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    15 December 2020, Volume 31 Issue 12
    Spatiotemporal variation of growing season length of vegetation in China.
    ZHENG Zhao-wen, XIAO Yuan-jun, SONG Wen-dan, MA Ting, CHENG Yong-xiang, HUANG Jing-feng
    2020, 31(12):  3979-3988.  doi:10.13287/j.1001-9332.202012.013
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    We analyzed the variation trend of growing season length (GSL) of different periods in provinces (regions) of China and the corresponding movement velocity of GSL isolines at 150, 200, 250, 300 and 350 days, based on daily mean temperature data of 822 meteorological stations from 1951 to 2017. In this study, the definition of GSL given by the world meteorological organization was adopted, together with Slope, Hurst and Mann-Kendall indices. The results showed that the GSL in northern China changed significantly during 1951-2017. The extension of GSL was faster in the north than the south, and faster in high-altitude areas than low-altitude ones. The trend of future GSL change in most regions of China converged with the current extension trend. The extension of GSL in northern provinces (regions) was generally 0.1-0.2 d·a-1, of which the fastest was Tibet with a speed of 0.44 d·a-1. The period 1981-2000 was the most changeable time of GSL in Chinese provinces (regions). The growing season start (GSS) of all provinces (regions) contributed more to the GSL extension, except for Xinjiang, whose GSL extension was dominated by the growing season end (GSE). In the high-latitude or high-altitude provinces, GSL was more sensitive to the change of mean annual temperature. The higher the mean annual temperature, the longer the GSL. Since 1951, China's GSL isolines of 150, 200, 250, 300 and 350 days showed notable variations. The fastest movement velocity was the 200 days isoline in Northeast China with an average northward movement velocity of 6.11 km·a-1. The general principle of the movement of China's GSL isoline was that the higher the value of the isoline, the slower the northward movement, with even a southward shift in part of the 350 days isoline. The extension of GSL in China would result in the northward shift of crop planting boundary and the extension of natural vegetation growth period. However, the specific impacts of this change on the quality, crop yield, and ecosystem carbon sequestration need further research.
    Spatial distribution and interspecific associations of regenerating saplings in karst secondary forests.
    CHI Sen, WANG Cong-jun, LI Qing-ju, WU Zhi-hong, CHAI Zong-zheng
    2020, 31(12):  3989-3996.  doi:10.13287/j.1001-9332.202012.006
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    A 140 m×120 m plot was set in a secondary forest with more than 30 years natural reco-very after abandonment in Ziyun Miao and Buyi Autonomous County, a typical karst area in Guizhou Province. We investigated the spatial distribution and interspecific associations of regenerating sapling population using spatial point pattern analytical method. There were 1291 saplings with 39 tree species. Betula luminifera, Platycarya strobilacea, Liquidambar formosana, Pinus massoniana and Populus davidiana were the dominant populations of regenerating saplings, accounting for 83.7% of the saplings and 77.8% of the total importance value. The spatial distributions of B. luminifera, P. strobilacea and L. formosana were strongly aggregated at a spatial scale of 0-60 m, while the spatial distributions of P. massoniana and P. davidiana were aggregated at small scale and randomly distributed at large scale. The spatial associations among those dominant populations were mostly positively correlated, with positive correlations of P. massoniana with L. formosana and P. davidiana at small scale but no associations at large scale. In conclusion, the spatial distributions and interspecific associations differed among the dominant sapling populations, due to the different biological characteristics of different tree species, habitats and uses of spatial resources. Most of the stands investigated were dominated by pioneering species, with poor stand quality and unstable community structure. A mixed forest dominated by P. massoniana and B. luminifera would be the next stage of succession. We recommended that measures of forest management should be adopted to accelerate vegetation restoration.
    Spatial heterogeneity of Ephedra przewalskii populations in the stony desert in the middle of southern foot of Tianshan Mountains, China.
    DING Jie, ZHANG Pu, ZHANG He-yu, LI Zhi-peng, FENG Yi-ming
    2020, 31(12):  3997-4003.  doi:10.13287/j.1001-9332.202012.003
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    Plots were set on the top, middle and bottom of the stony desert alluvial fan in the middle of southern foothills of the Tianshan Mountains. With plant height and crown size as indicators, the spatial heterogeneity of Ephedra przewalskii populations in the stony desert were studied using geostatistical methods. Understanding the spatial heterogeneity characteristics of E. przewalskii populations could provide scientific basis for vegetation protection and ecological restoration in stony deserts. The results showed that E. przewalskii had a patchy distribution at the top of the alluvial fan. At the middle and bottom of the alluvial fan, it showed a banded distribution. The band width in the middle was larger than that at the bottom. From the top to the bottom of the alluvial fan, the overall plant height and crown size of E. przewalskii populations decreased first and then increased. The average plant height on the top, middle and bottom of the alluvial fan was 40.34, 21.07, 36.96 cm, and the crown size were 1.09, 0.80, 1.43 m2, respectively. The best fitting models for plant height of E. przewalskii were the exponential model, the exponential model, and the linear model at the top, middle and the bottom of the alluvial fan, respectively, while the best fitting models for crown size were exponential model, spherical model, and linear model. From the top to the bottom of the alluvial fan, the fractal dimension value of plant height and crown size of E. przewalskii ranged from 1.909 to 1.889, indicating that the spatial pattern of E. przewalskii populations was simple and the spatial homogeneity was high. From the top to the bottom of the alluvial fan, the spatial distance of the anisotropy of plant height and crown size of E. przewalskii gradually shortened. At the top, middle and bottom of the alluvial fan, the spatial distances where the plant height and crown showed anisotropy were >60 m, 42-46 m and 23-27 m, respectively.
    Simulation and uncertainty analysis of natural regeneration for pine-oak forests.
    WANG Bin, TIAN Xiang-lin, LIAO Zi-yan, WANG Zhi-tao, GENG Sheng-lian, CAO Tian-jian
    2020, 31(12):  4004-4016.  doi:10.13287/j.1001-9332.202012.018
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    The complexity and uncertainty of forest regeneration is crucial for predicting forest ecosystem dynamics. A natural regeneration model of pine-oak forests in Qinling Mountains was constructed with competition, climate and topography factors using Bayesian statistics and global sensitivity analysis (GSA). The alternative models were based on Poisson, negative binomial (NB), zero-inflated Poisson (ZIP), and zero-inflated negative binomial (ZINB) models. According to the uncertainty of model parameter transfer, the analysis results were quantified, and the dominant factors of small probability events affecting forest regeneration were explained. The results showed that the ZINB model was the best one in the simulation of Pinus tabuliformis and Quercus aliena var. acuteserrata. Stand basal area, light interception, slope location and minimum temperature during growing season were the most critical factors affecting natural regeneration of P. tabuliformis, while stand basal area, cosine of aspect interacted with the natural logarithm of elevation, annual mean temperature, and precipitation of the warmest quarter were the most critical factors for Q. aliena var. acuteserrata. The contributions of various factors to the predictive uncertainty were: competition factor (25%) < climate factor (29%) < topography factor (46%) for the simulation of P. tabuliformis regeneration, and climate factor (12%) < competition factor (24%) < topography factor (64%) for the simulation of Q. aliena var. acuteserrata regeneration. The natural regeneration quantity of P. tabuliformis was positively correlated with mean annual temperature and minimum precipitation during growing season, and negatively correlated with the mean temperature in the driest quarter. The natural regeneration quantity of Q. aliena var. acuteserrata was positively correlated with mean annual temperature, minimum precipitation during growing season, precipitation of the warmest quarter, and negatively correlated with mean temperature of the driest quarter. The ZINB model based on Bayesian methods could effectively quantify the major factors driving forest regeneration and interpret the uncertainty propagated from parameters, which was useful for predicting forest regeneration.
    Responses of canopy stomatal conductance of Platycladus orientalis to soil water under water control.
    YAN Cheng-zheng, ZHENG Wen-ge, JIA Jian-bo, YAN Wen-de, WANG Zhong-cheng, JIA Guo-dong
    2020, 31(12):  4017-4026.  doi:10.13287/j.1001-9332.202012.010
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    A water-controlled experiment with four treatments (no rain, half raining, natural raining and double raining) was carried out in a Platycladus orientalis forest. The factors including soil water content (SWC), precipitation, sap flow density (Js), leaf area index (LAI), vapor pressure deficit (VPD) were monitored during August 2016 to August 2017. We further analyzed the response of canopy stomatal conductance (gs) to changes of SWC. The results showed that the SWC of plots (half, natural and double raining) showed a positive correlation with precipitation, and the range of SWC was 4.9%-16.0%, 7.2%-22.9%, 7.4%-29.6%, respectively. The SWC in the plot with no rain decreased by 50% from August to October. The daily gs reached a peak of 166.64 mmol·m-2·s-1 at 14:00 in July, which was significantly higher than other months. A bimodal phenomenon occurred. The daily gs reached a peak of 54.1 mmol·m-2·s-1 at 12:00 in January. Under the three rain plots, diurnal variation of gs and SWC showed a negative quadratic correlation. The SWC corresponding to the peak of gs was 8.5%, 12.5% and 18.5%, respectively, close to the annual average SWC. Sensitivity (δ) of gs to VPD /reference canopy stomatal conductance (gsref) was more than or equal to 0.6 in different water-controlled plots, indicating that soil water condition was more suitable for water demand of P. orientalis. When SWC was between 3.7% and 7.5%, the δ and gsref increased rapidly, indicating that stomata had better regulation ability, and that plant stomata was more sensitive to VPD. When SWC increased to 11%, SWC alteration did not affect the response sensitivity of gsrefand gs to VPD. There might be a SWC threshold value for the adaptation of P. orientalis. By closing or reducing stomatal aperture, leaf water potential decreased, P. orientalis could adapt to excessive VPD and avoid excessive transpiration, which was more effective in regulating transpiration.
