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    15 November 2020, Volume 31 Issue 11
    Soil C:N:P stoichiometry and nutrient dynamics in Cunninghamia lanceolata plantations during different growth stages
    WANG Zhen-yu, WANG Tao, ZOU Bing-zhang, WANG Si-rong, HUANG Zhi-qun, WAN Xiao-hua
    2020, 31(11):  3597-3604.  doi:10.13287/j.1001-9332.202011.005
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    We investigated soil C:N:P stoichiometry and nutrient dynamics of Cunninghamia lanceolata plantations at different stand ages (5, 8, 21, 27 and 40 years old) in Fujian Baisha Fores-try Farm. We measured the concentrations of soil total carbon (TC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), total calcium (Ca), total magnesium (Mg), and soil C:N:P stoichiometry at 0-10, 10-20, and 20-40 cm soil layers during different growth stages. The results showed that soil TC and TN concentrations and C:N remained unchanged during stand development. Soil TP content showed an increase-decrease-increase trend with increasing stand ages. Soil TP content was lowest, whereas C:P and N:P were highest at the mature stage of C. lanceolate plantation in the 0-10 and 10-20 cm soil layers. However, soil TP content showed no significant differences in all stand ages at the 20-40 cm soil layer. The contents of Ca and Mg were lowest at the mature stage of C. lanceolata stand. The TC was positively correlated with soil C:N, C:P and N:P. The TP was significantly and negatively correlated with soil C:P and N:P. Soil TP was a key factor regulating soil C:P and N:P stoichiometry. The development of mature plantation was mainly limited by soil P availability. To sustain the development of C. lanceolata plantations and improve nutrient cycling, phosphorus fertilizer could be applied during the rapid growth period of C. lanceolata. In addition, an appropriate extension of the rotation period of C. lanceolata plantation could facilitate soil nutrient restoration.
    Spatial distribution of plant diversity in shrub layer of Quercus variabilis plantation and its relationship with light environment
    YAN Dong-feng, HE Wen, YANG Xi-tian
    2020, 31(11):  3605-3613.  doi:10.13287/j.1001-9332.202011.002
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    We analyzed the spatial heterogeneity of plant species diversity in shrub layers and its relationship with light environment in Quercus variabilis plantation and Q. variabilis-Platycladus orientali mixed forest, following the method of geostatistics. The results showed that plant species diversity indices (Shannon H, Simpson Ds, Margalef Ma) of shrub layers in Q. variabilis plantation were significantly lower than that in Q. variabilis-P. orientalis mixed forest. The variation ranges and spatial autocorrelation distances of plant species diversity index in Q. variabilis plantation were higher than that in Q. variabilis-P. orientalis mixed forest, with lower spatial homogeneity but stronger spatial dependence. The plant species diversity indices of H, Ds and Ma structural ratios of shrub layers in Q. variabilis pure forest were 44.2%-49.7%, with moderate spatial autocorrelation. The structure ratios of H, Ds and Ma in Q. variabilis-P. orientalis mixed forest were 1.5%-3.3%, with strong spatial autocorrelation. The spatial distribution of biodiversity showed obvious strip-like gradient trend in Q. variabilis plantation and patchy gradient change in Q. variabilis-P. orientalis mixed forest, suggesting that the spatial continuity of plant species of shrub layers was worse in Q. variabilis-P. orientalis mixed forest and that the spatial variation was stronger than that in Q. variabilis pure forest. Results of correlation analysis and stepwise regression analysis showed that the total light and plant canopy openness were the most significant factors affecting plant species diversity of shrub layers in both forest types. Light environment formed by plant canopy structure played a crucial part in maintaining plant diversity in shrub layer.
    Population structure and point pattern analysis of rare and endangered plant Helianthemum soongoricum in Ningxia, China
    YAN Xiu, DOU Jian-de, HUANG Wei, HUANG Wen-guang, LI Xiao-wei
    2020, 31(11):  3614-3620.  doi:10.13287/j.1001-9332.202011.006
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    Helianthemum songaricum is a second-class protected plant in China, threatened by decreased population size and fragmentation of distribution area. It is a new record species in Ningxia. We analyzed population structure, spatial distribution, and relationship of different age classes of H. songaricum living in sandy and gravel habitats. The results showed that majority of H. songaricum individuals were belonged to age-class Ⅲ. The age structure of the population was inverted triangle. The population was at a declining stage. The spatial pattern and spatial association between different age class of H. songaricum were greatly affected by habitat condition, with strong dependence on spatial scale. Compared with sandy habitat, H. songaricum population in gravel habitat tended to be clustered distribution, with a more obvious positive correlation among different age classes. The difference between two habitats was related to environmental condition and plant community structure. H. songaricum from age-class Ⅰ and Ⅱ had mutually dependent ecological relationships.
    Net ecosystem carbon exchange and its affecting factors in a deciduous broad-leaved forest in Songshan, Beijing, China
    LI Run-dong, FAN Ya-qian, FENG Pei, SONG Ze, LI Xin-hao, YAN Hui-juan, Ma Li, ZHA Tian-shan
    2020, 31(11):  3621-3630.  doi:10.13287/j.1001-9332.202011.008
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    Forests play an important role in terrestrial carbon cycles. The mechanism underlying carbon balance in temperate deciduous broad-leaved forests is not clear. In this study, net ecosystem exchange (NEE) and environmental factors, including air temperature (Ta), soil temperature (Ts), photosynthetically active radiation (PAR), vapor pressure deficit (VPD), soil water content (SWC) and precipitation (P) were continually measured using eddy covariance techniques in 2019 in a deciduous broad-leaved forest in Songshan, Beijing. We analyzed the characteristics of NEE and its response to environmental factors. The results showed that, at diurnal scale, the monthly averaged NEE exhibited a “U” shape curve (i.e., being a carbon sink over daytime while being a carbon source during nighttime) over the growing season. During the non-growing season, NEE was positive (i.e., carbon source) at diurnal scale. At the seasonal scale, NEE exhibited a unimodal curve. The annual cumulative NEE was -111 g C·m-2·a-1. Annual ecosystem respiration was 555 g C·m-2·a-1, while gross ecosystem productivity was 666 g C·m-2·a-1. Carbon sequestration peaked in June, while emission peaked in November. PAR was the dominant factor affecting daytime NEE (NEEd). VPD was the main factor that indirectly affected daytime NEEd, with an optimal VPD value that maximizes daytime NEE around 1-1.5 kPa. Soil temperature was the main factor affecting nighttime NEE (NEEn). SWC was a limiting factor for NEEn. Too high or too low SWC would inhibit NEEn, with an optimal SWC value of 0.28 m3·m-3.
    Effects of exogenous nitrogen addition on litter decomposition and nutrient release in a temperate desert
    ZHANG Cai-yun, ZHAO Hong-mei, LIU Hui, ZHANG Wen-tai, SU Yan-gui, CHENG Jun-hui, YANG Wei-jun
    2020, 31(11):  3631-3638.  doi:10.13287/j.1001-9332.202011.001
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    A litterbag decomposition experiment was carried out in southern Gurbantunggut Desert, with four nitrogen treatments: N0(0 g N·m-2·a-1), N5(5 g N·m-2·a-1), N10(10 g N·m-2·a-1) and N20(20 g N·m-2·a-1). The aims were to examine the effects of exogenous nitrogen addition on decomposition rate and nutrient release of Tamarix ramosissima, Salicornia europaea and their mixture. Results showed that decomposition rates were significantly different among litter types. After 345 days, the decomposition rates of T. ramosissima, S. europaea and their mixture under different treatments were 0.64-0.70, 0.84-0.99 and 0.71-0.81 kg·kg-1·a-1, respectively. Both mono- and mixed-litters exhibited nutrient release during decomposition process, with the release rates being 60.6%-67.4%, 56.7%-62.6%, 57.4%-62.3%, 46.8%-63.0% for N, and 51.9%-77.9%, 59.9%-74.7%, 53.0%-79.9%, 52.3%-76.4% for P, respectively for the N0, N5, N10 and N20 treatments. Nitrogen addition did not affect litter decomposition rate. The dynamics of N and P during decomposition of different litter types showed different responses to nitrogen addition. Nitrogen addition inhibited N and P releases of S. europaea litter and P release of the mixed litter, but did not affect the nutrient release of T. ramosissima. The results suggested that nitrogen input would not promote litter decomposition in temperate desert ecosystems, but might retard the nutrient returning to soil system.
