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    20 March 2019, Volume 30 Issue 3
    Research paper
    Soil C:N:P stoichiometry at different altitudes in Mao’er Mountain, Guangxi, China.
    QIN Hai-long, FU Xuan-xuan, LU Ying, WEI Xiang-hua, LI Bo, JIA Chong-jian, JIANG Kun
    2019, 30(3):  711-717.  doi:10.13287/j.1001-9332.201903.027
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    We explored vertical distribution of soil organic carbon (C), nitrogen (N) and phosphorus (P) for examining the relationship between soil C:N:P stoichiometry and both altitudes and soil depths in Mao’er Mountain in Guangxi, South China. A total of ten sites from different altitudes were selected and soil genetic horizon samples were collected along soil profiles at each site. Soil organic C, N, P, pH, bulk density and particle size composition were measured. Results showed that soil C, N, C/P ratio and N/P ratio increased with the increases of altitude. Soil P concentrations and C/N ratio increased within low altitudes then decreased or with no obvious changes. Soil C, N, P, C/P and N/P ratios significantly decreased, whereas C/N ratio did not change with the increases of soil depth. Soil C and N highly coupled within horizons (CV of C/N was 4.0%) and soil P had little spatial variability (CV were 31.0% and 22.0% within altitudes and horizons, respectively). The results from redundancy analysis showed that the first two axes explained 74.8% of the variability of C:N:P stoichiometry. Soil pH, bulk density, and altitude had significant effects on C:N:P stoichiometry, whereas clay, silt, and sand had no effect.
    Responses of soil active carbon and nitrogen to short-term warming in alpine treeline of west Sichuan, China
    MA Cai-xia, LI Hong-jie, ZHENG Hai-feng, CHEN Ya-mei, YANG Lin, WANG Li-feng, ZHANG Jian, LIU Yang
    2019, 30(3):  718-726.  doi:10.13287/j.1001-9332.201903.006
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    Alpine treeline ecosystem is more sensitive to global warming under low temperature limitation with the aggravation of greenhouse effect, which may directly affect plant growth and soil carbon and nitrogen processes. We expected that climate warming would change soil active carbon and nitrogen content in alpine ecosystems. This experiment was conducted in long-term research station of alpine forest ecosystems, in Lixian County, Sichuan Province. The open top camber (OTC) was used to simulate warming, intact soil core (soil organic layer and mineral soil layer) of OTC and CK were collected in April, July and October 2017. Soil dissolved organic carbon (DOC), soil microbial biomass carbon (MBC), dissolved organic nitrogen (DON) and soil microbial biomass nitrogen (MBN) were measured. The results showed that average temperature increased by 0.88 ℃ for air, 0.48 ℃ for soil organic layer and 0.23 ℃ for mineral soil layer. The simulated warming did not significantly change soil organic matter and water content, but significantly increased pH of mine-ral soil layer, and significantly reduced DOC and DON contents of mineral soil layer in non-growing season. There was significant seasonal variation for the contents of DOC, DON and MBN in the two layers, but not for MBC. The MBC and MBN contents of soil organic layer were significantly higher than that of mineral soil layer. There was a significant positive correlation between active carbon and nitrogen with soil organic matter and water content. There was a significant positive correlation between MBC, MBN and soil pH, whereas MBN was negatively correlated with soil temperature.
    Water use efficiency and its influencing factors of Platycladus orientalis plantation in Beijing mountains area, China
    ZHENG Peng-fei, YU Xin-xiao, JIA Guo-dong, LIU Zi-qiang, ZHANG Yong-e, ZHU Xu-hui
    2019, 30(3):  727-734.  doi:10.13287/j.1001-9332.201903.026
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    Water use efficiency (WUE) is an important index to evaluate plant drought resistance. Studying the dynamics of WUE and its influencing factors can provide reference for the vegetation restoration in Beijing mountainous area. We measured WUE of Platycladus orientalis in growing season and investigated the influence of meteorological factors, soil factors, and atmospheric CO2 concentration on WUE, based on the stable carbon isotope techniques. The results showed that: 1) The short-term WUE decreased and then increased in the growing season, with minimum value (2.69 mmol·mol-1) in July and maximum value (13.88 mmol·mol-1) in October. 2) The vapor pressure deficit (VPD) had the most significant impacts on WUE, followed by air temperature (Ta), soil moisture (Ms), relative humidity (RH), and atmospheric CO2 concentration (Ca), explaining 89.7% of the total variance. Solar radiation (Ra) and wind speed (Ws) had no impacts on WUE. 3) VPD and Ta are the most two important factors influencing short-term WUE, explaining 53.9% of the total variance. The effects of VPD on short-term WUE was higher than that of Ta. Ms and RH were the second important factors of the short-term WUE, explaining 25.4% of the total variance. The effects of Ms on short-term WUE was higher than that of RH. Ca had little effect on the short-term WUE and could explain 10.3% of the total variance.
    Types and species diversity of Cupressus communities in Southeast Tibet, China
    GUO Qi-qiang, CHI Xiang, WANG Shu-li, REN Yi-hua, ZHENG Wei-lie
    2019, 30(3):  735-742.  doi:10.13287/j.1001-9332.201903.002
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    Cupressus communities are the important parts of natural forests in Southeast Tibet, with significance on plateau biodiversity conservation and ecological security. To clarify their types and plant species diversity, we analyzed species composition and diversity indices, diameter class pattern of constructive species in different communities in Milin County, Lang County and Bomi County, Southeast Tibet. The results showed that Cupressus communities could be classified into four types: C. torulosa-Lonicera lanceolate + Philadelphus tomentosus-Pteris cretica var. nervosa + Digitaria violascens community (CommunityⅠ), C. gigantea-Desmodium elegans + Sophora moorcroftia-na-Tripogon filiformis + Cymbopogon distans + Orinus thoroldii community (CommunityⅡ), C. gigantea-Leptodermis purdomii-Chenopodium hybridum + O. thoroldii community (Community Ⅲ), and C. gigantea-Ceratostigma minus-A. desertorum + O. thoroldii + Tribulus terrester community (Community Ⅳ). Across those four community types, Margalef index, Shannon index, Pielou index and interspecies encounter probability index all ranked with the decreasing order of CommunityⅠ, CommunityⅡ, Community Ⅲ and Community Ⅳ. Diameter class pattern of the constructive species showed that many young and few middle/old individuals were within the four communities. High mortality rate occurred during the interim period from young to middle age classes. In general, populations of Cupressus plants showed a declining trend.
    Stoichiometric characteristics of nitrogen and phosphorus in leaf-litter-soil system of Pinus sylvestris var. mongolica plantations.
    REN Yue, GAO Guang-lei, DING Guo-dong, ZHANG Ying, GUO Mi-shan, CAO Hong-yu, SU Min
    2019, 30(3):  743-750.  doi:10.13287/j.1001-9332.201903.040
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    To reveal the allocation pattern and stoichiometric characteristics of N and P in Pinus sylvestris var. mongolica plantation, we selected three P. sylvestris plantation with different stand ages (middle-aged, near-mature, mature) in the Hulunbuir, Horqin, and Mu Us sandy land as objects, and analyzed the contents of nitrogen, phosphorus and the N:P stoichiometry ratios in the leaf, litter, and soil. The results showed that the contents of N, P and N/P ratios in leaf, litter and soil varied in the range of 0.17-49.02, 0.11-3.01 g·kg-1 and 0.51-19.74, respectively, with the order of leaf>litter>soil. The content of N and N:P ratio were significantly different between leaf, litter and soil; the P content in leaf was significantly higher than that in litter and soil. The different areas and stand ages affected N, P content and N/P stoichiometry ratio, but the interaction of area and stand age had no significant effect on N/P stoichiometry ratio. The N, P contents in leaf, litter and soil increased with stand age, and were highest in the mature forest. The contents of N, P and N/P ratios were significantly positively correlated among the leaf, litter and soil. In the Hulunbuir and Horqin sandy land, the N/P ratros of leaf were between 14.53 to 15.57, which indicated that the P. sylvestris var. mongolica plantations was restricted by both N and P availability. In Mu Us sand land, the N:P ratios of leaf were between 18.56 to 19.71, which indicated P limitation. The stand age had no significant influence on soil N and P limitation. To improve the productivity of P. sylvestris var. mongolica plantations, we could appropriately add N or P fertilization in the plantation tending management based on local conditions. Our findings could contribute to a further understanding of the mechanism of interactions and constraints between N and P in the leaf-litter-soil system of P. sylvestris var. mongolica plantations, and provide a scientific guidance for the management.