    Effects of growth stage and altitude on twig functional traits and biomass allocation of Rhododendron przewalskii in the headwater region of Minjiang River, China.
    HE Jia-li, WANG Jin-niu, ZHOU Tian-yang, SONG Yi-ke, SHI Ning, NIYATI Naudiyal, WU Yan
    2020, 31(12):  4027-4034.  doi:10.13287/j.1001-9332.202012.001
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    This study aimed at understanding the differences in traits of functional twigs and leaves of a typical alpine shrub species, Rhododendron przewalskii, at Kaka Mountain in the headwater region of Minjiang River. Leaf and twig traits were compared for shrubs at different growth stages (flower bud stage and flowering stage) and altitude (3600 m and 3800 m). The effects of spatial heterogeneity on their correlations and trade-offs were evaluated at leaf and twig levels, respectively. Our results showed that twig length was significantly longer at low altitude than high altitude for the shubs at the same growth stage. The number and mass of flowers at flowering stage were significantly higher at high altitude than those at low altitude. At the same altitude, twig mass, number of leaves, total leaf mass, total leaf area and total petiole mass were all significantly greater at the flower bud stage than those at the flowering stage, while the individual leaf mass and individual petiole mass at flower bud stage were significantly smaller than those at flowering stage. Compared with the flower bud stage, the proportion of leaf mass decreased by 13% at the flowering stage, while biomass proportion of twig significantly increased. At the flower bud stage, twig mass had a higher contribution to total twig mass. In contrast, the contribution of total leaf mass to total twig mass was higher at flowering stage. More biomass of leaf was allocated to individual leaf mass at flower bud stage. More biomass of leaf was allocated to individual petiole mass and individual leaf mass at flowering stage at low altitude and high altitude, respectively. At low altitude, allometric growth patterns presented between twig mass and total leaf area, total leaf mass. Similarly, individual petiole mass and individual leaf area had allometric growth. Our results indicated that the functional traits of twigs and leaves varied across both altitude and plant growth stage.
    Seed rain dynamics of natural secondary forest in the central part of Greater Xing'an Mountains, China.
    ZHANG Ling-yu, DONG Ling-bo, CHEN Ying, LIU Zhao-gang
    2020, 31(12):  4035-4041.  doi:10.13287/j.1001-9332.202012.007
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    We monitored seed rain in three forest types for two years (2018-2019) in the central part of Greater Xing'an Mountains, and analyzed the seasonal seed rain dynamics, deciduous dynamics, seed rain thousand-grain weight, inter-annual variation of seed rain, and spatial pattern of seed rain of the main tree species in different forest types. The results showed that seed rain of Larix gmelinii and Betula platyphylla in each forest type showed unimodal distribution. The leaf litter amount of coniferous and broad-leaved species (L. gmelinii, Pinus sylvestris var. mongolica, Picea koraiensis, B. platyphylla and Populus davidiana) also showed obvious seasonal dynamics, with a peak in the middle and early September. In coniferous and broadleaved mixed forests and coniferous forests, the 1000-grain weight of L. gmelinii at the peak period was significantly greater than that at the initial and final stages. The 1000-grain weight of B. platyphylla in the three forest types did not show obvious seasonal variation. Seed rain of L. gmelinii and B. platyphylla showed obvious inter-annual change. The year 2018 was a large seed set year, whereas 2019 was a year with small seed set. The spatial pattern of all seed rain was mainly dominated by aggregated distribution in both years, which was consistent with that of seedlings and saplings.
    Characteristics of soil seed bank and their correlations with soil factors in the early restoration period of Populus deltoides cutting slash in Lake South Dongting, China.
    LIU Jing-yi, NIU Yan-dong, GUO Ke-ji, LUO Xue-wei, YANG Rui, JIANG Li-juan
    2020, 31(12):  4042-4050.  doi:10.13287/j.1001-9332.202012.005
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    To understand the potential role of soil seed bank in natural vegetation restoration of Populus deltoides cutting slash in Lake Dongting, the structure and diversity of soil seed bank and its relationship with vegetation and soil parameters were observed and analyzed on the lake beach in the first two years after P. deltoides cutting, with P. deltoides lake beach as control (CK). A total of 65 plant species germinated in soil seed bank, belonging to 59 genera and 23 families. The density of soil seed bank and number of species ranked as 1-year cutting slash (11810 seeds·m-2, 49 species)> 2-year cutting slash (9686 seeds·m-2, 44 species)> CK (6735 seeds·m-2, 29 species). Compared with CK, species diversity of the perennial mesophytes and hygrophytes in the soil seed bank and aboveground vegetation of cutting slash, as well as the similarity coefficient between soil seed bank and aboveground vegetation, increased. Soil water content and nutrient content increased, while the pH decreased. Soil water content and organic matter were closely related to the distribution of hydrophytes such as Polygonum hydropiper, while total potassium and phosphorus contents had a greater influence on the distribution of perennial species such as Phalaris arundinacea. In summary, during the natural restoration of P. deltoides cutting slash in Lake Dongting, with the changes of soil physicochemical properties, species richness and density of soil seed bank increased significantly, and the diversity of aboveground vegetation species therefore increased. Soil seed bank is an important propagule source for the restoration of wetland vegetation in cutting slash.
    Stoichiometry of carbon, nitrogen and phosphorus and their allometric relationship between leaves and fine roots of three functional tree seedlings.
    YANG Ting, ZHONG Quan-lin, LI Bao-yin, CHENG Dong-liang, XU Chao-bin, YU Hua, ZOU Yu-xing
    2020, 31(12):  4051-4057.  doi:10.13287/j.1001-9332.202012.004
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    We analyzed the contents and stoichiometric ratios of carbon (C), nitrogen (N) and phosphorus (P) in leaves and fine roots of Machilus pauhoi (an evergreen broad-leaved species), Cerasus campanulata (a deciduous broad-leaved species) and Fokienia hodginsii (an evergreen coniferous species) to compare the leaf and root stoichiometry and allometric relationship between different functional groups of trees. There were significant difference in the contents and stoichiometry of C, N and P in the leaves and fine roots among different functional groups. C content, C/N and C/P of the leaves and roots were the highest in M. pauhoi. N content and N/P of the leaves and roots were the highest in C. campanulata, whereas P content of the leaves and roots was the highest in F. hodginsii. The allometric relationship of C, N and P contents as well as their stoichiometric ratios between the leaves and fine roots showed significant difference, which was affected by functional difference. The allometric relationship between C/P and N/P with significantly different allometric indexes in leaves in seedlings of those three tree species, while the isometric relationship between the contents of N and P was found in fine roots. There were significant difference in the C, N and P stoichiometry between the leaves and fine roots. The allometric relationship between leaf C content and root P content in M. pauhoi was detected. C and N contents and C/N, N/P in leaves generally had the allometric or isokinetic relationships with C/N, N/P of fine roots. There were allometric relationships between the leaf C content and the root C, N and P contents in F. hodginsii. It was concluded that nutrient allocation between leaves and fine roots of C. campanulata was more strongly coordinated. The investment strategy of P for leaves and fine roots across those three tree species was similar. The results provided scientific reference for accurate nutrient management at seedling stage and efficient cultivation technique.
    Multiscale influences of urbanized landscape metrics on the diversity of indigenous plant species: A case study in Shunyi District of Beijing, China.
    PENG Yu, WANG Wen-tao, LU Yi-tong, DONG Ji-hui, ZHOU Yan-qiu, SHANG Jia-xin, LI Xiang, MI Kai
    2020, 31(12):  4058-4066.  doi:10.13287/j.1001-9332.202012.020
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    The effects of landscape pattern on plant diversity have been widely reported in literature, with that of urban landscape remaining largely unknown. To explore the impacts of urbanization landscape pattern on plant diversity and its scale effect, 105 plots were investigated in Shunyi District, Beijing. The α and β diversity of each plot were calculated, and 43 urban landscape indices of 10 scales in the range of 100-1000 m were analyzed with 100 m as the step. The results showed that the urban landscape area metric, core metrics and edge metrics were negatively related with diversity of indigenous plant species at all the examined scales. Shape complexity metrics contributed to plant diversity at small scale, while the area-weighted complexity metrics contributed at large scale. Other metrics, such as connection, proximity, cohesion, fragmentation and interspersion juxtaposition of urban patches showed a slight and unsteady relationship with the diversity of indigenous plant species. The urbanization intensity was negatively related with scales and with plant diversity at all scales. Urban landscape could better conserve indigenous plant diversity by reasonably dividing an urbanized area into many small patches with simple edge. Our results presented suitable urban landscape indicators for preserving plant diversity and suggestions for the construction of ecological cities.