    Effects of saline irrigation on CO2 emission and chemical properties of aeolian sandy soil under litter addition
    ZHANG Shao-lei, ZHANG Jian-guo, CHANG Wen-qian, WU Lu-yao, ZHANG A-feng
    2020, 31(11):  3639-3646.  doi:10.13287/j.1001-9332.202011.003
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    Calligonum mongolicum is one of the dominant species in the Taklimakan Desert highway shelterbelt, the litter of which plays an important role in carbon cycling. After litter addition, we carried out a laboratory incubation experiment to investigate the dynamics of soil CO2 emission, soil organic carbon (SOC), soluble organic carbon (DOC), pH, and electrical conductivity (EC) under the condition of salt water (SW) and fresh water (FW) with field water holding capacity of 25%, 50%, 75%, and 100%. The results showed that saline water irrigation had an inhibitory effect on soil CO2 emission. Under the four soil water content treatments, the cumulative CO2 emission of freshwater irrigation increased by 1.9%-29.1% compared with that of saline irrigation. Cumulative soil CO2 emissions increased with increasing soil water content. With litter addition, SOC decreased rapidly in the early stage, then gradually increased, and finally tended to be stable. The DOC contents of each treatment following the incubation increased by 41.3%-92.4% compared with that before the incubation. At the end of incubation, soil pH of each treatment increased by 0.20-0.35. The EC increased with the increases of soil water content. Under the four water content conditions and compared with the situation before the incubation, the EC values irrigated with SW increased by 0.11-0.79 mS·cm-1, while those with FW increased or decreased at the end of incubation. Cumulative soil CO2 emission was positively correlated with SOC, DOC, and pH, but not with soil water content. Both saline irrigation and lower water content could inhibit CO2 emission of aeolian sandy soil under litter addition, while EC was significantly affected by the quality of irrigation water and soil water content.
    Effects of plantation on aggregate distribution and stability of lateritic red soil in south subtropical China
    LIN Li-wen, DENG Yu-song, WANG Jin-yue, YANG Gai-ren, JIANG Dai-hua, WANG Ling
    2020, 31(11):  3647-3656.  doi:10.13287/j.1001-9332.202011.009
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    We examined the stability of soil aggregates in five typical plantations, i.e., Eucalyptus urophylla × E. grandis plantation, Cunninghamia lanceolata plantation, Pinus massoniana plantation, Mytilaria laosensis plantation and Castanopsis hystrix plantation, in the south subtropical China by the Elliott wet sieving and Le Bissonnais (LB) methods. The results showed that the content of water stability aggregate (WR>0.25) was more than 62.2% after wet sieving. The mean weight diameter (MWD) and geometric mean diameter (GMD) of aggregates were 1.58-3.71 mm and 0.57-2.02 mm, respectively, which were the largest in C. lanceolata plantation and the smallest in E. urophylla × E. grandis plantation. Percentage of aggregate destruction (PAD) of five kinds of plantations ranged from 4.6% to 31.5%. The transfer matrix method was used to evaluate the soil aggregates, with the aggregate stability index (ASI) following the order of C. lanceolata plantation > C. hystrix plantation > M. laosensis plantation > P. massoniana plantation > E. urophylla × E. grandis plantation. Under the three treatments of LB method, the FW treatment was the most destructive to the stability of soil aggregates, indicating that dissipation played a major role in the disintegration of soil aggregates. The WS treatment had the least damage to the aggregates. The effect of slow wetting (SW) treatment was between the fast wetting (FW) and wet stirring (WS). Both the MWD and GMD values followed the order of WS>SW>FW, which gradually decreased with the increases of soil depth. The GMD value of aggregates under FW treatment by LB method of five plantations was significantly positively correlated with ASI, MWD and GMD of wet sieving method, indicating that the traditional wet sieving method had a good correlation with FW treatment and was feasible to determine the stability of soil aggregates in the subtropical red soil. Based on the aggregate stability indices of MWD, GMD, PAD and ASI, C. lanceolata plantation was more conducive to the improvement of soil aggregation level, with more stable soil structure than the other four plantations.
    Carbon sequestration characteristics of typical temperate natural grasslands in Ningxia, China
    JI Bo, XIE Ying-zhong, HE Jian-long, WANG Zhan-jun, JIANG Qi
    2020, 31(11):  3657-3664.  doi:10.13287/j.1001-9332.202011.010
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    To accurately estimate ecosystem carbon storage of natural grassland in Ningxia, we examined ecosystem carbon storage in four types of typical temperate natural grasslands, including meadow steppe, warm steppe, steppe desert, and desert steppe in Ningxia. The results showed that the total vegetation biomass of meadow steppe, warm steppe, steppe desert and desert steppe were 1178.91, 481.22, 292.80 and 209.09 g·m-2, respectively. Root biomass was the main component of total vegetation biomass of meadow steppe and warm steppe, with a contribution of 73.1% and 56.6%, respectively. Aboveground biomass was the main component of total vegetation biomass of steppe desert and desert steppe, accounting for 50.3% and 47.6%, respectively. Litter made low contribution, being 8.5%, 8.0%, 6.4% and 16.2%, respectively. Ecosystem carbon storage of four typical natural grassland was 13.90, 5.94, 2.69 and 2.37 kg·m-2, vegetation carbon storage was 470.26, 192.23, 117.17 and 83.36 g·m-2, and soil organic carbon storage in 0-40 cm layers were 13.43, 5.75, 2.58 and 2.29 kg·m-2, respectively. Soil organic carbon storage was the main body of the total carbon storage of four typical natural grassland in Ningxia, accounting for 96.6%, 96.8%, 95.6% and 96.5%, respectively. The total vegetation biomass, vegetation carbon storage, soil organic carbon storage and ecosystem carbon storage of four natural grassland types were in the order of meadow steppe>warm steppe>steppe desert>desert steppe.
    Carbon budget estimation based on different methods of CO2 storage flux in forest ecosystems
    LI Ying-chi, LIU Fan, WANG Chuan-kuan, GAO Tian, WANG Xing-chang
    2020, 31(11):  3665-3673.  doi:10.13287/j.1001-9332.202011.004
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    Accurate measurement of CO2 storage flux (Fs) in forest ecosystems is of great significance for estimating ecosystem carbon budget by eddy covariance (EC). The errors in the estimation of ecosystem carbon budget caused by different methods for calculating Fs has yet not been comprehensively assessed. Using data from an open-path EC system and an eight-level CO2/H2O profile system (AP100, Campbell Scientific Inc., USA) in a broadleaved deciduous forest at the Maoer-shan in 2018, we evaluated the methodological effect of Fs[2-min mean profile (P2 min), 30-min mean profile (P30 min) and 30-min mean EC single point (Ps)] on the estimation of net ecosystem exchange (NEE), ecosystem respiration (Re), and gross primary productivity (GPP). The results showed that the impact of Fs methods on forest carbon flux generally increased with the increases of time scale, indicating that gap-filling of flux data would further amplify the impacts of Fs estimation methods. At the annual scale, NEE based on P2 min and Ps methods were 36.3% and 29.4% lower than that based on P30 min, while Re based on P2 min was higher than that based on P30 min and Ps by 8.7%. The GPP based on P2 min was 5.4% higher, while that based on Ps was 2.1% lower than that based on P30 min. The traditional P30 min ignored the instantaneous changes in CO2 concentration, Ps missed the changes of CO2 concentration within canopy, and thus both underestimated the actual Re. The approximately instantaneous profile (2-min mean profile) had higher temporal and spatial resolution and could more accurately estimate forest carbon budget with non-flat terrain and complex canopy structure. Our findings had great implications for solving the underestimation of forest Re and GPP as well as the overestimation of net carbon sink on complex conditions with the EC method.
    Response of photosynthesis and carbon/nitrogen metabolism to drought stress in Chinese chestnut ‘Yanshanzaofeng' seedlings
    ZHAO Jia-bing, DU Chang-jian, MA Chang-ming, SUN Jia-cheng, HAN Zhen-tai, YAN Dong-hui, JIANG Ze-ping, SHI Sheng-qing
    2020, 31(11):  3674-3680.  doi:10.13287/j.1001-9332.202011.027
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    Drought is a main factor affecting the growth and yield of Chinese chestnut trees in Yan-shan Mountains. To investigate the responses of chestnut seedlings to drought stress, the growth and physiological indices, including photosynthetic characteristics, biomass, proline, malondialdehyde, carbon and nitrogen contents were measured in roots, stems, and leaves after the Chinese chestnut ‘Yanshanzaofeng' seedlings in the pots were treated by simulating drought for 22 days. The results showed that, compared with the normal irrigation, water contents in the roots, stems and leaves were decreased by 18.3%, 29.0% and 62.8%, respectively, accompanied by the considerable increases in the contents of proline (355.0%-1586.7%) and malondialdehyde except in the stems (41.1%-81.3%). The non-photochemical quenching coefficiency and net photosynthetic rate in the leaves were significantly decreased by 49.4% and 77.4%, respectively. The contents of non-structural carbohydrates were increased by 21.4% in stems and 69.5% in leaves, but that in roots did not change. The contents of nitrate were increased by 28.9% in stems and 26.8% in leaves, but that in roots did not change. Ammonium nitrogen was increased by 16.2%, 12.9% and 217.6% in roots, stems, and leaves, but being statistically significant in the leaves. These results indicated that drought stress led to serious damage to ‘Yanshanzaofeng' chestnut seedlings, which inhibited photosynthetic performance, but they could improve their adaptation to drought stress by enhancing carbon and nitrogen metabolism. Our results provide a reference for the breeding and cultivation of drought resistance of the local Chinese chestnut resources.