    Response of photosynthetic nitrogen use efficiency in Betula utilis to altitudinal variation along Balang Mountain, Sichuan, China
    WU Jia-mei, TANG Jing-chao, SHI Zuo-min, FENG Qiu-hong, ZHAO Guang-dong, LIU Shun, CAO Xiang-wen
    2019, 30(3):  751-758.  doi:10.13287/j.1001-9332.201903.032
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    To better understand the response and adaptation of plants to altitudinal changes, four sites at the altitude of 2200 m, 2500 m, 3100 m and 3400 m on Balang Mountain were selected to test and calculate the eco-physiological parameters in leaves of Betula utilis, including photosynthetic nitrogen use efficiency (PNUE), CO2 diffusion conductance (stomatal conductance gs and mesophyll conductance gm) and nitrogen allocation in each component (fractions of leaf nitrogen allocated to Rubisco PR, to bioenergetics PB, to light-harvesting components PL, and to cell wall PCW). Their changes with altitudinal variations and the relationships between leaf PNUE and the other parameters were analyzed. The results showed that PNUE, PR, and PB of the leaves were relatively higher at 2500 m and 3100 m. With the increases of altitude, gs and gm increased and PL decreased. The correlations between PR, PB and PNUE were significant, indicating that PR and PB were the main factors driving the changes in leaf PNUE in response to altitudinal variations. Besides, the fraction of leaf nitrogen allocated to photosynthetic apparatus (PP) was relatively higher at 2500 m and 3100 m. With increasing altitude, PCW decreased and the fraction of leaf nitrogen allocated to the other components (Pother) increased, which suggested that B. utilis leaves tended to allocate more nitrogen to the other components instead of the photosynthetic apparatus and cell wall with the increasing altitude to well adapt environmental changes.
    Water source identification for plants growing on karst rock outcrops based on rainfall-exclusion experiment
    ZOU Qiao-yun, CHEN Hong-song, MA Xing-yu, NIE Yun-peng
    2019, 30(3):  759-767.  doi:10.13287/j.1001-9332.201903.012
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    Although lack of soil coverage, rock outcrops with developed fractures in karst region can maintain water consumption of plants with different life forms. Water sources for plants on these habi-tats are unclear. Isolated rocky outcrop with relatively simple sources of water was selected for this study. We focused on typical plant species that still thrived after excluding rainfall (removing the water supply to the shallow water) over one year, compared with the same plant species living without rain shelter (always receiving rainfall supplies). Water sources of three representative tree species (Radermachera sinica, Celtis biondii, and Pittosporum tonkinense) were analyzed by using stable isotope techniques and combining with the measurement of plant water potential. The results showed that all the three species depended on deep water sources with similar isotopic values to spring water under rain-sheltered condition, during the rainy season, which explained why plants could still grow normally after rainfall-exclusion over one year. The predawn water potential of R. sinica and P. tonkinense under rain-sheltered condition was not significantly different from those living in natural conditions, which indicated both species were not under water stress. The predawn water potential of C. biondii under rain-sheltered condition was significantly lower than individuals living in natural conditions, which indicated it was under water stress. Under natural condition, water isotope values of stems of all the three species were significantly lower than that under rain-sheltered condition and were within the range of fluctuation of recent rainwater isotope values, indicating that these plants relied on shallow water sources that dominated by recent rainfall. Under both rain-sheltered and natural conditions, there was no obvious difference between the predawn water potential and the midday water potential of P. tonkinense, showing a conservative water use strategy. The midday water potential of other two species was significantly lower than the predawn water potential, showing a profligate/opportunistic water use strategy. Our results indicated that the ability to utilize shallow and deep water sources is key for the plants growing on the habitat of Karst rock outcrops where they could adapt different water environments and maintain diversified water use strategies under the condition with no soil coverage.
    Photosynthetic characteristics and water use efficiency of Tamarix ramosissima in shelterbelt and natural communities in south fringe of Taklamakan Desert, China
    XING Peng, ZANG Yong-xin, MIN Xiao-jun, Bahjayrarl Timurbuick, MA Jian-ying
    2019, 30(3):  768-776.  doi:10.13287/j.1001-9332.201903.023
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    The growth and reproduction of shelterbelt plants in arid regions is mainly limited by water availability, which can be alleviated by drip irrigation. We measured water use efficiency (WUE), leaf gas exchange and carbon isotope composition of Tamarix ramosissima in shelterbelt and natural communities in south fringe of Takelamakan Desert to investigate water use efficiency and photosynthetic properties of T. ramosissima differed in water sources. Compared to natural community, T. ramosissima in the drip irrigation community had low water potential due to irrigation and soil salinity. For natural community, T. ramosissima had lower predawn and midday water potential than other plants, indicating that T. ramosissima suffered serious water stress. The net photosynthe-tic rate (Pn), stomatal conductance (gs), intercellular carbon dioxide concentration (Ci) and maximum photosynthesis rate (Pn max) of T. ramosissima in the drip irrigation community were significantly lower than that in the natural community, indicating the photosynthesis of T. ramosissima in the drip irrigation community was weaker. Compared to the natural community, T. ramosissima in the drip irrigation community had higher long-term water use efficiency, which was related to salt stress caused by irrigation. We concluded that the current irrigation model could meet the water needs of shelterbelt plants. However, the technical defects and soil salt accumulation might affect long-term stability of the shelterbelt community.
    Soil greenhouse gases fluxes and the affecting factors of natural secondary forest from seriou-sly burned area in Greater Khingan Mountains, China
    LIANG Dong-zhe, ZHAO Yu-sen, XIN Ying
    2019, 30(3):  777-784.  doi:10.13287/j.1001-9332.201903.018
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    To learn the intensity of greenhouse gases (GHG) fluxes source/sink from soil and the influence factors of a natural secondary forest from seriously burned area in Greater Khingan Mountains, we used static chamber-GC technique to measure soil GHG (CO2, N2O, CH4) in situ during the growing season (from June to September). The results showed that: 1) The soil of natural secondary forest was atmospheric CO2 and N2O source and CH4 sink. The mean fluxes of soil GHG (CO2, N2O, CH4) during the growing season were 575.81 mg·m-2·h-1, 17.81 μg·m-2·h-1 and -68.69 μg·m-2·h-1, respectively. The CO2 and CH4 fluxes showed an obvious double-peak trend and the change of N2O fluxes was a single-peak pattern during the growing season, with all maximum fluxes occurred in August. 2) Soil temperature was the predominant factor controlling the soil GHG fluxes. The correlation of soil/atmospheric humidity and soil GHG fluxes was complicated and differed between diurnal scale and seasonal scale. 3) The soil GHG fluxes measured at 9:00-12:00 am could represent the diurnal average fluxes on the same day after proper correction in this area. The findings supplemented the soil GHG fluxes data of fired forest ecosystem in Greater Khingan Mountains, which could provide a basis for related research of soil GHG source/sink in this area.
    Experimental study on soil fire temperature field of harvested site of Larix olgensis plantation
    XUE Wei, SHA Cong, ZHANG Hua-chao, GUO De-yu
    2019, 30(3):  785-792.  doi:10.13287/j.1001-9332.201903.001
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    We established a fire simulation experiment in the harvested site of Larix olgensis plantation and recorded the temperature of each test point at 500, 1000 and 1500 s during the fire by thermocouple temperature measurement. The data were displayed in the form of images to show soil temperature field at each layer during the fire. The results showed that when the wind speed was less than or equal to 2 m·s-1 or greater than or equal to 10 m·s-1, combustibles could not be fully burned. In the case of full combustion of combustibles, soil temperature at each layer was the highe-st when the wind speed was 6 m·s-1, with the affected soil depth being up to 12 cm or more. The maximum temperature at soil layer of 3 cm could reach 300 ℃. Compared with that at the non-cut stump, soil at the stump had a higher maximum temperature during the fire, with the soil temperature being higher near the stump. When the wind speed was 6 m·s-1, the temperature range at soil layer of 3 cm from the farthest and the nearest to the stump was from 198 ℃ to 315 ℃. With the deepening of soil layer, soil temperature sharply decreased. The temperature at the soil layer of 15 cm was almost unchanged during the fire test. The temperature at the soil layer of 12 cm was increased only when the wind speed was 6 m·s-1, and the temperature at the soil layer of 3 cm was the highest. When the wind speed was 6 m·s-1, the influence of fire on the soil temperature was the greatest, and soil at stump had the severest damage.