    Plant community and soil nutrient of alpine meadow in different degradation stages on the Tibetan Plateau, China.
    YANG Jun, LIU Qiu-rong, WANG Xiang-tao
    2020, 31(12):  4067-4072.  doi:10.13287/j.1001-9332.202012.008
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    We examined soil physical and chemical properties and plant community characteristics of four Kobresia alpine meadows at different degradation stages in Damxung County, Lhasa City, Tibet Autonomous Region, China, with the method of spatial sequence instead of time succession. The results showed that soil organic carbon, total nitrogen, available phosphorus, available potassium, ammonium, nitrate, and water content showed a decreasing trend as the degree of soil degradation increased, while pH showed an increasing trend. Plant community height, richness, diversity index and evenness index of the moderately degraded meadow were the highest. Community coverage and total biomass were the largest in undegraded meadow and the smallest in the severely degraded meadow. As the degree of meadow degradation intensifies, the biomass and proportion of Cyperaceae decreased, the biomass and proportion of legumes and weeds increased, and the biomass and proportion of Gramineae first increased and then decreased. The aboveground biomass of meadow was significantly positively correlated with soil organic carbon content, total nitrogen content, total phosphorus content, and soil water content, and significantly negatively correlated with soil pH. With the vegetation degradation in meadow, soil degradation had worsened, which ultimately manifested as a significant decline in grassland productivity.
    Prediction of potential geographical distribution patterns of Pyrus xerophila under different climate scenarios.
    LIU Chao, HUO Hong-liang, TIAN Lu-ming, DONG Xing-guang, XU Jia-yu, QI Dan, ZHANG Ying, CAO Yu-fen
    2020, 31(12):  4073-4079.  doi:10.13287/j.1001-9332.202012.012
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    Pyrus xerophila has strong resistance to drought, cold, salt, and rust. It is one of the main rootstock types of pear in Northwest China, with high production value. However, its habitat is seriously damaged. The prediction of the geographical distribution of P. xerophila under different climate scenarios will provide important scientific basis for rational development and utilization of resources and the protection of diversity. Based on MaxEnt model and ArcGIS spatial analysis, the potential spatial distribution pattern of P. xerophila in the current and future (2050, 2070) was constructed using comprehensive and accurate distribution records and high-resolution environmental data, and the relative importance of environmental factors was evaluated. The results showed that the suitable habitat area of P. xerophila was 3.32×105 km2, mainly located in eastern Qinghai, southern Gansu, southern Ningxia, central Shaanxi, southern Shanxi and western Henan. Mean UV-B of the month with lowest UV-B and altitude were identified as the critical factors shaping habitat availability for P. xerophila. Overall, with global warming, the potential habitat for P. xerophila might decrease in 2050 and 2070 under different CO2 climate scenarios. Real-time monitoring of P. xerophila populations should be enhanced.
    Spatial and temporal evolution of habitat quality in Fujian Province, China based on the land use change from 1980 to 2018.
    LI Sheng-peng, LIU Jian-ling, LIN Jin, FAN Sheng-long
    2020, 31(12):  4080-4090.  doi:10.13287/j.1001-9332.202012.019
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    Analyzing the characteristics of spatial-temporal evolution of habitat quality caused by land use change can provide a scientific basis for the coordinated development of regional ecological economy. With Fujian Province (the ecological civilization demonstration area of China) as an example,the InVEST model was used to evaluate the habitat quality based on the land use change data from 1980 to 2018. Further, the influencing factors were analyzed through Geodetector, and the spatial-temporal characteristics of habitat quality was analyzed by combining with the change of land use type. The results showed that the main land use change types included farmland translating to forest land and construction land, forest land translating to farmland, grassland and construction land, and grassland translating to forest land, which accounted for 8.4%, 14.5%, 7.6%, 17.1%, 6.4% and 31.7% of the total land use change, respectively. From 1980 to 2018, the overall habitat quality of Fujian Province was at a high level (0.6-0.8), showing a trend of habitat degradation and habitat quality reduction. The first leading factor for the spatial variation of habitat quality was the change of land use type, with the impact of socioeconomic factors on the habitat quality of coastal counties and cities being significantly higher than that of the entire region and inland counties and cities. The rapid encroachment of construction land on the surrounding forest and grassland accele-rated the degradation of habitat in coastal areas, the process of which was irreversible. The habitat degradation of central urban areas would undergo a similar process in inland area, but might be slower than coastal area in terms of speed and scale. In the long term, the speed of habitat degradation could be slowed by controlling the scale of cities, developing urban ecological greening, and buil-ding an ecological security pattern.
    Extraction of land-cover and wetland area in Bohai Rim region based on Google Earth Engine.
    YU Li-li, SUN Li-shuang, ZHANG Dan-hua, LIU Miao, XIE Zhi-wei, PING Xiao-ying
    2020, 31(12):  4091-4098.  doi:10.13287/j.1001-9332.202012.014
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    The land cover of Bohai Rim region has changed greatly due to urbanization and economic development. Monitoring the land cover with high accuracy and real time is the most important basis for relevant researches. Traditional single-machine processing mode is difficult to realize rapid monitoring for large-scale and long-time series. The emergence of remote sensing big data makes it possible to combine computing platform and massive data. The land cover maps of study area were interpreted based on Google Earth Engine (GEE) platform with decision tree (CART) method from 2000 to 2019. The land cover change was analyzed, and the interpretation results using different data sources were compared. The results showed that the GEE platform could realize the rapid land cover interpretation in a large area, which interpreted coastal wetlands and other cover types with high accuracy over 80% comparing the surveyed points. Compared with Landsat images, the Sentinel-2A images interpretation results had a great improvement in accuracy, which increased from 85% to 95%, and thus more detailed surface information could be reflected. In 2000, the area of wetland, build-up area, farmland, forest, and water in the study area were 1612.5, 5734.9, 32074.8, 11853 and 3504.3 km2, accounting for 2.9%, 10.5%, 58.6%, 21.6% and 6.4% respectively. By 2019, wetlands had been reduced by 775.1 km2, with a decline of 40.1%; built-up area increased by 5310.5 km2 with an increasing rate of 92.6%. The area of farmland, forestland and water area decreased 1841.6, 1823.5 and 870.3 km2, with a decreasing rate of 5.7%, 24.8% and 48.1%, respectively. The coastal urbanization process caused the occupation of built-up area to other land use types, which was the main driving force of land cover change in the study area.
    Spatial distribution of preferential flow paths in paddy field in the Karst Area of Guangxi.
    CHEN Xiao-bing, WU Han, JIANG Bo, WEI Ling, GUO Yi-xuan
    2020, 31(12):  4099-4108.  doi:10.13287/j.1001-9332.202012.016
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    The spatial distribution of the preferential flow path in soil affects the occurrence and movement of preferential flow. In afield soil staining and tracing experiment, with the help of morphological image analysis technology and community ecological analysis method, we examined the spatial distribution characteristics of preferential flow path in paddy fields under straw mulching (CM) and non-mulching (CK) in karst areas of Guangxi. The results showed that, under the same external water supply conditions, with the increases of soil depth, soil horizontal dyeing changed from overall distribution to clump aggregation distribution in paddy field under straw mulching. In the non-mulching paddy field, the main dyeing was branch, with an average shape coefficient of staining patch of 21.69. The dyeing morphology in the non-mulching paddy field was 1.04 times of straw mulching paddy field. The preferential flow paths of straw mulching and non-mulching paddy fields showed both clustered distribution. In straw mulching paddy field, the Morisita index was 1.28 as the preferential flow paths with radius of influence less than 1.0 mm were the main ones (importance value 0.31). The importance value of preferential flow paths with radius less than 1.0 mm was 0.28 in non-straw mulched rice field. Straw mulching affected the preferential flow paths in paddy fields, which could help to improve water and fertilizer utilization of crops in the field.
    Effects of different straw returning amount on the potential gross nitrogen transformation rates of fertilized Mollisol.
