Table of Content

15 September 2020, Volume 31 Issue 9

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Effects of warming on soil inorganic nitrogen in the young and mature Cunninghamia lanceolata plantations in humid subtropical region, China

YANG Cheng-bang, ZHANG Li, GAO Yan-li, WU Na, CHEN Shi-dong, LIU Xiao-fei, YANG Zhi-jie

2020, 31(9):  2849-2856.  doi:10.13287/j.1001-9332.202009.001

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Soil nitrogen cycling in forests may be accelerated or inhibited by global warming, with consequences on forest productivity. Such an impact will be more complicated with extending period of warming. We examined the effects of warming on soil inorganic nitrogen content in the young and mature Cunninghamia lanceolata plantations. Warming was simulated by means of soil cable warming, simulating a future climate change scenario of 4 ℃ warming. The results showed that after three years warming, both total soil inorganic nitrogen and ammonium contents in the young and mature plantations were significantly reduced. The sharp decline occurred in the young plantation, with soil ammonium content in 0-10, 10-20, 20-40, 40-60 cm soil layers decreased by 32.1%, 37.1%, 20.8% and 19.9%, respectively. Dissolved organic nitrogen was reduced and N₂O emission was accelerated in the both plantations. The main reasons for the reduction of soil inorganic nitrogen concentration were lower input of organic nitrogen substrate and higher gaseous nitrogen loss. The decrease in soil organic nitrogen substrate and increase in gaseous nitrogen emissions in the young plantation were larger than those in the mature plantation, indicating that soils in the young plantation were more sensitive to increasing temperature. The 3-year warming decreased soil inorganic nitrogen contents in the two C. lanceolata plantations, which might negatively affect productivity of the C. lanceolata plantations in subtropic China.

Effects of Cunninghamia lanceolata stand types on the changes of aggregate-related organic carbon and nutrients in surface soil

HUANG Yong-zhen, WANG Sheng-qiang, YE Shao-ming

2020, 31(9):  2857-2865.  doi:10.13287/j.1001-9332.202009.003

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Exploring the microscopic characterization of organic carbon and nutrients in surface soil of different Chinese fir stands at aggregate scale can lay a theoretical foundation for promoting the sustainable use of soil resources with implications for improving soil health and fertility. We mea-sured the concentrations of soil organic C (OC), total nitrogen (TN), alkali-hydrolyzed nitrogen (AN), Olsen-P (AP), and available K (AK) in aggregate fractions collected from 0-10 cm and 10-20 cm soil layers in three different stands, mixed plantation of Cunninghamia lanceolata and Michelia macclurei (Ⅰ), C. lanceolata and Mytilaria laosensis (Ⅱ) and pure plantation of C. lanceolata (Ⅲ) respectively. Soil aggregates were classified into >2, 0.25-2, and <0.25 mm fractions by a dry-sieving procedure. The organic carbon and nutrient contents of soil aggregates in different stands increased with the decreases of particle size while the contribution rate of aggregates with different particle sizes to soil organic carbon and nutrient storage in 0-10 cm soil layer mainly was (>2 mm)>(0.25-2 mm)>(<0.25 mm), which was (>2 mm)>(<0.25 mm)>(0.25-2 mm) in 10-20 cm soil layer. The average weight diameter (MWD), the contents and stocks of OC, TN, AN and AP in surface soil aggregates of different stands ranked as Ⅰ>Ⅱ>Ⅲ (except the AP in 10-20 cm soil layer), while the contents and stocks of AK ranked as Ⅲ>Ⅰ>Ⅱ. Compared with pure plantation, aggregate structure of surface soil of mixed plantations was more stable, and Ⅰ was better than Ⅱ, because Ⅰ was artificially disturbed but Ⅱwas not. Therefore, the mixed plantation of C. lanceolata and M. macclurei could effectively promote the formation and stability of soil aggregates, and alleviate decomposition of soil organic matter and nutrient loss in plantations.

Effects of thinning intensity on species composition and diversity of undergrowth vegetation community in Pinus massoniana plantation at initial stage of thinning

LIU Si-ze, YIN Hai-feng, SHEN Yi, KANG Wen-si, LUO Yan, FAN Chuan, LI Xian-wei

2020, 31(9):  2866-2874.  doi:10.13287/j.1001-9332.202009.009

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Species composition and diversity of undergrowth vegetation community under different thinning intensities (0, 10%, 20%, 30%, 40%, 50%) were examined at the initial stage of thinning in 29-year-old Pinus massoniana plantation in the low mountain region of eastern Sichuan. The results show that all the thinning treatments could reduce the absolute dominance of Miscanthus sinensis and Dicranopteris dichotoma. The dominant species composition of shrubs in each treatment was different. There were more extensive species in the medium thinning intensity (20%, 30% and 40%) treatments than other treatments. The diversity indices increased first and then decreased with increasing thinning intensity. The variation degree of herbs was stronger than shrubs. The diversity indices of herbs were positively correlated with soil water content. The explanation amount of thinning intensity and soil physicochemical properties to community differentiation was 81%. The vegetation communities in the medium thinning intensity forests showed positive correlation with all the factors except total phosphorus. At the initial stage of thinning, herbaceous communities were more sensitive to disturbance than shrub communities. The 40% thinning intensity treatment was more closely related to soil environmental factors, with high stability and the most abundant species, which would be the best thinning measure under the experimental condition.

Hydrogen and oxygen stable isotope characteristics of water in SPAC system of evergreen broadleaved forest in subtropical region

LI Long, TANG Chang-yuan, CAO Ying-jie

2020, 31(9):  2875-2884.  doi:10.13287/j.1001-9332.202009.017

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Forest soil-plant-atmosphere continuum (SPAC) is an important continuous process of water cycle. In this study, we analyzed hydrogen and oxygen stable isotope compositions of the precipitation, atmospheric water vapor, soil water, branch water, and leaf water to explain the characteristics of the continuous process and the associated controlling factors in a subtropical evergreen broadleaved forest. The results showed that the regression equations between hydrogen and oxygen stable isotopes were δD_P=7.97δ¹⁸O_P+12.68(R²=0.97) for precipitation, δD_S=4.29δ¹⁸O_S-18.62(R²=0.81) for soil water, δD_B=3.31δ¹⁸O_B-29.73(R²=0.49) for branch water and δD_L=1.49δ¹⁸O_L-10.09(R²=0.81) for leaf water of Podocarpus nagi, δD_V=3.89δ¹⁸O_V-51.29(R²=0.46) for atmospheric water vapor, respectively. In the process of water transport from precipitation to soil water to plant water, hydrogen and oxygen isotopes gradually enrich, while water vapor isotopes evaporated from soil and evaporated from plants were depleted. With the influence of precipitation and evaporation, soil water isotopes depleted with depth, and more enriched in the dry season than that in the rainy season. During the observation period, isotope content of branch water was slightly higher than that of soil water, indicating that water might be enriched by transpiration during the transportation process in plants. In the dry season, water isotope in branches of arbor plants was poorer than that of shrubs, indicating that arbor plants with deeper root distribution tended to use deep soil water. Because of the differences of leaf traits, transpiration rate and the response degree of environmental factors, the variation characteristics of water isotope composition in leaves of diffe-rent plants varied with the increases of leaf age. Environmental conditions in rainy season were more conducive to leaf transpiration, which made leaf water isotope enriched in rainy season than in dry season. The isotopic compositions in leaf water of Podocarpus nagi had a positive relationship with leaf water content (LWC), and a negative one with relative humidity, reflecting the water regulation function of plants in response to environmental changes.

Water utilization strategy of three soil and water conservation trees on Ordos Plateau, China

XU Su-han, ZHU Ya-juan, WU Cai-xia, LI Yun

2020, 31(9):  2885-2892.  doi:10.13287/j.1001-9332.202009.007

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To understand the adaptive strategies of three tree species used for soil and water conservation in the hilly area of eastern Ordos Plateau, Hippophae rhamnoides, Pinus tabuliformis and Armeniaca sibirica, we measured the δ¹⁸O value of xylem water of branch and potential water sources and the δ¹³C value of leaves, and analyzed the relative contribution of each potential water sources to different tree species by multiple linear mixing model. We further compared the seasonal dynamic and inter-specific variation of water source and water use efficiency (WUE). The results showed that H. rhamnoides, P. tabuliformis and A. sibirica mainly used soil water in 10 cm layer in May, accounting for 88.5%, 94.0% and 91.6% of their total water uptake, respectively. In July, H. rhamnoides mainly used soil water in 10-25 cm layer (44.6%) and rain water (35.4%), P. tabuli-formis mainly used rain water (93.7%), and A. sibirica mainly used soil water in 25-100 cm layer (55.9%) and rain water (36.8%). In September, H. rhamnoides mainly used soil water in 25 cm and 75-100 cm layers (88.9%), P. tabuliformis mainly used soil water in 10 cm and 50-75 cm layers (84.5%), and A. sibirica used that in 10-100 cm layer. WUE of H. rhamnoides in May was significantly higher than that in July and September. WUE of P. tabuliformis in July was significantly higher than that in September. WUE of H. rhamnoides was significantly higher than that of P. tabuliformis and A. sibirica in May and July. Three tree species use different depths of soil water or rainwater based on their availability in different seasons. H. rhamnoides and P. tabuliformis could improve their WUE to adapt to environmental change under drought, which might be more suitable for local semi-arid environment than A. sibirica.

