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    15 February 2020, Volume 31 Issue 2
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    Effects of stand structure on understory biomass of the Quercus spp secondary forests in Hunan Province, China
    CHEN Hao-hong, ZHU Xin, ZHU Guang-yu, LIU Fei-hu
    2020, 31(2):  349-356.  doi:10.13287/j.1001-9332.202002.008
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    We examined biomass characteristics and the potential driving factors of different forest types of Quercus spp. secondary forest in Hunan. A total of fifty plots were divided into five forest types: Castanopsis eyri - Rhododendron latoucheae mixed forest (CR), Fagus lucida - Fargesia spathacea mixed forest (FF), Lithocarpus glaber - Damnacanthus indicus + Camellia japonica mixed forest (LDC), C. eyri + Quercus serrata - R. latoucheae mixed forest (CQR), Cyclobalanopsis glauca - Camellia oleifera + R. latoucheae mixed forest (CCR). The biomass of understory vegetation was low in the five forest types, being smaller than 2.3 t·hm-2. There was no significant difference in the biomass of understory shrubs among the five forest types. The biomass of herbage layer in CR was significantly lower than that of the other four forest types. The factors affecting the biomass of understory vegetation varied in different forests types. In CR, biomass of herbaceous layer was negatively correlated with canopy and uniform angle index, whereas total understory biomass was positively correlated with opening degree index. In FF, biomass of shrub layer was negatively correlated with stand canopy density and uniform angle index, while herbaceous biomass and total understory biomass were positively correlated with stand closure. In LDC, herbaceous biomass was positively correlated with the stand aggregation index. In CQR, shrub biomass was negatively correlated with stand mingling index, while herbaceous biomass was positively related with stand density. In CCR, there was no significant correlation between stand structure and understory biomass. To adjust the understory biomass, we should first adjust the horizontal distribution pattern of stand and then adjust the degree of forest cover and tree species structure.
    Structure and dynamic characteristics of Betula luminifera populations in different regions of Southwest Hubei Province, China
    WANG Jin, YAO Lan, AI Xun-ru, ZHU Jiang, LIU Song-bai
    2020, 31(2):  357-365.  doi:10.13287/j.1001-9332.202002.010
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    We investigated Betula luminifera populations in three regions (Mulinzi, Qizimei Mountains, and Jinzi Mountains) in the southwest Hubei Province, China. Population structure was divided by age classes and height classes. Population structure figures were drawn. The static life tables of B. luminifera populations in different regions were analyzed using the method of substitution of space for time. The survival curve, mortality rate curve and disappearance rate curve were created. Four functions of survival analysis were used to analyze the dynamics of B. luminifera population in different regions. The results showed that the B. luminifera populations in three regions were the increasing type. The height class structures were relatively complete. Some age classes were absent from the age structures of B. luminifera populations in Qizimei Mountains and Jinzi Mountains. Although the dynamic index of trees number Vpi＞0, but it was sensitive to external disturbance. The survival of B. luminifera of different age classes varied greatly in static life table, which gradually decreased with increasing age class, with Deevey-type Ⅱ survival curve. The trend of mortality rate changed similarly to the disappearance rate, but fluctuated differently. All B. luminifera populations in different regions appeared to decrease in the early stage and keep dynamically stable in the medium-late stage.
    An ecological stoichiometry model based on the size of Nitraria tangutorum
    XING Lei, LIU Cheng-gong, LI Qing-he, DUAN Na, LI Hui-qing, SUN Gao-jie
    2020, 31(2):  366-372.  doi:10.13287/j.1001-9332.202002.019
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    Ecological stoichiometry provides a new method for understanding the characteristics, driving forces and mechanisms of C, N and P coupled cycles. However, there are few reports on the variation in ecological stoichiometry of plants during their growth. In this study, we fitted the total elemental mass of different module based on the size of Nitraria tangutorum, and derived the ecological stoichiometry models of different module and whole ramet by measuring the biomass and nutrient concentrations of the current-year stems in 2017, 2-year-old stems, more than 2-year-old stems, leaves, roots and layerings of N. tangutorum ramet. Our results showed that the derivation model could well reflect the changes in ecological stoichiometry during plant growth. The old stems and the layering had higher N:P and C:P, while leaves,current-year stems, and roots had lower N:P and C:P. The whole plant nutrient elements cumulative rate was P>N>C during the growth process. These results were consistent with the growth rate hypothesis and allometric theory, and provide evidence for nutrient reabsorption. This model could be used as an effective way to analyze the dynamic characteristics of elements in plant growth.
    Root architecture and fine root characteristics of Juglans mandshurica saplings in different habitats in the secondary forest on the west slope of Zhangguangcailing, China
    XU Li-qing, CUI Dong-hai, WANG Qing-cheng, ZHANG Yong, MA Shuang-jiao, ZHU Kai-yue, HU Jian-wen, LI Hong-li
    2020, 31(2):  373-380.  doi:10.13287/j.1001-9332.202002.009
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    The whole root excavation method was used to examine root configuration of Juglans mandshurica, with the age of 5-6 years in three habitats (forest edge, gap, and canopy) in a secondary forest on the western part of Zhangguangcailing Mountains. Root structure and fine root function were measured. The root topological index, average joint length, cross-sectional area ratio before and after root branching were calculated and fine root chemical compositions were analyzed. Roots of J. mandshurica at forest edge tended to be dichotomous branch (Topological index:TI=0.68), that under the canopy were herringbone-like branch (TI=0.79), and the gap was between the two (TI=0.72). The average connection length of roots among the three habitats was not significant. The cross-sectional area ratio of roots before and after root branching in three habitats was 1.06, 1.04 and 1.07, respectively, which was not affected by root diameter, in accordance with the Leonardo da Vinci rule. For the same order fine root in different habitats, its length and specific surface area gradually increased from the edge of the forest to the canopy. The N content decreased first and then increased, while the C content and C/N increased first and then decreased. From the forest edge to the gap and to the under canopy, roots tended to move from the dichotomous branch to the herringbone-like branch by reducing the overlap between the secondary branches and roots, increasing specific root length, specific surface area and changing the contents of C and N to cope with environmental change and improve nutrient absorption efficiency.
    Reconstruction of the March-April average maximum air temperature over 165 years based on Pinus tabuliformis tree-rings of Zhen’an County, Shaanxi Province, China
    HUA Ya-wei, ZHANG Hong-juan, LIU Kang
    2020, 31(2):  381-387.  doi:10.13287/j.1001-9332.202002.026
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    We used tree rings of Pinus tabuliformis sampled in the Muwang National Forest Park to establish a standardized chronology (STD) and calculated the correlation coefficients between the standardized chronology and climatic factors of Zhen’an meteorological station. With linear regression analysis, we reconstructed the March-April mean maximum temperature of Zhen’an over 165 years from 1853 to 2017. The highest correlation coefficient was observed between the standardized chronology and the March-April mean maximum temperature (r=0.596, n=60, P<0.01). The variance interpretation of the March-April mean maximum temperature reconstruction function was 33.2%, and the reconstruction function and results were credible and reliable. Warm years occurred 25 times and cold years occurred 29 times in the reconstruction sequence. The warm years were more accompanied by flood events, while the cold years were accompanied by more drought events. Temperature fluctuated obviously in the reconstruction sequence, with two cold periods (1902-1917 and 1953-2000) and four warm periods (1868-1892, 1917-1937, 1941-1953 and 2001-2012). The obvious periodic variations of 2-7, 8-15, 18-28, 75-96, and 100-125 years were found in the reconstruction sequence, in which the quasi-113, 88 and 22 years were the first, second and third main periods, respectively. These variations might potentially be the fingerprints of some climate change forces such as solar activity, monsoon and EI Niño-Southern Oscillation (ENSO) activity.