    HUO Hai-nan, LI Jie, YUAN Lei, XIE Hong-tu, ZHU Tong-bin, Christoph Müller, HE Hong-bo, ZHANG Xu-dong
    2020, 31(12):  4109-4116.  doi:10.13287/j.1001-9332.202012.026
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    Straw returning is one of the important measures for improving soil fertility. It is unclear, however, whether the regulation function of soil on nitrogen (N) cycle after fertilization is sustainable and the relationship between the regulation function and the amount of straw returned to the field. In this study, a 3-year straw returning field trial was set up in a field had been carried out straw returning of all the havested straw for nine years. The amount of straw returned was 100%, 67%, 33% and 0 of the average annual straw yield (7500 kg·hm-2) to identify the effects of different straw returned amount on N transformation in the fertilized soil (0-10 cm). Results showed that the amount of straw returning affected the production and consumption of NH4+-N and NO3--N by affecting the potential gross N transformation rate. When the amount of straw returning was less than 67%, the production rate of NH4+-N significantly reduced and the consumption rate significantly increased, and thus led to the decrease in soil NH4+-N retention capacity. The NO3--N production rate increased and the retention capacity decreased, and the NO3--N accumulation and leaching loss risk increased. Therefore, returning more than 67% of harvested straw was necessary to maintain the function of soil N conservation.
    Effects of chemical N fertilizer reduction combined with biochar application on soil organic carbon active components and mineralization in paddy fields of yellow soil.
    SHI Deng-lin, WANG Xiao-li, DUAN Jian-jun, LIU An-kai, LUO An-huan, LI Rui-dong, HOU Zai-fen
    2020, 31(12):  4117-4124.  doi:10.13287/j.1001-9332.202012.027
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    Reducing the application of chemical fertilizer and increasing fertilizer efficiency can contribute to the sustainable development of agriculture. To evaluate the impacts of N fertilizer reduction and biochar application on soil organic carbon active components and mineralization in yellow soil, an experiment was carried out with five different substitution rates of chemical N fertilizer by biochar under the same rate of N input, i.e., 0, 10%, 20%, 30%, 40% (CK, T1-T4). The results showed that chemical N fertilizer reduction combined with biochar application could significantly improve soil organic carbon (SOC), the magnitude of which was proportional to the amount of biochar application. Under the condition of 20% substitution rate (T2), soil microbial biomass carbon (MBC) and readily oxidized carbon (ROC) were the highest with 293.68 mg·kg-1 and 250.00 mg·kg-1, respectively, but the concentration of soil dissolved organic carbon (DOC) was the lowest. SOC mineralization rate reached the highest on the third day of incubation. Then, it decreased rapidly in the early period (day 3 of incubation to day 6), decreased slowly in the middle period (day 6 of incubation to day 18), and stabilized in the later period (day 18 of incubation to day 30). There was a logarithmic relationship between mineralization rate of soil organic carbon and incubation time. SOC cumulative mineralization amount and cumulative mineralization rate were the lowest in the T2 treatment with 0.66-0.86 g·kg-1 and 2.9%-4.0%, respectively. As the substitution rate of chemical N fertilizer by biochar increased, rice yield increased firstly and then decreased. Rice yield in the T2 treatment was the highest, which increased by 13.4% compared with the CK. The substitution of 20% chemical N fertilizer with biochar (5 t·hm-2) could effectively improve the contents of SOC, MBC, ROC, and rice yield, reduce the cumulative mineralization amount of organic carbon and cumulative mineralization rate, and enhance the capacity of soil carbon sequestration. Hence, it could be the most effective fertilizer practice for improving soil fertility and rice yield in paddy field of yellow soil in Guizhou Province.
    Environmental impact differences in Qingtian rice-fish culture system at different management scales in the context of land transfer: An empirical study with the carbon footprint method.
    CUI Wen-chao, JIAO Wen-jun, MIN Qing-wen, SUN Ye-hong, LIU Mou-cheng, WU Min-fang
    2020, 31(12):  4125-4133.  doi:10.13287/j.1001-9332.202012.017
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    Under rapid industrialization and urbanization, the conservation and management of agricultural heritage systems is facing many threats and challenges, such as the massive outflow of working labor, land abandonment, and the difficulty in maintaining traditional knowledge systems. Promoting land transfer and carrying out moderate-scale management play an active role in the conservation of agricultural heritage systems. While land transfer brings economic benefits to heritage sites, its environmental impacts to heritage sites are worthy of attention. However, empirical studies are scarce. This study took Qingtian rice-fish culture system in Zhejiang Province as an example, which was designated as Globally Important Agricultural Heritage Systems (GIAHS) in 2005. Small farmer management model and land scale management model were distinguished, while the life cycle method was used to calculate the carbon footprints of two models. The results showed that the carbon footprints of small farmer management model and land scale management model were 6510.80 and 5917.00 kg CO2-eq·hm-2, respectively, while the carbon footprints per unit output were 0.13 and 0.10 kg CO2-eq·yuan-1, respectively. Compared with small farmer management model, land scale management model had lower greenhouse gas emission and lower environmental impact of per unit output. As farmers expanded the scale of land management, local greenhouse gas emissions had been reduced by 4097.20 kg CO2-eq. Furthermore, the accumulation of CH4 in agricultural production accounted for the largest proportion of carbon footprint. The input of compound fertilizer among agricultural production materials was next to CH4 accumulation, becoming the second largest source of greenhouse gas emission. Corn and wheat being used as fish feed also had a significant impact on greenhouse gas emission in small farmer management model. Therefore, the promotion of moderate scale land management is conducive to the win-win of economic and environmental benefits of traditional agricultural systems and plays an important role in the conservation of agricultural heritage systems.
    Effects of the construction of fertile and cultivated upland soil layer on soil fertility and maize yield in black soil region in Northeast China.
    ZOU Wen-xiu, HAN Xiao-zeng, LU Xin-chun, CHEN Xu, YAN Jun, SONG Bao-hui, YANG Ning, LIN Qing-hua, HE Yu
    2020, 31(12):  4134-4146.  doi:10.13287/j.1001-9332.202012.030
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    Organic amendment return could enhance soil fertility, improve soil structure, and increase crop yield. However, how construction of soil layers can affect soil fertility and crop yield are not fully understood. We examined the effects of constructions of fertile and cultivated soil layer on soil fertility and maize yield in the upland black soil region in Northeast China, to provide theoretical guidance in increasing soil fertility and sustainable development of agriculture. Based on the combination of field plot experiments and demonstration regions, nine study sites with different ecological characteristics were selected from Heilongjiang, Jilin and Liaoning provinces from northeast China, covering dark brown, black, meadow, chernozem, albic, brown and cinnamon soils. There were three treatments in each study site, including maize straw return within 0-35 cm soil layer (CF), the combination of maize straw and organic manure return within 0-35 cm soil layer (CF) and conventional agricultural practice without organic amendmentas control (CK). The rate of straw return in CF and CF treatments were 10000 kg·hm-2, and full straw for demonstration regions. The rate of organic manure in CF treatment was 30000 kg·hm-2. Considerable difference in soil fertility were recorded among the nine study sites with the trend of tillage layer > sub-tillage layer, especially for dark brown soil and albic soil. Soil fertility of tillage layer and sub-tillage layer was relatively low both for brown soil and cinnamon soil. The heavy clay and plow pan were pivotal limiting factors of soil fertility for the black soil and the meadow soil. Compared with CK, the concentrations of soil organic matter (SOM), available nitrogen (AN), available phosphorous (AP), and available potassium (AK) in tillage layers was increased on average by 1.85 g·kg-1, 20.16 mg·kg-1, 1.56 mg·kg-1 and 17.2 mg·kg-1 in the CF and CF treatments in five study sites with more than two years of treatments. The contents of SOM, AN, AP and AK in sub-tillage layer increased by 2.09 g·kg-1, 12.06 mg·kg-1, 2.18 mg·kg-1 and 3.84 mg·kg-1, compared with tillage layer. CF treatment significantly enhanced the contents of SOM and AP in both tested soil layers, while CF treatment significantly enhanced all fertility indices in both tested soil layers. This indicated that the increase of organic amendment return is an effective way to improve soil fertility. Maize yield fluctuated under the combined effect of climatic conditions and soil types. The significant differences in maize yield under CK, CF and CF treatments were observed with a trend of CF > CF > CK. This result indicated that the construction of fertile and cultivated soil layer could significantly increase maize yield independent of soil types. The construction of fertile and cultivated soil layer based on maize straw return or maize straw and organic manure combined return within 0-35 cm soil layer, could simultaneously increase soil fertility in both tillage and sub-tillage layer, as well as maize yield. We suggested that the selection of approaches of the constructions of fertile and cultivated soil layer should consider soil types and the sources of organic amendments. It should also give priority to soil layers rich in organic manure source to construct fertile and cultivated soil layers.
    Effects of shading on photosynthetic characteristics and yield at different growth stages of potato.
