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    10 July 2019, Volume 38 Issue 7
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    Spatiotemporal patterns of the maximum primary productivity and driving factors in the eastern China’s forests.
    SHI Xu-xia, SONG Zhao-peng, HOU Jihua, ZHANG Lei-ming, NIU Shu-li, WANG An-zhi, XIANG Wen-hua, WANG Hui-min
    2019, 38(7):  1949-1961. 
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    The response of ecosystem carbon cycle to temperature is one of the major topics in the research field of global change ecology. The general pattern of the response of gross primary productivity (GPP) to temperature usually shows that GPP increases with temperature at the lower temperature range to reach a maximum value (GPPmax), and then declines as temperature increases further. Thus,GPPmax represents the photosynthetic potential of vegetation at the optimum temperature. However, our understanding on the spatial and temporal patterns and main driving factors of GPPmax in forest ecosystems are still limited. In this study, we analyzed the temporal and spatial distribution of GPPmax and main influencing factors in five typical forest ecosystems based on flux data (temperate coniferous and broad-leaved mixed forest of Changbaishan, subtropical Chinese fir (Cunninghamia lanceolata) plantation of Huitong, subtropical evergreen coniferous forest of Qianyanzhou, subtropical evergreen broadleaf and coniferous mixed forest of Dinghushan, and tropical monsoon forest of Xishuangbanna) along the NorthSouth Transect of Eastern China (NSTEC), which covered tropical, subtropical, and temperate climate zones. The results showed that the temperature response of GPP showed a unimodal pattern, with GPPmax occurring at the optimum temperature in each year for all ecosystems. GPPmax at the optimum temperature in forests were ranked following the order: Changbaishan > Qianyanzhou > Xishuangbanna > Huitong > Dinghushan. Temperature played the most important role in driving the spatial variation of GPPmax across sites, with GPPmax decreasing with the increases of temperatur. Solar radiation, precipitation and VPD affected GPPmax. For the interannual variation of GPPmax in each site, GPPmax in Changbaishan was mainly controlled by air temperature and by soil water content in Huitong, Qianyanzhou, and Dinghushan forests. We failed to find the main factors affecting interannual variation of tropical rainforest in Xishuangbanna. Our results benefit the understanding of GPP variation under climate change and provide evidence and parameter for accurate simulation of carbon cycle.
    Radial growth of Mongolian pine and its response to climate at different competition intensities.
    SeMyung Kwon, PAN Lei-lei, SHI Zhong-jie, YANG Xiao-hui, ZHANG Xiao, LIU Yan-shu, ZHANG Ke-bin
    2019, 38(7):  1962-1972. 
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    To understand the radial growth of Mongolian pine (Pinus sylvestris var. mongolica) and its response to climate at different competition intensities, the treering width chronology and its competition of Mongolian pine in Hulunbuir Sandy Land was analyzed using tree chronology analysis and competitive index. Results showed that competition significantly affected the radial growth of Mongolian pine. For the radial growth, large trees with low competition were more sensitive to the monthly average maximum temperature, precipitation, and relative humidity of the growing season, while small trees with low competition index were more sensitive to the lowest monthly temperature, precipitation and relative humidity in the previous year’s growing season. Drought had greater impact on large trees and small trees than on mediumsized trees, especially on large trees with strong competitiveness. In general, the radial growth and climate response of Mongolian pine in Hulunbeier Sandy Land were significantly affected by the competition. Our results provide scientific basis for the management of natural Mongolian pine forests under the background of climate change.
    Risk assessment of alien invasive plants in Inner Mongolia.
    ZHANG Pu-jin,ZHAO Li-qing, LIANG Chen-xia, ZHANG Guo-long, ZHANG Qian-qian, YUE Li, XU Bu-yun, YANG Jie, ZHANG Pei-qing, QING Hua
    2019, 38(7):  1973-1981. 