    Effects of thinning and reshaping on canopy micro-domain environment and leaf physiological characteristics in dense Fuji apple orchard on Loess Plateau of eastern Gansu, China
    NIU Jun-qiang, SUN Wen-tai, DONG Tie, YIN Xiao-ning, LIU Xing-lu, MA Ming
    2020, 31(11):  3681-3690.  doi:10.13287/j.1001-9332.202011.030
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    We examined the effects of thinning and reshaping on the canopy micro-domain environment, leaves micro-structure, physiological characteristics and photosynthetic capacity of 16 year-old Fuji apple dense orchards by measuring canopy relative light intensity, temperature, relative humidity, leaf chlorophyll content, micro-structure, and photosynthetic fluorescence. After thinning and reshaping, relative light intensity and temperature of tree canopy were significantly improved, and the distribution was balanced. Effective light intensity (>30%) was 57% higher than that of control (thinning and reshaping, CK), and temperature increased by 1.1 ℃. Due to the improvement of relative light intensity and temperature in the canopy, leaf chlorophyll, leaf thickness, and palisade tissue thickness of thinning trees were increased by 8.7%, 5.4%, and 9.2%, respectively. Net photosynthetic rate, transpiration rate and stomatal conductance of the leaves were also significantly increased, being 12.6%, 17.1% and 7.3% higher than CK, respectively. Leaf photosynthesis capacity of both treatments was limited by non-stomatal factors. After thinning and reshaping, Fm (maximum fluorescence) and qN(non-photochemical quenching coefficient) of PSⅡ in leaves were increased by 1.5% and 2.1%. Leaves did not suffer strong light photoinhibition, with ABS/RC (unit reaction center absorbs light energy), ETo/RC (energy used for electron transfer captured by unit reaction center) and TRo/RC (energy captured by the unit reaction center to reduce QA) of leaves being significantly improved. The physiological characteristics of leaves were closely related to light and temperature environment. After thinning, light and temperature of the orchard canopy were improved, which promoted leaves growth and development, improved foliar micro-structure and photosynthetic efficiency. Thinning and reshaping were suitable strategies for the adjustment and optimization of Fuji orchard density in Loess Plateau of eastern Gansu.
    Characteristics of uptake, residual and loss of nitrogen fertilizer in winter wheat after rice stubble
    LI Xin-xin, SHI Zu-liang, WANG Jiu-chen, WANG Fei, XU Zhi-yu, JIANG Rong-feng
    2020, 31(11):  3691-3699.  doi:10.13287/j.1001-9332.202011.021
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    To promote the rational application of nitrogen fertilizer in winter wheat after rice stubble, the effects of nitrogen application rate (0, 150, 225, 300 kg·hm-2, expressed as N0, N150, N225, N300) on nitrogen recovery, residue, loss and grain yield were examined using field 15N tracer technology. The results showed that with the increases of application rate, nitrogen accumulation from different sources significantly increased while nitrogen recovery significantly decreased. The accumulation of basal nitrogen in plants reached the peak during overwintering stage to jointing stage, while the accumulation of topdressing nitrogen peaked between jointing to flowering stage. At maturity, nitrogen accumulation of the top fertilizer was higher than that of the base fertilizer. Plant nitrogen accumulation from soil under N150 was higher than that from nitrogen fertilizer, but with an opposite tendency under N225 and N300. With the increases of nitrogen application rate, the residual nitrogen in the 0-100 cm soil layer in the maturing stage significantly increased, while the residual nitrogen ratio in the 60-100 cm soil layer gradually increased. In the whole growth period of wheat, both nitrogen loss and loss ratio were positively correlated with nitrogen application rate. The nitrogen loss of base fertilizer reached the highest during sowing to overwintering stage, while the nitrogen loss of top fertilizer was at the peak from jointing to flowering period. Taking grain yield into consideration, N225 treatment was the proper application rate for winter wheat after rice stubble, with grain yield being 6735 kg·hm-2, and the nitrogen fertilizer recovery rate, soil residue rate and loss rate being 42.6%, 34.0% and 23.3%, respectively.
    Effects of integration of micro-sprinkler irrigation and nitrogen on growth and development of winter wheat and water and fertilizer use efficiency
    DANG Jian-you, PEI Xue-xia, ZHANG Ding-yi, ZHANG Jing, CHENG Mai-feng, WANG Jiao-ai, GAO Lu
    2020, 31(11):  3700-3710.  doi:10.13287/j.1001-9332.202011.025
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    Under the same irrigation amount and nitrogen application rate and after the corn stalks being returned to the field in the wheat-corn crop rotation area, we examined the effects of the integrated water and nitrogen mode of micro-sprinkler irrigation on the growth and development and water and fertilizer use efficiency of winter wheat. In 2016-2018, we conducted a two-year field experiment with six types of micro-sprinkler irrigation water and nitrogen integration modes and seven treatments during the growth period, and investigated the population dynamics, dry matter accumulation transfer during the filling period, and nutrient accumulation during the mature period. There were three modes of irrigation, W1(overwintering water + jointing water + grouting water, 600 m3·hm-2 for each), W2(overwintering water + regreening water + jointing water + grouting water, each for 450 m3·hm-2), and W3(600 m3·hm-2 each for overwintering water and jointing water, and 300 m3·hm-2 each for regreening water and grouting water); two modes of nitrogen application, N1(basic nitrogen application 60% + jointing water nitrogen topdressing 40%) and N2 (basic nitrogen application 60% + jointing water nitrogen topdressing 30% + grouting water nitrogen topdressing 10%); with no fertilization under W1 as control (CK). The results showed that: 1) The amount of overwintering water irrigation increased from 450 m3·hm-2to 600 m3·hm-2, which was beneficial to the total number of both stems and panicles in the overwintering period and consequently to yield. Irrigation in the regreening stage increased the total number of stems at the jointing stage, but with limited effect on the number of panicles. Applying more nitrogen at the jointing stage increased the number of stems per plant, but decreased that of panicles. 2) Four times of irrigation (W2 and W3) during the growth period, combined with nitrogen (N2) in the jointing and filling phases, were conducive to the accumulation of dry matter during the filling period, increasing the number of grains per spike and 1000-grain weight, thereby increasing yield. 3) Compared with the three times of irrigation treatment during the growth period, water consumption and absorption of nitrogen, phosphorus and potassium under the four times of irrigation treatment were increased, and water and fertilizer use efficiency was improved. In W2 and W3 under the treatment of four times irrigation, water consumption of N2 during the growth period was lower than N1, absorption of nitrogen, phosphorus, and potassium were higher than N1, and the irrigation and utilization of nitrogen, phosphorus and potassium were significantly improved, of which W3N2 had the best effect. Therefore, W3N2 treatment (sowing winter wheat after returning corn stalks to the field, irrigating four times during the growth period of micro-sprinkler irrigation, increasing the amount of overwintering water and jointing water irrigation to 600 m3·hm-2, combined with jointing water and filling water topdressing nitrogen fertilizer) increased spike number and 1000-grain weight of wheat andincreased yield, with the highest water and fertilizer use efficiency. It was the best water and nitrogen management mode for the integration of micro-sprinkler irrigation and water and fertilizer for winter wheat in southern Shanxi.
    Effects of activated water irrigation on growth characteristics of soybean under drought stress
    LI Juan, FAN Jun, ZHU Zhi-mei
    2020, 31(11):  3711-3718.  doi:10.13287/j.1001-9332.202011.028
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    To understand the effects of activated water irrigation on soybean growth under different drought conditions and explore the underlying mechanisms, an indoor pot experiment was conducted under four moisture conditions of 95%-100%, 75%-85%, 55%-65% and 35%-45% of the maximum water holding capacity (80% moisture) of the medium. Soybean was irrigated with tap water, magnetized water, aerated water, and magnetized and then aerated water, respectively. The results showed that total biomass, leaf area, root to shoot ratio, and root length of magnetized water irrigation increased by 67.6%, 23.5%, 84.6% and 122.8%, respectively compared with tap water irrigation after 30 days of growth under 35%-45% severe drought condition. All the variables were increased by 70.8%, 24.0%, 61.9% and 162.3% respectively in magnetized and aerated water treatment. There was no significant difference for foliar chlorophyll content. The values of the other water treatments were slightly lower than that of tap water. In conclusion, magnetized water irrigation effectively enhanced root growth, root-shoot ratio, and water use efficiency of soybean, and alleviated the negative effects of drought stress under severe drought condition.