Effects of freeze-thaw on dissolved nitrogen pool, nitrogen transformation processes and diversity of bacterial community in temperate soils

PU Jia-hui, JIANG Nan, JUAN Ying-hua, CHEN Li-jun

2020, 31(9):  2893-2902.  doi:10.13287/j.1001-9332.202009.033

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Soil freeze-thaw could affect nitrogen (N) availability. The N transformation is closely related with soil microbes. The effect of soil freeze-thaw on the soil bacterial communities in the temperate zone is still not clear. We hypothesized that freeze-thaw events could affect the diversity and composition of bacterial communities, thereby changing the contents of soil dissolved nitrogen pools as well as the N transformation process. In this study, microcosms with different freeze-thaw cycles (six and fifteen cycles) were designed, with the constant temperature at 2 ℃ as the control. The results showed that the contents of dissolved total nitrogen, dissolved inorganic nitrogen, microbial biomass nitrogen and net nitrogen mineralization rate were decreased significantly in response to increasing cycles of freeze-thaw. The number of freeze-thaw cycles did not affect bacterial α diversity. In contrast, the duration of incubation was positively correlated with bacterial α diversity including Chao1 and Shannon indices. Freeze-thaw treatment significantly affected the function and composition of bacterial communities, but the number of freeze-thaw cycles had little effect on the bacterial community structure. The partial redundant analysis showed that under freeze-thaw treatments, both the composition and function of bacterial community were significantly related to soil dissolved N pools and N transformation processes.

Effects of biochar addition on soil moisture infiltration process of the yellow soil in Karst area

MAO Tian-xu, TU Dan, LIU Man-man, DONG Xiao-zhuan, ZHAO Qing-xia

2020, 31(9):  2903-2910.  doi:10.13287/j.1001-9332.202009.019

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To investigate the effects of biochar addition on soil moisture infiltration characteristics of sloping farmland in Karst area, we used soil column simulation to study the variation characteristics of cumulative infiltration volume, infiltration rate, and wetting peak process under the different biochar addition amount (0, 1% and 2%) and different particle sizes (<0.25, 0.25-1 and >1 mm), and simulated the infiltration process in yellow soil on slope farmland. The results showed that soil infiltration process after biochar addition was significantly inhibited under the condition of constant bulk density. The cumulative infiltration amount and infiltration rate under biochar addition were significantly lower than those without biochar addition. There was no significant difference in the cumulative infiltration amount and infiltration rate of the soil with 1% and 2% biochar addition. The cumulative infiltration amount of the soil with different particle sizes followed an order of <0.25, 0.25-1 and > 1 mm after biochar addition. When the addition amount was 1%, the cumulative infiltration amount of 300 min had decreased by 20.9%, 35.2% and 45.0% compared with CK. When the addition amount was 2%, the decrease rate was 21.5%, 37.5% and 44.2%, indicating that the inhibition effect of large particle size biochar on soil infiltration being stronger than that of small particle size biochar. The change trend of soil wetting peak process to biochar addition of different contents and different particle sizes was consistent with the change trend of cumulative infiltration volume. Horton model and Kostiakov model could be used to simulate soil moisture infiltration process. The Horton model had higher fitting accuracy, the largest R² (between 0.91 and 0.98), and the smallest RMSE (between 0.14 and 0.21). The initial infiltration rate obtained by Kostiakov model was closer to the measured result. Our results could provide scientific basis for the rational application of biochar and provide a useful reference for soil improvement and soil and water conservation in slope farmland of Karst area.

Differentiation of ectomycorrhizal morphology in Abies faxoniana along an elevation gradient in a subalpine forest of western Sichuan Province, China

CHEN Lu-lu, FENG Qiu-hong, SUN Jian-xin

2020, 31(9):  2911-2922.  doi:10.13287/j.1001-9332.202009.040

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Ectomycorrhizal fungi are an important group of symbiotic fungi beneficial to plant growth and their environmental adaptation. An explicit clarification of the trait of ectomycorrhizal fungi would facilitate our understanding of plant responses to environmental change. We set up sampling plots at five elevations (2850, 3000, 3194, 3413, 3593 m) in the Balong Mountain within the Wolong Nature Reserve of Sichuan Province, and collected cubic soil samples (10 cm×10 cm×10 cm) from those plots by point centered quarter method. Based on examination of the morphological types and diversity of ectomycorrhizal roots of Abies faxoniana in each soil sample, we examined the variations in morphological traits of ectomycorrhizal roots of A. faxoniana along the elevational gra-dient and the effects of soil environmental factors. Results showed that: 1) The major ectomycorrhizae of A. faxoniana in Wolong Nature Reserve was orange or yellow in color, with smooth mantle and no or few extensional hyphae, and cylindric or inflated root tips. This type of ectomycorrhizae occurred with highest rate of colonization (12.4%) in the study area. 2) With the increases of elevation, the morphological diversity of ectomycorrhizae in A. faxoniana declined and the morphological types per cubic soil sample significantly decreased. 3) There were significant differences between the ectomycorrhizae of contact exploration type (CE) and short distance exploration type (SDE) at different elevations, while the colonization rate of CE increased significantly with elevation. 4) Soil factors drove the variations of ectomycorrhizal morphology in A. faxoniana along the elevational gradient. Redundancy analysis (RDA) showed that soil total nitrogen (TN), soil temperature (Ts), soil water content (SWC), pH, soil acid phosphatase (ACP) and soil total phosphorus (TP) had significant effects on ectomycorrhizal morphology in A. faxoniana, among which TN and Ts being the greatest and explaining 5.4% and 4.9% of the total variations. Our results clari-fied the variations in the occurrence of ectomycorrhizal morphology in A. faxoniana along elevational gradient, which provided scientific evidence for further studying the mechanisms underlying the responses to environmental changes in mycorrhizal strategy in coniferous species of subalpine forests.

Screening and identification of an efficient phosphate-solubilizing Burkholderia sp. and its growth-promoting effect on Pinus massoniana seedling

LYU Jun, YU Cun

2020, 31(9):  2923-2934.  doi:10.13287/j.1001-9332.202009.031

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We isolated phosphate solubilizing bacteria (PSB) from the rhizosphere soil of P. massoniana by the standard dilution plating technique, and determined the phosphate solubilizing characteristics of PSB by the Molybdenum antimony resistance colorimetric method. We explored the mechanism of phosphorus dissolution through analysis of the relationship between the phosphate-solubilizing ability of PSB and the pH of the fermentation broth and the determination of organic acids in the fermentation broth by HPLC-MS. The effects of PSB on the growth and physiology of P. massoniana were clarified by measuring the growth, physiology, soil nutrients, and soil enzyme activity of potted P. massoniana seedlings inoculated with PSB. The results showed that 16 strains of PSB were screened from the rhizosphere of P. massoniana. Among those strains, WJ27 had the best effect of solubilizing phosphorus, with the amount of phosphate solubilized reaching 411.98 mg·L^-1 after five days of liquid culture. The strain was identified as Burkholderia sp. by phenotype observation, physiological and biochemical identification and phylogenetic tree analysis. The highest phosphate solubilizing capacity in four phosphorus sources mediums was Ca₃(PO₄)₂(220.85 mg·L^-1) > AlPO₄(182.33 mg·L^-1) > FePO₄·2H₂O (129.19 mg·L^-1) > CaHPO₄·2H₂O (115.23 mg·L^-1). WJ27 could reduce the pH of fermentation broth by secreting organic acids, such as citric acid and malonic acid, which contribute to phosphorus solubilization. Results from pot experiments showed that WJ27 had positive effects on the growth, physiology, soil nutrients, and soil enzyme activities of P. massoniana seedlings. Compared with the control, seedling height, main root length, total lateral root number, shoot (stem, leaf and branch) fresh weight, shoot dry weight, root fresh weight and root dry weight of P. massoniana inoculated with WJ27 increased by 14.3%, 36.9%, 56.1%, 44.7%, 60.0%, 158.3% and 100.0%, respectively. Chlorophyll b, total chlorophyll, shoot soluble protein, shoot soluble sugar, root activity, and root soluble protein increased by 145.8%, 45.2%, 206.3%, 59.4%, 80.5% and 260.0%, respectively. The SOD and POD acti-vities of root, and CAT activities of shoot of P. massoniana seedlings increased by 71.2%, 197.5% and 36.6%, respectively. Contents of available N, available K, available P, urease, catalase and phosphatase increased by 18.1%, 17.0%, 11.9%, 34.3%, 45.5%, and 62.6%, respectively. Burkholderia sp. WJ27 could improve soil nutrient concentrations and enzyme activities and thus facilitate the growth of P. massoniana seedlings.

Applicability of thermal dissipation probe in the determination of trunk flow of Platycladus orientalis under cyclic heating mode

MA Yu-jie, ZHANG Han-han, LI Chun-you, ZHANG Jin-song, MA Chang-ming

2020, 31(9):  2935-2942.  doi:10.13287/j.1001-9332.202009.002

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To evaluate the adaptability of the cyclic heating mode in the thermal diffusion probe method (TDP) in the measurement of trunk sap flow and the accuracy of the measurement of tree transpiration water consumption, we selected Platycladus orientalis as the research object and set three different heating modes: 60 min/0 min (continuous heating mode), 30 min/30 min (cyclic heating mode with 30 min heating and 30 min cooling), 10 min/50 min (cyclic heating mode with 10 min heating and 50 min cooling). Based on the measured value of the whole tree container wei-ghing method, the temperature gradient characteristics of different heating modes were analyzed using the measurement technology of thermal diffusive trunk sap flow. The Granier’s corrected formulas of cyclic heating modes were constructed, with its error being analyzed by validity verification. The results showed that sap flow rate calculated by the cyclic heating mode was consistent with the diurnal variation of the transpiration rate measured by the whole tree weighing method. The temperature of cyclic heating mode could quickly rise, fall and performed stably. The sap flow calculated by Granier’s original formula was 61.3% lower than that by weighing method. The corrected Granier formula in the mode of 10 min/50 min and 30 min/30 min were F_d=0.0177K^0.9457 (R²=0.88) and F_d=0.0378K^1.3146(R²=0.85), respectively. The difference of sap flow rate in P. orientalis by the new formula was smaller than that measured by the whole tree weighing method, and the error of transpiration rate calculated by the 10 min/50 min correction formula was the smallest, 5.9% lower than that calculated by the weighing method, and thus could express the real flow rate. The 10 min/50 min cyclic heating mode could be used to reduce the effect of natural temperature difference, cut down power consumption, and accurately reflect the actual sap flow rate of P. orientalis.