    LI Chen-yang, LI Lin, QI Li-pan, GUO Xiao-min, GONG Xue-chen, LIU Yi-qiang, ZHAO Yue, SONG Ya-hui
    2020, 31(12):  4147-4152.  doi:10.13287/j.1001-9332.202012.029
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    We examined the effects of shading photosynthetic characteristics, yield, and tolerance to low light in two potato varieties (Jizhangshu 12 and Jizhangshu 8) at four growth stages (seedling, seedling/budding, budding/early flowering and flowering/harvest). There were three shading treatments (0(CK), 20% and 50%). The results showed that at both 20% and 50% shading rates, the SPAD value (a measure of leaf cellular chlorophyll content) of the two varieties decreased significantly at the seedling stage compared with CK treatment. No significant change in the SPAD value occurred at the seedling/budding stage or the budding/early-flowering stage. However, the SPAD value increased marginally after shading at the initial flowering stage. Under the 50% shading regime, the SPAD values of both varieties followed the same trend as the 20% regime. The range of changes at different growth stages remained similar. The only exception was that shading at the beginning of flowering increased SPAD value. Shading had little effect on leaf stomatal conductance (gs) at each developmental stage. There was no significant difference between all treatments and the control, except that the gsvalue of Jizhangshu 8 decreased significantly (43.9%) compared with the control under 50% shading at the beginning of flowering. After the shading treatment, the intercellular CO2 concentration (Ci) of leaves showed an upward trend. 50% shading at the seedling and seedling/budding stages could significantly increase Ci, but not at other stages. The net photosynthetic rate (Pn) of the four periods were all decreased after 15 d of shading. The Pn reduction of the two varieties, 50% shading, was greater than 20% shading. The decline range of Pn of Jizhangshu 12 was less than that of Jizhangshu 8 at all stages, except for that at the seedling stage. The yield of shading treatments decreased in all four stages, with the decrease rate of 50% shading treatment being greater than that of the 20% shading treatment. ‘Jizhangshu 12'was not tolerant to low light at the seedling stage but performed better than ‘Jizhangshu 8' at other stages. The comprehensive analysis of two test varieties implied that varieties with strong tolerance to low light experienced a smaller boost in intercellular CO2 concentration and a smaller drop in net photosynthetic rate, stomatal conductance, and yield post-shading.
    Allelopathy of rape on seed germination and seedling growth of three crops
    GAO Yu-lian, LI Rui-guang, CHANG Jing, LI Yan, LI Hai-ping
    2020, 31(12):  4153-4160.  doi:10.13287/j.1001-9332.202012.002
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    Rape is an important green manure crop in China. It could increase soil fertility, but might have allelopathic effect on subsequent crops. We examined the effects of rape water-extract (at 0.025, 0.05 and 0.1 g·mL-1 concentrations) on seed germination, seedling growth, physiology and biochemistry of three crops including oat (Avena sativa), corn (Zea mays), and sunflower (Helianthus annuus). The results showed that water extract of rape did not affect seed germination rate of three crops. Oat had a trend of “low promotion and high inhibition”, while sunflower had a trend of inhibition. High concentration of rape water extract inhibited root and stem length of oat seedling, corn seedling stem length and sunflower seedling root length, while low concentration treatment promoted root and stem length of corn seedling. The highest protein contents in oats and sunflower presented at the treatment of 0.05 g·mL-1, and that of corn at the treatment of 0.025 g·mL-1, which were significantly higher than that of control. The proline contents in sunflower decreased significantly in different treatments, while the proline content of corn was significantly higher than that of control at 0.05 g·mL-1. POD activity of corn was at a maximum at 0.05 g·mL-1, and that of sunflower was at 0.025 g·mL-1, which were significantly higher than control. There was no significant difference between control and other concentration treatments. The SOD activity of oat was significantly decreased at 0.025 g·mL-1. There was no significant difference in CAT activity between the three crops and the control. The MDA content in sunflower seedlings increased significantly at 0.1 g·mL-1, while that in corn seedlings was significantly lower than control. Our results indicated that the allelopathic inhibitory effect of rape water extract was the strongest on sunflower, followed by corn and oat.
    Evaluation of pre-harvest sprouting resistance of wheat varieties from different ecological regions.
    WANG Zhen, LI Jin-xiu, ZHANG Bin, SHI Li-chao, OU Bao-hong, LI Jin-bang, ZHANG Li-jun
    2020, 31(12):  4161-4170.  doi:10.13287/j.1001-9332.202012.022
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    The pre-harvest sprouting (PHS) resistance of 137 wheat varieties from different regions was evaluated and the relative germination index (RGI) was calculated. The relationships between PHS and grain quality traits, amylase activity and related gene expression level of these varieties were analyzed. The results showed that wheat varieties from the middle and lower reaches of Yangtze River Valley winter wheat region had the lowest RGI value and the highest ratio of resistant pre-harvest sprouting wheat varieties, followed by the varieties from the upper reach of Yangtze River Valley winter wheat region and from the Yellow and Huai River Valley. Red-grain wheat had lower RGI than white-grain wheat. RGI was positively correlated with seed length, seed width, and spikelet number, but not correlated with other grain traits (panicle type, ear color, ear length, and spikelet density, grain per spike and 1000-grain weight). RGI was negatively associated with the test weight, dough development time, and flour yield, but not with other quality indices (protein content, wet gluten content, water absorption, stability time, sedimentation, extension area, extensibility and max resistance). Amylase activity of different varieties increased with seed imbibition time. RGI was positively associated with α-amylase activity after germinating for 24-72 hours. The cluster analysis results of resistant varieties were consistent with the PHS resistance evaluation after 48 hours. RGI was positively associated with the related gene expression with seed imbibition time.
    Effects of intercropping on soil nitrification and nitrogen supply in potato field.
    ZHAO Wei, YI Wen-bo, WANG Ding, WU Kai-xian, ZHAO Ping, LONG Guang-qiang, TANG Li
    2020, 31(12):  4171-4179.  doi:10.13287/j.1001-9332.202012.023
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    Nitrate supply in soils is essential to meet nitrogen (N) demand of crops. However, how intercropping would affect soil nitrate supply and the underlying mechanisms remain unclear. Based on a field experiment of mono- and inter-cropped potato amended with four N application rates (N0, 0 kg·hm-2; N1, 62.5 kg·hm-2; N2, 125 kg·hm-2; N3, 187.5 kg·hm-2), we analyzed the differences in soil nitrate content and intensity, nitrification potential, and ammonia oxidation gene abundance. We further explored the mechanisms underlying the effects of intercropping on nitrate supply and N regulation. The results showed that both content and intensity of soil nitrate increased with N application rate. Under the same N level, nitrate content in intercropping soil was lower than that in monocropping soil. Nitrogen application increased soil nitrification potential, with stronger effects in monocropping than that of intercropping. The amoA gene abundance of AOB in soil was greater than that of AOA. The abundance of amoA gene for both AOA and AOB were increased firstly and then decreased with increasing N application rate when potato intercropped with maize. Under the same N application rate, AOA gene and AOB gene in all treatments (except N2) in intercropping were lower than those in the monocropping. The amoA gene abundance of soil AOB and AOA decreased and nitrification potential was weakened when potato intercropped with maize, resulting in a decrease of soil nitrate content and intensity. Therefore, intercropping led to a reduction of soil nitrate supply, which was related to the microbial process of soil N transformation. Much attention should be paid to soil N supply under the condition of potato and maize intercropping.
    Impacts of transgenic insect-resistant maize HGK60 with Cry1Ah gene on biodiversity of arthropods and weeds in the field.
    CHEN Yan-jun, GUAN Xiao, REN Meng-yun
    2020, 31(12):  4180-4188.  doi:10.13287/j.1001-9332.202012.031
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    Transgenic technology has developed rapidly in recent years. The environmental risk of the release of transgenic organisms is still a key issue. Research on the impacts on biodiversity is an effective way to objectively evaluate the risk. By taking transgenic maize HGK60 with insect-resis-tant gene Cry1Ah and common maize Zheng58 as control, we examined the diversity of arthropods and weeds in spring and winter of 2018 in Hainan Province. 43753 arthropods belonging to 69 species, 19 families, and 7 orders were obtained. There was no significant difference in arthropod community composition, structure and ecological indices between HGK60 and Zheng58. Compared with Zheng58, the transgenic insect-resistant maize HGK60 had obvious resistance to wood boring beetles. 16 species of weeds belonging to 8 families were recorded in the field. There was no significant difference in the density and ecological indices of weeds between HGK60 and Zheng58, with almost the same change trends in the whole growth period. Our results suggested that planting transgenic maize HGK60 with insect-resistant gene Cry1Ah did not affect biodiversity of arthropods and weeds. The results provided scientific support for the further studies of environmental risk of transgenic crops.
    Effects of lime and ammonium carbonate fumigation coupled with bio-organic fertilizer application on banana fusarium wilt and bacterial community.