    Application effects of fertilizer recommendation by Nutrient Expert System on radish
    SHAN Nan, CHUAN Li-min, LIU Ji-pei, ZHENG Huai-guo, ZHAO Tong-ke
    2020, 31(11):  3719-3728.  doi:10.13287/j.1001-9332.202011.022
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    A field experiment was conducted for two seasons to evaluate the application effects of a decision support system named Nutrient Expert on radish based on yield response and agronomic efficiency, to provide theoretical and technical support for convenient and quick recommendation on fertilization management. There were seven treatments: farmer's practice treatment (FP), recommended fertilization treatment based on Nutrient Expert (TE), recommended fertilization treatment based on soil testing (TS), treatment of replacing 30% nitrogen fertilizer with organic fertilizer based on TE (TE+OM), and corresponding nitrogen omission treatment (TE-N), phosphorus omission treatment (TE-P), and potassium omission treatment (TE-K). We measured and compared the effects of different fertilization managements on radish yield, nutrient uptake, fertilizer utilization and fertilization benefit. The results showed that the N, P2O5 and K2O fertilizer applications based on Nutrient Expert were 200, 132 and 215 kg·hm-2 in the first half of the year, and 171, 204 and 251 kg·hm-2 in the second half of the year, respectively. The Nutrient Expert recommended fertilization adjusted the application amount of nitrogen, phosphorus, and potassium fertilizer. Compared with FP treatment, the economic yield of radish in the two-season experiments increased by 14.8% and 18.4%, and the profit of fertilization increased by 20115 and 14905 yuan·hm-2, respectively. Compared with the TS treatment, the economic yield of radish over the two seasons increased by 9.8% and 16.8%, and the profit of fertilization increased by 9076 and 9987 yuan·hm-2, respectively. The Nutrient Expert recommended fertilization improved the agronomic efficiency and nutrient recovery efficiency of radish, and promoted the efficient utilization of nutrients. The reasonable proportion of organic fertilizer in radish production could promote the transfer of plant nutrients to roots to a certain extent. In general, the application of Nutrient Expert on radish was feasible. This method could make full use of the indigenous nutrients of soil, consider the balance and sustainable supply, and reasonably regulate the supply of nitrogen, phosphorus and potassium, and finally result in high yield, high efficiency and sustainable development of radish production.
    Responses of denitrifying functional gene abundance to long-term fertilization regimes in an upland Ultisol
    WAN Song, DUAN Chun-jian, FAN Jian-bo, YE Gui-ping, WANG Quan-cheng, HE Ji-zheng, LIN Yong-xin
    2020, 31(11):  3729-3736.  doi:10.13287/j.1001-9332.202011.024
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    Fertilization affects soil nitrogen cycling and nitrous oxide (N2O) emissions, which are mainly driven by microbes. A 32-year field experiment was conducted to investigate the effects of chemical fertilizers and their combination with organic materials on the abundance of denitrifying functional genes (nirS, nirK, nosZ I and nosZ II) in Ultisol. The treatments comprised no fertilizer (CK), chemical fertilizer, chemical fertilizer+peanut straw, chemical fertilizer+rice straw, chemical fertilizer+radish and chemical fertilizer+pig manure. Compared with the single chemical fertilizer treatment, soil pH and organic carbon content increased in the chemical fertilizer plus organic material treatments, with chemical fertilizer+pig manure having the strongest effect. Long-term fertilization did not affect the abundance of nirK gene, but significantly altered the nirS gene abundance. Compared to CK, long-term chemical fertilizer application increased the abundance of nirS gene by 426%. However, partial replacement of chemical fertilizer by organic materials decreased the abundance of nirS gene. The abundance of nosZ I gene was one order of magnitude higher than that of nosZ II, indicating the domination of nosZ I in the acidic Ultisol. Long-term fertilization did not affect the abundance of nosZ II, whereas chemical fertilizer+pig manure increased the abundance of nosZ I by 138%. Results of stepwise regression analysis showed that available phosphorus content was the primary factor regulating the abundance of nosZ I gene, whereas the abundance of the nosZ II gene was mainly regulated by nitrate content. Moreover, the lowest (nirS+nirK)/(nosZ I+nosZ II) value in the chemical fertilizer+pig manure treatment indicated that long-term manure application might reduce N2O emission potential in Ultisols.
    Distribution characteristics of exogenous carbon in different carbon fractions in biocrusts-covered soil
    YAO Xiao-meng, XIAO Bo, WANG Guo-peng, ZHANG Xin-xin, LI Sheng-long
    2020, 31(11):  3737-3748.  doi:10.13287/j.1001-9332.202011.039
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    The distribution characteristics of exogenous carbon (C) in the C fractions of biocrusts-covered soil are critical for understanding the geochemical cycling of C with biocrusts in drylands. A 13C pulse labeling experiment was conducted for moss-dominated biocrusts-covered soil and bare soil on the Loess Plateau of China with semiarid climate, with the content of 13C in different C fractions being continuously measured to determine the biocrust effects on the distribution of exogenous C in each C fraction. Our results showed that, 1) the 13C abundance of each C fraction in the biocrusts-covered soil was steadily changed with time, due to the relatively low rate of nutrient cycling in the biocrusts-covered soil and also to the relatively low biomass of moss in the biocrusts-covered soil as compared with vascular plants. 2) The 13C content of each C fraction in the biocrusts-covered soil was significantly higher than that in the bare soil. Specifically, the 13C content of total organic C (TOC), microbial biomass C (MBC), and dissolved organic C (DOC) in the biocrusts-covered soil was 0.258, 0.078, and 0.004 mg·kg-1, respectively, which was 3.1, 18.5, and 2.6 times higher than that in the bare soil. Moreover, the 13C content in the moss of the biocrusts-covered soil was 1.45 mg·kg-1. 3) The presence of biocrusts changed the distribution characteristics of each C fraction, with the newly assimilated C being mainly distributed in active organic C and biological components of the biocrusts-covered soil. In the biocrusts-covered soil, the 13C distribution in MBC (30.6%) was higher than that in DOC (1.7%), and the 13C distribution in the C of moss was 20.3%. 4) The transferred amount and storage capacity of MB13C in the biocrusts-covered soil were 15.7 and 19.5 times of that in the bare soil, respectively. The turnover rate of MB13C in the biocrusts-covered soil and bare soil was 2.94 and 3.30 times per month, respectively, implying that the turnover time of MB13C in the biocrusts-covered soil was 1.1 times longer than that in the bare soil. In conclusion, biocrusts could greatly change the distribution characteristics of each C fraction and increase C turnover rate, highlighting its important roles in C cycling in dryland ecosystems.
    Effects of organic fertilizer application on flag leaf C/N ratio, photosynthetic characteristics and yield of spring wheat with full plastic film mulching
    YIN Jia-de, HOU Hui-zhi, ZHANG Xu-cheng, WANG Hong-li, YU Xian-feng, FANG Yan-jie, MA Yi-fan, ZHANG Guo-ping, LEI Kang-ning
    2020, 31(11):  3749-3757.  doi:10.13287/j.1001-9332.202011.029
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    A field experiment was conducted in the rain-fed semi-arid region of central Gansu in 2016 and 2017, with the treatments 1) hill-drop flat planting with full plastic film mulching (PMS), 2) hill-drop flat planting with full plastic film mulching plus organic fertilizers (PMO), and 3) hill-drop flat planting without soil mulching (CK). We investigated the relations among soil moisture, photosynthetic rate (Pn), stomatal conductance (gs) and transpiration rate (Tr), C/N ratio, and total nitrogen of flag leaf from the heading stage to the seed-filling stage in different treatments to probe into their effects on the yield and yield components of spring wheat variety ‘Longchun 27'. The results showed that organic fertilizer application could increase soil moisture at the middle and late growth stages of spring wheat. PMO increased soil water storage in 0-300 cm depth from the heading stage to the seed filling stage by 4.6% and 8.5%, decreased population canopy temperature by 0.1-1.3 ℃ and 1.4-4.9 ℃, increased net photosynthetic rate of flag leaf by 9.3% and 29.7%, stomatal conductance by 30.9% and 103.8%, transpiration rate by 5.1% and 55.0%, total nitrogen content by 6.6% and 18.9%, and decreased C/N ratio by 6.4% and 22.8%, respectively. Compared with PMS and CK, PMO significantly improved grain number per spike and 1000-grain weight, and increased grain yield by 9.1% and 53.7%, respectively. From the heading stage to filling stage, the Pn and gs of flag leaf had negative correlation with C/N, while C/N was negatively correlated with grain yield. Consequently, PMO could improve soil water storage and promote photosynthesis of flag leaf, reduce the intensity of physiological drought stress and the limitations of nitrogen absorption and assimilation in flag leaf from the heading stage to the seed-filling stage, and increase grain number and grain weight and consequently the yield of spring wheat in semi-arid region.