    Quantitative analysis of impact factors on net primary productivity of Tahe forest based on InTEC model
    SUN Jing, FAN Wen-yi, YU Ying, WANG Bin, CHEN Chen
    2019, 30(3):  793-804.  doi:10.13287/j.1001-9332.201903.009
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    Net primary productivity (NPP) is an important character reflecting forest carbon source/sink capability, with the spatial-temporal change of which being affected by meteorological change (air temperature, precipitation, etc.), changes in atmospheric composition (CO2 concentration, nitrogen deposition) and various disturbances. However, the key factor driving the changes of forest NPP is still unclear. In order to explore this issue, the relationship between NPP and forest age under different site class index (SCI) was re-simulated and embedded the forest fire data in 1987-2015 to simulate the change characteristics of average NPP of Tahe forest from 1901 to 2015 by comprehensively considering the disturbance and non-disturbance factors of InTEC model, nine scenarios were considered to quantitatively analyze the contribution of different influence factors to the changes of NPP in Tahe forest from 1961 to 2015, and to explore the main influencing factors of the interannual and chronological changes of the Tahe forest NPP to provide a guiding strategy for forest management. The results showed that NPP in Tahe forest was relatively stable from 1901 to 1960, but had a significant trend with the disturbance factors after 1960. The embedding of forest fire and SCI data had different effects on the distribution characteristics of NPP at different times. After 1960, the main reason for the significant change of NPP in Tahe forest was stand age and fire disturbance, with an average annual contribution rate of -49%, followed by precipitation and CO2, which were -28% and 17% respectively. The average contribution rates of temperature and nitrogen deposition were only 5% and 1%, respectively.
    Variations of mean sensitivity of tree rings in Asia and their influencing factors
    ZHENG Zhuang-peng, ZHAO Si-yuan, ZHOU Fei-fei, HE Jin-fu, HU Shan-bin, DONG Zhi-peng, CHEN Shi-yin, FANG Ke-yan
    2019, 30(3):  805-813.  doi:10.13287/j.1001-9332.201903.003
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    Mean sensitivity (MS) of tree ring is a key index representing the sensitivity of tree rings to climate. Understanding the variation of MS and its influencing factors at a large area is helpful to understand the interaction between tree growth and climate. We used 573 tree-ring width chronologies in Asia from the International Tree Ring Date Bank (ITRDB) to examine the variation of tree-ring sensitivity and potential influencing factors. The results showed that the MS of trees was high in the arid regions and cold regions. Precipitation was more important than temperature in diriving MS. Consistent with the pattern of up-down-up for precipitation, MS showed a down-up-down fluctuation with increasing altitude, indicating that precipitation affected by altitude was a key climate factor for the MS. MS had great difference due to different physiological traits among tree species. Light-adapted species, such as Juniperus przewalskii and Pinus gerardiana, had high MS due to drought tole-rance. Shade-adapted species, such as Picea and Abies, had low MS. Old trees may have high MS.
    Prediction model system with dummy variables for carbon storage of larch plantation in Heilongjiang Province, China
    JIA Wei-wei, SUN He-ming, LI Feng-ri
    2019, 30(3):  814-822.  doi:10.13287/j.1001-9332.201903.013
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    Based on monitoring data from fixed plots of larch plantation in Heilongjiang Province obtained in 2005 and 2010, we analyzed the relationship among stand variables of larch plantation in Heilongjiang Province and established site class index curve model and stand density index model. A two-stage least square method was used to establish a simultaneous equations system for predicting average basal area and carbon storage of stands. Together, they were called prediction model system for carbon storage of larch plantation in Heilongjiang Province. The system included two dummy variables of age group and region. Results showed that the determination coefficients of those models were all greater than 0.98, and the root mean square errors were less than 4, except for the site class index curve model. The model with dummy variables increased the determination coefficient, and the root mean square error was less than 3, indicating that the model had good stability with accutrate estimated parameters. The average relative error of all models was less than 2%, the absolute value of the average relative error of most models was less than 15%, and the accuracy of all models was above 95%, indicating that the models could be used to accurately predict the carbon storage of larch plantations in different regions and age groups in Heilongjiang Pro-vince. According to the analysis of the site class index curve model and the estimated parameters of the simultaneous equations, the greater stand age, the larger stand average height, average basal area and carbon storage when the survey plots were located in the same area, which fitted natural growth rules. Under the same stand but different regions, the stand average height decreased in the order of plain area, southern slope area of Xiao-xing’anling, eastern slope area of Zhangguangcai-ling, Wandashan area, western slope area of Zhangguangcailing, and northern slope area of Xiao-xing’anling, while the order of stand basal area and carbon storage was eastern slope area of Zhangguangcailing, northern slope area of Xiaoxing’anling, western slope area of Zhangguangcailing, southern slope area of Xiaoxing’anling, Wandashan area, and plain area.
    Response of sap flow rate of apple trees to environmental factors in Loess Platea of Western Shanxi Province, China
    DANG Hong-zhong, QUE Xiao-e, FENG Jin-chao, WANG Meng-meng, ZHANG Jin-xin
    2019, 30(3):  823-831.  doi:10.13287/j.1001-9332.201903.015
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    To clarify the effects of environmental factors on transpiration process of apple trees in rain-fed ecosystem, the dynamics of sap flow in apple trees from Loess Plateau area in western Shanxi Province of China were monitored using the thermal diffusion technique. Meanwhile, environmental factors including meteorological elements and soil moisture content were measured. The results showed that both net solar radiation (Rn) and atmospheric vapor deficit (VPD) were closely correlated with sap flow rate (Js), as the main ones among all the measured environmental factors. At both hourly and daily scales, the cumulative variances of the three principal components of the environmental factor were above 86%. The first principal component contained VPD and Rn, and explained the variance of over 52% (at hour scale) and 63% (at daily scale), which could be classified as the evaporation demand index (EDI) and as the key comprehensive environmental varia-bles affecting tree sap flow. The second principal component mainly included soil moisture content (SWC) and other factors, which were referred to the soil water and heat supply index. The third principal component mainly included wind speed and other factors, and could be classified into the hydrothermal dissipation index. At the scale of hourly or daily, the response of Js to EDI showed a significant exponential growth relationship. At the hourly time scale, Js of apple trees could be accurately modelled based on the first principal component EDI (R2=0.72). At the daily scale, Js of apple trees could be better modelled based on potential evapotranspiration (ET0) (R2=0.88). Our results were of great significance for clarifying the responses of water transport in apple tree to environmental factors, estimating water consumption of apple tree based on meteorological factors, as well as directing orchard water management.
    Effects of soil warming on soil microbial extracellular enzyme activities with different depths in a young Chinese fir (Cunninghamia lanceolata)plantation of subtropics
    ZHENG Wei, ZHOU Jia-cong, LIN Wei-sheng, ZHENG Yong, LI Chao, LI Xian-feng, JI Yu-huang, YANG Zhi-jie
    2019, 30(3):  832-840.  doi:10.13287/j.1001-9332.201903.025
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    Extracellular enzyme activitie (EEAs) are a sensitive indicator of microbial function and soil organic matter decomposition in response to climate warming. Up to now, most studies of climate warming and their effects on EEAs have been restricted on the relatively carbon rich topsoil (the upper 20 cm of the soil), whereas little is known about EEAs in subsoil (below 30 cm depth). This study focused on the responses of EEAs to soil warming in a subtropical forest at depths of 0-10 cm, 10-20 cm, 20-40 cm and 40-60 cm. The examined extracellular enzymes included β-glucosidase (BG), cellobiohydrolase (CBH), phenoloxidase (PHO) and peroxidase (PEO), all being involved in the C-cycle. The results showed that, 1) warming significantly increased all EEAs (18%-69%) at the depth of 0-10 cm and 10-20 cm. Below the depth of 20 cm, warming did no affect or suppressed EEAs (13%-31%), except increasing PHO (10%) at 20-40 cm. 2) Results from the redundancy analysis showed that the EEAs were mainly driven by ammonium nitrogen (NH4+-N) and soil moisture (M) in organic carbon rich topsoil. Warming enhanced nutrient competition between soil microorganisms and plants. Thus, it increased EEAs to meet NH4+-N demands of microorganisms. In subsoil with relatively low substrate availability, the EEAs were dominated by dissolved organic matter and microbial biomass (MBC). Warming increased dissolved organic matter and thus provided more substrates for microorganisms, which relieved the dependence of microbes on EEAs. Consequently, warming diminished EEAs in subsoils. Our results suggested that EEAs at the four depths showed different responses to warming. In addition, environmental factors accounting for the variances in EEAs under soil warming condition were different at topsoil and subsoil. Paying more attention to microbes at different soil depths has important implications to precisely predict ecosystem C cycling in response to global warming.