    LIU Shan-shan, XIA Meng, HU Xia-ru, WANG Yun-zhou, LI Chun-yu, TAO Cheng-yuan, SHEN Zong-zhuan, ZHANG Nan, LI Rong, SHEN Qi-rong
    2020, 31(12):  4189-4196.  doi:10.13287/j.1001-9332.202012.032
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    Taking banana continuous planting soil with high banana fusarium wilt disease incidence as a test site, we examined the effect of lime and ammonium carbonate fumigation coupled with bio-organic fertilizer on the suppression of banana fusarium wilt disease and the structure and composition of bacterial community, using real-time quantitative PCR and high-throughput sequencing. The results showed that the disease incidence was reduced by 13.3% and 21.7% in the treatments of LAOF (lime and ammonium carbonate fumigation coupled with organic fertilizer) and LABF (lime and ammonium carbonate fumigation coupled with bio-organic fertilizer), respectively, compared with OF (application of organic fertilizer without fumigation), while the copy number of Fusarium was decreased by 22.4% and 33.0%, respectively. Compared with non-fumigation treatment, lime and ammonium fumigation coupled with different fertilizer applications significantly reduced bacteria richness and diversity, with different community structure, while fumigation had a decisive effect on bacterial community composition. Bacterial richness and diversity of LABF were lower than those of other treatments, while microbial community structure was clearly disparate from other treatments. Compared with non-fumigation treatment, the relative abundance of Mizugakiibacter, Brucella, and Rhodanobacter were significantly improved in the fumigation coupled with different fertilization treatments. Those three genera in LABF were higher than those in LAOF, with significant differences for the relative abundances of Mizugakiibacter and Brucella. Therefore, fumigation combined with bio-organic fertilizer application could reduce the copy number of pathogen, alter soil bacterial community structure and stimulate beneficial bacteria in the resident soil, and thus reduce the occurrence of banana fusarium wilt.
    Effect of methyl jasmonate on aphid resistance of chrysanthemum.
    FAN Jie, ZHANG Xue-ying, SUN Xian-zhi, XU Bing-yan
    2020, 31(12):  4197-4205.  doi:10.13287/j.1001-9332.202012.039
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    We examined the effects of methyl jasmonate on aphid resistance of Chrysanthemum ‘Hangbai'. Leaves of chrysanthemum cuttings were sprayed by methyl jasmonic with different concentrations (0.01, 0.05, 0.1, 0.5 and 1 mmol·L-1) and then inoculated with the aphids Macrosiphoniella sanborni. The following parameters are measured, including protective enzymes activities, defense enzyme activities, osmotic substances, secondary metabolites, and key genes of the jasmonic signaling pathway. The relationship between aphid resistance and the jasmonic signaling pathway in chrysanthemum was probed. The results showed that, under the treatments of all the five concentrations of methyl jasmonic, the activities of leaf protective enzymes and defense enzymes as well as the contents of secondary metabolite were increased in Chrysanthemum, whereas the contents of malondialdehyde and soluble sugar were reduced. Moreover, exogenous methyl jasmonate treatment induced the expression of CmAOS and CmCOI1, enhanced the content of endogenous jasmonic acid and the aphid resistance of chrysanthemum.
    “Safe and just operating space” for the sustainable development of the social-ecological system in the Liangzi Lake Catchment, Hubei Province, China.
    SU Yan-yu, LI Yan, DONG Xu-hui
    2020, 31(12):  4206-4214.  doi:10.13287/j.1001-9332.202012.011
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    The increases of human activities threaten the health of the earth's ecosystem, and pre-sent a big challenge to regional sustainable development and environment conservation. How to maintain a safe ecological environment together with social and economic development is an important issue for sustainable development. Under the theoretical framework of “safe and just operating space”, we integrated lake sediment records, environmental monitoring data, and socio-economic data in Liangzi Lake Catchment, analyzed the status of key eco-environmental processes and achievement degree (the completion of the current value of social basic indicators relative to the target value) of residents' social welfare, and constructed a “safe and just operating space” for the sustainability of local social-ecological system. The results showed that the indicators including freshwater utilization, cultivated land resources, air quality, soil and sediment regulation, and chemical pollution in the catchment had exceeded the environmental ceiling and were at the “dangerous” level, which should be regulated in the future. As for the social welfare, the achievement degree of clean water, sanitation facility, and industrial innovation were relatively low. The per capita GDP was negatively correlated with soil and water conservation and air quality, indicating the negative effects of social and economic development on water, soil, and air. With multi-source environmental data, especially long-term limnological records, we effectively reconstructed the historical environmental change process, revealed the deficiency of environment and residential well-being in local social ecosystem management, which would provide important insights for regional sustainable development.
    Petroleum pollution and microbial community structure in the soil of Liaohe Oilfield.
    ZHAO Ming-yang, WANG Sa, LI Feng-mei, GUO Shu-hai, GAO Peng
    2020, 31(12):  4215-4224.  doi:10.13287/j.1001-9332.202012.040
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    We analyzed the soil physico-chemcial properties, microbial community structure, petroleum hydrocarbon contents and components in soil samples from the well sites of Shuguang, Huanxi-ling and Jinzhou oil exploitation sites in Liaohe Oilfield, with uncontaminated paddy soil as a control. The results showed that: 1) The soil around all the three oil exploitation sites were seriously polluted by petroleum with certain differences in the petroleum hydrocarbon contents and components. The average content of petroleum hydrocarbon in the soil of Shuguang and Huanxiling oil exploitation sites was two times higher than that of Jinzhou oil exploitation site. The content of resins and asphaltenes in the soil of Shuguang oil exploitation site was the highest, while the soils of Huan-xiling and Jinzhou oil exploitation sites had the highest alkane content, which accounting for more than 40% in all the sites. 2)Compared with the paddy soil, the microbial OTU numbers, Chao1 and Shannon indices in the soil of Jinzhou oil exploitation site increased. The dominant phyla and genera were similar in the soil of all oil exploitation sites but with large differences in abundance. The soil in Jinzhou oil exploitation site had higher abundance of Mycobacterium and Pseudomonas, while Sphingomonas and Nocardioides, Massilia in the soil of Shuguang oil exploitation site, and Lysobacter, Thiobacillus and Pseudomonas in the soil of Huanxiling oil exploitation site. 3) The abundances of Sphingomonas, Nocardioides, Thiobacillus, Massilia, Pseudomonas and the contents of total petroleum hydrocarbons, total organic carbon and resins and asphaltenes were significantly positively correlated, while Mycobacterium, Lysobacter and Pseudomonas were significantly positively correlated with the contents of total nitrogen and total phosphorus. This study systematically analyzed the petroleum hydrocarbon, physico-chemcial properties and microbial communities in the soil of different oil exploitation sites, and revealed the specific dominant bacterial genera and microbial communities in the soil of Liaohe Oilfield. Our results provided a theoretical basis for functional bacterium screening and microbial community construction in the remediation process of petroleum contaminated soil in Liaohe Oilfield, and a reference for efficient degradation bacteria screening in other oilfields.
    Spatial variation and source identification of heavy metals in sediments in Shaanxi section of Weihe River, Northwest China.
    LI Xuan-tian , ZHANG Feng-bao, YANG Ming-yi
    2020, 31(12):  4225-4234.  doi:10.13287/j.1001-9332.202012.035
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    In order to understand the spatial variation of heavy metals in Shaanxi section of Weihe River, the contents and sources of Cd, Co, Cu, Pb, Sb, As, Ni, Cr, Zn, Mn in sediments at 17 sampling sites in Shaanxi section of Weihe River and its tributaries were analyzed. The results showed that the average contents of Cd, Co, Cu, Pb, Sb, As, Ni, Cr, Zn, Mn were 0.10, 1.24, 11.73, 11.95, 24.90, 24.91, 29.31, 54.18, 72.74, 626.85 mg·kg-1, respectively. Except for that of Cd being greater than 1, the coefficient of variation for each of other heavy metals was less than 0.5. The peak contents of Cd, Pb and Cr were found at the sampling site of Bahe River, of Co and Mn at Heihe River, of Cu and Zn at Qingjiang River, and of Sb, As and Ni at Shawang Ferry, Xianyang Railway Bridge and Linjia Village, respectively. According to the results of correlation analysis, principal component analysis and cluster analysis, the elements of Cd, Co, Cu, Pb, Ni, Cr, Zn and Mn mainly originated from industrial and domestic sources, but Sb and As mainly originated from agricultural and geochemical sources.
    Effects of IAA on physiological response to aluminum stress and DNA damage of Trichosanthes kirilowii.