    Soil phosphorus forms and phosphorus solubilizing bacteria distribution after restoration from seriously burning in Greater Khingan Mountain areas, China
    CHUN Xue, ZHAO Yu-sen, XIN Yin, LI Jin-xiang, LIANG Dong-zhe
    2020, 31(2):  388-398.  doi:10.13287/j.1001-9332.202002.033
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    To understand the contents of various phosphorus forms, phosphorus solubilizing bacte-rial community structure and the relationship between them in soils after restoration from the seriously burning, we collected soil samples from artificial restoration (Pinus sylvestris var. mongolica plantation, Larix gmelinii plantation), artificial accelerated natural restoration (secondary forest) and natural restoration (natural secondary forest) stands in Greater Khingan Mountain area. Using methods of Sui et al. modified from Hedley phosphorus fractionation, we measured the contents of different phosphorus forms in rhizosphere soil and bulk soil (0-10, 10-20 cm). Abundances of phosphorus solubilizing bacteria were quantified by high-throughput sequencing method. The results showed that the contents of H2O-Pi, NaHCO3-Pi and NaHCO3-Poin 0-10 cm bulk soil and NaHCO3-Po in rhizosphere soil followed the order of L. gmelinii plantation > P. sylvestris var. mongolica plantation > natural secondary forest > secondary forest. The contents of H2O-Pi, NaHCO3-Pi, NaHCO3-Po in 10-20 cm bulk soil and H2O-Pi, NaHCO3-Pi in rhizosphere soil followed the order of L. gmelinii plantation > P. sylvestris var. mongolica plantation > secondary forest > natural secondary forest. The ratios of contents of H2O-Pi, NaHCO3-Pi and NaHCO3-Po in rhizosphere to those in bulk soil (R/S) were higher than 1 in all forest stands. The moderately labile NaOH-P included NaOH-Pi and NaOH-Po. The content of NaOH-P was in order of L. gmelinii plantation > natural secondary forest > secondary forest > P. sylvestris var. mongolica plantation in 0-10 cm layer of bulk and rhizosphere soil, and ranked as L. gmelinii plantation > P. sylvestris var. mongolica plantation > secondary forest > natural secondary forest in 10-20 cm layer of bulk soil. There was rhizosphere effect of NaOH-P in the soil. The stable HCl-P included HCl-Pi and HCl-Po. The content of HCl-P followed the order of L. gmelinii plantation > natural secondary forest > P. sylvestris var. mongolica plantation > secondary forest in 0-10 cm layer of bulk soil,and ranked as L. gmelinii plantation > P. sylvestris var. mongolica plantation > natural secondary forest > secondary forest in the 10-20 cm layer. The content of residual-P in the soil was not sensitive to restoration methods. Bradyrhizobium, Streptomyces, Burkholderia and Bacillus were the main phosphorus solubilizing bacteria across all forest stands. The abundances of phosphorus solubilizing bacteria in soil of L. gmelinii plantation and P. sylvestris var. mongolica plantation were significantly higher than that of secondary forest and natural secondary forest. Results of redundancy analysis showed that the correlation between phosphorus solubilizing bacteria and various phosphorus forms was different. Our results showed that artificial afforestation was more conducive in improving the availability of phosphorus in soil and the abundance of phosphorus solubilizing bacteria.
    Seasonal variation and driving factors of forest fire in Zhejiang Province, China, based on MODIS satellite hot spots
    ZENG Ai-cong, CAI Qi-jun, SU Zhang-wen, GUO Xin-bin, JIN Quan-feng, GUO Fu-tao
    2020, 31(2):  399-406.  doi:10.13287/j.1001-9332.202002.015
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    Understanding the changes and driving factors of forest fire can provide scientific basis for prevention and management of forest fire. In this study, we analyzed the changes and driving factors of forest fire in Zhejiang Province during 2001-2016 based on trend analysis and Logistic regression model with the MODIS satellite fire point data combined with meteorological (daily ave-rage wind speed, daily average temperature, daily relative humidity, daily temperature difference, daily cumulative precipitation), human activities (distance from road, distance from railway, distance from resident, population, per capita GDP), topographic and vegetation factors (elevation, slope, vegetation coverage). The results showed that the number of forest fires in spring and summer had significantly increased, while the forest fires in the autumn and winter increased first and then decreased. Forest fire in autumn significantly declined. The four seasons’ fire occurrence prediction models had good prediction accuracy, reaching 75.8% (spring), 79.1% (summer), 74.7% (autumn) and 79.6% (winter). The meteorological, human activity, topographic and vegetation factors significantly affected fire occurrence in spring and summer, while meteorological factors were the main fire drivers in autumn and winter in Zhejiang. The focus of forest fire management should be on human activities. Fire prevention campaign should be done in spring and summer when high-risk forest fires were scattered in the study area. In autumn and winter, observatory and monitoring equipment could be built to facilitate fire management and detect in the area of high fire risk that was concentrated in the southwest region.
    Effects of undergrowth vegetation management measures on the soil bacterial community structure of large diameter timber plantation of Cunninghamia lanceolata
    FEI Yu-chong, WU Qing-zhui, LU Jin, JI Chun-shan, ZHENG Hong, CAO Shi-jiang, LIN Kai-min, CAO Guang-qiu
    2020, 31(2):  407-416.  doi:10.13287/j.1001-9332.202002.035
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    Given the importance of undergrowth vegetation to plantation ecosystem, this study analyzed the effects of three kinds of understory management measures, including understory preservation, understory removal, and interplanting, on the soil bacterial diversity, community structure and relative abundance under large diameter timber plantation of Cunninghamia lanceolata using high-throughput sequencing technology. The relationship between soil physical and chemical properties and bacterial community diversity were analyzed. The results showed that Chao1, Ace and Shannon indices of soil bacterial communities of understory preservation were higher than those of understory removal and interplanting. Actinobacteria, Acidobacteria and Chloroflexi were the dominant bacteria groups in the soil of C. lanceolata plantation. Compared with understory removal and interplanting, the relative abundance of Proteobacteria, Planctomycetes, Firmicutes and Verrucomicrobia in the soil of understory preservation was relatively high, while that of Actinobacteria, Acidobacteria and Chloroflexi was relatively low. There were significant differences in the relative abundance of Firmicutes, Planctomycetes, Verrucomicrobia, Parcubacteria and Actinobacteria among three understory management measures. The contents of moisture, total nitrogen, total phosphorus, hydrolyzed nitrogen and available phosphorus in the soil were important factors affecting soil bacterial community structure. Soil bacterial diversity indices had significant positive correlation with the contents of total nitrogen, total phosphorus, total potassium, hydrolyzed nitrogen and available potassium in the soil.
    Variation characteristics of soil seed bank during vegetation restoration in red soil erosion area
    WANG Chang-hui, LIU Qing-qing, WEN Zhu-mei, WANG Zi-rui, CHEN Yan-fang, LIU Bo, WANG Zheng-ning
    2020, 31(2):  417-423.  doi:10.13287/j.1001-9332.202002.027
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    As a natural disturbance agent, soil erosion could affect secondary distribution and species composition of soil seed bank. The composition, storage and distribution pattern of the soil seed banks in five different vegetation recovery areas, including bare ground (Ⅰ), pine forest land (Ⅱ-Ⅳ) and secondary forest (Ⅴ) in the typical red soil erosion area, were studied to explore the effects of soil erosion on soil seed bank during vegetation restoration. The results showed that a total of 21 species were recorded in the soil seed bank. Species richness was low, and dominated by herbaceous species. The density of soil seed bank varied from 56.7 to 793.3 seeds·m-2 and differed significantly among the sampling plots. Further, the density of soil seed bank decreased obviously with the increasing soil erosion intensity. The seed bank density of 0-2 cm soil layer increased along uphill, middle slope, and downhill. The soil seed banks of severely eroded and strongly eroded plots were mainly distributed in the 5-10 cm soil layer, with almost no seeds in 0-2 cm soil layer on the middle slope and uphill. Soil erosion made the distribution of soil seed bank to deeper soil layer, the accumulation of which will need a long time after vegetation restoration.
    Spatio-temporal variation of NPP from 1999 to 2015 in Zoige grassland wetland, China
    GUO Bin, WANG Shan, WANG Ming-tian
    2020, 31(2):  424-432.  doi:10.13287/j.1001-9332.202002.018
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    Net primary productivity (NPP) is one of the core components of the grassland wetland ecosystem carbon balance and climate change. Based on data of vegetation index, meteorology (precipitation and temperature), and vegetation type, we used the CASA (Carnegie-Ames-Stanford Approach) model to estimate NPP of the Zoige grassland wetland from 1999 to 2015. The spatial and temporal patterns of NPP in the Zoige grassland wetland ecological function area and its relationship with precipitation and temperature were examined. The results showed that the measured values of NPP were close to the simulated values, with the root mean square error being 120.3 g C·m-2 and a R2 of 0.78. The annual mean and the growth season (April-September) mean of NPP of the study area were 329.0 and 229.4 g C·m-2·a-1, respectively, with obvious inter-annual fluctuations, with a weak trend of decline (2.3, 1.6 g C·m-2·a-1). The inter-annual fluctuations of NPP in different vegetation types were basically consistent with the overall fluctuations of NPP of the whole study area. The slope of NPP in annual and growing seasons was from -21.3 to 18.7, -31.5 to 23.1 g C·m-2·a-1. The area with significant increase (mainly distributed in forest coverage area and wetland ecological compensation area) only accouned for 0.3% and 0.7% of the total area, and the area with significant decline (mainly distributed in areas where human activities were concentrated) only accounted for 1.4% and 6.4% of the total area, respectively. The carbon sequestration capacity of different vegetation types was different, among which the forest was the strongest, the grassland was the second, and the wetland vegetation was the weakest. Precipitation was the dominant climatic factor affecting NPP in grassland wetland.