    Effects of stand type of artificial forests on soil microbial functional diversity
    SONG Xian-chong, WANG Hui-li, QIN Wen-di, DENG Xiao-jun, TIAN Hong-deng, TAN Yi-bo, WANG Shao-neng, CAO Ji-zhao
    2019, 30(3):  841-848.  doi:10.13287/j.1001-9332.201903.036
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    We explored the changes of soil microbial biodiversity in response to forest ecological restoration. Soil samples were collected from the close-to nature managed Chinese fir plantation (CF), Moso bamboo plantation (MB), and natural secondary forest (NF). Soil microbial community diversity was analyzed by Biolog-Eco micro-plate technique. The results showed that plant diversity was significantly different among the three stands. Plant diversity of NF was significantly higher than MB and CF, and MB was higher than CF. Soil pH and bulk density showed a great difference, while there was no difference of other soil physiochemical properties among the three stands. Avera-ge well color development (AWCD) of soil in various stands followed the order of NF>MB>CF, consistent with the changes of utilization of six types of carbon sources. Shannon index of NF was the highest, and the index of MB was significantly higher than that of CF. Soil physical and chemical properties in different stands were not significantly different, except soil pH and bulk density. The Shannon diversity index (H), Shannon species richness index (S), Simpson dominance index (D) and McIntosh index (U) were the highest in NF, second in MB, and the lowest in CF. Results from principal component analysis (PCA) showed that two factors from 31 carbon sources could explain 60.0% and 12.4% of the variation and that carboxylic acids, carbohydrates and its derivatives, amino acids were the main carbon sources of the two principal component factors. Correlation analysis indicated that plant species richness and Shannon diversity indexes, soil bulk density were significantly correlated to soil microbial community diversity. The microbial community of NF was more efficient in carbon utilization than that in MB and CF, while that in MB was more efficient than that of CF. Based on plant diversity and soil microbial carbon utilization, MB is much better than CF in the artificial forest restoration and improvement in South China.
    Archaeal community succession with fine root growth in poplar plantation
    ZHU Qi-liang, LIU Hong-kai, CHEN Xu, DONG Yu-feng, WANG Yan-ping
    2019, 30(3):  849-856.  doi:10.13287/j.1001-9332.201903.034
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    The archaeal community structure in the rhizosphere soils might change with root growth, which is of great importance for understanding the interaction between roots and microbes. According to root colors, three groups of rhizosphere soils from first-order fine roots of poplar trees (Populus × euramericana) were sampled, including rhizosphere soils surrounding newly born roots (white color, WR), mature roots (yellow color, YR) and aged roots (brown color, BR). Total microbial DNA was extracted from the soils associated with poplar fine roots. The specific primers were used to amplify the 16S rDNA V4-V5 region of soil archaea, and the Illumina MiSeq platform was used for high-throughput sequencing analysis. The results showed that the observed OTU (operational taxonomic unit) abundance of archaeal community in WR and BR rhizosphere soils were similar, while the OTU abundance in YR rhizosphere soil were lower. The WR and BR shared 134 OTUs of archea, the YR and BR shared 87 OTUs, and the WR and BR shared 90 OTUs. The Chao1 index and the ACE index of archaeal community in YR rhizosphere soil were significantly lower than those of WR and BR, while the Simpson index and the Shannon index of BR were significantly lower than WR to YR. Results from the PERMANOVA analysis showed that archaeal community compositions in WR and BR rhizosphere soils were significantly different. Species annotation showed that there were 12 genera of archea in three rhizosphere soils, five genera in WR, 10 genera in YR, and six genera in BR, respectively. The similarity of the archaeal community composition in poplar rhizosphere soils gradually decreased from WR to BR, with large differences among different growth stages of fine roots. The dominant genus was Candidatus_Nitrososphaera, with a relative abundance of more than 70%, indicating this archaea group might be closely related to poplar fine roots development.
    Greenhouse gas fluxes at different growth stages of biological soil crusts in eastern Hobq desert, China
    WANG Bo, DUAN Yu-xi, WANG Wei-feng, LIU Zong-qi, LI Xiao-jing, LIU Yuan, LI Shao-bo, XI Wen
    2019, 30(3):  857-866.  doi:10.13287/j.1001-9332.201903.004
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    We analyzed greenhouse gas fluxes at the different growth stages of algae and lichen crusts in fixed sand with mobile dune as control in the eastern Hobq Desert, China, using the spatio-temporal substitution method. We explored the correlation of these fluxes with environmental factors and with biological soil crust growth. The results showed that variation of CO2 fluxes followed the order: lichen crust (128.5 mg·m-2·h-1) > algae crust (70.2 mg·m-2·h-1) > mobile dune (48.2 mg·m-2·h-1). CH4 absorption rates were in the following order: lichen crust (30.4 μg·m-2·h-1) > algae crust (21.2 μg·m-2·h-1) > mobile dune (18.2 μg·m-2·h-1). The N2O fluxes were in the following order: lichen crust (6.6 μg·m-2·h-1) > algae crust (5.4 μg·m-2·h-1) > mobile dune (2.5 μg·m-2·h-1). CO2 emission had obvious seasonal variation, with higher emission in the growing season. CH4 and N2O fluxes had no seaonal variation. CH4 absorption mainly occurred in the growing season and N2O emission mainly occurred in non-growing season. Contents of soil total nitrogen and organic carbon and the abundance of microorganisms were important factors affecting greenhouse gas fluxes. Hydrothermic factors were important for soil CO2 emission, but not for CH4 and N2O fluxes. The cumulative greenhouse gas emissions were gradually increased with vegetation restoration and the development of biological soil crust. The global warming potential increased following an order: lichen crust (1135.7 g CO2-e·m-2·a-1) > algae crust (626.5 g CO2-e·m-2·a-1) > mobile dune (422.7 g CO2-e·m-2·a-1).
    Simulation of evapotranspiration for the mobile and semi-mobile dunes in the Horqin Sandy Land using the Shuttleworth-Wallace model
    BAO Yong-zhi, LIU Ting-xi, DUAN Li-min, WANG Guan-li, TONG Xin
    2019, 30(3):  867-876.  doi:10.13287/j.1001-9332.201903.014
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    Terrestrial evapotranspiration (ET) plays a crucial role in climate regulation and the maintenance of regional water balance. Quantitative estimation of ET and its partitioning are important for revealing the eco-hydrological processes in arid and semi-arid areas. Using the in situ data sampled by the meteorological monitoring system, the Shuttleworth-Wallace (S-W) model was applied to simulate and partition ET in the mobile and semi-mobile dunes of the Horqin sandy land during the growing season in 2017. The eddy covariance system was used to verify the simulated ET. The results were as follows: the simulated ET (308 mm) was very close to the eddy covariance observed ET (296 mm) during the whole growing season, indicating the applicability of the S-W model for ET estimation in this area. The ET rate at the vigorous growth stage (192 mm) was larger than those at the late and early growth stages (71 and 45 mm, respectively) which accounted for 62.3%, 23.1%, and 14.6% of the total, respectively. The simulated ET was close to the eddy covariance observed ET at the daily time-scale. The simulation performance of the S-W model for clear days was better than for cloudy or rainy days. The simulated ET rate was always smaller than the eddy covariance observed ET in the cloudy or rainy days. According to the model, the evaporation (E) from soil was 176 mm and the transpiration (T) from plants was 132 mm, accounting for 57.1% and 42.9% of the ET, respectively, suggesting that water use efficiency of the sand dune was low. The characteristics of ET varied substantially under the sustained drought and precipitation events. Compared to T from plants, E from soil was more sensitive to precipitation.
    Dynamic monitoring of eco-environmental quality in arid desert area by remote sensing: Taking the Gurbantunggut Desert China as an example
    JIANG Chao-liang, WU Ling, LIU Dan, WANG Shao-ming
    2019, 30(3):  877-883.  doi:10.13287/j.1001-9332.201903.008
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    Using remote sensing ecological index (RSEI) to evaluate regional ecological changes can obtain the ecological environment changes quickly, efficiently, and objectively. In this study, RSEI of four ecological factors, greenness, humidity, heat, and dryness were calculated using the Landsat data and the spatial and temporal patterns of ecological environment in the Gurbantunggut Desert from 2006 to 2017 were qualitatively and quantitatively evaluated, based on the weights determined by principal component analysis. The results showed that humidity and greenness played a positive role in the eco-environment quality of the Gurbantunggut Desert, whereas heat and dryness had negative effects. Normalized vegetation index (NDVI) representing the greenness was the top contributor among those four factors. The RSEI of the Gurbantunggut Desert declined from 2006 to 2017, with a 20.1% decrease of the mean value from 0.294 in 2006 to 0.243 in 2017. The ecological environment of the study area showed a deterioration. The eco-environmental quality of the central part of the Gurbantunggut Desert was relatively stable. The eco-environment quality of the dense vegetation areas in the northeast and the irrigated areas in the south was getting better, but that of southern and northwestern parts of the desert was getting worse.