Prediction models of knot volume inside the stem for Korean pine plantation

JIA Wei-wei, HONG Yan-hu, LI Feng-ri

2020, 31(9):  2943-2954.  doi:10.13287/j.1001-9332.202009.004

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Based on 1207 knots from 49 sample trees of 29 standard plots of Korean pine plantations in Linkou and Dongjingcheng Forest Bureau of Heilongjiang Province, China, we extracted longitudinal sections of knots using the image processing software Digimizer and represented the shape of knots using two-dimensional scatter plots. According to the two-dimensional scatter plots, knots of Korean pine plantation were divided into three types: 1) alive knots (whole knot contained only sound knot portion); 2) non-occluded dead knots (whole knot contained both sound and loose knot portions); 3) occluded dead knots (the sound and loose portion of the knot were partially occluded by the bark). For all the three types of knots, the volume of sound knot was calculated by mathematical integral of the sound knot shape equation. The volume of loose knot was calculated using the volume equation of a cylinder. The total volume of knots was calculated as the sum of sound and loose knot volume. Finally, based on knot variables (diameter, relative height and total length of knots) and tree variable (diameter at breast height), we established the prediction models for sound knot volume, loose knot volume, and total volume of knot using the linear mixed model at plot level and tree level. Compared with fixed-effects model, the mixed effects models of the volume of sound knot, loose knot, and total knots provided more accurate parameter estimation, more uniform residual distribution, and higher model fitting precision. The validation results showed that prediction precision of each fixed-effect model was higher than 90%, while that of the mixed models with plot and tree effect was above 93%, indicating that the established model could well predict the volume of knot for Korean pine plantation.

Construction and application of a new index for quantifying root erosion resistance: Root framework erosion resistance index

LI Qiang, LIU Guo-bin, YANG Jun-cheng, TUO Deng-feng, ZHANG Zheng

2020, 31(9):  2955-2962.  doi:10.13287/j.1001-9332.202009.010

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The matching of root system is a key factor driving the resistance of plant community to soil erosion. In this study, Amoeba graphical method was used to establish a root framework erosion resistance index (ERI_rf, %) from three dimensions of root morphology, quantity and spatial concerns to quantify the effective of root erosion resistance by plant community. We analyzed root growth characteristics of plant community from abandoned land, Caragana korshinskii and Robinia pseudoacacia communities in loess hilly area. The results showed that the parameters of constructing the root framework erosion resistance index included the acting coefficient of root framework (α), root density (R_b, kg·m^-3), root framework degree (S), soil bulk density (ρ, g·cm^-3), and soil and water conservation coefficient (φ). The equation could be expressed as ERI_rf=α×R_d×S×φρ×100%. This root framework erosion resistance index well represented the erosion resistance effects of plant root system. Logarithmic function could better fit the relationship between soil erosion resis-tance ability and root framework erosion resistance index. Our findings would provide scientific reference for the construction of anti-erosion vegetation community and assessment of ecological construction.

Characteristics of light energy utilization of intercropping alfalfa/gramineae forage based on yield effect

LIN Fang, LIU Xiao-jing, TONG Chang-chun, WU Yong

2020, 31(9):  2963-2976.  doi:10.13287/j.1001-9332.202009.026

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Based on field experiments in 2017-2019, we examined the characteristics, yield effect and regulatory mechanism of light energy utilization in alfalfa/gramineous forage grass intercropping. With monoculture of alfalfa, forage triticale (C3 plant), and forage maize (C4 plant) as control, we measured the yield effect, the effect of light energy utilization factor on yield formation, the characteristic difference and mechanism of light energy utilization under alfalfa/triticale and alfalfa/maize intercropping patterns. Results showed that land equivalent ratios of both intercropping patterns were all greater than 1, indicating that land utilization ratio and yield benefit of the two intercropping patterns were higher than that of monoculture, among which alfalfa/triticale intercropping pattern was the most promising one. The contribution of light energy utilization factors to yield was following an order of leaf area index (1.531) > net photosynthetic rate (0.882) > intercellular CO₂ concentration (0.282) > transpiration rate (-0.229) > canopy opening (-0.291) > PAR interception rate (-0.681) > stomatal conductance (-0.751). Among them, leaf area index was not only one of the important indices to characterize photosynthetic capacity, but also an important component factor of forage crop yield aiming at harvesting nutrients. Therefore, among all factors of photosynthetic characteristics, net photosynthetic rate was the main factor affecting yield. The net photosynthetic rate of alfalfa, triticale and maize under intercropping showed the same pattern, and being different from that of monoculture. The main ways for intercropping to increase net photosynthetic rate included: triticale and maize increased net photosynthetic rate and yield by enhancing the carboxylation fixation capacity of CO₂ and the utilization capacity of strong light, while alfalfa could improve its net photosynthetic rate and promote growth under low light, by increasing the content of chlorophyll b in functional leaves, changing chlorophyll composition and enhancing the collection and transmission of light energy.

Population structure and quantitative dynamics of Stellera chamaejasme in degraded typical steppe

GUO Li-zhu, ZHAO Huan, LYU Jin-ying, WANG Kai-li, LIU Ke-si, WANG Kun, HUANG Ding

2020, 31(9):  2977-2984.  doi:10.13287/j.1001-9332.202009.008

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Stellera chamaejasme is one of most common poisonous plant species in degraded grasslands of China. S. chamaejasme could dominate the community in some severely degraded grasslands, which is a serious threat to the sustainable development of animal husbandry in natural grasslands. In this study, S. chamaejasme population was divided into 10 age classes according to the number of branches. We investigated the age structure of S. chamaejasme population and population dynamic indices, and quantified the survival status of S. chamaejasme population by compiling a static life table, drawing a survival curve, conducting survival analysis. The age structure of S. chamaejasme population in the study area was growth type. The number of individuals in Ⅰ age class was sufficient but with relatively low survival rate. The population structure of S. chamaejasme was fitted the growing type. The development process of population was fluctuating. The number of individuals would drop sharply in Ⅱ and Ⅷ, indicating that these two age classes were the bottleneck period in the development of S. chamaejasme population. The survival curves of S. chamaejasme population was the Deevey-Ⅱ type. The results of survival analysis showed that the population had a sharp decrease in the early stage and was stable in the later stage, which was because the value of f_x and λ_x of S. chamaejasme in Ⅰ or Ⅱ age class were the highest. In conclusion, sufficient young individuals (Ⅰ) was the basis for the expansion of S. chamaejasme population in the degraded typical steppe. The low transformation rate of young individuals to adults might be one of the reasons explaining why S. chamaejasme population could not expand rapidly in the early stage of grassland degradation. Therefore, it was suggested to intervene early when the number of S. chamaejasme was limited.

Effect of nitrogen additions on soil pH, phosphorus contents and phosphatase activities in grassland

TIAN Mu-yu, YU Chun-jia, WANG Jing-kuan, DING Fan, CHEN Zhen-hua, JIANG Nan, JIANG Hui, CHEN Li-jun

2020, 31(9):  2985-2992.  doi:10.13287/j.1001-9332.202009.034

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Phosphorus is a key nutrient for all plant species and a limiting factor for grassland ecosystem function. In recent years, in response to the rapid increase of global nitrogen deposition, soil phosphorus contents and phosphatase activities changed to varying degrees in grassland ecosystems. We conducted a meta-analysis to examine the responses of soil pH, total phosphorus (TP), available phosphorus (AP), as well as activities of alkaline phosphatase (AlP) and acid phosphatase (AcP) in soils to nitrogen addition amount, nitrogen type, experimental duration, and sampling depth. The correlation between soil pH and phosphatase response ratio was investigated. The results showed that nitrogen addition significantly reduced soil pH, TP and AlP activity, while significantly increased AcP activity, but had no significant effect on AP. Soil pH and AlP activity significantly decreased under nitrogen addition >5 g·m^-2·a^-1, and AcP activity significantly increased under high nitrogen addition (>10 g·m^-2·a^-1). The contents of TP and AP significantly decreased when nitrogen addition was 5-10 g·m^-2·a^-1. NH₄NO₃ treatment significantly reduced soil TP and increased AcP activity, while urea treatment significantly reduced soil pH and AlP activity. Across all nitrogen addition amounts, when the experiment duration was 3 to 10 years, soil TP content and AlP activity were significantly reduced. Soil pH was significantly reduced after three years nitrogen addition, and AcP activitiy was significantly increased after 10 years nitrogen addition. In the 0-10 cm soil layer, the TP content and AlP activity significantly decreased, while the AP content significantly increased. In >10 cm soil layer, the AP content was significantly decreased. The significant negative correlation between soil pH and AcP activity indicated that change in soil pH caused by nitrogen addition may be an important factor for the variation of soil phosphatase activity.