    Potential geographical distribution and changes of Artemisia ordosica in China under future climate change
    LU Ke, HE Yi-ming, MAO Wei, DU Zhong-yu, WANG Li-jun, LIU Guo-min, FENG Wen-jia, DUAN Yi-zhong
    2020, 31(11):  3758-3766.  doi:10.13287/j.1001-9332.202011.017
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    Artemisia ordosica is a forerunner species of wind-break and sand-fixation in desert steppe in China, which plays an important role in ecosystem restoration and reconstruction. How-ever, it could influence human health. Based on 89 valid data of current distribution of A. ordosica in China and 19 typical climatic factors, the MaxEnt model was used to simulate the potential distribution of A. ordosica in China under current and two scenarios (RCP 4.5 and RCP 8.5; 2050s and 2070s). The SDM toolbox of ArcGIS software was used to analyze the potential distribution range of A. ordosica and its changes in China. The importance of key climatic factors was evaluated by comprehensive contribution rate, Jackknife method, and response curve of environmental variables. The accuracy of model was tested and evaluated by area under the curve (AUC) of the test subject working characteristic (ROC). The results showed that the MaxEnt model worked well (AUC=0.980). which predicted that A. ordosica was mainly concentrated in and around Mu Us Sandy Land, consistent with the current actual distribution range. The distribution area of A. ordosica of potential high fitness under the future two scenarios decreased by 5.2%-26.8%, which was negatively affected by future climate change. Seasonal variation of temperature, mean precipitation in the coldest season, and mean annual temperature had the greatest impact. The core area of future potential distribution of A. ordosica in China was located in Mu Us Sandy Land, with a tendency for spreading to northeast (Jilin, Heilongjiang, Liaoning and some parts of Hebei).
    Construction and optimization of ecological network in Xi'an based on landscape analysis
    LIANG Yan-yan, ZHAO Yin-di
    2020, 31(11):  3767-3776.  doi:10.13287/j.1001-9332.202011.019
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    Ecological network can connect fragmented habitat patches to increase the connectivity among landscapes, which plays an important role to landscapes and ecological problems caused by urbanization. In this study, the ecological networks of Xi'an City were constructed using landscape pattern index and morphological spatial pattern analysis to reveal landscape pattern features. The performance of the network was evaluated with the gravity model to provide an optimization strategy. The landscape richness index was relatively high, with significant differences of landscape patterns between north and south parts. The ecological sources were predominated in the south and east areas, while a higher comprehensive resistance with low connectivity was found in the north and central areas. The ecological corridors were unevenly distributed, with the radiation channels derived from hydrological analysis providing a supplementary role. Furthermore, ecological networks could be optimized by introducing other ecological sources, supplementing stepping stones, and repairing fracture points, to reduce the problems of uneven distribution of ecological sources, the excessively long ecological corridors in local regions, and the obstruction of road networks. Our optimization method provided an optional way to assist urban planning of Xi'an City.
    Dynamic change and prediction of vegetation cover in Shenzhen, China from 2000 to 2018
    WU Bing-lun, SUN Hua, SHI Jun-nan, ZHANG Yu-tian, SHI Ling-jie
    2020, 31(11):  3777-3785.  doi:10.13287/j.1001-9332.202011.012
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    With landsat-series multi-temporal image data, percentage of vegetation cover (PVC) was estimated by pixel dichotomy. The linear regression analysis and center of gravity migration methods were used to explore the characteristics of the spatiotemporal changes of vegetation cover in Shenzhen from 2000 to 2018. The CA-Markov model was combined to predict future land cover in Shenzhen. The results showed that the PVC in Shenzhen demonstrated obvious regional differentiation characteristics from 2000 to 2018. The eastern region occupied larger proportion than the wes-tern part, while the southern region was larger than the north part. This feature exhibited good consistency with regional topographic effect. The spatial migration characteristic of the center of gravity of PVC was from northwest to southeast, and then from southeast to northwest, with a migration rate of 551.2 m·a-1. This process was closely related to urbanization in Shenzhen. The PVC in Shen-zhen tended to be generally improved from 2000-2018, with a improvement rate of 0.005·a-1. The percentage of significantly improved and degraded PVC area was 30.8% and 12.8%, respectively. The CA-Markov method was used to predict the land cover/use pattern of Shenzhen in 2024 under two scenarios, theoretical scenario and natural scenario. There was no significant difference in proportion of the area of the land cover/use patterns obtained by the two kinds of prediction method, with the difference threshold being 0-1.2%. Compared with the data before 2018, the proportion of arbor forests and arable land converted into construction land in Shenzhen would be significantly reduced in 2024, whereas the contradiction between supply and demand would be still tense.
    Air quality assessment and health site guidelines for city squares based on RANS method
    YAN Li, HU Wen, YIN Ming-qiang
    2020, 31(11):  3786-3794.  doi:10.13287/j.1001-9332.202011.016
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    The concentration of pollutants and pathogens in the air directly affects human health. When the pollution source remains unchanged, effective ventilation determines air quality. It is therefore critically needed to establish a quantitative determination index for effective ventilation, which can be used for real-time evaluation of air quality in specific areas, so as to guide residents to choose healthy outdoor activity places. In this study, Reynolds average Navier-Stokes (RANS) method was used to establish urban air pollution simulation system by computational fluid dynamics (CFD) technology. The correlations among wind speed, pollutant concentration, and pollutant diffusion efficiency were analyzed. With real-time meteorological data, wind field simulation and air quality evaluation were carried out for different periods of urban square space. The results showed that the critical wind speed value at pedestrian height (1.5 m) for the effective diffusion of pollutants was 1.0 m·s-1, which could be used as an air quality evaluation standard. With reference to this judgment index and the real-time weather system link, the pedestrian height wind speed distribution could be obtained through simulation. Therefore, the spatial variation of air quality could be visually displayed in real time, which help realize fair, efficient and reasonable use of urban space resources. This work could provide guidelines for choosing healthy outdoor venues, and provide technologies and means for public disease prevention and health promotion.
    Improvement of remote sensing ecological index in arid regions: Taking Ulan Buh Desert as an example
    WANG Jie, MA Jia-li, XIE Fei-fei, XU Xi-jie
    2020, 31(11):  3795-3804.  doi:10.13287/j.1001-9332.202011.011
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    The arid area is mainly composed of desert, with fragile eco-environment and being extremely vulnerable to the influence of natural and human perturbations. Based on the remote sen-sing ecological index (RSEI), the arid remote sensing ecological index (ARSEI) was formed to improve the remote sensing ecological index for arid area, which was coupled with the information of greenness, humidity, salinity, heat and land degradation to quantitatively evaluate the eco-environment quality. We used ARSEI and RSEI to dynamically monitor and evaluate the eco-environment quality of Ulan Buh Desert from 2000 to 2019, and analyzed their differences and their applicability in arid area. We further examined the characteristics and reasons of the temporal and spatial variations of the eco-environment quality of Ulan Buh Desert. The results showed that the ARSEI index had better applicability to the eco-environment quality in arid area than the RSEI, and it enhanced the role of land use changes in the ecological environment quality assessment. From 2000 to 2019, the overall eco-environmental quality of Ulan Buh Desert was worse. The parts under better, good, and medium grades were mainly distributed in the northern region, the parts with worse grades were mainly concentrated in the gobi and sandy land, and the poor ones were mainly located in area with low coverage vegetation. From 2000 to 2019, the overall quality of the eco-environment in the Ulan Buh Desert were becoming better. Meanwhile, the eco-environment quality of towns and farms in the northern part of the desert changed complexly, with deterioration and improvement alternately distributed. The main reason for the changes in the eco-environment of Ulan Buh Desert was the positive effects of ecological agriculture and sand industry.
    Quantitatively evaluate the effects of precipitation and vegetation variation to flood under the condition of single rainstorm: A case study of Pengchongjian small watershed, Jiangxi, China
    SHENG Fei, ZENG Jian-ling, LIU Shi-yu, WANG Yan-yan, ZHOU Chang-ming, ZHANG Ting, ZHAO Li-wen
    2020, 31(11):  3805-3813.  doi:10.13287/j.1001-9332.202011.020
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    Precipitation and vegetation are two key factors affecting floods in the watershed. Quantitative evaluating their contribution to flood is of great scientific significance to vegetation construction and water resources management. Based on the geographic information data and hydrometeorological data from 1983 to 2014, we analyzed the characteristics of rainstorm and flood in Pengchongjian small watershed in red soil region of South China by Mann-Kendall test method, cumulative anomaly method and HEC-HMS model, and quantitatively evaluated the contribution rate of precipitation and vegetation variation to flood. The results showed that the rainstorm volume and total flood volume in Pengchongjian small watershed from 1983 to 2014 showed a non-significant upward/downward trend, respectively. HEC-HMS model had good simulation effect on single rainstorm flood, with the evaluation results being within the error range. The contribution rates of precipitation and vegetation variation of different rainstorm floods were different with respect to the total flood volume or to the peak flow. The average contribution rate of precipitation and vegetation variation to the total flood volume was 66.5% and 33.5%, while to the peak flow was 58.9% and 41.1%, respectively. Our results could provide scientific basis for flood evaluation, vegetation construction and comprehensive control of soil erosion in small watershed.