    LI Wen-jing, MAO Ji-long, WU Yu-huan, TANG Ke, PAN Fang-fang, FANG Fang, CAI Miao-zhen, LIU Peng
    2020, 31(12):  4235-4242.  doi:10.13287/j.1001-9332.202012.009
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    To investigate the physiological response of IAA (indoleacetic acid) to Trichosanthes kirilowii under aluminum stress and the mitigation of DNA damage, the effects of IAA (0, 10, 25, 50, 75 μmol·L-1 denoted by I0, I10, I25, I50 and I75, respectively) on antioxidant enzyme activity, malondialdehyde (MDA), photosynthetic characteristics, root activity, chlorophyll content and DNA damage of two varieties of T. kirilowii under 300 and 800 μmol·L-1 aluminum environment (denoted by Al300 and Al800, respectively) were examined in hydroponic culture experiments with Hebei Anguo (aluminium tolerant variety) and Zhejiang Puyang Trichosanthes kirilowii (aluminum sensitive variety). The results showed that the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), photosynthesis ability, and root activity of both varieties were inhibited to different degrees by aluminum stress, MDA content was significantly increased, and DNA damage was aggravated. The maximum increase of SOD, CAT and POD activities in Anguo and Puyang T. kirilowii under aluminum stress by IAA application were 15.0%, 31.2%, 72.3% and 13.8%, 26.9%, 26.4%, respectively, chlorophyll content increased by 49.9% and 17.9%, MDA accumulation decreased by 39.2% and 22.4% and fluorescence parameters were significantly improved. The treatment of 25 μmol·L-1 IAA significantly increased root activity by 159.1% and 90.9%, while 50 μmol·L-1 IAA effectively slowed the DNA tailing phenomenon in roots, with the product (OTM) value of tail DNA percentage content and tail moment being decreased by 27.6%. 10-50 μmol·L-1 IAA could effectively improve the physiological activity of T. kirilowii under aluminum stress and slow the degree of DNA damage. The tolerance of Anguo variety to aluminum stress was stronger than that of Puyang variety.
    Effects of phytoremediation on soil enzyme activity and thermodynamic characteristics of enzymatic reaction in severe saline-alkali land.
    LUO Hui, FENG Cheng-cheng, YUE Zhong-hui, ZHAO Jing-yi, TANG Zhuo-lei
    2020, 31(12):  4243-4250.  doi:10.13287/j.1001-9332.202012.025
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    With the environmental changes and the increases of anthropogenic disturbance, the area and degree of salinization in saline-alkaline lands of Songnen Plain have been increasing with an unprecedented rate. In this study, the effects of restoration of natural vegetation, Leymus chinensis, Avena sativa and Medicago sativa, on the enzymatic activities and thermomechanical characteristics of enzyme catalyzed reaction of two oxidoreductases (catalase, polyphenol oxidase) and three hydrolases (alkaline phosphatase, sucrase, urease) were investigated in heavily saline-alkaline soils from western Songnen Plain. The results showed that the activities of those five soil enzyme as well as the activation free energy (ΔG) increased with increasing temperature, reaching respective maximum at 40 and 45 ℃. The activation enthalpy (ΔH) and entropy (ΔS) of soil enzyme did not change with increasing temperature. The temperature coefficient (Q10) slightly changed and ranged from 1.05 to 1.36 by every 10 ℃ enhancement of temperature. Compared with the bare land, catalase activity increased in natural vegetation and L. chinensis rehabilitated land, but decreased in A. sativa and M. sativa remediation land. The change of ΔG of catalase showed a contrary trend with that of enzyme activities, while ΔH and ΔS increased in the restoration areas of L. chinensis and A. sativa, and decreased in the restoration of natural vegetation and M. Sativa. The activity of polyphenol oxidase decreased or remained unchanged in all restoration sites, and ΔH and ΔS decreased in natural vegetation and L. chinensis restoration sites, while remained unchanged in A. sativa and M. sativa restoration sites. ΔG of polyphenol oxidase reached the maximum at 40 ℃ in each restoration site and decreased or remained unchanged at other temperatures. The activities of three hydrolytic enzymes increased in each restoration site compared with the bare land, and the ΔG of the enzymes decreased or remained unchanged in each repaired area, while ΔH and ΔS varied greatly among the restoration sites. Taken together, significant responses of soil enzyme activity and their thermodynamic characteristics to temperature change and vegetation restoration were detected, which would provide better understanding for the restoration of heavily salinized soil.
    Sunshine environment in different forms of communities in Guiyang, China.
    YAO Xia, LIN Tao, YE Hong, SUI Jin-ling, HU Kai-qun, ZHOU Hao, ZHOU Chang-wei
    2020, 31(12):  4251-4257.  doi:10.13287/j.1001-9332.202012.015
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    In this study, six different types of residential areas in Guiyang were selected as the research objects, including high-rise high-density, high-rise low-density, middle-rise high-density, middle-rise low-density, low-rise high-density and low-rise low-density. The indices of sunshine compliance rate and the building's sunshine hour ratio were constructed to compare and analyze sunshine environment across those six different residential areas. The factors influencing sunshine environment in different residential areas were studied. The results showed that the average sunshine compliance rates of the six types of residential areas were 36.9%, 61.9%, 20.6%, 69.6%, 26.5% and 45.0%, respectively. The average sunshine compliance rate of low-density residential areas was 2.25 times higher than that of high-density residential areas within the same type, among which the sunshine environment of low-density residential areas was better. The sunshine environment of different types of low-density residential areas was different. The sunshine hours for high-rise low-density and middle-rise low-density forms were concentrated in 5-6 hours, while the building's sunshine hour ratio was 0.24 and 0.32, respectively. The sunshine hours for low-rise low-density forms were mainly 6-7 hours, with a building's sunshine hour ratio of 0.28. Compared with other types of residential areas, the low-rise low-density type of sunlight environment was the best. The plot ratio was significantly positively correlated with the building's sunlight ratio of 0-1 h sunlight hours in the residential area.
    Effects of spatial expansion of Phragmites australis and Cyperus malaccensis on distributions and stocks of phosphorus in marshes in the Minjiang River estuary, China.
    ZHANG Peng-fei, SUN Zhi-gao, CHEN Bing-bing, HU Xing-yun, LI Xiao, HE Tao, MAO Li, ZHANG Wen-ting
    2020, 31(12):  4258-4266.  doi:10.13287/j.1001-9332.202012.036
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    To investigate the distributions and stocks of total phosphorus (TP) in plant-soil systems of marshes in Shanyutan of the Minjiang River estuary and explore its influencing factors, Phragmites australis (PA) marsh and Cyperus malaccensis (CM) marsh before spatial expansion and ecotonal marsh (EM, P. australis and C. malaccensis in EM were denoted by PA′ and CM′, respectively) during spatial expansion were studied. Results showed that, as affected by spatial expansion, the contents of TP in both plant and soil in different marshes showed great variations. Compared with PA and CM marshes, soil TP in EM increased by 20.0% and 7.1%, respectively. The variation of soil TP in EM might be attributed to the alteration of soil particle composition, plant bio-mass and root/shoot ratio during spatial expansion. Except for leaves, TP in organs of P. australis in P. australis-C. malaccensis community (PA′) was lower than that in C. malaccensis in P. australis-C. malaccensis community (CM′), due to the differences in absorption, utilization and translocation way of P among organs between the two species. The competition effect caused by spatial expansion greatly changed plant P allocation ratio of the two species. Compared with PA and CM, the allocations of P in roots and leaves of PA′ increased, while only that in roots of CM′ rose. During spatial expansion, the two species might adopt different adaptation strategies for P absorption and utilization to maintain their competitiveness. The PA might compete primarily by strengthening the P accumulation capacities of its roots and promoting leaf photosynthesis, whereas the CM might resist the spatial expansion of PA by increasing its underground biomass to enhance P absorption.
    Characteristics of fish aggregation devices (FADs)and associated tuna schools behavior in Chinese tuna purse seine fishery.
    WANG Yu-cheng, ZHOU Cheng, XU Liu-xiong, WAN Rong, WANG Xue-fang, XIE Cheng-lan, TANG Hao
    2020, 31(12):  4267-4276.  doi:10.13287/j.1001-9332.202012.037
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    The use of fish aggregation devices (FADs) can increase catchability of tuna purse seine for associated tuna schools. In the past decades, large scale deployments of FADs have drawn the international attention due to their negative effects on the marine environment. Finding a FAD design ecologically and economically compatible has therefore become a challenge for tuna purse seine fishe-ry. Nowadays, knowledge and comprehension of interaction between FADs and catch species are quite lacking as a result of limited experimental investigation. We interviewed the captain of Chinese tuna purse seiner based on questionnaire to summarize the status of FADs deployment strategy, structural design, capture and ecological characteristics, and the behavior characteristics of associa-ted schools from the perspective of fishermen's knowledge and experience. We also quantified the cognitive differences of the investigated issues based on the index of consistency (IoC). Our results showed that: 1) the average number of year-round FADs deployment was (102±37) per vessel, and the number of that being lost was (72±1). 2) empirical knowledge from fishing masters indicated that man-made FADs could attract more tuna than natural floating objects (e.g. logs). Submerged structure was the predominant mechanism for aggregating tunas around the FADs. Hanging attractors (e.g. palm leaves) would facilitate the aggregation of tunas. 3) Fishing masters' observations in practical operation revealed that the duration needed for tunas to be associated with a FAD was around 32 days, and fish aggregation would tend to stabilize in the following month. Entanglement of sea turtles and sharks by netting was incidental events. 4) Most fishing masters had identical opinion on “bio-fouling was helpful for FADs to attract tunas” (IoC=0.73) and “modifying FADs design to reduce the detectability by other vessels” (IoC=0.73), while the answers for “the effect of raft type on tuna attraction capability” (IoC=0.34) were quite different. 5) The results of questionnaire suggested that the current design of FADs used by Chinese tropical tuna purse seiner had high risks of detected by other vessels and increased vulnerability of non-target species to fishery. Moreover, our results provided valuable references that promote sustainable exploitation of purse seine in a way of reconciling profitability with ecological preservation.