    Model construction and application for nitrogen nutrition monitoring and diagnosis in double-cropping rice of Jiangxi Province, China
    LI Yan-da, CAO Zhong-sheng, SUN Bin-feng, YE Chun, SHU Shi-fu, HUANG Jun-bao, WANG Kang-jun, TIAN Yong-chao
    2020, 31(2):  433-440.  doi:10.13287/j.1001-9332.202002.029
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    The spectrometer-based nitrogen (N) nutrition monitoring and diagnosis models for double-cropping rice in Jiangxi is important for recommending precise N topdressing rate, achieving high yield, improving grain quality and increasing economic efficiency. Field experiments were conducted in Jiangxi in 2016 and 2017, involving different early rice and late rice cultivars and N application rates. Plant N accumulation (PNA) and canopy spectral vegetation indices (VIs) were measured at tillering and jointing stages with two spectrometers, i.e., GreenSeeker (an active multispectral sensor containing 780 and 660 nm wavelengths) and crop growth monitoring and diagnosis apparatus (CGMD, a passive multispectral sensor containing 810 and 720 nm wavelengths). The VI-based models of PNA were established from a experimental dataset and then validated using an independent dataset. The N topdressing rates for tillering and jointing stages were calculated using the newly developed N spectral diagnosis model and higher yield cultivation experience of double-cropping rice. The results showed that the VIs from two spectrometers were strongly positively correlated with PNA at both growth stages, with the model performance for tillering or jointing stages was better than that for the early growth stages. The exponential equation of normalized difference vegetation index (NDVI(780,660)) from GreenSeeker could be used to estimate PNA with a determination coefficient (R2) in the range of 0.92-0.94, the root mean square error (RMSE), relative root mean square error (RRMSE) and correlation coefficient (r) of model validation in the range of 3.09-5.96 kg·hm-2, 5.8%-18.5% and 0.92-0.98, respectively. The linear equation of difference vegetation index (DVI(810,720)) from CGMD could be used to estimate PNA with a R2 in the range of 0.90-0.93, the RMSE, RRMSE and r of model validation in the range of 3.71-6.33 kg·hm-2, 11.7%-14.3% and 0.93-0.96, respectively. The recommended N topdressing rate with CGMD was higher than that with GreenSeeker. Compared with conventional farmer’s plan, the precision N application plan reduced N fertilizer application rate by 5.5 kg·hm-2, while N agronomic efficiency and net income was improved by 0.8% and 128 yuan·hm-2, respectively. Application of the spectral monitoring and diagnosis method to guiding fertilization could reduce cost and increase grain yield and net income, and thus had great potential for guiding double-cropping rice production.
    Differences of wheat yield and economic benefits between soybean-wheat and rice-wheat cropping under different nitrogen fertilization patterns in Jianghan Plain, China
    YANG Rui, GENG Shi-ying, WANG Xiao-yan
    2020, 31(2):  441-448.  doi:10.13287/j.1001-9332.202002.022
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    We analyzed winter wheat yield and growth pattern of soybean-wheat and rice-wheat rotation systems in response to different nitrogen fertilization patterns with the aim to provide theoretical basis for narrowing the wheat yield gap between the two rotations in Jianghan Plain. Field experiments were conducted with three treatments, control without nitrogen, traditional nitrogen management (70% nitrogen as basal and 30% nitrogen as topdressing at overwintering), and improved nitrogen management (one third of N was applied at sowing, wintering and jointing, respectively). The growth pattern, grain yield, yield components, fertilizer use-efficiency and economic benefit under the different nitrogen fertilization patterns were examined. Results showed that grain yield was significantly affected by both nitrogen fertilization pattern and crop rotation. Grain yield under improved nitrogen treatment was significantly higher, with the yield gap being 920 kg·hm-2 in soybean-wheat rotation and 2195 kg·hm-2 in rice-wheat rotation. Traditional nitrogen management showed advantage in establishing winter and spring population. Dry matter accumulation was higher under improved nitrogen treatment than traditional treatment with 5%-31% and 14%-28% increases for soybean-wheat and rice-wheat rotations, respectively. The higher yield in the soybean-wheat rotation was due to greater panicle numbers, higher percentage of tiller ears, and dry matter accumulation. The rice-wheat rotation under improved nitrogen showed a significant increase in grain yield compared with soybean-wheat rotation. This result indicated that yield gap between the two crop rotations could be narrowed through suitable nitrogen management. Grain weight after anthesis showed “slow-fast-medium” in soybean-wheat rotation and “medium-fast-slow” in rice-wheat rotation. Nitrogen use efficiency and net benefit of wheat season were higher in rice-wheat system. Overall, the rice-wheat system showed obvious advantages in population structure, dry matter accumulation, grain yield and benefit under improved nitrogen pattern, which was the optimum pattern for both wheat yield and benefit in Jianghan Plain.
    Effects of optimal nitrogen fertilizer management on water and fertilizer utilization efficiency and yield under double-ridge-furrow sowing with the whole plastic film mulching in maize in a semi-arid area
    WANG Hong-li, ZHANG Xu-cheng, YU Xian-feng, HOU Hui-zhi, FANG Yan-jie, MA Yi-fan
    2020, 31(2):  449-458.  doi:10.13287/j.1001-9332.202002.028
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    Improper fertilization style is one of the main reasons for low water and fertilizer use efficiency of double-ridge-furrow sowing with the whole plastic film mulching in maize production in the semi-arid area. Understanding the effects of reduction, postponing, and organic fertilizer substitution of nitrogen fertilizer on water and fertilizer use efficiency and yield of maize can provide theore-tical basis for effective management of water and fertilizer in maize production. Based on a 4-year field experiment with three treatments: all fertilizers as base fertilizer under double-ridge-furrow sowing with the whole plastic film mulching (CK), nitrogen fertilizer reduced by 15% and topdres-sing in tasseling stage (RN), 30% of the chemical fertilizer replaced by organic fertilizer and topdressing in tasseling stage (RNM), we measured water consumption characteristics, growth and development, water and fertilizer utilization efficiency of maize. The results showed that fertilization pattern significantly affected water and fertilizer utilization efficiency and yield of maize, which was dependent on annual rainfall. In dry and normal rainfall year, water consumption in pre-flowering stage of RN was decreased by 16.1%-18.8% and that in post-flowering stage was increased by 18.0%-22.2%, while water consumption in pre-flowering and post-flowering stages of RNM did not differ from that in CK. In wet year, water consumption in pre-flowering stage of RN and RNM was decreased by 16.7% and 6.3%, while that in post-flowering stage was increased by 11.4% and 29.7%, respectively. Compared with CK, RN significantly increased the relative content of chlorophyll (SPAD) of maize leaves after topdressing, the biomass in post-flowering stage was increased by 15.6%-44.9%, the ear length, the number and weight of grains per spike and the 100-grain weight were increased significantly, yield was increased by 9.8%-17.0%, and water use efficiency (WUE) was increased by 6.3%-21.4%, with the partial productivities of fertilizer (PEPT), N (PEPTN), P (PEPTP) and K (PEPTK) were all increased significantly. In conclusion, RN could improve water consumption and the SPAD value in post-flowering stage of maize in different precipitation years, increase post-flowering biomass, and optimize the ear character, obviously improve yield, water and fertilizer use efficiency. It was a effective fertilizer management mode with high-efficiency utilization of water and fertilizer under double-ridge-furrow sowing with the whole plastic film mulching in maize in the semi-arid area.
    Effects of tillage alternation pattern with subsoiling on soil physical and chemical properties and spring maize yield in the Loess Plateau, China
    ZHANG Qi, WANG Hao, WANG Shu-lan, ZHANG Yuan-hong, WANG Rui, WANG Xiao-li, LI Jun
    2020, 31(2):  459-466.  doi:10.13287/j.1001-9332.202002.024
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    Straw mulching and subsoiling can protect soil and improve soil structure. However, long-term continuous subsoiling cannot continuously gain yield increasing and soil improvement. To realize continuous soil improvement and yield enhancement, a long-term experiment on subsoiling alternation patterns was carried out with spring maize continuous cropping in the Loess Plateau in 2007-2016. The subsoiling alternation patterns were no-tillage/conventional tillage/subsoiling (NT/CT/ST) and subsoiling/conventional tillage (ST/CT), with continuous subsoiling (ST) as control. We analyzed the effects of the different patterns on soil physical and chemical properties and maize yield. The results showed that, compared with the ST, the mechanical-stable aggregates (DR0.25) and water-stable aggregates (WR0.25) in NT/CT/ST were significantly increased by 9.2% and 21.9%, with the mean weight diameter (MWD) and geometrical mean diameter (GMD) being significantly increased. The WR0.25 in ST/CT was significantly increased by 11.9%. In 0-20 cm soil layer, soil bulk density in NT/CT/ST and ST/CT decreased by 7.0% and 11.5%, and soil porosity increased by 8.4% and 13.9%, respectively. In 20-40 cm soil layer, soil bulk density in ST/CT increased by 6.9%, and soil porosity decreased by 5.7%. In the NT/CT/ST, soil total nitrogen and organic matter contents significantly increased, but soil total phosphorus and total potassium contents reduced. The multi-year average grain yield of spring maize in NT/CT/ST was 10.2% higher than ST and 4.8% higher than ST/CT. The DR0.25, WR0.25, soil total nitrogen content and soil organic carbon content were all positively correlated with maize yield, indicating such changes faci-litated corn grain yield. Considering the effects on soil fertility and corn yield, the NT/CT/ST model was conducive to soil fertility, soil structural stability and higher maize yield.