    Effects of elevated atmospheric CO2 concentration on photosynthsis of hybrid rice varieties in cloudy and sunny days: A FACE study
    JING Li-quan, HU Shao-wu, LU Qi, NIU Xi-chao, WANG Yun-xia, ZHU Jian-guo, WANG Yu-long, YANG Lian-xin
    2019, 30(3):  884-892.  doi:10.13287/j.1001-9332.201903.024
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    Light and carbon dioxide (CO2) are two essential components for plant photosynthesis. To understand the effects of elevated CO2 concentration on photosynthetic characteristics of hybrid rice under different light conditions, two hybrid rice varieties (YLY900 and YY538) were grown in the field using a free-air CO2 enrichment facility (FACE) in 2017 with two CO2 concentration treatments (ambient CO2 and elevated 200 μmol·mol-1 above ambient CO2), the photosynthesis traits of top full expansion leaves were measured in both sunny and cloudy days at jointing and grain filling stages. Elevated CO2 increased net photosynthetic rate (Pn) of two rice varieties. The increase in sunny days (31%) was greater than in cloudy days (21%), and the increase at jointing stage (37%) was greater than at grain filling stage (21%). There were significant interactions between CO2 with weather, and between CO2 with growth stage. Water use efficiency (WUE) of leaves in response to elevated CO2 showed the similar trend as Pn. Elevated CO2 decreased stomatal conduc-tance (gs) and transpiration rate (Tr), and the decreases in sunny days were greater than that in cloudy days. The Pn, gs, Tr, WUE and stomatal limit (Ls) measured in cloudy days were significantly lower than that measured in sunny days by 41%, 18%, 41%, 26% and 27%, respectively. Results from the correlation analyses showed that the Pn, gs, and Tr in sunny days were significantly positively correlated with the corresponding parameters in cloudy days. The results indicated that cloudy weather conditions reduced photosynthesis and its response to elevated CO2 of two hybrids rice varieties at middle and late growth stages. Therefore, weather variation should be considered when assess rice yield potential in the future environment.
    Impacts of different soil fertility improvement practices with film mulched ridge-furrow til-lage on soil nutrient content, maize yield, and water use efficiency in Northwest China
    YANG Feng-ke, HE Bao-lin, ZHANG Guo-ping, ZHANG Li-gong, GAO Ying-ping
    2019, 30(3):  893-905.  doi:10.13287/j.1001-9332.201903.029
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    Improvement of soil quality is one of the most important ways to enhance fertility for efficient dryland crop production. However, the effects of different fertilization measurements with film mulched ridge-furrow tillage on soil fertility, crop yield, and water use efficiency (WUE) of maize largely remain unknown. A three-year field experiment was conducted at the Zhuanglang Experimental Station, Gansu Academy of Agricultural Sciences, located in the semiarid region of the Loess Plateau, Northwest China during 2014-2016. Maize breed Funong No.1 was used during the study. There were four treatments, including: 1) conventional planting (CP, served as control), 2) film mulched ridge-furrow with straw incorporation (FS), 3) film mulched ridge-furrow with optimizing fertilization (FF), and 4) film mulched ridge-furrow with controlled fertilization (FC). Seasonal and yearly changes of soil water content, topsoil organic matter (SOM), soil available nitrogen (AN), phosphorus (AP) and potassium (AK) concentration and crop yield were measured. Nitrogen and phosphorus fertilizer partial factor productivity (PFPN and PFPP), soil profile water storage (WC), crop seasonal water consumption (ET) and water use efficiency (WUE) were calculated. The results showed that FS, FF and FC effectively improved soil fertility via synergistic regulation of soil hydrothermal and nutritional condition. Water-fertilizer interaction effect greatly enhanced incorporated straw decomposition and crop growth, resulting in more returning of straw nutrients and crop biomass to soil, thus significantly increased soil water and fertilizer supply capacity. Compared to CP, the three treatments of FS, FF and FC efficiently increased the concentrations of SOM, AN, AP, and AK by 0.27 g·kg-1, 4.44 mg·kg-1, 0.20 mg·kg-1 and 4.53 mg·kg-1 with an order of FC>FF>FS, but had no significant difference among them. Meanwhile, in contrast to pre-sowing WC200, the three year’s sum of FS,FF and FC increased WC200 at the end of growing season by 107.41, 38.99 and 28.35 mm, respectively. On average, FS, FC and FF significantly reduced maize ET by 60.50, 37.7 and 34.15 mm to CP, with a relative decrease of 12.6%, 7.9% and 7.1% respectively. By the synergistic effect of modified water and fertilizer environment, the three soil fertility improvement strategies greatly enhanced maize growth from tasseling to maturity stages in the relatively dry year. They affected maize growth in relatively more rain and warmer year, resulting in significantly increased maize yield by improving the yield traits (double ear rate, grain number per ear and 100-grain mass), PFPN, PFPP and WUE. Compared to CP, the PFPN,PFPP of FS, FF and FC increased by 1.82, 1.65, 1.62 and 2.41, 1.69, 1.63 times respectively. Yield and WUE were increased by 5986.1, 4972.31, 4585.63 kg·hm-2 and 13.27, 12.65, 14.01 kg·mm-1·hm-2 correspondingly raised by 81.5%, 67.7%, 62.5% and 86.5%, 82.5%, 91.3%. In conclusion, FS was more effective in water harvesting and drought resistance, while FC and FF were effective for high yield.
    Application of cosmic-ray fast neutron method in soil moisture measurement of typical farmland in North China Plain
    SONG Shang-kun, TIAN Jing, HE Hong-lin
    2019, 30(3):  906-912.  doi:10.13287/j.1001-9332.201903.030
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    Cosmic-ray neutron sensing (CRNS) is a new method for measuring mean soil moisture at regional scale. On the basis of continuous observation data of CRNS and the measurements of soil moisture with the distributed sensor network in Yucheng Comprehensive Experimental Station of the Chinese Academy of Sciences, we examined the applicability of the CRNS method to the agroecosystem in North China Plain. The stability of the neutron number in dry conditions (N0) and the effects of rainfall and irrigation on soil moisture estimation were investigated. The results showed that N0 was significantly affected by the underlying surface. The changes of N0 corresponded well to the planting and harvesting time of winter wheat and summer maize. Soil moisture estimated by the CRNS method had obvious response to rainfall and irrigation. When irrigation or rainfall occurred, soil moisture was overestimated. The CRNS method could effectively estimate regional soil moisture for the agroecosystem in North China Plain. The estimates of soil moisture were closest to the soil moisture in 10 cm depth.
    Dynamic and its driving factors of soil potential acid in croplands of Fujian Province, China
    ZHOU Jie-ying, ZHANG Li-ming, YANG Wen-hao, ZHOU Bi-qing, XING Shi-he
    2019, 30(3):  913-922.  doi:10.13287/j.1001-9332.201903.011
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    Soil potential acid is one of the potential factors limiting plant growth, and also an important base in soil acidity regulation. The potential acid and pH value of surface soil samples of cultivated lands in Fujian Province were proportionally selected and measured, and then the optimized relational model between soil pH and potential acid value was fitted. The 1:50 000 databases of cropland soil potential acid in 1982, 2008 and 2016 were established by using the topsoil pH data of 36777, 236445 and 21269 sampling sites collected in 1982, 2008 and 2016 respectively. The dynamics of cropland soil potential acid in Fujian Province and its driving factors were explored by the integrative method of GIS and grey correlation analysis. The results showed that the quantities of soil potential acid in cropland generally increased in Fujian Province from 1982 to 2016. Compared with 1982, the averages of soil potential acid in 2008 and 2016 increased 1.30 and 1.49 cmol·kg-1, respectively. The increase rate of soil potential acid from 1982 to 2008 was 0.03 cmol·kg-1·a-1 higher than that from 2008 to 2016. Meanwhile, the changes of cropland soil potential acid showed significant spatial difference. The change of cropland soil potential acid in Sanming was minimum, and the change in Longyan was maximum, being four times higher than that in Sanming. The change of soil potential acid in different use types of cropland was following the order: paddy field > irrigated land > dry land. The changes of soil potential acid in acid sulfate paddy soils, gleyed paddy soils and submergenic paddy soils were maximum, which were one time higher than the mean change across the whole Province, while the changes in latosolic red earths and salinized paddy soils were minimum, which were 25.7% and 28.4% of the mean change in the Province, respectively. The driving factors for the dynamics of cropland soil potential acid in Fujian Province included the application rates of nitrogen and phosphorus fertilizer, cation exchange capacity (CEC), clay content, pH and silt content, with grey correlation coefficient (absolute value) being higher than 0.92. Accordingly, it would be an effective approach to slow down the increase of cropland soil potential acid in Fujian Province to optimize fertilization management and apply alkaline ameliorant scientifically.