Suitable summer habitat of the khulan in the Mt. Kalamaili Ungulate Nature Reserve and estimation of its population

ZHANG Xiao-chen, SHAO Chang-liang, GE Yan, CHEN Chen, XU Wen-xuan, YANG Wei-kang

2020, 31(9):  2993-3004.  doi:10.13287/j.1001-9332.202009.032

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The khulan (Equus hemionus hemionus) is a representative species in desert, semi-desert and desert steppe in Asia. The estimation of suitable habitat and population density of khulan can provide scientific decision-making basis for the conservation management. We investigated the distribution and population density of khulan in the Mt. Kalamaili Ungulate Nature Reserve in Xinjiang during May-August in 2018 and 2019, using the line transect method. The khulan population density, number and the encounter rate were estimated by the Distance 7.0 software, and through the MaxEnt model analysis and combining environmental variables, we assessed the most suitable habitats and main influencing factors. In total, we recorded 4782 individuals from 718 groups and 363 effective occurrences. Our results showed that the suitable summer habitat covered an area of 6737.5 km², accounting for 45.4% of the total reserve area and located mainly in the central and eas-tern parts of the reserve. We estimated that the density of the summer khulan population was (0.5±0.1) individuals·km^-2 and the total khulan population were (3246±575) individuals in the Mt. Kalamaili Ungulate Nature Reserve. The prediction accuracy of MaxEnt model was relatively high, with an average AUC of 0.890. The results of the Jackknife test showed that the distance to water sources, vegetation type, distance to human interference, distance to national highway G216, altitude, and precipitation of driest areas were the most important factors affecting the habitat suitability for khulan. For improving the protection of the khulan population in this reserve, we suggested strengthen the protection of water sources, adjust the core areas, monitor wildlife passages, and enhance traffic construction.

Effects of micro-ridge-furrow with plastic mulching and bunching seeding on soil hydrothermal environment and its response to photosynthesis and grain yield of spring wheat

HOU Hui-zhi, ZHANG Xu-cheng, YIN Jia-de, FANG Yan-jie, WANG Hong-li, MA Yi-fan, ZHANG Guo-ping, LEI Kang-ning

2020, 31(9):  3005-3014.  doi:10.13287/j.1001-9332.202009.023

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The relieving of drought and cold restriction on spring wheat development is one of the key factors increasing wheat yield in arid areas of central Gansu Province. A field experiment with spring wheat (Longchun No. 35) was carried out in central Gansu Province from 2016 to 2018. There were three treatments: 1) micro-ridge-furrow with whole field plastic mulching and bunching seeding (PRF), 2) whole field soil plastic mulching and bunching seeding (PMS), 3) bunching seeding without mulching (CK). We measured soil temperature in 0-25 cm profile, soil water content in 0-300 cm profile, leaf SPAD, photosynthetic rate, transpiration rate, aboveground biomass in different growth stages, and grain yield to understand the effect of PRF on soil hydrothermal environment, spring wheat yield and water use efficiency (WUE) from the aspect of soil hydrothermal, canopy development and grain yield. The results showed that mean soil temperature in 0-25 cm profile of PRF and PMS increased by 2.8 ℃ and 2.5 ℃ at the seedling stage, decreased by 1.4 ℃ and 0.9 ℃ from filling to maturity stage, respectively. Soil water storage in 0-300 cm profile of PRF and PMS increased by 59.7 mm and 41.8 mm from sowing to seedling stage. Water consumption of PRF and PMS increased by 46.1 mm and 39.8 mm from seedling to filling stage. PRF increased average soil temperature in 0-25 cm profile by 0.3 ℃ at seedling stage, but decreased by 0.5 ℃ from filling to maturity stage, and increased soil water storage in 0-300 cm profile by 18.0 mm from sowing to seedling stage. PMF increased water consumption by 13.0 mm from booting to maturing stage, as compared with PMS. Based on the optimizated soil hydrothermal conditions, leaf SPAD value, aboveground biomass, net photosynthetic rate, and transpiration rate of PRF increased, as compared with PMS and CK. The PRF increased grain yield by 9.1% and 36.5%, WUE by 5.9% and 30.8% compared to PMS and CK, respectively. Consequently, PRF increased soil temperature at wheat seedling stage, reduced it from filling to maturing stage, improved wheat water consumption from sowing to filling stage, increased leaf SPAD value and aboveground biomass, promoted photosynthetic function in leaf from seedling to filling stage, and consequently led to increased yield and water utilization. Such effects were more significant in dry year (2016 and 2017).

Economical nitrogen application rate of winter wheat under rice-wheat rotation in the Yangtze River basin of China

LI Xin-xin, SHI Zu-liang, WANG Jiu-chen, WANG Fei, JIANG Rong-feng

2020, 31(9):  3015-3022.  doi:10.13287/j.1001-9332.202009.027

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To promote the rational application of nitrogen fertilizer for winter wheat under rice-wheat rotation in the Yangtze River Basin, we examined the effects of nitrogen application rates (0, 120, 210, 300 kg·hm^-2, expressed as N₀, N₁, N₂, and N₃ respectively) on soil nitrate content, nitrogen balance of soil-plant system and yield. The results showed that soil nitrate content increased with increasing nitrogen application rates. Under different nitrogen application treatments, all the nitrate was significantly transfered to the 60 cm soil layer till jointing stage. After jointing stage, topdressing nitrogen significantly increased nitrate content in 0-40 cm soil layer under N₁ and N₂ treatments and that in the 0-60 cm soil layer under N₃ treatment. Soil nitrate mainly accumulated in the 0-40 cm soil layer in the mature stage. Results from nitrogen balance analysis showed that nitrogen absorption, residue and loss varied across different growth stages of wheat, with the period from overwintering to jointing being the principal time of apparent nitrogen loss. The amount of plant nitrogen accumulation, inorganic nitrogen residue and soil nitrogen apparent loss all positively correlated with the nitrogen application rate. Based on the comprehensive analysis through Coase principle and marginal revenue of environmental economics, the optimum nitrogen application rate for production, ecology and economic benefits of winter wheat under rice-wheat rotation was 250 kg·hm^-2, and the ratio of base fertilizer to jointing fertilizer was 5:5, while the corresponding grain yield was 6840 kg·hm^-2.

Hydrogen sulfide acted as a downstream signal was involved in the regulation of salicylic acid on photosynthesis of cucumber seedlings under low temperature and low light intensity

PAN Dong-yun, FU Xin, ZHANG Xiao-wei, LIU Feng-jiao, BI Huan-gai, AI Xi-zhen

2020, 31(9):  3023-3032.  doi:10.13287/j.1001-9332.202009.028

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Both salicylic acid (SA) and hydrogen sulfide (H₂S) play an important role in regulating plant growth and development and physiological metabolism under abiotic stresses. As signal molecules, the interaction between them in regulating cucumber photosynthesis under low temperature and low light is still unclear. Here, we examined the regulation and interaction of SA and H₂S on photosynthesis in cucumber seedlings under low temperature (8 ℃/5 ℃, day/night) and low light (100 μmol·m^-2·s^-1). Seedlings were foliar-sprayed with SA, sodium sulfide (NaHS, H₂S donor), and their scavenger or biosynthesis inhibitors, respectively. Seedlings treated with deionized water at suitable temperature and light condition were used as the control. The results showed that SA increased the L-/D-cysteine desulfhydrase (LCD, DCD) activities and relative mRNA expression, and consequently promoted the endogenous H₂S production. However, NaHS did not affect the activities and gene expressions of phenylalnine ammonialyase and isochorismate and endogenous SA level. Compared with the H₂O-treated seedlings under low temperature and low light, SA- and NaHS-treated seedlings showed an increase in the photosynthetic rate, stomatal conductance and transpiration rate, while a decrease in intercellular CO₂ concentration. SA and NaHS increased the CO₂ assimilation, which mainly attributed to the increases in the activities of the ribulose-1, 5-bisphosphate carboxylase, rubisco activase, sedoheptulose-1, 7-bisphosphatase and fructose-1, 6-bisphosphatase, as well as their mRNA expression. Meanwhile, SA and NaHS improved the actual photochemical efficiency and maximal photochemical efficiency of PSII, and therefore alleviated the damage in photosynthetic apparatus and negative effect on growth from low temperature and low light stress. The SA-induced higher photosynthesis and growth in stressed seedlings were suppressed by addition of H₂S scavenger hypotaurine. However, the H₂S-induced tolerance of photosynthetic apparatus to low temperature and low light was not affected by SA biosynthesis inhibitor paclobutrazol and 2-aminoindan-2-phosphonic acid. Our results suggested that H₂S, as a downstream signal of SA, was involved in regulating photosynthesis in cucumber seedlings under low temperature and low light.

Change of root morphology in intercropping systems of wheat and faba bean under different phosphorus levels and its relationship with endogenous hormones

WANG Yu-yun, LI Lan, WANG Rui-xue, TANG Li, ZHENG Yi

2020, 31(9):  3033-3039.  doi:10.13287/j.1001-9332.202009.029

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We examined the correlation between changes of root morphology and endogenous hormones in intercropping systems of wheat and faba bean under different phosphorus levels by hydroponics. Compared with monocropping wheat (MW), the intercropping of wheat and faba bean (W∥F) significantly increased root length of wheat, reduced root average diameter of wheat, and increased root surface area under the condition of 1/2P (low P) level. At the conventional phosphorus level, intercropping significantly reduced root average diameter of wheat, and increased root length and root surface area. Compared with monocropping faba bean (MF), W∥F significantly promoted the growth of faba bean root and increased root surface area of faba bean. At the level of 1/2P, intercropping significantly increased the content of auxin (IAA), abscisic acid (ABA), sali-cylic acid (SA) and jasmonic acid (JA). At the conventional phosphorus level, intercropping could significantly increase the content of IAA, ABA and JA in wheat root, while no significant difference in the SA content of wheat root between monocropping and intercropping wheat was found. Intercropping could increase the content of ABA and SA in faba bean roots, but did not affect IAA and JA contents of faba bean roots. There was no significant correlation between the contents of endogenous hormones (IAA, ABA, SA and JA) and root morphology (root length, root average diameter and root surface area) of wheat and faba bean roots in wheat or faba bean monocropping system. In wheat and faba bean intercropping system, there was a positive correlation between IAA contents of wheat and faba bean and their root length and root surface area. W∥F enhanced IAA of wheat and faba bean root, which was an important factor driving the change of root morphology in the intercropping system of wheat and faba bean.