    Sub-cloud secondary evaporation effect of precipitation isotope in Shaanxi-Gansu-Ningxia region, China
    XIAO Han-yu, ZHANG Ming-jun, WANG Sheng-jie, CHE Cun-wei, DU Qin-qin, ZHANG Yu, HAN Ting-ting, SU Peng-yan
    2020, 31(11):  3814-3822.  doi:10.13287/j.1001-9332.202011.013
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    During atmospheric precipitation, the evaporation of raindrops falling from the bottom of cloud layer to the ground and passing through unsaturated air, a process was called sub-cloud secondary evaporation, which will change the isotopic composition of precipitation. Using the hydrogen and oxygen stable isotope method to understand the temporal and spatial variation of secondary evaporation effect under clouds and its causes is important to understand regional water cycle process. Based on hourly meteorological data of 187 meteorological stations in Shaanxi-Gansu-Ningxia region from March 2018 to February 2019, the spatial and temporal variations of evaporation surplus ratio (f) and precipitation excess deuterium variation (Δd) were analyzed using the improved Ste-wart model, and the relationships between f and meteorological elements and Δd were examined. The results showed that, at the hourly scale, the minimum values of f and Δd in all provinces of the region appeared in the daytime, and the maximum values appeared in the night, indicating that the secondary evaporation effect under the cloud was more obvious in the daytime. At the monthly scale, the monthly variation trend of f and Δd in each province was relatively consistent, with the minimum value appearing in the summer half year, and the maximum value appearing in the winter half year, indicating that the second evaporation effect under cloud was more significant in the summer half year. From the spatial perspective, the spatial variation of f and Δd values in the region was consistent with that at the seasonal scale. In spring, the eastern and western regions were larger while the central part was smaller. In summer, the northwest region was smaller, and other regions were larger. In autumn, it decreased from south to north. In winter, the central and southern regions were smaller, and the western and northeast regions were larger. The spatial differences of secondary evaporation effects under clouds in different seasons was significant. The slopes of the linear relationship between f and Δd in Shaanxi, Gansu and Ningxia provinces were all less than 1‰·%-1, which may be caused by the arid and semi-arid climate in this area. When air temperature was higher and the relative humidity, vapor pressure, precipitation and raindrop diameter were smaller, the value of Δd was smaller, and the secondary evaporation effect under the cloud was more obvious.
    Climatic ecological suitability and potential distribution for Boletus edulis in mountainous areas of Western Sichuan Plateau, China
    ZHANG Li-ping, XUE Yan, GUO Xiang, WANG Ming-tian
    2020, 31(11):  3823-3832.  doi:10.13287/j.1001-9332.202011.015
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    The ecological climate suitability of Boletus edulis was systematically analyzed in mountainous areas of the Western Sichuan Plateau using DEM, land cover data and meteorological data from 52 weather stations in Sichuan Province and four weather stations in other provinces. Factors such as temperature, precipitation and vegetation cover were selected as the regionalization index to analyze the potential spatial distribution of B. edulis in Western Sichuan Plateau by GIS technology. The results showed that the northern boundary of potential distribution area for B. edulis was near 32° N, the upper and lower limits of the altitude were about 800 m and 3000 m. The total distribution area was 2863000 hm2, accounting for about 9.7% of the whole study area. The Panxi area at south of 29° N was the main distribution area, accounting for about 90% of all potential distribution areas. Among the main distribution area, the suitable area was about 20%, and the remaining is the secondary suitable area. The suitable area was mainly distributed in the Anning River basin at the elevation of 1000 m to 2600 m in East of the Yalong River in the Panxi area. The secondary suitable area was mainly located in forest area extending upward and downward from suitable area at an altitude of about 3000 m and 800 m, respectively. The unsuitability areas were the alpine regions at altitude above 3000 m and the dry-hot valley regions at altitude below 800 m.
    Quantitative assessment of surface hydrological connectivity in Momoge National Nature Reserve, Northeast China
    CHEN Yue-qing, WU Li-li, ZHANG Guang-xin, TAN Zhi-qiang, QIAO Si-jia
    2020, 31(11):  3833-3841.  doi:10.13287/j.1001-9332.202011.041
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    Quantitative assessment of hydrological connectivity is a hot but difficult issue in current research. Using the 30-m resolution global monthly surface water remote sensing dataset released by the EU Joint Research Center and three indicators of geostatistical connectivity, maximum distance of connection (MDC), and surface water extent of connectome (i.e., seasonally connected water bodies), we quantified the hydrological connectivity of surface water in Momoge National Nature Reserve in different months of a normal year (May to October 2016), and in September of different hydrological years (a wet year, namely 1998; a normal year, namely 2016; a drought year, namely 2002), and different directions (west-east and north-south). Our results showed that: 1) the geostatistical connectivity function (GCF) along the west-east direction was better than that along the north-south direction. The GCF in August and July was better than that in other months. The GCF along the west-east direction of each hydrological year was better than that in the drought year, whereas the GCF in the drought year was better than the corresponding value in the normal year. The GCF along the north-south direction in each hydrological year was better than that in the normal year, whereas the GCF in the normal year was better than that in the drought year. The MDC along the west-east direction in June, July, September, and October of the normal year was all concentrated at 25.26 km. MDC was more concentrated along the north-south direction, with 10 km for all months. The MDC in the normal and drought years was relatively close, but both were much smaller than that in the wet year. 2) frequent seasonal connections between the Yuelianghu Reservoir and the Nenjiang River, and between Etoupao and its neighboring lakes occurred in the study area during the normal year, while most of the other lakes remained isolated. The patterns of hydrological connection in the study area differed across different hydrological years: two giant connectomes were formed in the wet year, some lakes are periodically connected in the normal year, and all lakes remain isolated in the drought year. 3) As a drainage area for farmland receding water, the surface water extent of the Etoupao connectome increased visibly during the three water supplement seasons (spring, summer, and autumn). By quantifying the surface hydrological connectivity in Momoge National Nature Reserve with multiple water sources from different perspectives, our results provide a scientific basis for wetland protection and restoration and integrated management of watershed water resources.
    Effects of nitrogen-doped carbon nanoparticles on bacterial community in paddy rhizosphere soil
    HU Wei, XIANG Jian-hua, XIANG Yan-ci, CHEN Yan
    2020, 31(11):  3842-3850.  doi:10.13287/j.1001-9332.202011.033
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    The nitrogen-doped carbon nanoparticles (N-CNPs) has a high potential of increasing nitrogen efficiency in farmland. However, little has been known about the effects of N-CNPs on soil microbial communities. In this study, paddy rhizosphere samples were collected from soils being treated with different nitrogen-doped amount of carbon nanoparticles (low, 1.2%, N-CNPs1; medium, 6.7%, N-CNPs2; high, 9.3%, N-CNPs3) for three years. We analyzed the bacterial community structure and diversity using the high-throughput sequencing. PICRUSt gene prediction analysis was used to determine soil community composition and metabolic function. Our results showed that treatment with N-CNPs changed the structure and diversity of soil microbial communities. Soil bacterial community diversity in adding medium amount of nitrogen-doped nanoparticles group (N-CNPs2) was the highest among all the treatments. Crenarchaeota, Acidobacteria and Planctomycetes were the most dominant groups in the soil microbial community. The relative abundances of Crenarchaeota, Acidobacteria and Verrucomicrobia increased, whereas Planctomycetes, Chloroflexi and Nitrospirae decreased with adding N-CNPs. Results of PICRUSt analysis revealed a wide genetic diversity of organisms involved in adding N-CNPs, such as amino acid metabolism, carbohydrate metabolism, lipid metabolism and environmental information processes. Heat map analysis of KEGG demonstrated that adding medium amount of nitrogen-doped nanoparticles (N-CNPs2) group increased the relative abundance of bacterial community associated with soil carbon and nitrogen metabolism.
    Effects of broadleaved tree species on soil microbial stoichiometry in clear-cut patches of Cunninghamia lanceolata plantation
    WANG Tao, WAN Xiao-hua, CHENG Lei, YANG Jun-qian, ZHANG Bing-bing, ZOU Bing-zhang, WANG Si-rong, YU Zai-peng, HUANG Zhi-qun
    2020, 31(11):  3851-3858.  doi:10.13287/j.1001-9332.202011.034
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    Investigating the response of soil microbial biomass and ecological stoichiometry to tree species transition is of great significance for understanding soil nutrient cycling and availability in forest ecosystems. We measured soil microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP) and their stoichiometry across 0-40 cm soil depth between Mytilaria laosensis and Cunninghamia lanceolata plantations by the chloroform fumigation extraction method, which were replanted after the harvest of C. lanceolata plantation. The results showed that soil MBC in the 0-10 cm layer and soil MBN and MBP in the 0-20 cm layer under the M. laosensis were significantly higher than those under the C. lanceolata. The MBC/MBP in the 0-20 cm layer and MBN/MBP in the 10-20 cm layer were significantly lower under the M. laosensis plantation. The MBC/MBN showed no significant differences between the two forests. Soil moisture, organic carbon, total nitrogen, total phosphorus, available phosphorus were positively correlated with MBC, MBN and MBP, but negatively correlated with MBC/MBP and MBN/MBP. Results of stepwise linear regression analysis showed that MBN and MBP were mainly affected by soil total nitrogen and available phosphorus, while MBC/MBP and MBN/MBP were mainly driven by available phosphorus and organic carbon, respectively. Our results indicated that tree species transition from C. lanceolata to M. laosensis could increase soil microbial biomass in the surface layers, accelerate soil nutrients turnover and enhance soil nutrient supply. The increases of MBP under M. laosensis indicate alleviation of soil phosphorus limitation for tree growth.