    Effects of exogenous Ca2+ on stomatal traits, photosynthesis, and biomass of maize seedings under salt stress
    ZHANG Hao, ZHENG Yun-pu, YE Jia, GAO Wei, QIAO Ya-jun, DAI Chuan-jing, ZHAO Yu-xin, SHI Shao-jie
    2019, 30(3):  923-930.  doi:10.13287/j.1001-9332.201903.020
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    Understanding the responses of stomatal structure, photosynthesis and biomass of maize to exogenous Ca2+ addition under NaCl stress has important significance for further uncovering the alleviative mechanism of exogenous Ca2+ on maize under salt stress. We examined the effects of exogenous Ca2+(0, 5, 10, 20, 40, 80 mmol·L-1) on the stomatal structure, photosynthesis and biomass of maize (Zea mays L. cv. Jingke 665) seedlings under NaCl stress (100 mmol·L-1). Our results showed that exogenous Ca2+ addition had limited effect on stomatal density, but significantly decreased stomatal shape index, stomatal area, stomatal length, stomatal width, and stomatal cir-cumference. Meanwhile, the net photosynthetic rate (Pn) initially increased and then decreased with the increases of exogenous Ca2+ concentration, whereas both the stomatal conductance (gs) and intercellular CO2 concentration (Ci) were decreased, suggesting that the decrease of Pn was mainly due to stomatal limitation under high Ca2+ concentration. The biomass of maize seedlings was increased and the root/shoot ratio was decreased with the increases of exogenous Ca2+ concentration, suggested that the alleviated effect of exogenous Ca2+ on aboveground biomass was higher than that on belowground biomass of maize under salt stress.
    Regulation of mulch conditions on photosynthesis and water utilization of spring wheat in northwest semi-arid area of China
    HOU Hui-zhi, ZHANG Xu-cheng, YIN Jia-de, FANG Yan-jie, YU Xian-feng, WANG Hong-li, MA Yi-fan
    2019, 30(3):  931-940.  doi:10.13287/j.1001-9332.201903.021
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    A field experiment was conducted from 2015 to 2016 in the northwestern Loess Plateau, China, to analyze the relationships among flag-leaf photosynthetic characteristics, water-consumption characteristics, and yield components of spring wheat (Triticum aestivum ‘Longchun 35’). There were three treatments: whole-field plastic mulching (PMS), sand mulching (SM), and uncovered (CK). The results showed that soil-water storage levels at 0-300 cm of soil profile before wheat filling under PMS and SM treatments were greater than that in CK by 47.8 and 31.6 mm, respectively, while that under PMS was lower than CK by 15.6 mm at the filling stage. Water consumption under PMS and SM increased in the flagging-heading and flowering-filling stages compared with the CK. Leaf area indices under PMS and SM were increased by 59.0%-73.7% and 40.1%-52.7%, respectively, and leaf SPAD values were increased by 3.5%-28.4% and 2.9%-23.9%, respectively, compared with CK. The net photosynthetic rate of PMS was increased by 23.5%, 33.0% and 17.7% at the flagging, heading, and flowering stages. The corresponding stoma-tal conductance rate was increased by 32.6%, 76.4% and 66.9%, respectively. Net photosynthetic and stomatal conductance rates at the filling stage were decreased by 26.2% and 16.4%, respectively. At the heading, flowering, and filling stages, stomatal limitation values in PMS were decreased by 14.6%, 23.9% and 22.3%, respectively, and by 25.7%, 29.8% and 17.4%, respectively in SM. The instantaneous water-use efficiency of spring wheat in PMS was increased by 57.8% at the flagging stage and decreased by 11.2% at the flowering stage. At the heading and flowering stages, the apparent quantum efficiency was increased by 22.6% and 18.7% in PMS, and by 26.8% and 14.3% in SM, respectively. Plant height and yield component indices in PMS and SM were significantly greater than that in CK, with the enhancement being greater than that in dry years. Grain yield was increased by 36.2% and 8.7% and water-use efficiency increased by 9.4% and 3.4% in PMS and SM, respectively. PMS and SM treatments increased soil water storage before the pre-filling stage of wheat, aggravated water consumption during the flagging-shooting and flowering-filling stages, resulting in greater SPAD values and leaf area indices, which promoted the photosynthetic functions of flag leaves, facilitated sink formation and photosynthetic assimilate transportation, resulting in increased grain yields and water use efficiency of spring wheat. The effects of PMS treatment were more remarkable than those of SM in terms of increasing spring wheat’s yield potential in wet years and adaptability in dry years.
    Effects of copper treatment on mineral nutrient absorption and cell ultrastructure of spinach seedlings
    GONG Qin, WANG Ling, DAI Tong-wei, KANG Qun, ZHOU Jing-yi, LI Zhao-hua
    2019, 30(3):  941-950.  doi:10.13287/j.1001-9332.201903.031
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    The accumulation of heavy metals in soil has serious influence on plant growth and ecosystem balance. It is of great importance to explore the mechanism of plant tolerance to heavy me-tals. Although spinach is supposed to have strong Cu tolerance, the effects of Cu on mineral element absorption and cell ultrastructure are still unclear. In this study, the growth of spinach seedlings, the absorption of mineral elements and the ultrastructure of leaf cells were examined in a pot experiment. The results showed that Cu2+ accumulation in the root of spinach seedling was less than that in the shoot when CuSO4 concentration was 100 mg·L-1, with root growth being increased and shoot growth being slightly decreased. When copper concentration continued to increase, the growth parameters continuously declined. When the CuSO4 concentrations were less than 400 mg·L-1, the foliar N, K, Ca, Mg and Fe concentrations of spinach seedling increased, and that of P decreased. The concentrations of N, P and K in roots went down and that of Ca, Mg and Fe went up. All organelles in leaf cells were clearly visible. The basal granule layer was arranged orderly, and the inner and outer membranes of chloroplasts were intact. When the CuSO4 concentrations exceeded 600 mg·L-1, foliar N concentration increased while that of P, K, Ca, Mg and Fe decreased. The concentrations of N, P, K, Ca, Mg and Fe in roots declined. The cell ultrastructure of spinach seedlings substantially changed with the increases of CuSO4 treated concentrations. The chloroplast in leaf cells became rounder, the chloroplast membrane became thinner, the stroma and basal granule layer became less, and the layer accumulation height decreased. The nucleus was broken up and small black spots were found in vacuoles and cell walls, which might be attributed to the enhancement of intracellular swelling pressure caused by high accumulation of Cu2+. In conclusion, low concentration of CuSO4 had little negative effect on the life activities of spinach seedlings, and the high concentrations of CuSO4 did not terminate their growth, indicating that spinach seedlings had strong copper resistance.
    Effects of N application on faba bean chocolate spot and canopy microclimate in wheat and faba bean intercropping system
    MA Lian-kun, DONG Kun, ZHU Jin-hui, DONG Yan
    2019, 30(3):  951-960.  doi:10.13287/j.1001-9332.201903.022
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    A field experiment was conducted to examine the effects of nitrogen application levels, i.e. N0 (0 kg·hm-2), N1 (45 kg·hm-2), N2 (90 kg·hm-2), N3 (135 kg·hm-2), on the severity of chocolate spot and canopy microclimate in wheat and faba bean intercropping system, and to explore the relationship of canopy microclimate change and severity of chocolate spot. The results showed that the disease index of chocolate spot increased by 27.2%-58.0% in the peak infection stage, and the area under disease progress curve (AUDPC) increased by 15.0%-101.8% for both monocropped and intercropped faba bean after nitrogen application. The peak value of disease index and AUDPC appeared at N3 (135 kg·hm-2) level. After nitrogen application, canopy temperature decreased by 0.2-1.1 ℃ and canopy light transmittance decreased by 1.7%-29.7%, but canopy relative humidity increased by 0.5%-28.7%. Compared with monocropped faba bean, wheat and faba bean intercropped significantly decreased the chocolate spot disease index by 36.3%-48.1% and AUDPC by 44.0%-53.6%. Canopy temperature and light transmittance of intercropped faba bean increased by 2.1%-8.7% and 12.0%-53.8%, respectively. The canopy relative humidity was decreased by 11.6%-31.6%. There were significantly negative correlation between canopy temperature and light transmittance with disease index of faba bean chocolate spot. The canopy humidity was positively correlated with disease index. Our findings showed that high nitrogen application deteriorated canopy microclimate of faba bean that led to occurrence and harm of chocolate spot, and that the improvement of canopy microclimate by intercropping would be helpful for controlling faba bean chocolate spot.