Monitoring leaf nitrogen concentration and nitrogen accumulation of double cropping rice based on crop growth monitoring and diagnosis apparatus

LI Yan-da, YE Chun, CAO Zhong-sheng, SUN Bin-feng, SHU Shi-fu, HUANG Jun-bao, TIAN Yong-chao, HE Yong

2020, 31(9):  3040-3050.  doi:10.13287/j.1001-9332.202009.012

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To verify the accuracy and adaptability of crop growth monitoring and diagnosis apparatus (CGMD) in monitoring nitrogen nutrition index of double cropping rice, we established a monitoring model of leaf nitrogen concentration (LNC) and leaf nitrogen accumulation (LNA) for double cropping rice based on CGMD. Eight early and late rice cultivars were selected and four nitrogen application rates were set up. The differential vegetation index (DVI), normalized difference vegetation index (NDVI) and ratio vegetation index (RVI) were collected using CGMD. Meanwhile, ASD FH2 high spectrometer was used to collect canopy spectral reflectance and calculated DVI, NDVI, and RVI. To verify the accuracy of CGMD, we compared the canopy vegetation indices change characteristics collected by CGMD and ASD FH2. The CGMD-based monitoring models of LNC and LNA were established, which was tested with independent field data. The results showed that LNC, LNA, DVI, NDVI and RVI of early and late rice increased with increasing nitrogen application rate, and increased first and then decreased with the advance of growth progress. The determination coefficient (R²) of fitting for DVI, NDVI and RVI from CGMD and ASD FH2 were 0.9350, 0.9436 and 0.9433, respectively. This result indicated that the measurement accuracy of CGMD was high, and that the CGMD could be used to replace ASD FH2 to measure canopy vegetation indices of early and late rice. Compared with the three canopy vegetation indices based on CGMD, the correlation between NDVI_CGMD and LNC and that between RVI_CGMD and LNA was the highest. The exponential model based on NDVI_CGMD could be used to accurate estimate LNC with the R² in the range of 0.8581-0.9318, and the root mean square error (RMSE), relation root mean square error (RRMSE) and correlation coefficient (r) of model validation in the range of 0.1%-0.2%, 4.0%-8.5%, and 0.9041-0.9854, respectively. The power function model based on RVI_CGMD could be used to estimate LNA with the R² in the range of 0.8684-0.9577, and the RMSE, RRMSE and r of model validation in the range of 0.37-0.89 g·m^-2, 6.7%-20.4% and 0.9191-0.9851, respectively. Compared with the chemical testing method, using the CGMD could conveniently and accurately measure LNC and LNA of early and late rice, which had a potential to be widely applied for high yield and high efficiency cultivation and precise management of nitrogen fertilizer in double cropping rice production.

Current status of fertilizer application and utilization efficiency of winter wheat in Anhui Province, China

LI Min, BU Rong-yan, HAN Shang, CHENG Yi, YU Zong, WANG Hui, CHENG Wen-long, WU Ji

2020, 31(9):  3051-3059.  doi:10.13287/j.1001-9332.202009.030

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Winter wheat is an important crop in Anhui Province. Rational use of fertilizers is crucial for the achievement of successful yield. It is urgently needed to reveal the status of fertilizer application and existing problems in winter wheat planting in Anhui for better fertilization. We conducted a survey on 1591 farmers in the main winter wheat producing areas of Anhui Province. The contents of survey included fertilizer type, fertilizer dosage, fertilization method, planting area and yield level. Based on the survey results, we analyzed the current fertilization status of winter wheat growing areas in Anhui Province. Referred to the average wheat yield and fertilizer usage in Anhui, the relationship between wheat yield and fertilizers, including nitrogen (N), phosphorus (P₂O₅) and potassium (K₂O), was evaluated by Cate-Nelson method (cross-over method) to explore the ways to increase yield and fertilizer utilization efficiency of winter wheat. The results showed that the average yield of winter wheat in Anhui Province was 5185 kg·hm^-2, and the average application rates of N, P₂O and K₂O fertilizers were 206, 80 and 78 kg·hm^-2, respectively. Compared with wheat following rice, the N, P₂O and K₂O fertilization rates of dry stubble wheat was higher by 14, 16 and 3 kg·hm^-2, respectively. Overall, the average amount of chemical fertilizer in winter wheat cultivation in Anhui Province was rational, but there were still some problems in fertilization methods, nutrient management and fertilizer types. The results of Cate-Nelson method showed that 23.8%, 21.2% and 25.7% (for N, P₂O₅ and K₂O fertilizers respectively) of winter wheat were below the average level that achieved high yield, reaching highest partial productivity of N, P₂O₅ and K₂O fertilizers. There were 26.3%, 19.3% and 22.5% (for N, P₂O₅ and K₂O fertilizers respectively) of winter wheat were below the average use level which did not achieve high yield. There were 26.2%, 29.6% and 25.0% (for N, P₂O₅ and K₂O fertilizers respectively) of winter wheat realized high yield, but the fertilization rate was high and the partial productivity of N, P₂O and K₂O fertilizers was relatively low. Our results suggest that the yield and efficiency of winter wheat in Anhui Pro-vince should be improved. The percentage of mechanical fertilization in winter wheat was 62.7% for base fertilizer and 10.0% for topdressing fertilizer, respectively. Though nitrogen fertilizer was applied at different stages, the proportion of base fertilizer that accounted for 69.0% of the total should be decreased appropriately. It’s a problem that farmers preferred to use chemical fertilizers but not organic substitution.

Effects of different fertilization managements on microbial necromass and plant lignin accumulation in a Mollisol

HUO Hai-nan, LI Jie, ZHANG Xiao-chen, ZHU Ping, WANG Li-chun, SHI Yuan-liang, HE Hong-bo, ZHANG Xu-dong

2020, 31(9):  3060-3066.  doi:10.13287/j.1001-9332.202009.021

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Fertilization is an effective management to maintain and increase soil organic carbon (SOC) level in agroecosystems. Both microbial metabolism and plant component retention control SOC sequestration. Here, we used amino sugars and lignin as biomarkers to investigate the responses of distribution of microbial necromass and plant debris in a long-term cultivated soil (30 years) and SOC accumulation to different fertilization regime. The results showed that, compared with unfertilized treatment, inorganic fertilizer application (N fertilizer-only or the combination of organic or inorganic fertilizers) increased crop production and soil amino sugar accumulation, but did not affect the concentrations of lignin and SOC, indicating that inorganic fertilizer stimulated the assimilation of microbial substrate and accelerated the turnover of SOC and lignin in the plough layer. Compared with inorganic fertilizer treatment, long-term organic fertilizer application promoted SOC accumulation (38.3%), but did not affect amino sugar concentration in SOC, which indicated that soil could reach a ‘saturation’ state with respect to microbial residue accumulation. In contrast, the application of organic fertilizer increased the proportion of lignin in SOC,indicating that the contribution of plant residues to SOC persistence was enhanced. Compared with the manure-only treatment, organic-inorganic combined application mainly increased the contribution of amino sugar to SOC accumulation. Our findings indicated that long-term fertilization could affect SOC dynamics through modulating the accumulation processes of microbial necromass and plant debris.

Life history traits of an Echinochloa crus-galli var. crus-galli population with extreme adaptations to rice planting systems

LIAO Ping-qiang, MASOOM Aatiqa, MAO Hai-yan, FANG Xian-yang, HUO Zhong-yang, CHEN Guo-qi

2020, 31(9):  3067-3074.  doi:10.13287/j.1001-9332.202009.005

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Long-term herbicide application may facilitate the adaptive evolution of weed populations. With Echinochloa crus-galli var. crus-galli population A from a rice field used for the experiment of effectiveness of herbicide in Nanling County, Anhui Province, we conducted common garden experi-ments with seeds of population A and three control populations collected from normal rice fields. Compared with the three control populations, population A had significantly lower seed production for individual plant, but higher 1000-seed weight. Population A had faster in seedling growth, higher in number of reproductive tillers, shorter life span, lower in height and biomass of individual plant, as well as lower in sensitivity to herbicide penoxsulam. Individuals from population A survived from 2× label dose (60 g·hm^-2) of penoxsulam treatment at the three- to four-leaf stage showed significantly reduction in plant height, biomass, and mature seed production (1066 seeds per plant), but no difference in heading period, number of reproductive tillers, number of seeds per raceme and 1000-seed weight. The short lifespan, heavy seeds, dwarf architecture, more reproductive tillers and penoxsulam resistance made E. crus-galli var. crus-galli population A extremely adapting to rice planting systems, which should be prevented to spread to normal rice fields.