    Responses of soil respiration to temperature under different mulching modes in a dryland corn field
    XIE Meng-yi, SHANG Yu-qing, ZHAO Fa-zhu, WANG Jun
    2020, 31(2):  467-473.  doi:10.13287/j.1001-9332.202002.021
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    Based on a 9-year field experiment, soil samples under straw mulching (SM), plastic film mulching (FM) and no mulching (CK) were incubated at 15, 25 and 35 ℃ for 60 d to investigate the responses of soil respiration to warming and its temperature sensitivity. The results showed that during the whole incubation period, soil respiration rate exhibited a unimodal distribution, while the cumulative soil respiration increased with an “S” curve. The cumulative soil respiration during the first 30 d accounted for about 75%-85% of total during the whole incubation period. The cumulative SM increased by 19.4% compared with CK, whereas no difference was detected between CK and FM. At 25 ℃ and 35 ℃, the mean soil respiration rate increased by 17.0% and 36.8%, and the cumulative CO2 release of soil respiration increased by 13.1% and 33.6%, respectively, compared with 15 ℃. No interaction was detected between mulching method and temperature. 97.7%-99.9% of variation in soil respiration could be explained by temperature change, with soil respiration being positively correlated with organic carbon and total nitrogen content. Compared with no mulching and plastic film mulching, straw mulching could significantly promote soil respiration by increasing the input of organic matter in the soil, but reduced the temperature sensitivity of soil respiration. Straw mulching rather than plastic film mulching would be more efficient at reducing CO2 emission in the Loess Plateau dryland farming area under the context of global warming.
    Remote sensing retrieval of maize residue cover on soil heterogeneous background
    HUANG Jin-yu, LIU Zhong, WAN Wei, LIU Zhi-yu, WANG Jia-ying, WANG Si
    2020, 31(2):  474-482.  doi:10.13287/j.1001-9332.202002.012
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    Maize stalk mulching is a conservation tillage method that has been currently promoted in northeastern China Plain. Remote sensing estimation of regional crop residue cover (CRC) can quickly obtain the information of straw mulching in a large area, which plays an important role in monitoring and popularizing the work of straw mulching. In this study, the normalized difference til-lage index (NDTI), simple tillage index (STI), normalized difference residue index (NDRI), and normalized difference index 7 (NDI7) were extracted from Sentinel-2A image and used to establish a linear regression model for CRC and spectral indices in Lishu County of Jilin Province. The results showed that soils had strong spatial heterogeneity in the study area, which would lead to a significant impact on the spectral index regression model. Using soil texture classification (zoning) to establish regression model could improve the inversion accuracy. Soil spatial heterogeneity would increase the estimation error of the model. The four spectral indices had a strong correlation with CRC, among which the NDTI and STI models performed better. The zonal linear regression model based on NDTI and STI verified that R2 was 0.84 and RMSE was 13.3%, which was better than the non-zonal model (R2 was 0.75 and RMSE was 16.5%) and thus effectively improved the inversion accuracy.
    Optimization of mulched drip irrigation amount for peanut based on AHC model in northwestern Liaoning, China
    HUANG Zhen-yu, XIA Gui-min, HU Jia-qi, CHEN Tao-tao, ZHENG Jun-lin, WU Qi, CHI Dao-cai, WANG Feng
    2020, 31(2):  483-492.  doi:10.13287/j.1001-9332.202002.013
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    To evaluate the applicability of AHC (agro-hydrological & chemical and crop systems simulator) model and explore the suitable irrigation amount for peanut (Arachis hypogaea) under mulched drip irrigation in the semi-arid areas of northwestern Liaoning Province, based on the two-year field experimental data of peanut in 2016 and 2017, the model parameters were firstly chosen for global sensitivity analysis. Then, module parameters of soil moisture and crop growth were calibrated and validated. Finally, AHC model was used to analyze the responses of peanut yield and water use efficiency (WUE) to different irrigation amounts. The results showed that the two extremely sensitive parameters of the model were saturated hydraulic conductivity in the first and second layers of soil. Root mean square error (RMSE) and mean relative error (MRE) between simulated and measured values of soil water content ranged from 0.02 to 0.03 cm3·cm-3 and 1.5% to 2.3%, respectively. The RMSE and MRE of leaf area index and plant height were 0.3-0.6, 4.2-4.5 cm, and 5.0%-8.9%, 5.2%-6.8%, respectively. The MRE of peanut yield and water consumption were both within 5%, indicating that the model was suitable for simulating soil moisture and peanut growth in the northwest Liaoning Province. With the increases of irrigation amounts, peanut yield increased and water use efficiency decreased. Considering both peanut yield and WUE, we recommend that the optimal mulched drip irrigation amounts for peanut in the semi-arid areas of Northwestern Liaoning in test year (normal year) was 80-97 mm.
    Effects of irrigation lower limit and straw returning amount on yield, quality and water use efficiency of greenhouse tomato
    LI Bo, BAO Zheng-rong, YAO Ming-ze, LI Chang-xin, SUN Xiang-long
    2020, 31(2):  493-500.  doi:10.13287/j.1001-9332.202002.030
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    A split plot experiment was conducted in greenhouse to investigate the effects of irrigation lower limit and maize straw returning on the yield, quality, and water use efficiency (WUE) of tomato. Maize straw was applied for 1 (2018, A1), 2(2017, A2), and 3 (2016, A3) years at different amounts (0, 1.5×104, 3×104, 4.5×104 kg·hm-2) and different irrigation lower limits (50%θf, 60%θf, 70%θf, 80%θf, θf was the field water capacity). Variance analysis, entropy-weight and TOPSIS methods were used to examine the responses of yield, quality and water use efficiency (WUE) of tomato. The results showed that tomato yield was enhanced by the increases of irrigation lower limit. The maximum value of yield was observed in the 80%θf treatments, with the maximum average yield of 93.55 t·hm-2 in A1, 87.23 t·hm-2 in A2, and 99.34 t·hm-2 in A3, respectively. WUE and quality of tomato decreased with increasing irrigation lower limit. In the first year of straw returning, the maximum average yield of tomato was 99.60 t·hm-2 in straw returning 1.5×104 kg·hm-2 . In the second and third years, 4.5×104 kg·hm-2 straw returning had the highest average yield of tomato, which was 92.50 and 107.75 t·hm-2, respectively. The maximum WUE was observed with the straw returning of 1.5×104 kg·hm-2 in A1 and A2, while in the A3 treatment it happened in straw returning of 4.5×104 kg·hm-2. The quality index of tomato showed different trends with the increases of straw returning years and amount.
    Effects of environmental conditions on absorption and distribution of silicon and formation of bloom on fruit surface of cucumber
    ZHOU Xin, FENG Gai-li, LI Zhi-hong, LIU Shu-xia, ZHAO Sheng, LI Yan, WEI Min
    2020, 31(2):  501-507.  doi:10.13287/j.1001-9332.202002.023
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    To elucidate the mechanism of bloom formation on fruit surface of cucumber, we investigated silicon absorption and bloom formation on fruit surface of cucumber with ‘Shannong No. 5’ (Cucumis sativus) as scion, ‘Yunnan figleaf gourd’ (Cucurbita ficifolia, weak de-blooming ability) and ‘Huangchenggen No. 2’ (C. moschata, strong de-blooming ability) as rootstocks in solar greenhouse at winter-spring and autumn-winter growing seasons. Experimental conditions inclu-ded: T1 with temperature 28 ℃/18 ℃ (day/night), relative humidity 55%/65%, photosynthetic photon flux density 600 μmol·m-2·s-1, and T2 with temperature 22 ℃/12 ℃ (day/night), relative humidity 85%/95%, photosynthetic photon flux density 300 μmol·m-2·s-1. We examined environmental effects on silicon absorption and expression of silicon transporter genes in. The amount of bloom on cucumber fruit surface at winter-spring growing season dramatically increased compared with autumn-winter season. ‘Yunnan figleaf gourd’ grafted cucumber was more heavily affected by the cultivation season than self-rooted and ‘Huangchenggen No. 2’ grafted cucumber. In the same cultivation season, ‘Yunnan figleaf gourd’ grafted cucumber had the highest amount of bloom on fruit surface and silicon content, while own-rooted and ‘Huangchenggen No. 2’ grafted cucumber had the medium and least amount of bloom and silicon content. Silicon content in each organ and expression of silicon transporter genes in cucumber leaves and roots under T1 environment were significantly increased compared with T2. ‘Yunnan figleaf gourd’ grafted cucumber had the highest contents of silicon in each organ and expression of silicon transporter genes in leaves in the same environment, followed by own-rooted and ‘Huangchenggen No. 2’ grafted cucumber. In conclusion, environmental conditions affect absorption and allocation of silicon in cucumber plants, with conseuqnece on bloom formation on fruit surface. Suitable environmental conditions, including temperature, humidity and light, are beneficial to reduce the bloom formation on cucumber fruit surface. High temperature, strong light, and low humidity will increase bloom amount on cucumber fruit. Rootstocks have significant effects on silicon absorption and fruit bloom formation of grafted cucumber.