    Characteristics of soil animal community with different garden plants and various planting periods in Wenjiang District, Chengdu, China
    HUANG Yu-mei, LI Xiang, ZHANG Dan-ju, DENG Chu-xuan, LUO Chun-lan, LUO Zi-wei, SHEN Jin-liang, XIE Wen-feng
    2020, 31(11):  3859-3868.  doi:10.13287/j.1001-9332.202011.031
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    In order to provide scientific guidance for soil quality evaluation and optimum management of flower and seedling industry, we investigated the characteristics of soil animal community with different garden plants and various planting periods in Wenjiang District, Chengdu. A total of 10258 soil animals belonging to 26 orders and 78 families were captured in four sampling times. There were significant differences in the taxonomic richness in the plots with different garden plants, generally highest in plots with Loropetalum chinense var. rubrum or Ginkgo biloba and lowest in plot with Zoysia japonica. The taxonomic richness was lower in the plots with different garden plants than the control. Taxonomic richness and abundance of soil fauna in Osmanthus fragrans plot did not change across sampling seasons. The abundance but not taxonomic richness of soil fauna in other plots had obvious seasonal variations. Different garden plants and various planting periods significantly influenced soil faunal diversity indices. Density-group index (DG) and Margalef richness index (D) in G. biloba plot, as well as Shannon diversity index (H) and D index in Z. japonica plot decreased significantly with the increases of planting period. The DG and D indices of soil animals in O. fragrans plot increased significantly with increasing planting period. The indices of soil animal diversity in L. chinense var. rubrum plot did not change regularly with planting period. The DG, D, and H indices were lowest in O. fragrans plot with different planting periods. Results of hierarchical clustering and canonical correlation analyse (CCA) indicated that garden plant species had stronger effects on the habitat than planting period. Responses of soil fauna to various habitats were different, with available P and soil pH having stronger effects on soil fauna. Our results indicated that soil animal community shifted with the changes of garden plant and planting period as well as management and cultivation methods. Excessive human interference and monoculture had negative effects on soil animal community and caused soil degradation.
    Isolation, screening and identification of anantagonistic actinomycetes to control Fusarium wilt of Momordica charantia
    LI Xiao-fang, TIAN Ye-han, PENG Hai-ying, HE Bang-ling, GAO Ke-xiang
    2020, 31(11):  3869-3879.  doi:10.13287/j.1001-9332.202011.036
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    Fusarium oxysporum f. sp. momordica was used as the target pathogenic fungus to screen actinomycetes that were isolated from rhizosphere soil of Momordica charantia by confrontation culture and antifungal tests of fermentation filtrate. The candidate strain 0250 had broad antifungal activity. According to cultural characteristics, physiological and biochemical properties, as well as average nucleotide identity analysis of the strains with similar homology, the strain 0250 was identified as Streptomyces rhizosphaericus. Its effects on growth promotion and control of bitter gourd wilt were evaluated in both greenhouse and field. The results showed that the plate inhibition percentage of S. rhizosphaericus strain 0250 against F. oxysporum f. sp. momordica was 69.2%, while the plate inhibition percentage against 17 plant pathogenic fungi reached 64.3%-85.6%. The suspension treatment of the strain could promote the growth and development of roots and stems and improve production of bitter gourd in pots and field. The control efficacy of Fusarium wilt of bitter gourd was 66.9% and 61.5%, respectively. When soils were treated with the strain 0250 suspension in advance and inoculated with the fungal pathogen, the inhibition percentage on the soil F. oxysporum reached 62.1%. The activity of phenylalanine ammonia-lyase, peroxidase and β-1,3-glucanase as well as root activity were significantly improved in bitter gourd seedlings. In summary, strain 0250 is an actinomycetes resource with biocontrol potential to Fusarium wilt of bitter gourd.
    Distribution pattern of macroinvertebrate community and its relationships with environmental factors in the Yongding River Basin
    ZHANG Yu-hang, ZHANG Min, PENG Wen-qi, ZHANG Hai-ping, QU Xiao-dong, LUO Zun-lan
    2020, 31(11):  3880-3888.  doi:10.13287/j.1001-9332.202011.038
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    Human disturbances have altered global stream ecosystems in multiple ways. Understan-ding spatio-temporal dynamics of aquatic organism composition and their relationships with environmental factors play an important role in revealing changes in the structure and function of river ecosystems. The macroinvertebrates and environmental parameters were sampled in the Yongding River Basin at spring (March), summer (July), and autumn (November) in 2017. The results showed that chironomids were the dominant group in the Yongding River Basin, including Orthocladius, Chironomus, Glyptotendipes, and Polypedilum. Results of the cluster analysis showed significant spatial variations of macroinvertebrate community. Sampling sites were clustered into two groups based on the similarities of macroinvertebrate composition in the Yongding River. Sampling sites belonging to group 1 mainly located in the Sanggan River and Dongyang River, with Orthocladius sp.being the dominant species. Sampling sites belonging to group 2 mainly located in the Yang River, Guishui River and main section of the Yongding River, with Glyptotendipes sp. being the dominant species. The biomass, Shannon index, Margalef index, Pielou evenness index and taxa richness of group 2 were significantly higher than those of group 1. Higher values of biological indices indicated better ecological condition of the stream ecosystem. The density, biomass and diversity indices of summer were significantly lower than those of both spring and autumn. Results of Canonical correspondence analysis (CCA) showed that the spatio-temporal distribution of macroinvertebrate in the Yongding River was mainly influenced by water temperature, ammonium, pH, dissolved oxygen, and total phosphorus. From the perspective of hydrological characteristics, flow velocity and flow capacity were significantly correlated. The significant positive correlations between hydrological parameters of velocity and capacity and biological indices of density and EPT% in group 2 indicated the preference of fast flow to sensitive taxa of EPT (Ephemeroptera, Plecoptera, and Trichoptera). The negative correlations between flow capacity and biodiversity indices implied the adverse effects of high flow on macroinvertebrate biodiversity. Our results confirmed that the composition and biodiversity of macroinvertebrate were affected by both water environment and hydrology, which reflected the multiple human activities in aquatic ecosystems of the Yongding River. It is important to control water contamination and sustain environmental flow at the specific reaches for the restoration of Yongding River.
    Identification of keystone predators in Haizhou Bay food web based on the revised SURF index
    XU Cong-jun, ZHANG Chong-liang, XU Bin-duo, REN Yi-ping, XUE Ying
    2020, 31(11):  3889-3894.  doi:10.13287/j.1001-9332.202011.040
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    Keystone predator species play an important role in regulating the number, richness and distribution of prey species. Based on the bottom trawl surveys in Haizhou Bay, keystone predator species in fish communities were identified by the revised SURF (supportive role to fishery ecosystems) index. Conger myriaster, Saurida elongata, Hexagrammos otakii, Chelidonichthys spinosus, and Larimichthys polyactis were the keystone predators in the fish community. They had high number of nodes degree, and were also the main predators of many species. Further, they had strong ability of clustering. The fluctuations of their density would have great impacts on ecosystem energy flow and food web structure. The method not only considered the feeding ratio between species, but also took the amount of catch and abundance of species as important factors in the identification of keystone predators. Compared with the traditional method, this method had great improvement and provided a new one for the identification of key predators. Our results showed that the strong inter-specific interactions played an important role in maintaining the structure and function of food webs. Protection of key predators would benefit the stability of biological communities and species diversity. Therefore, ecosystem-based fisheries management (EBFM) should give priority to the protection of key species. The important economic fish species, C. myriaster and L. polyactis, should be protected with high priority as they suffered from higher fishing pressure.
    Reviews
    Research progress on the methods for measuring xylem embolism vulnerability
    WANG Ting, GUO Wen, PAN Zhi-li, CHEN Fang, YANG Shi-jian
    2020, 31(11):  3895-3905.  doi:10.13287/j.1001-9332.202011.007
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    Changes in the frequency and severity of drought events associated with climate change could affect plant growth, development, and adaptability. Hydraulic failure caused by xylem embo-lism is the main physiological consequences of drought stress. How to accurately quantify xylem embolism is particularly important for understanding plant responses to drought stress. The vulnerability of xylem to embolism is usually evaluated by constructing vulnerability curves (VCs). Several methods have been developed to construct VCs, but be inconsistent in their results. A deep understanding of the design principles of xylem embolism measurement methods and comparison of the similarities and differences of various methods in actual research are particularly important for the rational interpretation of literature results, and properly using VCs in models for predicting plant responses to water deficits. Here, we compared seven methods for constructing xylem vulnerability curves to embolism: bench dehydration, centrifugation, air injection, acoustic measurements, synchrotron and X-ray microtomography (Micro-CT), optical visualization method, and pneumatron method. We summarized current achievements and controversial viewpoints of the application of these methods in specific research. Finally, we provided prospects for measuring the vulnerability of xylem embolism and the selection of relevant methods for practical application in future studies.