Effects of Solanum lycopersicum rootstock on biomass, amnio acid content and reactive oxygen species metabolism of grafted seedlings under salt stress

JIA Qiu-ying, WU Xiao-lei, JI Sheng-xin, CHU Xin-pei, LIU Hui-lan, GONG Bin-bin, LI Jing-rui, GAO Hong-bo

2020, 31(9):  3075-3084.  doi:10.13287/j.1001-9332.202009.024

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To explore the mechanism of Solanum lycopersicum rootstock function in enhancing salt tolerance of grafted seedlings, we examined the growth, Na⁺ accumulation, amino acid contents and active oxygen metabolism (ROS) in three grafted seedlings treated with and without 175 mmol·L^-1 NaCl conditions. RS grafted seedlings were formed by split grafting using salt-sensitive variety ‘Zhongza 9’(S) as scion and salt-tolerant variety ‘OZ-006’(R) as rootstock, while the other two experiment materials were the scion self-grafted (SS) and rootstock self-grafted (RR) seedlings. The results showed that NaCl stress significantly increased the salt damage index and Na⁺ content, concomitantly with substantial decrease in growth rate and chlorophyll content of seedlings. More-over, there were significant differences among the grafting combinations, with an order of SS>RS>RR. NaCl stress significantly increased total amino acid content in the leaves and roots of the grafted seedlings. The amino acid contents were significantly higher than those in the control. There were 9 kinds of amino acid in RR and RS leaves, and 8 kinds in RR and RS roots, with the most significant change in proline. Only 2 and 4 kinds of amino acids in leaves and roots of SS were significantly higher than those in control, respectively. Amino acid contents among three grafted seedlings showed RR>RS>SS under NaCl stress. The contents of amino acid in RR and RS leaves increased by 32.8% and 16.6% compared with SS, and those in RR and RS roots increased by 53.1% and 32.5%, respectively. The changes of ROS were caused by NaCl stress, which enhanced the activities of antioxidant enzymes, the production rate of O₂^-· and MDA content in both leaves and roots. Among different grafted seedlings, RR had the most prominent increase of antioxidant enzymes activities in leaves and roots, followed by RS, and SS showed the smallest. The active oxygen levels among the three grafted seedlings were show as SS>RS>RR. In summary, rootstock alleviated salt damage of grafted seedlings by inhibiting Na⁺ transport upward, enhancing amino acid content and antioxidant enzyme activities. The salt tolerance ability showed remarkable difference among three different combinations of rootstock and scion, with a order of RR>RS>SS. Our results suggested that salt tolerance of S. lycopersicum grafted seedlings was mainly affected by the ability of rootstock salt tolerance, followed by scion, and also closely related to the regulation of both amino acid and active oxygen metabolism in seedlings.

Effects of dazomet fumigation on growth, biological characteristics of Malus hupehensis seedlings and soil environment

JIANG Wei-tao, CHEN Ran, WANG Hai-yan, XU Shao-zhuo, CHEN Xue-sen, SHEN Xiang, YIN Cheng-miao, MAO Zhi-quan

2020, 31(9):  3085-3092.  doi:10.13287/j.1001-9332.202009.022

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In this study, we examined the effects of dazomet fumigation with different concentrations (0, 0.1, 0.2, 0.4 g·kg^-1) on the microbial characteristics of continuous cropping soil and growth of Malus hupehensis seedling in greenhouse and open-field pot. The results showed that all the treatment of dazomet fumigation could promote the growth of M. hupehensis seedlings in continuous cropping soil, with 0.2 g·kg^-1 treatment showing the strongest effect. Compared to the control, plant height, stem diameter, dry weight of M. hupehensis seedlings in 0.2 g·kg^-1 dazomet fumigation were increased by 192.9% and 91.8%, 72.8% and 60.1%, 196.8% and 195.0%, 138.5% and 130.7%, respectively in greenhouse and open-field. The root related indices (root length, root area, root volume, root respiration rate) were significantly promoted. The activities of SOD, POD, CAT in roots were increased by 114.6% and 118.5%, 123.5% and 107.6%, 164.6% and 175.6% respectively compared with the control, whereas the content of malondialdehyde was significantly lowered. Soil bacterial content, fungal content, copy number of Fusarium oxysporum gene and soil enzyme activity were significantly decreased with the increasing dazomet concentrations. In conclusion, 0.2 g·kg^-1 dazomet fumigation could increase the biomass of M. hupehensis seedlings in continuous cropping, improve soil environment, and effectively alleviate the continuous cropping obstacle. Therefore, 0.2 g ·kg^-1 dazomet fumigation could be given priority during the reconstruction of old apple orchards.

Effects of dicyandiamide on cadmium accumulation in pakchoi under instant soluble nitrogen fertilizers

YOU Yue, WU Cai-nan, ZHONG Wei-jie, HOU Zhi-lin, LIU Yue, DU Shao-ting, JIN Chong-wei

2020, 31(9):  3093-3100.  doi:10.13287/j.1001-9332.202009.035

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We investigated the effects of dicyandiamide (DCD) on the growth and Cd concentrations in pakchoi cultivated under different instant soluble N fertilizers [ammonium sulfate, ammonium sulfate and sodium nitrate (1:1, ammonium/nitrate), and urea] in Cd-contaminated soils. The results showed that the fresh weight of the edible parts of Cd-stressed pakchoi were increased by 583.3%, 41.5%, and 206.8% under ammonium, ammonium/nitrate, and urea treatments in the presence of DCD, respectively compared with control, and the tolerance index and photosynthetic rate significantly increased, whereas no significant changes were observed under nitrate supply. Under all N treatments with DCD, the MDA and H₂O₂ contents and the superoxide radical production rate in the leaves of pakchoi were decreased, with the highest reduction occurred in ammonium and urea treatments. Cd concentrations in the leaves of pakchoi fertilized with ammonium, ammonium/nitrate, and urea were lowered by 58.3%, 34.0%, and 44.5% and those in the petioles were lowered by 61.8%, 29.4%, and 55.6%, respectively. Cd concentration in the leaves and petioles of pakchoi in the nitrate treatment did not differ significantly from control. These changes could be attributable to the reduction in the acidification of rhizosphere soil in response to the combined application of N fertilizer and DCD. Accordingly, in Cd-contaminated soils with a low buffering capacity, the application of DCD combined with ammonium, ammonium/nitrate, or urea N fertili-zers could alleviate Cd-induced growth stress and inhibit photosynthesis in pakchoi plants and effectively minimize the Cd accumulation.

Effects of biochar and EM application on growth and photosynthetic characteristics of Sesbania cannabina in saline-alkali soil of the Yellow River Delta, China

CUI Qian, XIA Jiang-bao, LIU Jing-tao, YANG Hong-jun, PENG Ling

2020, 31(9):  3101-3110.  doi:10.13287/j.1001-9332.202009.006

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We examined the effects of biochar and effective mircoorganisms (EM) application on growth and photosynthetic characteristics of Sesbania cannabina in the Yellow River Delta, by a pot experiment with different EM treatments (without EM addition, EM-; with EM addition, EM+) and a gradient of biochar treatments (0, B₀; 0.5%, B₁; 1.5%, B₂; 3%, B₃; biochar weight/soil weight). The growth parameters, photosynthetic light response curve and chlorophyll fluorescence characteristics of S. cannabina were measured. The results showed that the EM+B₃ treatment had the best effect among all the treatments. Compared with the EM-B₀ treatment, the EM+B₃ treatment increased height, stem diameter, and total biomass by 69.5%, 90.0% and 141.1%, respectively. Biochar and EM significantly improved photosynthetic capacity. Compared with the EM-B₀ treatment, the EM+B₃ treatment significantly enhanced the maximum light response of net photosynthetic rate, transpiration rate, water use efficiency, and stomatal conductance by 93.8%, 35.1%, 43.4%, and 34.8%, respectively. Biochar and EM improved the parameters of chlorophyll fluorescence. Compared with the EM-B₀ treatment, the EM+B₃ treatment significantly increased the potential photochemical efficiency, the actual photochemical efficiency, the apparent electron transport rate and the non-photochemical quenching coefficient by 25.8%, 31.5%, 37.2%, and 56.8%, respectively. The parameters of growth, photosynthesis and chlorophyll fluorescence increased with the increasing biochar under EM+ treatments, whereas the B₃ treatment had negative effect under EM- treatments. The co-addition of EM and 3% biochar (EM+B₃) could improve the photosynthetic capacity and chlorophyll fluorescence characteristics of S. cannabina, broaden light ecological amplitude, boost the water retention and drought resistance property, and promote the growth of S. cannabina.

Strengthening the effect of Bacillus megaterium on remediation of Cd-contaminated farmland soil by Sedum plumbizincicola

DENG Yue-qiang, CAO Xue-ying, TAN Chang-yin, SUN Li-juan, PENG Xi, BAI Jia, HUANG Shuo-pei

2020, 31(9):  3111-3118.  doi:10.13287/j.1001-9332.202009.036

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Sedum plumbizincicola is a Cd and Zn hyperaccumulator, widely used for the phytoremediation of Cd-contaminated soil. Bacillus megaterium, a phosphate-solubilizing bacteria, can promote plant growth and improve the bioavailability of heavy metals in soil, and thus has a strengthening effect on the remediation of heavy metal-contaminated soil. Here, a pot experiment was carried out with S. plumbizincicola as a hyperaccumulator to investigate the effects of different inoculation amounts (10-60 mL) of B. megaterium on the phytoremediation efficiency of Cd-contaminated farmland soils. The results showed that inoculation of B. megaterium increased soil available Cd content by 15.0%-45.0% compared with the CK. Biomass of shoots and roots of S. plumbizincicola increased by 8.7%-66.7% and 13.6%-81.8%, respectively. Shoot Cd concentration was significantly increased by the application of B. megaterium by 29.2%-60.4%. Under the conditions of S. plumbizincicola inoculated with B. megaterium, Cd removal rate of soil reached 26.7%-42.9%. In conclusion, application of B. megaterium in phytoremediation significantly enhanced the Cd removal efficiency and increased plant biomass, which promoted Cd remediation efficiency.