    Effects of root abscisic acid on Na+ transport and photosystem Ⅱ in Helianthus tuberosus under salt stress
    BIAN Tian-tian, YAN Kun, HAN Guang-xuan, AN Meng-xin, YANG Run-ya
    2020, 31(2):  508-514.  doi:10.13287/j.1001-9332.202002.005
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    The effects of root abscisic acid (ABA) signal on Na+ transport and photosystem Ⅱ (PSⅡ) in Jerusalem artichoke (Helianthus tuberosus) under salt stress (150 mmol·L-1 NaCl) were examined by applying ABA synthesis inhibitor sodium tungstate to roots. Sodium tungstate inhibited ABA synthesis in roots, reduced root Na+ efflux, and increased the efficiency of Na+ transport from roots to leaves under salt stress. Salt stress increased leaf Na+ content and did not affect leaf membrane lipid peroxidation, PSⅡ reaction center protein and PSⅡ maximum photochemical efficiency (Fv/Fm ). The inhibition on root ABA synthesis significantly increased leaf Na+ accumulation, aggravated leaf membrane lipid peroxidation, impaired PSⅡ reaction center protein, decreased Fv/Fm, and induced PSⅡ photoinhibition. In conclusion, root ABA signal was beneficial to reducing leaf Na+ accumulation and preventing PSⅡ oxidative damage by inducing root Na+ efflux and inhibiting Na+ transport to the aerial part in H. tuberosus under salt stress.
    Effects of fertilizer application on yield and fertilizer utilization of Coffea arabica in southwest dry-hot region of China under different shading levels
    ZHANG Yu-yang, LIU Xiao-gang, YU Ning, ZHAO Zhi-hao, YANG Qi-liang, GAO Yan-li, FAN Cheng, DONG Jian-hua
    2020, 31(2):  515-523.  doi:10.13287/j.1001-9332.202002.004
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    The fertilizer and shading management of Coffea arabica in dry-hot area is extensive, resulting in lower yield and fertilizer utilization efficiency. A field experiment was carried out to find the coupling mode of shading and fertilizer for fertilizer-saving and high yield of C. arabica in dry-hot region. Four shading levels (100% NR, 75% NR, 60% NR, 45% NR, NR was natural radiation) and four fertilizer levels (No fertilization and 666.67, 1000, 1333.33 kg·hm-2) were set to examine the effects of different radiations and fertilizer treatments on canopy structure, yield, ferti-lizer use efficiency, soil nutrient content and microbial biomass carbon of C. arabica. The results showed that canopy structure, yield, fertilizer use efficiency, soil nutrient content and microbial biomass carbon were significantly affected by shading and fertilizer treatments. Soil nutrient content and microbial biomass carbon decreased with the increases of shading levels. Soil nutrient content increased with the increases of fertilizer application, while microbial biomass carbon increased first and then decreased, with a peak at the rate of 1000 kg·hm-2(200.30 mg·kg-1). Shading and fertilizer had significant effects on the canopy structure including leaf area index and openness. There were significant negative correlations of leaf area index with openness, gap fraction, total fixed-point factor and total radiation under canopy. Results of response surface analysis and spatial analysis showed that the combination of shading level and fertilizer application were 80% NR and 666.67 kg·hm-2, 79% NR and 1286.81 kg·hm-2, 79% NR and 967.74 kg·hm-2, 82% NR and 1075.27 kg·hm-2, respectively, when partial fertilizer productivity, yield, fertilizer agronomic efficiency and yield increase of fertilizer reached the maximum. The ranges of shading and fertilizer were 68%-77% NR and 946.24-1178.79 kg·hm-2 when the yield, agronomic efficiency and yield increasing rate by fertilizer reached 80% of the maximum value. In this experiment, the optimum combination of shading level and fertilizer application was 75% NR and 1000 kg·hm-2.
    Effects of glyphosate and paraquat on root morphology and aboveground growth of Prunus persica seedlings
    GUO Lei, ZHANG Bin-bin, SHEN Jiang-hai, HE Xin, SONG Hong-feng
    2020, 31(2):  524-532.  doi:10.13287/j.1001-9332.202002.036
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    To ascertain the safety of herbicides in peach production, we examined the effects of two herbicides (glyphosate and paraquat) on vegetative growth, root structure, root-tip cell mitosis and photosynthesis in rootstock Prunus persica seedlings. The results showed that the growth of both shoot and root of the P. persica seedlings was significantly inhibited under the glyphosate treatment. Compared with the control, plant height decreased by 31.5%, total root length, root surface area, root volume and the number of root tips decreased by 39.5%, 39.5%, 49.8% and 44.6%, respectively. The paraquat treatment had no significant differences compared with the control. The mitotic index of root tip cells decreased by 38.0% and 35.9% under both herbicide treatments, respectively. The proportion of cells at metaphase against the total number of mitotic cells in the root tips was significantly reduced by glyphosate treatment compared with the control and the paraquat treatment. Root tip cells of peach were sensitive to both kinds of herbicides. The leakage of electrolytes from the cells in root tips was significantly higher than that of the control from the second day to the thirtieth day after treatments. After five days of glyphosate treatment, electrolyte leakage rate of leaves was raised, the bases of young leaves turned yellow, and spread to leaf tips, parts of which ultimately withered. Net photosynthetic rate, stomatal conductance, and transpiration rate were reduced more strongly under the glyphosate treatment than the paraquat treatment. In conclusion, both kinds of herbicides reduced cell mitotic index of root tip cells and leaf net photosynthetic rate, increased the electrolyte leakage rate of the root tip cells in P. persica seedlings. Glyphosate had a greater effect on vegetative growth and leaf photosynthesis, which could cause young leaves yellowing and leaf tips scorching.
    Assessing fractional vegetation cover changes and ecological quality of the Wuyi Mountain National Nature Reserve based on remote sensing spatial information
    YANG Hui-ting, XU Han-qiu
    2020, 31(2):  533-542.  doi:10.13287/j.1001-9332.202002.014
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    The Wuyi Mountain National Nature Reserve (WYS), established in 1979, is the largest and most intact subtropical forest ecosystem in southeastern China. No study has assessed the vegetation coverage change along with its ecological effect after the protection of the reserve for almost 40 years. In this study, the NDVI data of Landsat Image was corrected using the NDVI data of MODIS, the fractional vegetation cover (FVC) and the remote sensing based ecological index (RSEI) were calculated to assess the change of FVC and ecological quality in WYS with five Landsat images representing a period from 1979 to 2017. The results showed that after protection for nearly 40 years the FVC of the reserve had been significantly increased from 73.6% in 1979 to 89.5% in 2017, which consequently improved ecological quality from 0.801 in 1988 to 0.823 in 2017. In 2017, the area with the good and excellent ecological quality grades accounted for 98.7% of the total. Spatially, the ecologically-improved areas mainly distributed in the northeast core area and the center of the southwest core area. The ecologically-declined areas mostly occurred along roadsides and peaks. Vertically, the highest FVC and ecological quality areas distributed in the elevations between 1300-1900 m. In general, the improvement of FVC and ecological quality in the Wuyi Mountain National Nature Reserve was due largely to the effective policies and the successful protection by local government and people, except for some special year that may be affected mainly by climate conditions.
    Spatial-temporal evolution pattern and terrain gradient differentiation of ecosystem service value in Zhangye, Northwest China at the grid scale
    ZHANG Xue-bin, LUO Jun, SHI Pei-ji, ZHOU Liang
    2020, 31(2):  543-553.  doi:10.13287/j.1001-9332.202002.007
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    Zhangye serves as a good case for studying ecological services because of its fragile ecological environment and its ecological importance. Using land use data from 1987, 2000 and 2016 as well as the modified ecosystem service value (ESV) equivalent, the ESV was estimated and its spatial and temporal changes and gradient differentiation characteristics were analyzed by dividing the studied region into a grid of 3 km×3 km in size. The results showed that from 1987 to 2016, the ESV in Zhangye increased by 564 million Yuan, with the mountainous areas in the south and the desert areas in the north being stable. The ESV of central oasis areas with concentrated human acti-vities significantly changed. Forests contributed to most of the ESVs. Water regulation value was the strongest among all the individual ESVs. The ESV showed strong spatial dependence. Based on the spatial pattern of the two aggregated poles, it shaped three “flower arrangement” clusters, including Ganzhou District, Yanzhi Mountain, and Jingtie Mountain. The ESV distribution showed a topographic differentiation as the value decreased from the Qilian Mountains to the plain oasis, and further to the desert areas. The linear correlation of the terrain and the ESV was negative. As the increasing elevation gradient, the ESV showed a “decreased-increased-decreased” trend, while and it had a “decreased-stable-decreased” in the increasing slope gradient. Overall, the ESV presented two turning zones on the terrain gradient, indicating that both the piedmont zone and the oasis desert transition zone acted as transition zones of the ESV. Areas with the strongest ESV were distributed in the low slope and low terrain relief zones, and the development of oases in flat terrain areas were strongly constrained by water resources.