    Progress in the effects of warming on soil N2O and CH4 emission and the underlying micro-bial mechanisms
    HAN Xue, CHEN Bao-ming
    2020, 31(11):  3906-3914.  doi:10.13287/j.1001-9332.202011.026
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    Global warming has received widespread concern. The increasing concentration of greenhouse gases (GHG) is one of the major factors contributing to global warming. Soil is a major source of GHG. Global warming could feed back on soil GHG emission. Warming influences the growth of plants, animals, microbes and their interactions, as well as the cycling of soil matters (especially nitrogen and carbon). Consequently, warming has the potential to affect soil GHG emission. We summarized the effects of warming on soil N2O, and CH4 emissions and the underlying mechanisms. In general, warming increased the emission of these two greenhouse gases, which are mainly related to the effects of temperature on the abundance and composition of ammonia oxidizing bacteria, denitrification functional genes, methane-producing bacteria and methane-oxidizing bacteria. Soil GHG emissions are affected by plant species characteristics, nutrient uptake and community composition, as well as soil nutrient element content, water content, pH and other physical and chemical properties. Further studies are needed to elucidate the microbial mechanisms of GHG emission. In addition, various warming patterns should be considered in the study of GHG emissions, and more attention should be paid on the interactive effects between warming and other environmental factors. It will provide solid theoretical basis for the prediction of global climate change and GHG emissions.
    Influencing mechanism of soil salinization on nitrogen transformation processes and efficiency improving methods for high efficient utilization of nitrogen in salinized farmland
    LI Hong-qiang, YAO Rong-jiang, YANG Jing-song, WANG Xiang-ping, ZHENG Fu-le, CHEN Qiang, XIE Wen-ping, ZHANG Xin
    2020, 31(11):  3915-3924.  doi:10.13287/j.1001-9332.202011.023
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    Based upon the review of the status of nitrogen use efficiency in salinized farmland in China, we summarized the effect of salinization on key processes of nitrogen transformation in farmland soil, analyzed the microbial mechanism underlying nitrogen transformation, and summed up the main ways for high efficient utilization of nitrogen in salinized farmland. Salinization had thre-shold effects on mineralization, nitrification, and denitrification of nitrogen from farmland soil, with the influence varying greatly in different scopes. Salinity and secondary barriers had different effects on microorganisms, with threshold in their effects. The most widely used methods for nitrogen synergism regulation in salinized farmland include soil conditioner, biomass material, growing salt-tole-rant plants, optimizing the ratio of different nitrogen forms, and biological inhibitor. We proposed current research shortcomings and future research directions of nitrogen cycle processes in salinized farmland. This study was of great significance for reducing nitrogen loss, enhancing utilization of nutrient from fertilizers, and controlling agricultural non-point source pollution in salinized farmland.
    Research progress on the differences and connections between supply and demand of urban green space
    CHEN Zhang-hao, HUANG Gan-lin
    2020, 31(11):  3925-3934.  doi:10.13287/j.1001-9332.202011.018
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    As an important concept connecting urban green space (UGS) with the residents' demands, supply and demand of UGS is an important part of UGS research and planning. Identifying the difference and connection between UGS supply and demand contributes to proper configuration of UGS, human well-being improvement and urban sustainability. We reviewed literature on UGS supply and demand from 2016 to 2020, summarized common research topics and paradigms, examined associations among these topics, and proposed suggestions for future studies. We found that most studies focused on either USG supply or demand, and rarely analyzed match between UGS supply and demand. The studies of UGS supply mainly focused on the spatial and temporal patterns and the ecosystem services they provided, while the studies of demand focused on residents' subjective preference and behavior. Studies on supply and demand often differ in research objects, scales, and indicators, which was a major obstacle to construct relationships between them. We proposed that future studies should focus on the match of supply and demand. A possible way to achieve this goal is to measure UGS demand by both objective indicators and subjective preference.
    Planning approach of urban blue-green space based on local climate optimization: A review
    CHENG Ya-tian, WU Chang-guang
    2020, 31(11):  3935-3945.  doi:10.13287/j.1001-9332.202011.014
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    Local climatic problems are widespread in cities under high-density and high-intensity construction mode in China, including heat island effect, poor ventilation, and frequent haze wea-ther. Urban blue-green space is vital for mitigating wind and heat, and for improving air quality, and therefore has become a hotspot of urban planning and design research dealing with climatic problems. Here, we reviewed the climate effects of urban blue-green space. In particular, we summarized the research progress of planning approaches to cool island landscape features optimization, cooling island configuration, ventilation corridor network connection and ventilation corridor interface control based on the levels of planning layout and network construction. We proposed a basic framework of urban blue-green space planning optimizing local climate by combining intelligent simulation platform, evaluation index system, planning and design guide, and guarantee mechanism for implement, aiming to provide key evidence for urban climate adaption and design.
    Advances in ecological risk assessment of soil in contaminated sites
    WANG Mei-e, DING Shou-kang, GUO Guan-lin, LI Xu-zhi, JIANG Rong, ZHANG Yuan, XIE Tian
    2020, 31(11):  3946-3958.  doi:10.13287/j.1001-9332.202011.035
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    With the rapid urbanization and industrial structure adjustment in China, many contaminated sites have been left for remediation. It is essential to develop and implement ecological risk assessment (ERA) before remediating contaminated sites at a large scale as well as sequential management. In this review, we discussed the key problems in ecological risk assessment of soils in contaminated sites focusing on scientific principles, frameworks, techniques, and approaches, including 1) the site-specific framework, 2) uncertainty of conceptual model, 3) toxic mechanisms of combined contamination in soil, 4) screening of assessment endpoints, and 5) development of assessing approaches and frameworks. Then, two perspectives were addressed: the toxicological mechanism of soil combined pollution including bioavailability of contaminants in soil and their joint effect is the scientific problem in ecological risk assessment of soil in contaminated site; and weight of evidence approach based on USEPA four-step approach and EU Tier approach is applicable for ecological risk assessment in field conditions. Future studies should focus on: 1) the coordination of ecological risk assessment (ERA) framework and risk management framework, 2) conceptual mo-del, 3) process-based reactive transport models for exposure evaluation, 4) ecotoxicological mechanism of combined contamination in site soil, and 5) high ecological level endpoints. The aim of this review was to provide theoretical base and framework for the establishment of local guideline of ecological risk assessment in China.
    Interaction between intestinal microorganisms and carbohydrates of mammals and its influence
    ZOU Yao, HAN Chong-xuan
    2020, 31(11):  3959-3968.  doi:10.13287/j.1001-9332.202011.037
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    The intestinal microorganisms have physiological functions, including regulation of nutrition, immunity, and energy metabolism of host. Diet is one of important factors affecting the intestinal microorganism of mammals. It is important to investigate the interaction between intestinal microorganism and carbohydrates metabolism and its influence, because carbohydrates were the main food source for mammals. We reviewed related literature from three aspects: the effects of carbohydrates on intestinal microorganisms, the metabolic mechanism of intestinal microorganisms on carbohydrates, and the effects of carbohydrates fermentation products on the host. The main types of carbohydrates that intestinal microorganisms can use for fermentation are resistant starch and non-starch polysaccharides. Different types of carbohydrates can induce adaptive changes in different microorganisms. Short-chain fatty acids fermented from complex polysaccharide play an important role in regulating host energy balance and immune response. This review would deepen the understanding of the contribution of intestinal microorganisms to host carbohydrates metabolism, and provide a refe-rence for the nutritional regulation of mammalian health.
    Regulation mechanism of ocean acidification on key physiological processes of microalgae and the effect of environmental factors: A review
    XUE Yin-hao, LIU Zhuo-miao, WANG Hao, ZHAO Jian
    2020, 31(11):  3969-3978.  doi:10.13287/j.1001-9332.202011.032
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    The inputs of carbon dioxide from anthropogenic activities to ocean through the sea-air interface exchange disturbs the balance of seawater carbonate system, resulting in ocean acidification (OA). OA affects the physical and chemical properties of both seawater and marine pollutants, which significantly regulates the physiological processes of planktonic algae living on the surface of ocean. As the main primary producers, the physiological function and processes of marine algae play an important role in marine ecosystem. We reviewed the underlying mechanisms of OA on the three key physiological processes of photosynthetic carbon fixation, calcification and nitrogen fixation of marine microalgae. OA could alter environmental factors (e.g., solar radiation, temperature, nutrient elements) and typical marine contaminants (e.g., organic contaminants, heavy metals, microplastics). We further summarized the effects of these factors on the regulation of physiological processes of microalgae. Finally, current research status and prospects for future research were addressed. This review provided important information for better understanding the potential impacts of OA on marine ecosystems.