Characteristics of heavy metals and bacterial community in manure and surrounding soil of cattle farm in Xiji, Ningxia, China

ZHANG Jun-hua, SHANG Tian-hao, LIU Ji-li, SUN Yuan, JIA Ping-ping

2020, 31(9):  3119-3130.  doi:10.13287/j.1001-9332.202009.038

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To understand the contamination status of heavy metals and bacterial community in the manure and surrounding soils of cattle farm in Ningxia, we collected cattle manure at different breeding periods (lactation, calf, growing, pre-fattening and post-fattening periods) and soil samples from the largest beef breeding area in the region by different distances, with the waste land far away as control. We measured heavy metal contents and the composition and diversity of bacterial community in manure and soil samples. The results showed that: 1) The contents of Cu, Zn, Cd, Pb and Hg in cattle manure were 33.8%-95.8% lower than the national average, while As content was 94.7% higher than the national average. During the breeding periods, the change tendencies of seven kinds of heavy metals in cattle manure were different. The contents of Cu, Cd, Hg and Cr of cattle manure in the pre-fattening period were the highest across all periods. The comprehensive pollution index of heavy metals in pre-fattening and post-fattening periods of cattle manure was highest in all periods. 2) The contents of Cu and Zn in the soils with cattle manure application were higher than control, and the content of Zn were significantly higher than surrounding soil samples. All single and comprehensive soil pollution indices of soil were safe. 3) During the breeding periods, Sequence, OTU and Chao1 index of cattle manure had no specific change. Sequence, OTU and Chao1 of soil with cattle manure application were higher than the soil around the farm. 4) The types of dominant phylum were less in the manure. The relative abundance of Firmicutes was the highest, followed by Bacteroidetes and Proteobacteria. The relative abundance of Firmicutes in the growing period was significantly lower than other breeding periods, and that of other phylum had little variation among periods. The cattle farm did not affect bacterial community in the surrounding soil. The cattle manure application didn’t change the relative abundance of bacteria at the phyla level. The abundance of Gp, Gemmatimona, Lysobacte, Subdivision3_genera_incertae_sedis were significantly higher than control and surrounding soil. 5) Organic matter, pH, EC, total nitrogen, total potas-sium, Cd and As significantly affected bacterial diversity and component abundance in cattle manure. Soil pH, total phosphorus and Hg significantly influenced soil bacterial diversity and component abundance. On the whole, the effects of physicochemical properties in cattle manure and soil on bacterial community were more significant than heavy metals. Our results could provide scientific basis for selecting the variety and dosage of feed and veterinary drugs in local cattle farms, as well as the rational application of organic fertilizers.

Spectrum characteristics of habitat quality changes in Gansu Province, China

HUANG Xin, CHENG Wen-shi, LI Xiao-dan, YANG Chang-yu, XING Xiu-wei

2020, 31(9):  3131-3140.  doi:10.13287/j.1001-9332.202009.015

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Habitat quality is an important factor affecting regional ecosystem service value and protecting the biodiversity of the earth. Gansu Province is located in the intersection of the three nature areas in China. On the basis of quantitative estimation of the regional habitat quality in Gansu during 2000 to 2018, based on the spectrum change analysis theory and InVEST model, we explored the spatio-temporal differentiation pattern of the regional habitat quality status and its spectrum transformation and change intensity. The results showed that the habitat quality of Gansu Province generally maintained a middle level and improved slightly, showing a step-by-step change from the north to south in the spatial distribution, with the coexistence of both high and low habitat quality. The structure of habitat quality in Gansu Province was stable based on the view of the spectrum transformation, and the spectrum units which did not appear state transition were dominant in quantity. The transition of each other of those spectrum units which had occurred transition of the habitat quality, such as higher  lower, higher  high, higher  low was most obvious, with the spatial distribution in aggregation. The change intensity of habitat quality in Gansu Province presented a general tendency with active in the north and moderate in the south, presenting as active intensity area, complex intensity area, moderate intensity area, and slight intensity area from the north to south.

Runoff-sediment relationship and erosion dynamic characteristics for two types of engineering deposits under rainfall condition

NIE Hui-ying, WANG Wen-long, GUO Ming-ming, KANG Hong-liang, LI Jian-ming, BAI Yun

2020, 31(9):  3141-3153.  doi:10.13287/j.1001-9332.202009.013

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The engineering deposits produced by the increasing frequency of production and construction activities are the main source of man-made soil erosion. In this study, we examined the change of runoff-sediment relationship and erosion hydrodynamic characteristics with the engineering deposits of aeolian sandy soil and red soil, based on simulated rainfall experiments with different gravel contents (0, 10%, 20%, 30%) and rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min^-1). The results showed that the sediment yield rate of the aeolian sandy soil deposits gradually increased with the duration of rainfall. The sediment yield rate of red soil deposits under 1.0 mm·min^-1 rainfall intensity increased first and then gradually stabilized. Under other rainfall densities, there was a trend of fluctuation after rapid decline, the greater the rainfall intensity and the smaller the gravel content, the more intense the fluctuation. When the gravel content was 0 and 10%, there were rills erosion on the slope surface of aeolian sandy soil accumulation, and the sediment yield rate of rill development stage was 6.74-57.40 times of that of the sheet erosion stage. The erosion process of red soil deposits could be divided into two stages: the loose particle erosion and the soil-rock erosion stage. The sediment yield rate of the loose particle erosion stage was 1.05-3.49 times that of the soil-rock erosion stage. In general, the sediment yield rate of two soil deposits increased with increasing rainfall intensity. The sediment yield rate fluctuated with the increases of gravel content at 1.0 and 1.5 mm·min^-1, with a decreasing trend under >1.5 mm·min^-1. The sediment yield rate of aeolian sandy soil deposits was 1.45-4.14 times of that of red soil deposits under the same rainfall and gravel content conditions. During the erosion process of aeolian sandy soil deposits, the runoff-sediment relationship changed from low sediment concentration to high sediment concentration, while there was a reverse relationship for red soil deposits. During the high sediment concentration period, the increasing rate of the sediment yield rate of aeolian sandy soil deposits was 1.94-37.60 times of that of red soil deposits. For low sediment concentration period, the decreasing rate of the sediment yield rate of red soil deposits was 1.40-21.30 times of that of aeolian sandy soil deposits. In general, the runoff power was better than the runoff shear force in describing the erosion dyna-mics of these two types of deposits. The critical runoff power increased with increasing gravel content. The critical runoff power of aeolian sandy soil deposits during the rill erosion stage (0.02-0.04 W·m^-2) was two times of that of the sheet erosion stage, while the critical stream power was lower than that of the red soil deposits. These results provide a scientific reference for modelling soil erosion processes for engineering deposits.

Analysis on coupling development of agricultural eco-economic system in Yan’an City under the background of gully control and land consolidation project

WANG Jing, Hu Yi, BAI Qing-jun

2020, 31(9):  3154-3162.  doi:10.13287/j.1001-9332.202009.020

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The gully control and land consolidation project is another major project of ecological environment management in Yan’an City following the Grain-for-Green project. Understanding the development and changes of the coupling relationship within agricultural eco-economic system in Yan’an City under the background of gully control and land consolidation project has important implications for scientific evaluation of ecological and economic benefits of the project as well as the coordination and sustainable development of agricultural eco-economy in the Loess Plateau. By constructing the coupling coordination degree model and coupling degree model of agricultural eco-economy system, we quantitatively analyzed the change of comprehensive evaluation index, state of coupling coordination, and trend of coupling degree evolution of the agricultural eco-economic system in Yan’an City from 2010 to 2018. The results showed that the comprehensive evaluation index of agricultural ecology and agricultural economy systems in Yan’an City from 2010 to 2018 both followed an S-shaped growth curve, with consistent trend. The coupling coordination index of the agricultural eco-economic system increased from 0.51 to 0.72, while the coupling coordination state developed from the primary coordination level to a good coordination level. Such a result indicated continuous improvement of the relationship between agricultural ecology and economy in the region and the coupling relationship of the system were developing with the direction of mutual coordination. During the study period, the agricultural eco-economic system coupling evolution was complicated and experienced different stages, including decline coupling, coordination coupling, repair coupling, and coordination coupling again. The coupling relationship was at the stage of coordinated development of rapid economic growth in 2018. The gully control and land consolidation project promoted the coupled and coordinated development of agricultural eco-economic system, but with a lagging effect.

Surface water change characteristics of Taihu Lake from 1984-2018 based on Google Earth Engine

LIU Yao-yi, TIAN Tian, ZENG Peng, ZHANG Xin-yu, CHE Yue

2020, 31(9):  3163-3172.  doi:10.13287/j.1001-9332.202009.011

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Lakes are important fresh water resources. Accurate understanding of lake dynamic changes benefits the sustainable development of water resources and socio-economic development. Based on the Google Earth Engine (GEE), we analyzed the dynamics of Taihu Lake from 1984 to 2018 by adopting the dataset of Joint Research Centre’s Global Surface Water and Landsat imagery. The modified normalized difference water index (MNDWI) was used to explore the changes in the area of Taihu Lake in recent 35 years. The results showed that the area of Taihu Lake increased during 1984-2018, with a total increase of 45.31 km². The area in spring and winter was larger than that in summer. Eastern Taihu Lake was the main part of Taihu Lake showing area change. Compared with 1984, 88.9% of the water area of Taihu Lake in 2018 did not change, and 0.3% of the water area disappeared permanently. Lake area changes were affected by both natural and anthropogenic factors. Agricultural irrigation, fish farming, reclamation of surrounding lakes, water conservancy engineering facilities, and the transformation of land-use types caused the reduction in lake area. Increased annual precipitation and the implementation of environmental protection policies were the main factors for the increases in lake area. The results provide reference for effective sustainable water resource management and verify the feasibility of monitoring long-term surface water change based on the GEE platform.