    Nitrogen fixation characteristics of root nodules in different peanut varieties and their relationship with yield
    ZHENG Yong-mei, DU Lian-tao, WANG Chun-xiao, WU Zheng-feng, SUN Xue-wu, YU Tian-yi, SHEN Pu, WANG Cai-bin
    2019, 30(3):  961-968.  doi:10.13287/j.1001-9332.201903.019
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    Root nodules in peanut (Arachis hypogaea L.) could directly utilize nitrogen (N) in the atmosphere as N source, which plays an important role in the N supply in peanut. However, little is known about the mechanism of efficient N fixation by root nodule. In this study, 15N tracer technology was used to investigate the characteristics of N fixation by root nodule and its relationship with peanut yields of 19 varieties in a pot culture experiment. Results showed that there were significant differences in nodule number, fresh quality, internal material, N fixation amount and other related indices among different varieties. The range of number and fresh mass of root nodule was 170.59-696.15 per pot and 0.83-3.74 g per pot, with coefficients of variation (CV) of 36.1% and 41.1%, respectively. The range of leghaemoglobin content and nitrogenase activity was 15.51-23.23 mg per pot and 2.75-20.46 μmol C2H4·h-1 per pot, with CV of 13.1% and 57.2%, respectively. The CV of nitrogenase activity was significantly higher than that of leghaemoglobin content, indicating that nitrogenase activity was not only affected by leghaemoglobin content but also other factors. The range of N fixation by root nodule and total N accumulation was 0.71-1.82 and 2.16-3.72 g per pot, with CV of 21.6% and 12.9%, respectively. The CV of the former was significantly higher than that of the latter, indicating that other N sources could automatically compensate the deficit when N fixation of root nodule was insufficient. Nitrogen fixation by root nodule was one of the main N sources for peanut, while the average N supply percentage was more than 40% of the total N, with a maximum of 50%. Cultivating the variety with high N supply capacity is an effective way for N-saving cultivation in the peanut production. Except for nodule number, there were significantly positive correlations between the other indices and peanut yield, indicating that the physiological indicators of N fixation were closely related to N fixation capacity by root nodule and the final yield. Therefore, enhancing these characters would help achieve high yield of peanut and simultaneously reduce fertilizer application.
    Effects of salt and drought stresses on antioxidant system and RbohC and RbohF genes expression in Brassica campestris
    ZHANG Teng-guo, LI Qiao-li, DIAO Zhi-hong, LI Ping, WANG Juan, ZHENG Sheng
    2019, 30(3):  969-978.  doi:10.13287/j.1001-9332.201903.017
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    To investigate the effects of salt stress and PEG-6000 simulating drought stress on the active oxygen and antioxidant enzyme activities, as well as the expression level of RbohC and RbohF genes, the seedlings of two Brassica campestris, Longyou 6 and Tianyou 2, were treated with U0126 (a MAPKK inhibitor), DMTU (a H2O2 scavenger), as well as DPI and IMD (NADPH oxidase inhibitors). The results showed that under both stresses, H2O2 accumulation as well as antioxidant enzyme (SOD, CAT, APX, GR) activities and the expression of RbohC and RbohF genes increased, while O2 accumulation decreased. The O2 accumulation, antioxidant enzyme activity and RbohC and RbohF genes expression in both varieties all significantly decreased. Compared to seedlings with on pretreatment before salt and PEG-6000 simulating drought stress, the accumulation of H2O2 decreased in seedlings pretreated with DMTU, DPI and IMD. However, the accumulation of H2O2 increased in those pretreated with U0126. Those results indicated that the NADPH oxidase, MAP kinase cascade and H2O2 were involved in the regulation of active oxygen production and antioxidant enzyme activity, as well as the expression of RbohC and RbohF under salt stress and drought stress.
    Evaluation of ecosystem service value of the grape industry at the eastern foot of Helan Mountain, Ningxia, China
    SONG Zhen-wei, SUN Mei-ying, YANG Rong-jin, DOU Guang-yu, ZHANG Yi, ZHANG Le
    2019, 30(3):  979-985.  doi:10.13287/j.1001-9332.201903.028
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    Using statistical data from Statistics Bureau of Ningxia Hui Autonomous Region, the Grape Industry Development Bureau of Ningxia Hui Autonomous Region, and National Bureau of Statistics, ecosystem service value of grape industry at the eastern foot of Helan Mountain in Ningxia was evaluated from eight facets, i.e., food production, carbon fixation and oxygen release, air purification, soil conservation, water-holding, water conservation and efficiency, eco-tourism, and ecological poverty alleviation. The results showed that: 1) ecosystem service value of the grape industry was 3.6 billion (RMB), with direct benefit of 2.2 billion and the ecological benefit of 1.4 billion. Ecological benefit accounted for 38.85% of the total ecosystem service value. 2) The service value of the grape industry was in the order of ecological poverty alleviation> eco-tourism> carbon fixation and oxygen release> water conservation and efficiency > air purification > soil conservation> water-holding. 3) Among the ecological benefits, the value of ecological poverty alleviation was the highe-st, accounting for 64.39%; the value of ecotourism was the second, accounting for 24.47%. The results indicated the necessity of assessing ecosystem service value of the grape industry, which could enable people to realize the direct economic benefits as well as the ecological benefits. This study had important reference value for comprehensively guiding the healthy and sustainable deve-lopment of the grape industry.
    Carbon sink calculation model of urban construction land based on building capacity
    LI Sui, SHI Tie-mao, WANG Zi-tong, LI Tao, ZHOU Shi-wen, LI Pei-ying
    2019, 30(3):  986-994.  doi:10.13287/j.1001-9332.201903.016
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    The exploitation and utilization of mineral materials during urban construction causes a large amount of carbon emission, but could also contribute to carbon sequestration. In the related literature, carbon sequestration process of building mineral materials has received limited attention and scientific quantification. On the basis of extracting building capacity and identifying building types, we used the technology of remote sensing image shadow height inversion to quantify mineral material consumption and carbon content parameters. Carbonization rate was measured by thermogravimetric analysis (TGA). Finally, a calculation method for carbon sink in urban buildings was constructed. We investigated the uncertainty of this method with Puhe New Town in Shenyang as an example. The results showed that the order of carbon sink density of different types of buildings followed the order of residential buildings > public service buildings > other types of buildings > commercial and financial buildings > industrial buildings; the ratio of carbon sink volumetric in diffe-rent types of construction land followed the order of commercial and financial buildings > residential buildings > public service buildings > other types of buildings > industrial buildings. The carbon sink calculation method based on the urban scale of building capacity in this study could quickly and accurately estimate the magnitude of carbon sinks from the inorganic materials in various types of urban construction lands. Under the background of limited urban natural carbon sequestration, using building carbon sequestration to enhance the urban carbon sequestration could provide new ideas for the low-carbon development of cities in China.
    Spatiotemporal patterns of the trade-off and synergy relationship among ecosystem services in Poyang Lake Region, China
    RAN Feng-wei, LUO Zhi-jun, WU Jia-ping, QI Song, CAO Li-ping, CAI Zheng-mei, CHEN Yao-yao
    2019, 30(3):  995-1004.  doi:10.13287/j.1001-9332.201903.005
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    Poyang Lake region is the largest freshwater lake impacted area in China. Quantitative analysis of trade-off and synergy in ecosystem service is of great significance for realizing regional sustainable development. Based on multi-source data of remote sensing, soil, meteorology and DEM, we quantitatively measured food supply service, soil conservation service and water yield service in Poyang Lake region from 2005 to 2015, and analyzed their spatiotemporal patterns and evolution characteristics. The spatial and temporal characteristics of trade-off and synergy between services on the scale of 1 km×1 km were analyzed by using correlation analysis, hot spot analysis and spatial mapping method. The differences of ecosystem services and their relationships in the perspective of land use were studied. The results showed that food supply service increased, soil conservation service decreased, and water yield service increased first and then decreased during the study period. In terms of spatial distribution, food supply service presented “low-high-low-high” in the northwest-southeast direction, soil conservation service was concentrated in high and low values, and water yield service was high in south and low in north. There were trade-off relationships between food supply and soil conservation, and between food supply and water yield. There was synergistic relationship between soil conservation and water yield. Moreover, the relationship between food supply and soil conservation showed a spatial pattern of synergy in northern but trade-off in southern region. There was a clear spatial trade-off between food supply and water yield, and from north to south the relationship between soil conservation and water yield existed synergy-tradeoff-synergy differentiation, like a “sandwich”. Among different land use types, there was a significant synergy between cultivated land and food supply, garden land and soil conservation, water area and water yield, but trade-off relationships between construction land and three services. The relationship between food supply and soil conservation and water yield was mainly trade-off in different land use types. The relationship between soil conservation and water yield was synergy in cultivated land, garden land, grassland and construction land, but was trade-off in water and unused land. The hot spots of multiple ecosystem services in the Poyang Lake region were mainly in the eastern and sou-thern plain areas, with a decreasing trend.