    Dependence of farmers’ livelihoods on environmental resource in key ecological function area: A case study of Gannan Plateau, China
    WANG Rong, ZHAO Xue-yan, LIU Jiang-hua, WANG Xiao-qi, LAN Hai-xia, XUE Bing
    2020, 31(2):  554-562.  doi:10.13287/j.1001-9332.202002.016
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    The key ecological function area plays an important role in providing ecosystem service. As the main players of economic activities in this area, the excessive dependence of local farmers on environmental resource will seriously influence ecological environment quality, and thus impair the ecosystem service. At present, it is urgent to explore the dependence of farmers’ livelihoods on environmental resource and its influencing factors in key ecological function areas, which would provide reference for the formulation of environmental friendly regional development policies. We selected the Gannan Plateau as study area. Based on 581 survey data, we analyzed the dependence of farmers’ livelihood on environmental resource, and used the ordinal multi-class Logistic regression model to identify its key impact factors. The results showed that local farmers were highly dependent on environmental resource in Gannan Plateau, which was mainly reflected in three aspects of food self-sufficiency, daily energy consumption and income source, with the dependence of 57.3%, 56.9% and 37.4%, respectively. There were significant differences in the dependence of different types of farmers’ livelihoods on environmental resource, in that farmers with higher levels of education and higher non-agricultural levels had lower dependence and the farmers with high dependency ratio were more dependent on environmental resources. The factors including family dependency ratio, labor education level, proportion of migrant workers in labor force, family member leadership, ecological policy, and altitude had significant impact on farmers’ environmental resource dependence. Among them, family dependency ratio and altitude had positive impact on it, while the proportion of migrant workers in labor force, labor education level, family member leadership, ecological policy had negative impact.
    Regional environment, family’s endowment and straw disposal behavior: A case study of dry farming areas in Gansu Province, China
    CHEN Qiang-qiang, YANG Qing, YE De-ming
    2020, 31(2):  563-572.  doi:10.13287/j.1001-9332.202002.001
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    Understanding the treatment and influencing factors of straw is important to improve the utilization efficiency of straw resources and alleviate the negative external effects of the environment. Here, we proposed an analysis framework of farmers’ straw disposal behavior based on ecological rationality. The Logit model was used to analyze the farmers’ willingness and influencing factors for the selection of straw burning and feed utilization with a dataset of 424 valid questionnaires in dry farming areas of Gansu Province. The results showed that the straw disposal behavior of farmers was the result of decision-making cognition formed in the process of long-term adaptation and co-evolution between farmers and the surrounding environment. In dry farming area, the straw treatment methods were diversified, with feed utilization and fuel as the two main forms and straw incineration and discard being ubiquitous. Among the factors that affect farmers’ straw burning behavior, householder age (P<0.1), education level (P<0.01), the scale of livestock raising (P<0.05), the proportion of agricultural income (P<0.1), and government policy propaganda (P<0.01) had significant inhibitory effect. The gender of householder (P<0.1) and cognition level (P<0.01) helped farmers to choose the non-pro-environmental behavior, and the environmental awareness of farmers was weak. In terms of straw feed utilization behavior, householder age (P<0.1), education level (P<0.05), the situation of family members serving as village cadres (P<0.05), feed proces-sing technical guidance (P<0.01) and subsidy for prohibition of straw burning (P<0.1) had positive effect on straw forage utilization, while the topography (P<0.1) had a negative effect. Some policy recommendations were given to promote utilization of straw resources: constructing a combination mechanism of “prohibition of burning and subsidies”, strengthening the extension of straw feed utilization technology, and accelerating the improvement of straw collection-store-transportation service system.
    Spatiotemporal variability characteristics and driving forces of land use in the Pan-Pearl River Basin, China
    ZHANG Shi-xiao, ZHANG Jun-mao, ZHANG Wen-kang, ZHANG Dan-ni, FU Jia-yi, ZANG Chuan-fu
    2020, 31(2):  573-580.  doi:10.13287/j.1001-9332.202002.017
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    The Pan-Pearl River Basin is a bridgehead for China’s reform and opening-up and the construction of the Belt and Road at Sea, with vital strategic significance in Chinese overall development. Land use data and climate and socio-economic indicators were integrated to probe the spatiotemporal change and its driving forces of land use in the Pan-Pearl River basin with ArcGIS spatial analysis tool and SPSS factor analysis tool. Results showed that land use in the Pan-Pearl River Basin significantly changed between 1990 and 2015, with decreases of the area of paddy field and woodland and rapid increases of urban land and other construction land. Outflow of grassland occurred in the northwestern part of the basin. Reduction of cultivated field was mainly concentrated in the central part of the basin and coastal areas. Increases in urban and rural land, industrial and mining land, and residential land were centrally distributed in the Guangdong-Hong Kong-Marco Greater Bay Area. The prominent change areas were Guangdong-Hong Kong-Marco Greater Bay Area > central and southeast of Guangxi Province > northern Hainan Province. Land use changes during 1990-2000 were most obvious in the basin. The main driving factor of spatiotemporal variation of land use was the rapid development of social economy and industry and the improvement of residents’ consumption level.
    A river stretch scale assessment of urban river habitat in the Taihu Lake Basin
    ZENG Peng, WANG Yu-kun, LIU Yao-yi, WANG Hua-xiang, CHEN Shi-quan, CHE Yue
    2020, 31(2):  581-589.  doi:10.13287/j.1001-9332.202002.006
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    Under the background of rapid urbanization, the degradation of urban river water environment and ecological function in the Taihu Lake Basin has become increasingly prominent. Consequently, it is particularly important to systematically assess urban river habitat. This study referred to and corrected the British Urban River Survey evaluation system. Based on the characte-ristics of urban rivers in the Taihu Lake Basin, we established the evaluation system of stretch habitat quality index (SHQI) of urban river stretches and analyzed the urban river habitat status and spatial variation in the Taihu Lake Basin. The results showed that the SHQI values of the 50 river stretches ranged between 8 and 21, with 3 river stretches classified as “excellent” habitat level, 6 as “good”, 27 as “moderate”, 9 as “poor”, and 5 as “very poor”. The vegetation index in urban river habitats in the Taihu Lake Basin was good, whereas that of the physical habitat and material index were bad. The overall ranking of habitats was Zhenjiang> Huzhou> Hangzhou> Jiaxing> Suzhou> Wuxi> Changzhou. There were significant differences in physical habitats, material indices and pollution indices among different cities. The main stream and the tributary section significantly differed in the material index and pollution index, but not significant for SHQI. The evaluation system constructed in this study reflected the current situation of urban river habitats in the Taihu Lake Basin, and could provide guidance for ecological restoration of urban rivers.
    Variation trend and the influencing factors of runoff and sediment flux in the Mun River Basin, Thailand
    LI Chao-yue, FANG Hai-yan
    2020, 31(2):  590-598.  doi:10.13287/j.1001-9332.202002.011
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    The variations of runoff and sediment flux are important factors influencing the socioeconomic development of Thailand. Based on the dataset of runoff and sediment flux during 1980-2014 at the Ubon hydrological station in the lower Mun River, a tributary of the Mekong River, the temporal variations of runoff and sediment flux were analyzed with the linear regression method, Mann-Kendall test, and wavelet transform method. The driving forces for the variations of runoff and sediment flux were discussed. The results showed that annual runoff in the Mun River basin increased slightly, while the sediment flux presented a decreasing trend. The changes of sediment flux and runoff were consistent before 2000. However, the sediment flux significantly decreased after 2000. During the study period, both the runoff and sediment flux during the flood seasons showed decrease trend. The abrupt change points of runoff and sediment flux did not occur in the same year, which were in 1999, 2006 and 2011 for runoff and in 1986, 1999 and 2011 for sediment, respectively. The main cycles of runoff amount were 14, 8 and 4 years, respectively, while those of sediment flux were 32, 12, 9 and 4 years, respectively. Except for the 32-year cycle of sediment flux, the main cycles of runoff and sediment flux were almost similar and both were mainly related to the Southern Oscillation, polar movement, sunspot activity, and other factors. There was a significant correlation between monthly runoff and sediment flux. Sea-air interaction and human activity were important factors influencing runoff and sediment flux in the Mun River basin. El Nino and La Nina were closely related to rainfall which in turn affected the runoff and sediment flux in the basin. Since 2000, the construction area increased and the forest area decreased, which increased the runoff in the basin, while the reservoirs and other engineering measures reduced the runoff and sediment flux, and thus offset the impact of decreased forest lands on sediment flux.