    Feeding habits of Saurida elongata in Haizhou Bay, Shandong, China, based on stomach contents and stable isotope.
    GAO Yuan-xin, SUI Hao-zhi, REN Xiao-ming, XU Bin-duo, ZHANG Chong-liang, REN Yi-ping, XUE Ying
    2020, 31(12):  4277-4283.  doi:10.13287/j.1001-9332.202012.038
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    Saurida elongata, a warm-water offshore benthic fish, is one of the dominant species in Haizhou Bay and plays an important role in the food web. Based on samples collected from bottom trawl surveys in Haizhou Bay, we examined the feeding habits of Saurida elongata based on both stomach content and stable isotope analyses. The results showed that the main prey species of Saurida elongata were Metapenaeopsis dalei, Loligo spp., Cryptocentrus filifer, Engraulis japonicus, Chaeturichthys hexanema, Apogonichthys lineatus, Syngnathus acus and Callionymus beniteguri. The range of δ13C value was -19.39‰ to -16.23‰, with an average value of (-18.01±0.85)‰. There was no correlation between body length and δ13C values. The value of δ15N ranged from 9.56‰ to 13.36‰, with an average value of (11.77±0.86)‰, which was significantly positively correlated with body length. There was substantial difference in the contribution of food organism among diffe-rent body length groups. With the increases of body size, predation ability and morphology of feeding organs gradually improved, and the proportion of prey organisms changed, which might be the main reason for the ontogenetic variation in feeding habits. This study could contribute to understand the feeding ecology of snake mullet in Haizhou Bay and provide basic information for the nutritional dynamics of the Haizhou Bay food web.
    Trophic niche and interspecific diet relationship of Gymnocypris in autumn from Langcuo Lake of Tibet, China.
    LI Lei, JIN Xing, MA Bo, WU Song, TANG Shi-zhan
    2020, 31(12):  4284-4290.  doi:10.13287/j.1001-9332.202012.034
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    Langcuo Lake is a typical plateau lake in the southern Tibet, with an altitude of 4300 m. Gymnocypris chui and Gymnocypris scleracanthus coexisted in this lake. In this study, we investigated the food composition and trophic niche of two Gymnocypris fishes in autumn by carbon and nitrogen stable isotopes technique in 2018. We further analyzed their interspecific diet relationship, including the diet similarity index and overlap coefficient. The results showed that G. chui mainly feed on ephemeroptera larvae, chironomidae larvae, periphytic algae, gammarus and plankton, while G. scleracanthus mainly feed on ephemeroptera larvae, periphytic algae, chironomidae larvae, gammarus and aquatic vascular plants. Two Gymnocypris fishes had trophic niche overlap. The δ13C range value (CR=1.60), δ15N range value (NR=1.89), and total area of convex hull (TA=1.80) of G. chui were lower than those of G. scleracanthus, with the difference values being 0.09, 0.57 and 1.29, respectively. The diet similarity index and overlap coefficient of those two species were higher, with a value of 94.2% and 91.5%, respectively. Our results suggested that the interspecific diet competition may be intense between the G. chui and G. scleracanthus in Langcuo Lake in autumn.
    Reviews
    Applications of compound-specific isotope analysis in tree non-structural carbohydrates research: A review.
    DIAO Hao-yu, WANG An-zhi, YUAN Feng-hui, GUAN De-xin, SUN Yu, WU Jia-bing
    2020, 31(12):  4291-4300.  doi:10.13287/j.1001-9332.202012.024
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    Compound-specific isotope analysis (CSIA) can precisely determine the carbon isotopic composition (δ13C) of specific compounds in a complex substrate. The δ13C values in tree non-structural carbohydrates (NSC) compounds, e.g. sugars, organic acids, and sugar alcohols, measured via CSIA could help tracing the newly assimilated photosynthate during carbon transfer and exchange with atmosphere. Further, they can act as sensitive indicators of the physiological response of trees to environmental change. In this review, we first systematically introduced the methods of CSIA with respect to sampling, purification, and analysis. Then, compound-specific δ13C difference among different NSCs and across tree carbon pools, as well as temporal pattern and mechanism underlying the variation of δ13C were described. Finally, we discussed the interaction between δ13C in tree NSCs, the main substrates of respiration, and respired CO213CR). Further studies on the post-photosynthetic discrimination, tree stress physiology, and tree-ring δ13C formation with the promising applications of CISA were suggested.
    Effects of ant disturbance on soil organic carbon cycle: A review.
    ZHANG Xue-hui, ZHANG Zhong-sheng, WU Hai-tao
    2020, 31(12):  4301-4311.  doi:10.13287/j.1001-9332.202012.033
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    The impact of ants, as consumer and decomposer in ecosystems, on soil organic carbon pool is a hotspot in soil fauna research. Recently, effects of ants on soil organic carbon pool dynamics have been mainly documented in terms of soil macro-elements storage, physical and chemical properties, and microbial community. We summarized the effects of ant disturbance on soil organic carbon cycle. Ant nesting alters microhabitat, microclimate, and physicochemical properties of ant nested soils. By re-shaping soil microbial community structure, regulating the succession process and pattern of vegetation, ant nesting directly or indirectly affects the source, allocation, stability, and microcosmic molecular characteristics of soil organic carbon, scaling from micro, local, to landscape scale. In the future, more attentions should be paid on quantifying the contribution of ant disturbance combined with the fluctuations in environmental factors to soil carbon flux dynamics, establishing quantitative model to link and unify ant-induced soil carbon cycle process, and clari-fying mechanisms underlying the impacts of ants on the stability of soil organic carbon pool, and finally revealing the “ecological engineers” role of ants in regulating soil organic carbon cycling.
    Effects of biochar on ammonia volatilization from farmland soil: A review.
    XU Yun-xiang, HE Li-li, CHEN Jin-yuan, LIU Yu-xue, LYU Hao-hao, WANG Yu-ying, YANG Sheng-mao
    2020, 31(12):  4312-4320.  doi:10.13287/j.1001-9332.202012.021
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    Reducing soil ammonia volatilization is one of the key ways to reduce soil nitrogen loss and improve nitrogen utilization efficiency in farmlands. Biochar has unique physico-chemical pro-perties, which can change soil physical and chemical properties, affect soil nitrogen cycle, and affect ammonia volatilization in farmland soil. Firstly, we reviewed the ammonia volatilization process and its influencing factors (climatic condition, soil environment, and fertilization management, etc.) in paddy fields and upland fields. Then, research progress on the impacts of biochar on ammonia volatilization from farmland ecosystem was reviewed. Furthermore, the mechanisms underlying the responses of ammonia volatilization to biochar intervention were discussed from the aspects of physical adsorption, gas-liquid equilibrium, and biochemical progress regulation. The reduction of soil ammonia volatilization is mainly based on the adsorption of soil NH4+ and NH3 by oxygen-containing functional groups on the surface of biochar and the promotion of soil nitrification. How-ever, the increases of soil ammonia volatilization are mainly related to the increases of soil pH, air permeability, activities of microorganisms related with soil organic nitrogen mineralization. Finally, the research direction of reducing soil ammonia volatilization and improving nitrogen utilization efficiency by biochar was prospected.
    Research progress of the response mechanism of wheat growth to waterlogging stress and the related regulating managements.
    GAO Jing-wen, SU Yao, SHEN A-lin
    2020, 31(12):  4321-4330.  doi:10.13287/j.1001-9332.202012.028
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    The frequency of waterlogging events is increasing in recent years due to climate change. Wheat, a dryland crop, is particularly sensitive to waterlogging. Moreover, waterlogging stress is especially serious in the main wheat-producing regions at the middle and lower reaches of the Yangtze River as influenced by regional climate, soil, rotating system and other factors. Oxygen content in soil decreases under waterlogging condition, which inhibits root growth, restricts plant growth, and eventually reduces wheat yield and grain quality. In the present study, we reviewed the current national and international research progress in the underlying physiological mechanisms of inhibitory wheat growth by waterlogging stress, from the aspects of root respiration, water transport, mineral nutrient absorption, photosynthesis, redox metabolism. We discussed the physiological adaptions of wheat to waterlogging, including maintaining energy supply through anaerobic respiration and oxygen supply through changes of root morphology. We listed the application of cultivation measures such as fertilizer regulation, growth regulator regulation and stress memory in improving waterlogging stress-tolerance in wheat with the underlying physiological mechanisms summarized. We also prospected the future study on waterlogging stress-tolerance in wheat, aiming to provide theoretical foundation for waterlogging-tolerant cultivation and maintaining high yield of wheat.