    Simulation of the distribution of main atmospheric pollutants and the influence of land use on them in central urban area of Nanchang City, China
    LIANG Zhao-feng, CHEN Wen-bo, ZHENG Jiao, LU Tao-jie
    2019, 30(3):  1005-1014.  doi:10.13287/j.1001-9332.201903.010
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    With the rapid urbanization and industrialization in China, atmospheric pollution becomes increasingly urgent. It is of great importance to examine the distribution of atmospheric pollutants and the influence of land use for sake of reducing pollution. We simulated and analyzed the temporal and spatial distribution characteristics of the six main atmospheric pollutants in the central urban area of Nanchang City, i.e. PM2.5, PM10, SO2, NO2, CO and O3 based on land-use regression models (LUR). Four types of area, i.e. residential, commercial, educational and industrial area, were defined according to dominated land use type. Fifteen samples from each type were collected. The concentration of six air pollutants of fifteen sample areas for each type and each season were averaged to reduce the influence of meteorological factors. By means of double factor varian-ce analysis and multiple comparisons, we analyzed the effects of land use (expressed by sample area) on those atmospheric pollutants. The results showed that the concentrations of all the six atmospheric pollutants were well simulated by LUR model, with an average absolute error were 11.9%, 13.4%, 12.5%, 12.0%, 12.7% and 13.5% respectively. The concentration of six atmospheric pollutants showed obvious temporal and spatial distribution characteristics, with O3 presenting the highest in summer, then spring, autumn, and winter in order, and the remaining five pollutants peaked in winter, then spring, autumn and summer in order. The concentrations of PM2.5, PM10, SO2, NO2 and CO showed a decreasing trend from urban center to suburb, while the concentration of O3 was the opposite. The concentrations of varied seasons or land use sample areas were all significantly different, indicating that both meteorology and land use had significant effects on air pollution. The effects of land use on main atmospheric pollutants varied, with stronger effects on PM2.5, NO2 and O3 than on CO.
    Construction of ecological security pattern based on habitat quality in Tang County, Hebei, China
    HAO Yue, ZHANG Na, DU Ya-juan, WANG Yi-hui, ZHENG Yan-dong, ZHANG Chang-chun
    2019, 30(3):  1015-1024.  doi:10.13287/j.1001-9332.201903.007
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    As the key and hot topic in landscape ecology, ecological security pattern plays an important role in maintaining regional ecological security and achieving regional sustainable development. Based on land use data of 2016, we used the InVEST model to evaluate the habitat quality of Tang County to determine the ecological source. The resistance surface was constructed by selecting the resistance factors such as land use type, habitat quality index, vegetation coverage, distance to water, distance to settlements, distance to roads, with the resistance threshold being used to partition the ecological security pattern. Finally, the ecological security pattern of Tang County was constructed by determining the ecological corridor with the MCR model. The results showed that the ecological source of Tang County accounted for 3.3% of the total area, mainly distributed in forest land and waters with large plaque area, and the Western Ocean Reservoir (one of the four major reservoirs in Hebei Province). According to the cost resistance mutation point, the research region could be divided into prohibited development zone, restricted development zone, optimized development zone, and key development zone. The percentage of each zone was 18.9%, 43.6%, 27.6% and 9.9%, respectively. The total length of the potential ecological corridors in Tang County was 333.52 km, and was 263.91 km after optimization, which was helpful for various ecological exchanges. Our results had important guiding significance for the rational and sustainable use of land resources in Tang County, and could provide theoretical and technical supports for the decision-making of land planning and layout in Tang County.
    Reviews
    Research advances in using constructed wetlands to remove pesticides in agricultural runoff
    ZHANG Xi-li, YU Zheng-da, WANG Sen, LI Yue, KONG Fan-long
    2019, 30(3):  1025-1034.  doi:10.13287/j.1001-9332.201903.033
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    Constructed wetlands (CWs) performs excellently in removing pollutants from agricultural runoff, and thus have been widely used as an effective measure to control agricultural runoff pollution. Based on reviews on domestic and overseas literature, we introduced the current situation of water bodies polluted by pesticides. The removal mechanisms of pesticides by CWs were elucidated according to physical, chemical and biological processes, and the main processes were discussed in detail. The removal efficiency of pesticides in CWs vary greatly with pesticide types. Based on their uses, the average removal efficiency of pesticides are in the order of insecticides > fungicides > herbicides. According to their chemical constitution, they follow the order of pyrethroid > organopho-sphorus > triazole > amide > triazine > ureas. Considering comprehensively, subsurface flow CWs perform better than surface flow CWs in removing pesticides. Furthermore, the effects of the physicochemical properties of pesticides, the types and operating parameters of CWs, pesticides concentration in influent, as well as vegetation on the removal of pesticides in CWs were also analyzed. Finally, problems in the current research and the future application of CWs in treating pesticides were discussed.
    Research progress in arbuscular mycorrhizal technology
    CHEN Bao-dong, YU Meng, HAO Zhi-peng, XIE Wei, ZHANG Xin
    2019, 30(3):  1035-1046.  doi:10.13287/j.1001-9332.201903.037
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    Arbuscular mycorrhizal (AM) symbiosis facilitates plant mineral nutrient acquisition and plays key roles in plant adaptation to environmental stresses. The application of AM fungi is a component of sustainable agriculture and ecological restoration. We introduced the current status of AM fungi collections, production of commercial inocula and AM fungi related patents, summarized the research advances in inoculum production, inoculation techniques, and factors influencing the success of inoculation practice in the field, based on case studies of mycorrhizal technology in agriculture, horticulture, and ecological restoration. Finally, we proposed some basic scientific questions and technical bottleneck that deserve futher studies, to promote the development and application of mycorrhizal technologies.
    Process and mechanism of nitrogen loss in the ocean oxygen minimum zone.
    TIAN Dong-fan, LI Xue-gang, SONG Jin-ming, LI Ning
    2019, 30(3):  1047-1056.  doi:10.13287/j.1001-9332.201903.038
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    There is a big imbalance between the input and output of oceanic nitrogen in global ocean nitrogen cycles, because a part of the fixed nitrogen is reduced to N2 or N2O and then lost from the ocean. Oxygen minimum zone (OMZ) is the most important area for nitrogen loss, which could lose fixed nitrogen up to 40 to 450 Tg·a-1 through the denitrification and anammox. A summary of the two main roles of nitrogen loss in the different OMZ sea areas reveals that heterotrophic denitrification dominates in eastern tropical Pacific, Arabian Sea, and marine sediments. The autotrophic denitrification has been found in Chile, Peru’s coastal waters, and Arabian waters. In the Black Sea, the Benguela upwelling in southwestern Africa, and the northern coast of Chile, anaerobic ammonia oxidation is strong, with greater effects on the continental shelf than that in the ocean. In addition to the loss of nitrogen, nitrogen fixation, nitrification, and dissimilatory nitrate reduction to ammonium may affect the imbalance of nitrogen budget in the OMZ. The effects of nitrogen fixation can’t be ignored. The total amount of nitrogen fixed in the global OMZ can reach 15-40 Tg·a-1, which is an important supplement to the loss of nitrogen in OMZ. Disentangling the relative contribution of denitrification and anammox to the loss of nitrogen, ascertaining the formation mechanism and quantitative evaluation method of N2O (another product of nitrogen loss) are the most important challenges in the current study of OMZ. Focusing on the existing problems, we put forward corresponding research ideas with references for related studies of the OMZs in the ocean.
    Research progress in scyphozoan polyp strobilation-induced factors and regulation mechanism
    LIN Zheng-fei, WANG Shu-hong
    2019, 30(3):  1057-1066.  doi:10.13287/j.1001-9332.201903.039
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    Strobilation is a key stage for polyp-to-jellyfish transition. Knowledge about the strobilation-induced factors and the underlying molecular regulation mechanism could help control jellyfish bloom in nature, improve jellyfish artificial breeding, as well as get insight about the ancestral molecular origin of metamorphosis of amphibians, insect and cnidarians. Natural factors, including temperature, illumination, salinity, and symbiotic zooxanthellae, could induce strobilation. The mode of strobilation and how these natural factors irritate strobilation are distinct in different jellyfish species. Chemicals including indole derivates, 9-cis retinoic acid, elemental iodine, hydrogen peroxide, could also induce strobilation in laboratory. Indole derivates are effective inducers to most scyphozoan species. The molecular mechanism of strobilation is unclear. Results from moon jelly reveal that RxR signaling pathway plays an important role during strobilation. A secreted moon jelly-special protein named CL390 may serve as a strobilation-induced hormone precursor. These results imply that morphological differences in medusa production may mask similarities at the cellular level in different jellyfish species. The molecular mechanism of metamorphosis in jellyfish may share some consistency with amphibians and insects.
    Research progress on international studies on applied ecology based on Web of Science
    SONG Jie, LIU Xue-lu
    2019, 30(3):  1067-1078.  doi:10.13287/j.1001-9332.201903.035
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    Applied ecology is one of the most important scientific and technological tools for natural resources management and environment protection. Under the current situation of natural resource shortage, serious environmental pollution, and ecosystem degradation, understanding the theoretical basis, research methods and research hotspots of international studies on applied ecology is of great significance for consolidating the knowledge base, indicating the research direction, defining the strategic position of China’s studies on applied ecology. Based on the principle of bibliometrics and information visualization software (CiteSpace and Carrot2), we took two document datasets as research objects which were searched from Web of Science based on different search strategies in the field of international studies on applied ecology from 1980 to 2018. We analyzed the spatial and temporal distribution of the literature, the core research forces, the evolution and frontier trend of research hotspots from three dimensions, i.e. research carrier, research strength, and research content. Our results could reveal its evolutionary trajectory, research status and development trend and provide reference for future studies on applied ecology in China.