    Spatial variability and agglomeration of soil salinity in Minjiang estuary wetland, Southeast China
    CHEN Si-ming, WANG Ning, ZHANG Hong-yue, QIN Yan-fang, ZOU Shuang-quan
    2020, 31(2):  599-607.  doi:10.13287/j.1001-9332.202002.037
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    Understanding the spatial variability and agglomeration of soil salinity is of great significance for the sustainable development of estuarine wetland. Landsat 8 OLI remote sensing image, digital elevation mode and soil surface samples of Minjiang estuary wetland of Fuzhou were used as the data sources. The correlation analysis and principal component analysis were combined to select significant environmental variables and to reduce their dimensions. We analyzed the spatial variability of soil salinity with support vector regression ordinary kriging model (SVROK) and regression kri-ging model (RK), and quantified spatial agglomeration of soil salinity by the spatial autocorrelation analysis. The results showed that three principal components (PCs) extracted by the principal component analysis could explain at least 85% of the total variance in the original dataset and reflected the comprehensive information of vegetation cover, soil properties and topography. Both soil salinity and its residuals were affected by structural factors and random factors. The SVROK model based on principal component (PCs) as input variables can more accurately reflect the spatial variability of soil salinity, with a trend of “higher in the north and lower in the south”. The Moran’s I of soil salinity was more than 0.5, with significant positive spatial autocorrelation and a higher spatial aggregation degree, displaying the spatial agglomeration characteristics of “high value agglomeration, high value widespread, high value surrounded by low value”.
    Remediation performance and mechanism of aquatic plants for iron polluted water
    CHU Shu-yi, JING Chuang-xin, ZHANG Xia-ying, HUANG Zhi-da, XIAO Ji-bo
    2020, 31(2):  608-614.  doi:10.13287/j.1001-9332.202002.025
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    To solve the yellow colorization in water caused by iron ion, we evaluated the remediation performances of six aquatic plant species (Hygroryza aristata, Myriophyllum verticillatum, Hydrocotyle verticillata, Jussiaea stipulacea, Pistia stratiotes and Rotala rotundifolia) using hydroponic experiment. Effects of iron concentration, pH, plant biomass on iron removal were investigated, and the intensification of removing iron incurred by aeration was also discussed. Results showed that all the examined plant species could improve both divalent iron and total iron removal, but with significant difference in their performance. Divalent iron concentrations were decreased by H. aristata and H. verticillata from 5.0 mg·L-1 to 0.23 and 0.26 mg·L-1 within 24 h, respectively, meeting the standard of supplementary items for the drinking water and surface water sources (divalent iron concentration ≤0.3 mg·L-1), while total iron concentrations declined to 0.84 and 1.21 mg·L-1 with removal efficiency of 83.2% and 75.8%, respectively. Concentrations of divalent iron and total iron of plant treatment plots at pH 5, 6, 7, 8 were not significantly different, with removal efficiency of divalent iron and total iron being among 95.4%-98.4% and 92.2%-94.6%, separately. When initial divalent iron concentration was less than 5.0 mg·L-1, removal efficiency of divalent iron and total iron increased with the increases of divalent iron concentration. The growth of H. aristata was inhibited at divalent iron concentration of 10.0 mg·L-1. Total iron removal was not stable during the trial. Removal efficiency of plant treatment rose only by 7.0% compared with the control, which was much lower than other concentration treatments. The divalent iron concentration was decreased to < 0.3 mg·L-1 in 24 h at plant biomass >300 g, with no difference of removal efficiency among biomass treatments. Both intermittent and continuous aeration enhanced iron removal by H. aristata, but continuous aeration was more favorable for the removal of total iron due to stabilization.
    Effects of exogenous arsenic stress on bacterial and archaeal communities in two types of soils
    WANG Ya-nan, ZHAO Jing, YANG Xiao-dong, ZENG Xi-bai
    2020, 31(2):  615-624.  doi:10.13287/j.1001-9332.202002.031
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    Mining, smelting and other activities result in arsenic accumulation in soils, with adverse impacts on the quality and safety of agricultural products and soil microorganisms. We monitored the changes of available arsenic content with incubation time after the addition of exogenous arsenic to the yellow soil (YS) and soil derived from purple sandy shale (RS). The community changes of bacteria and archaea in soils without spiked arsenic and soils after 1, 30 and 360 days of exogenous arsenic stress were measured by MiSeq high-throughput sequencing, to investigate the community adaptative mechanism of bacteria and archaea in soil under arsenic stress. Results showed that the available arsenic content in soils decreased gradually with time, which significantly affected the composition of soil bacteria and archaea community. The abundance of dominant bacterial group changed significantly, whereas only archaea with lower abundance changed obviously, and little change occurred in dominant archaea group, indicating that archaea community had high arsenic tolerance and stability. Compared with the arsenic stress time, soil arsenic availability had greater impacts on community structures of bacteria and archaea. The results could provide refe-rences for safe utilization and microbial remediation of arsenic-contaminated cropland.
    Symbiotic bacteria facilitate algal growth and oil biosynthesis in Scenedesmus obliquus
    DUAN Lu-lu, CHEN Wei-lan, ZHANG Jing-jie, MA Hao-tian, JI Chun-li, CUI Hong-li, WANG Ji-ping, LI Run-zhi
    2020, 31(2):  625-633.  doi:10.13287/j.1001-9332.202002.034
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    We isolated bacteria from the phycosphere of Scenedesmus obliques and sequenced 16S rDNAs to establish algae-bacterial co-culture systems. Further, we examined effects of the bacteria on algal growth, and parameters associated with physio-biochemical and oil-producing characteristics of S. obliquus. Seven bacterial strains were isolated, including Micrococcus (strains 1-1, 1-2 and 1-3), Pseudomonas sp. (strains 2-1 and 2-2), Exiguobacterium (strain-3) and Staphylococcus sp. (strain-4). Among them, two bacteria (strain 1-2 and strain 2-1) were characterized as the dominant growth-promoting bacterial strains, which significantly increased algal growth, pigment production, and oil enrichment. After eight days cultivation under microalgal-bacterial (strain 1-2) symbiotic systemat at an initial ratio of 1:10, biomass of S. obliquus was 4.27 g·L-1, about 46.0% higher than that of the control. The contents of chlorophyll a, chlorophyll b and carotenoids were increased by 12.1%, 16.7% and 25.0%, respectively. Oil content was increased by 14.0% and reached to 25.7%, and the oleic acid content was significantly higher than that of the control and up to 16.4%. When co-cultured with Pseudomonas sp. (strain 2-1) for eight days at an initial ratio of 1:5, algal biomass, chlorophyll a, chlorophyll b and carotenoids contents were higher than that of the control by 47.9%, 16.0%, 17.5% and 19.9%, respectively. The total oil (27.1%) and oleic acid (18.2%) contents were increased by 20.4% and 64.0%, respectively. We concluded that Micrococcus (strain 1-2) and Pseudomonas sp. (strain 2-1) could significantly promote algal growth and increase oil production by their beneficial interaction with S. obliques, which could be potentially used in commercial production of S. obliques.
    Genetic diversity and genetic structure of Sorex isodon in Northeast China
    LIU Zhu, WANG Qing-qing, BAI Wei, LI Bo-qi, TIAN Xin-min, LI Dian-wei, ZHANG Jun-sheng
    2020, 31(2):  634-642.  doi:10.13287/j.1001-9332.202002.038
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    A total of 64 haplotypes were obtained from the complete Cytochrome b gene (Cyt b) of 77 Sorex isodon collected from three populations (Daxing’anling, Xiaoxing’anling, and Changbai Mountains) in Northeast China. The haplotype diversity was 0.9920 and the nucleotide diversity was 0.0105, indicating high genetic diversity. The genetic diversity of Changbai Mountains population was significantly higher than that of Daxing’anling and Xiaoxing’anling populations. The F-statistics, the number of migrants per generation and the genetic distance results showed that the genetic distances among the populations and among the sampling sites were generally consistent with geographical distance. Analysis of molecular variance showed that the differentiation among populations, among sampling sites, and within sampling site accounted for 33.4%, 10.2% and 56.4% of total variation, respectively. The analysis of population history showed that S. isodon in Northeast China experienced no population expansion. The reported complete sequence of Cyt b gene of S. isodon (GenBank) of Europe and other parts of Asia was downloaded to examine the genetic structure of S. isodon. The phylogenetic tree was divided into two large branches. One branch consisted mainly of Daxing’anling and Xiaoxing’anling samples. The other branch was departed into two sub-branches. Median-joining network analysis showed that there were three lineages: one lineage mainly consisted of haplotypes from Daxing’anling and Xiaoxing’anling, and also four haplotypes of Changbai Mountains, while the other lineage included a few haplotypes of three populations in Northeast China, and those from Baikal Lake, Russia and Finland. The last lineage was entirely composed of haplotypes from Changbai Mountains. The results of genetic diversity, phylogenetic tree and median-joining network all suggested that the Changbai Mountains was the refuge for S. isodon during last glacial.
