1000-4890.202307.013
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    Landscape ecological risk assessment is a comprehensive means for the spatial optimization allocation of land resources and the decision-making design of ecological resources management, which can provide a new idea for quantitative assessment of regional ecological security. We analyzed the characteristics of the temporal and spatial variations of land use in Xining City from 1980 to 2020, and explored the characteristics of the temporal and spatial variations of landscape ecological risks. The results showed that: (1) Grassland accounted for more than 51% of the total area of Xining City, mainly with medium/low coverage grassland. From 1980 to 2020, the area of cultivated land decreased by 97.42 km2, while the construction land increased by 103.89 km2. (2) The land use structure was relatively stable before 2000, and the degree of land use change was active after 2000. During the four decades, the area of transferred from cultivated land was the largest at 109.69 km2, while the area transferred into construction land was the largest at 104.44 km2. (3) The landscape ecological risk index of Xining City was 0.288, and the landscape ecological security status was generally stable. The ecological risk levels were mainly at low and the relatively low ecological risks, accounting for more than 70% of Xining’s area. (4) The global Moran’s I values of Xining’s landscape ecological risk in the five periods were 0.712, 0.720, 0.724, 0.741, 0.764 respectively, with a spatial distribution pattern being dominated by low-low and high-high clusters. The degree of spatial autocorrelation increased gradually, and the trend of spatial convergence strengthened continuously. The paths of optimal allocation of land resources include: scientifically estimating the scale threshold of production, living, and ecological lands in the land use structure, avoiding excessive development and utilization of production and living land and occupying ecological space, improving the quality of grassland and arable land resources, and strengthening the overflow benefits of ecological functions and values of woodland resources, rational planning of the scale and intensity of construction land development, cultivating landscape ecological corridors of waters and construction land, and moderately increasing the area of ecological land in the urban area. Such suggestions may ensure the continued improvement of ecological security pattern in Xining City.

    Hydrolase properties of a strain of Bacillus subtilis and its response to salt stress.
    LI Qiaoling, LI Aibo, HUANG Zhiyuan, ZHANG Xiaoping, BIAN Fangyuan, ZHONG Zheke
    2023, 42(8):  2032-2039.  doi:10.13292/j.1000-4890.202306.032
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    To screen microbial resources for decomposing organic carbon in high-salt organic wastewater, one strain of salt-tolerant enzyme-producing bacterium was isolated and screened from bamboo shoot processing waste by dilution coating method and decolorization circle plate test method. The strain was identified based on morphology, scanning electron microscopy observation, physiological and biochemical characteristics, and 16S rRNA gene sequence analysis. A single-factor control method was used to optimize the growth conditions of the strain. The growth of the strain under salt stress and the activities of hydrolytic enzymes (protease, cellulose, and amylase) were measured. A salt-tolerant and organic carbon decomposing strain of Bacillus stubilis ACP81 was obtained, which was able to grow in NaCl solutions with concentrations ranging from 1% to 19%, with optimal growth at 1% NaCl and 5% NaCl as the semi-inhibitory concentration of the strain. The activity of cellulase, neutral protease, and β-amylase in the culture of the strain was 72.4, 3.2, and 0.3 U·mL-1 respectively at the semi-inhibitory concentration (5% NaCl). Under salt stress, the cellulase and β-amylase activities of strain ACP81 increased with increasing NaCl salt concentration, while the neutral protease showed an opposite trend and the generation time became gradually longer. The isolated Bacillus subtilis ACP81 reached the salinity tolerance range of moderately salinityloving bacteria and had an advantage of cellulase and β-amylase production in hypertonic environment, which can be used as a candidate strain for biochemical treatment of high-salt organic wastewater.

    Assessment of a cold temperate mountain river based on the benthic macroinvertebrate-based index of biotic integrity: A case of Huma River.
    DOU Qianming, WANG Huibo, SONG Dan, DU Xue, WANG Le, HUANG Xiaoli, ZHAO Chen, HUO Tangbin
    2023, 42(8):  2040-2048.  doi:10.13292/j.1000-4890.202308.021
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    Based on the data of benthic macrobenthos and water physicochemical indices of 25 sampling points (9 reference points and 16 disturbed points) in Huma River, the benthic index of biotic integrity (B-IBI) was deve-loped to evaluate the health of mountain river in the cold temperate zone. According to the distribution range, discriminant ability, and the correlation analysis of 27 biological indicators, the final B-IBI system was composed of the relative abundance of Plecoptera individuals, the relative abundance of EPT (Ephemeroptera, Plecoptera, Trichoptera) individuals, the relative abundance of sensitive taxa individuals, the biotic index  (BI), and the relative abundance of shredder individuals. The ratio method was used to unify the index dimensions. The 25% quantile of the B-IBI value distribution at the reference points was used as health evaluation standard. The results showed that eight out of the 25 sampling points were healthy, and the number of points with status of sub-healthy, fair, poor, and very poor was 8, 6, 2, and 1, respectively. The B-IBI system showed that the health status of the Huma River was generally good. The health status of the trunk stream from good to bad was: upstream, midstream, and downstream. Among tributaries, Ganbu River, Walagan River, Daxiluga River, Aokusakaai River and Xilinixi River were at healthy status; Tahe River, Xiaoxiluga River and Wolegen River were at sub-healthy status; Muwulu River and Manlakai River were at fair status; and Hailai River and Taha River were at poor status. Results of Pearson correlation analysis showed that the B-IBI value was significantly positively correlated with dissolved oxygen content and negatively correlated with ammonia nitrogen content (P<0.05). Results of redundancy analysis showed that the B-IBI system had a high degree of explanation for environmental factors. The B-IBI system based on the Huma River was suitable for health assessment of cold temperate mountain rivers in China.