Dynamics of three-dimensional ecological footprint of Zhejiang coastal zone and its influencing factors based on GTWR model

TIAN Peng, LI Jia-lin, WANG Li-jia, LIU Rui-qing, SHI Xiao-li

2020, 31(9):  3173-3186.  doi:10.13287/j.1001-9332.202009.016

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Clarifying the consumption of local natural capital stock and natural capital flow and its influencing factors can help alleviate the tension between the socio-economic development of the coastal zone, natural resources, and the ecological environment, and promote regional coordinated and sustainable development. Based on the two-dimensional and three-dimensional ecological footprint evaluation models, we analyzed the spatial and temporal variations of ecological footprint in the coastal zone of Zhejiang Province from 2006 to 2016, and explored the regional natural capital stock and capital flow occupancy based on footprint depth and footprint width. We analyzed the spatial and temporal heterogeneity of its influencing factors using a geographically and temporally weighted regression model. The results showed that ecological crisis in the coastal zone of Zhejiang Province deepened during the study period. The average per capita ecological deficit was 3.5 hm²·cap^-1, and the per capita ecological deficit increased by 15.5%. Among them, the contribution of energy consumption account to the per capita ecological footprint was greater than that of the biological resources account. The per capita ecological footprint of each county showed an increasing trend, with significant spatial variation. The coastal zone of Zhejiang Province mainly consumed the natural capital stock, with a significant inhibitory effect on the renewal of natural capital flows. The consumption of natural capital stock was 14.87 times that of capital flow in 2016. Urban scale, economic development level, and people’s income level had positive impacts on the ecological footprint of coastal counties of Zhejiang Province, while fishery production had negative effect on the ecological footprints, with transition trend to a positive one. The influence mechanism of the three factors had significant spatial and temporal differentiation.

Community structure of macrozoobenthos and its relationship with environmental factors in Sanmen Bay, Zhejiang, China

LIANG Jing-xiang, ZHOU Yong-dong, WANG Zhong-ming, ZHANG Ya-zhou, JIN Hai-wei, XU Kai-da

2020, 31(9):  3187-3193.  doi:10.13287/j.1001-9332.202009.037

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To understand the status and dynamics of macrozoobenthos community in Sanmen Bay, we collected benthos samples by Agassiz trawl in November 2015, and February, May and August in 2016. The results showed that: 1) A total of 119 macrozoobenthos species were recorded, with main groups of fishes, crustaceans and molluscs, accounting for 79% of the total number of species. 2) The dominant species of macrozoobenthos throughout the year were Leptochela gracilis, Hyperacanthomysis longirostris and Amblychaeturichthys hexanema. The identity of dominant species changed significantly in different seasons. 3) The annual average biomass and density were 0.025 g·m^-2 and 0.07 ind·m^-2, respectively. 4) The Shannon’s diversity index of macrozoobenthos in Sanmen Bay varied from 2.21 to 3.18, the Margalef’s species richness index varied from 3.25 to 3.78, and the Pielou’s evenness index varied from 0.53 to 0.79. Results from abundance-biomass curve analysis showed that the community was moderately disturbed in spring and winter, and slightly disturbed in summer and autumn. Results from Canonical correspondence analysis showed that water depth, temperature, salinity, and pH were the most important environmental factors affecting macrozoobenthos community.

Erosion morphology and the characteristics of runoff and sediment yielding in platform-slope system of opencast coal mine

SU Huan, WANG Wen-long, KANG Hong-liang, BAI Yun, GUO Ming-ming , CHEN Zhuo-xin

2020, 31(9):  3194-3206.  doi:10.13287/j.1001-9332.202009.018

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In the open pit, runoff from the platform is large discharge and rapid afflux, which often results in serious gully erosion of dump slope. The study of erosion process under catchment conditions of the platform-slope system is still backward. In this study, field scouring experiments were conducted to investigate runoff characteristics and sediment yield processes of the platform-slope system under different flow discharges (48, 60, 72 and 84 L·min^-1). Our results showed that rill erosion dominated the platform-slope system under the flow discharge of 48 L·min^-1, and gully was formed under 60-84 L·min^-1. The flow velocity of the platform and the slope showed an abrupting-fluctuating-stable trend with the duration of discharge. The flow velocity of the platform was smaller than that of the slope, with the magnitude of reduction at 8.3%-67.1%. The highest flow velocity appeared on the up-slop/down-slope, being 18.5%-44.6% higher than that of the middle-slope. In general, the sediment yield rate of the platform and the slope varied with the duration of discharge, with the sediment yield rate of the slope being 17.4 times as that of the platform. The ratio of gully width to depth showed substantial difference between the platform and slope. The platform generally had the largest ratio than the slope. For the slope, the largest ratio appeared on the middle-slop/down-slope, being 1.36-1.93 times as that of the up-slope. The morphology of rill and gully along the platform to down-slope presented in the form of “wide and shallow-narrow and deep-wide and shallow”. Rill erosion mainly concentrated in the platform and the middle slope under the flow discharge of 48 L·min^-1, contributed 29.9% and 26.8% of the total erosion volume, respectively. When the flow discharge increased to 60-84 L·min^-1, the largest average across-section areas (1083.25-1737.86 cm²) formed on the up-slope accounted for 36.1%-44.7% of the total erosion volume. Our results provided evidence for modelling soil and water erosion of the platform-slope system in opencast coal mine.

Reviews

Research advances in gene flow between transgenic plants and their relatives

WANG Xin-yu, LIU Yong-bo

2020, 31(9):  3207-3215.  doi:10.13287/j.1001-9332.202009.025

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With increased cultivation area of transgenic plants worldwide, the ecological risks of cultivating transgenic plants have received wide concerns. One of the risks is the occurrence and consequences of gene flow between transgenic plants and their relatives. Here, we reviewed the ratio and the maximum occurrence distance of gene flow for transgenic oilseed rape (Brassica napus), cotton (Gossypium hirsutum), maize (Zea mays), soybean (Glycine max), rice (Oryza sativa), and wheat (Triticum aestivum). The former four species have been commercially released, while the latter two species have not been commercially released yet. We introduced some possible means in mitigating the occurrence of gene flow from transgenic plants to their relatives. The ratio of pollen-mediated gene flow is affected by genetic relationship between species, overlap time of flowering, wind speed and direction, and other factors. The maximum occurrence distance of gene flow is affected by climate, pollinators, geographical environment and other factors. The ratio of gene flow was negatively related with distance between donor and recipient plants (y=-0.59x-0.46, R²=0.25, P<0.01; logarithmic-conversion), and the ratio was high in closely related species. To reduce the occurrence ratio of gene flow between transgenic plants and their relatives, policy-makers should adopt a “partition management” strategy and pay more attention on the ecological risks of post-gene flow in the framework of biosafety assessment of transgenic plants.

Ecological significance of arbuscular mycorrhiza on plant rhizosphere stress

LI Jiao-jiao, ZENG Ming

2020, 31(9):  3216-3226.  doi:10.13287/j.1001-9332.202009.039

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In recent years, Chinese scientists have made remarkable achievements in on mycorrhizal molecular biology, nutrition, taxonomy, and ecology, with arbuscular mycorrhizal fungus (AMF) having been mostly studied. AMF can form symbiotic relationship with roots of most terrestrial plants, promote plant growth and development, improve plant stress resistance, maintain ecological balance, and protect ecological environment. This review mainly introduced the ecological function and mechanism of AMF in plant rhizosphere stress from the aspects of abiotic (drought stress, heavy metal pollution, saline-alkali stress) and biotic stresses (pathogenic bacteria and nematode infection). We proposed the remaining deficiencies and research prospects in this field to provide refe-rence for future research of AMF.

A review of models of forest fire occurrence prediction in China

GAO Chao, LIN Hong-lei, HU Hai-qing, SONG Hong

2020, 31(9):  3227-3240.  doi:10.13287/j.1001-9332.202009.014

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We summarized research progress of forest fire occurrence prediction model in China based on the literature review, from the prospects of forest fire drivers, models of forest fire occurrence probability, models of forest fire occurrence frequency and model validation methods. The main conclusions are: 1) Meteorology, terrain, vegetation, fuel and human activities were the main driving factors of forest fire occurrence and model prediction accuracy. 2) In the models of forest fire occurrence probability, the geographically weighted logistic regression model considered the spatial correlation between model variables, the Gompit regression model could fit the asymmetric structure fire data. The random forest algorithm had a high prediction accuracy without the requirement of multicollinearity test and excessive fitting, which made it as one of the optimal methods of forest fire occurrence probability prediction. 3) Among all the forest fire occurrence frequency models, the negative binomial regression model was suitable for fitting the over discrete data, the zero-inflated model and hurdle model could deal with fire data that contained a large number of zeros. 4) ROC test, AIC test, likelihood ratio test, and Wald test were the most common methods for evaluating the accuracy of fire occurrence probability and frequency models. The study of forest fire occurrence prediction model should be the main focus of the forest fire management. Model selection should base on fire data structure of different forests. More influencing factors should be taken into account to improve the prediction accuracy of model. In addition, it was necessary to further explore the application of other mathematical methods in forest fire prediction, to improve the accuracy of the models.