    Spider diversity and community characteristics in cropland and two kinds of recovery habitats in Bashang area, China
    HU Wen-hao, DUAN Mei-chun, NA Shu-hao, ZHANG Feng, YU Zhen-rong
    2020, 31(2):  643-650.  doi:10.13287/j.1001-9332.202002.020
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    Spiders are important natural enemies in agricultural ecosystems. The biodiversity and community characteristics of spider directly determine the quality of ecosystem services such as pest control in cropland. Cropland and its surrounding recovery habitats are important for spiders. We used trap method to examine species composition, species diversity, and functional characteristics of spider communities at three altitudes (871, 1360 and 1635 m) and three habitats (cropland, natural recovery grassland, artificial restoration woodland) in Chongli District, Zhangjiakou, Hebei Province, China. The results showed that diversity index of different habitats was significantly diffe-rent. The abundance of spiders in artificial restoration woodland was 124.3, which was significantly higher than that in natural recovery grassland (70.1) and cropland (38.6). Species richness of artificial restoration woodland (16.3) and natural recovery grassland (21.4) were not significantly different, but both were significantly higher than those of cropland (8.9). The Shannon diversity index of artificial restoration woodland (2.04) and natural recovery grassland (2.05) was not significantly different, and both were significantly higher than that of cropland (1.55). There were significant differences in community composition among all three habitats. Spider body length was positively correlated with spider hunting types. Large spiders tended to get food by hunting. Natural recovery grassland and cropland spiders were dominated by safari, and artificial restoration woodland with more web-forming spiders. Spiders at higher altitude were generally small. Both natural recovery grassland and artificial restoration woodland could increase spider diversity and played important roles in regional biodiversity protection. Spider community composition differentiated in different habitats, with the overall functional characteristics of spider communities being changed and some habitats being retained. The index of spider diversity of the two recovery habitats was higher than that of cropland habitats, with differences in the species composition of the two recovery habitats, both of which had the function of protecting endemic species. Our results were useful for the protection and restoration of spider biodiversity on cropland and regional scales.
    Comparison on feeding habits of Cervus wallichii and sympatric ungulates and domestic animals in green grass period
    LYU Zhong-hai, ZHANG Wei-qi, LIU Hao, ZHANG Ming-hai, LI Yi-ran
    2020, 31(2):  651-658.  doi:10.13287/j.1001-9332.202002.002
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    Tibetan red deer (Cervus wallichii) is an endemic species to China, which was once considered extinct in the wild. As there are several other wild ungulates and domestic animals with similar feeding habits within its habitat range, it’s thus essential to study interspecific competition and co-existence between Tibetan red deer and other cohabiting ungulates in the highly unique environment of Qinghai-Tibet Plateau. Using microscopic analysis on fresh fecal samples collected in Sangri Tibetan Red Deer Nature Reserve from August to September in 2013 and 2014, the trophic niche width and overlap index were calculated on the basis of diet composition of C. wallichii, Cervus albirostris, Procapra picticaudata, Bos mutus and Capra hircas in green grass period. We analyzed and compared the overlap and differentiation of feeding habits between Tibetan red deer and other wild ungulates and domestic animals. The results showed that C. wallichii fed on similar edible plants with other species, but differed in proportion of different dietary components, with the main edible plants of C. wallichii being mostly the secondary edible plants to other species. Leontopodium pusillum was the common main edible plant for C. wallichii (percentage in animal recipes was 11.2%) and B. mutus (10.2%), Salix xizangensis was the common main edible plant of C. wallichii (9.6%) and C. albirostris (11.4%). At plant family level, Leguminosae was the common main edible plant family for C. wallichii (21.4%) and P. picticaudata (42.5%). Cyperaceae was the common main edible plant family for C. albirostris (49.2%), B. mutus (33.4%) and C. hircas (50.3%). Compositae was main edible plant family for C. wallichii (29.6%), as well as the secondary edible plant family for C. albirostris (7.6%), P. picticaudata (11.6%), B. mutus (17.3%) and C. hircas (14.1%). As the secondary edible plant family for C. wallichii (7.1%), Gramineae took up a lower proportion than that of the other ungulates (C. albirostris (13.6%), P. picticaudata (12.3%), B. mutus (11.5%) and C. hircas (16.0%)). Food overlap indices between C. wallichii and the other ungulates were all higher than 0.5, and the highest with B. mutus (0.65). The food diversity index (1.32), evenness index (0.37) and niche width index (15.79) of C. wallichii were all at high values. Compared with the results from 2007 to 2008, dietary composition of Tibetan red deer changed greatly as the proportion of Leguminosae increased while that of Cyperaceae decreased, resulting in improvement of food quality. In addition, there was greater competition of food resources between C. wallichii and domestic animals, which would further affect the distribution range and living space of C. wallichii.
    Spatial niche of major fish species in spring in the coastal waters of central and southern Zhejiang Province, China
    ZHANG Lin-lin, ZHOU Yong-dong, JIANG Ri-jin, LI Zhe, FAN ZI-wei, YIN Rui, ZHU YU-dan, RUI Yin, XIAO Yi
    2020, 31(2):  659-666.  doi:10.13287/j.1001-9332.202002.040
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    The relative importance index (IRI), mean crowding, niche breadth, and niche overlap (Qik) of major fish species were calculated based on two fishery resource surveys from April to May 2016 (spring) in the coastal waters of central and southern Zhejiang Province. The results showed that there were 24 major fish species (IRI>100), the niche breadth values of which differed greatly and were positively correlated with IRI. The niche overlaps of fishes were extremely low in spring. The total amount of species pairs with niche overlap 0.6 (Qik >0.6) were six in April and five in May, which represented 3.9% and 4.8% of the total pairs, respectively. Results from the redundancy analysis showed that the distribution of major fish species were mainly affected by temperature, salinity, water depth, and dissolved oxygen, which caused ecological differentiation of fish species.
    Reviews
    Plant diversity monitoring: A review
    LIU De-tuan, MA Yong-peng
    2020, 31(2):  667-673.  doi:10.13287/j.1001-9332.202002.003
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    Plant diversity monitoring is an essential basis for plant conservation and policy making, and is critical to the sustainable use and protection of biological resources. We reviewed the research progress on plant diversity monitoring, and proposed further research direction. Plant diversity monitoring is developing rapidly at a new situation, and enters a new era referring to intelligent, integration of macroscopic and microscopic, networked monitoring, big data, large-scale, multidisciplinary, all-dimensional, from species level to family level, community level or ecosystem level, and even the global level. The construction of biodiversity monitoring network promotes the uniform of essential biodiversity variables and networked monitoring. Internet information and database had become a main data source of plant diversity. There are many new challenges in plant diversity monitoring, including standardization, effective utilization and sharing of the monitoring data, as well as the monitoring for genetic diversity and individuals. Ecological monitoring would be large-scale, automated and standardized. Many things should be addressed in further research, including to improve the monitoring networks, to find innovative ways and build new models, to carry out monitoring at hotspots and give priority to important species as well as community or even larger scale, to pay more attention to the background investigation of plant resource.
    Research progress on non-point source pollution models for semi-arid and semi-humid watersheds
    BAO Xin, JIANG Yan
    2020, 31(2):  674-684.  doi:10.13287/j.1001-9332.202002.039
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    Affected by the unique geographical environment and climate, the hydrological cycle and the underlying mechanisms of the occurrence, migration, and transformation of non-point source pollution are more complicated in semi-arid and semi-humid watersheds. Non-point source pollution models are effective means for quantitatively describing the complex hydrological cycle and the process of pollutants migration and transformation, and thus served as important tools for watershed ecosystem management. Based on the unique climate, hydrological characteristics, and underlying surface conditions in semi-arid and semi-humid areas, we elaborated on the occurrence mechanism of non-point source pollution, and summarized the status, progress, and shortage of the research and application of solving water environmental problems by using non-point source pollution models. Moreover, the scheme for constructing non-point source pollution models applied to semi-arid and semi-humid areas was put forward. Finally, we discussed the development trend of non-point source pollution models.
    Research progress and ecological roles of phytoplankton cysts
    WEI Guang-ling, ZHANG Shi-chun, CAI Zhong-hua, ZHOU Jin
    2020, 31(2):  685-694.  doi:10.13287/j.1001-9332.202002.032
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    Phytoplankton have a complex life-cycle. Resting cysts are formed like terrestrial plants. Cysts play important roles in resisting environmental pressure, surviving adverse environment, maintaining physiological homeostasis, and maintaining species reproduction. In some ecological events, cysts were served as “seed bank” for periodical algal blooming. However, compared with the mature cells, the ecophysiological research on cysts is relatively limited. To deepen our understanding on life-cycle and ecological roles of cysts, we reviewed the researches on cysts in the past two decades. Firstly, we outlined the types (resting cysts, zoocysts, mature cysts) and factors that affected the formation of cysts of typical dinoflagellates and diatoms. Secondly, we summarized the formation mechanism, physiological characteristics and germination factors of cysts. Finally, we discussed the significance of cysts in algal evolution and in ocean carbon cycle. This review, summarizing the adaptability and plasticity of cysts, would shed light on ecological mechanism of algae survival strategy.