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    Based on the demands for preventing, controlling, and managing the invasion of alien species in Inner Mongolia, an investigation of species composition and invasion status of alien plant species in Inner Mongolia was conducted. There are a total of 55 alien plants belonging to 17 families. We established a risk assessment indicator system that could be adapted to the characteristics of ecological, economic and social development of Inner Mongolia. Using this indicator system, the invasion risks of 53 alien plant species were evaluated and the levels of the invasion risks were assessed. For each risk level, the corresponding risk management strategies were presented. Our results provide a favorable guarantee for prevention and control of alien plants and consequently the ecological security in Inner Mongolia.
    Analysis of flora, life form and reproductive characteristics of alien species in Jiangsu Province.
    HOU Xin-xing, XIN Jian-pan, LU Meng-ting, TIAN Ru-nan
    2019, 38(7):  1982-1990. 
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    Under the background of global economic integration and ever-increasing international trade, biosecurity incurred by the invasion of alien species may threaten ecosystem sustainability. Through field investigation and literature reviews, we analyzed the floristic composition, genus composition, geographical composition, origins, life forms and reproductive characteristics of the invasive species in Jiangsu Province. The results showed that there are 229 invasive species, belonging to 140 genera and 51 families. For angiosperm, there are 227 species in total from 138 genera in 49 families, which are dominated by monocotyledon. In the perspective of the composition of families and genera, large families, singlespecies genera and oligospecies genera composed the main body of the flora, but larger genera have higher abundance at the level of the species, indicating that the internal structure of the invasive flora in Jiangsu Province is complex. Furthermore, the invasive flora of Jiangsu Province has a strong tropical affinity and is largely influenced by temperate flora. Most of invasive species are from the Americas and dominated by herbaceous species. 49.56% of the invasive species are propagated with small flowers and short flowering period. The main fruit type of invasive species is capsule, which is beneficial to seed dispersal. Most invasive species are mainly seed propagation. 28.82% of the invasive species have both seed and clonal propagation, with the latter being the main way that is beneficial to improving its invasion ability.
    Effects of simulated rainfall on leaf particulate matter of different size fractions of evergreen plants.
    GUO Ruo-yan, WANG Hui-xia, SHI Hui
    2019, 38(7):  1991-1999. 
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    Plants can recover their ability in capturing particulate matter (PM) deposited on leaf surface through the washing of rainfall. In this study, six evergreen plant species (Osmanthus fragrans, Pittosporum tobira, Ligustrum lucidum, Photinia serrulata, Magnolia grandiflora, and Pinus bungeana) were selected to investigate the washoff effects, retention threshold, and the relationships between rainfall and washoff efficiency under two rainfall intensities (60 and 90 mm·h-1) and different duration (0, 5, 10, 15, 20, 30, 45, 60 min). The PM deposited on leaf surface were classified into three size fractions: PM>10 (particles intercepted by 10  μm membrane), PM2.5-10 (particles pass through 10  μm membrane and intercepted by 2.5  μm membrane), and PM2.5 (particles pass through 2.5  μm membrane). The results showed that rainfall can remove most of the PM and its size fractions deposited on leaf surfaces. The elution rate ranged from 54.55% to 95.07%, 49.83% to 96.00%, 63.15% to 93.63% and 75.80% to 91.84% for PM, PM>10, PM2.5-10 and PM2.5, respectively. The elution rates of PM and PM>10under the rainfall intensity of 90 mm·h-1 were higher than those of PM2.5-10 and PM2.5. Rainfall intensity had significant effects on the elution rates of PM>10, but with no effects on PM2.5-10 and PM2.5. The threshold of retaining PM and PM>10 for the six species ranked as (from large to small): P. bungeana>L. lucidum>M. grandiflora>P. serrulata>P. tobira>O. fragrans. The washoff efficiency increased sharply at the beginning of rainfall, and then increased very slowly. The rainfall and particulate matter washoff efficiency were well correlated. As rainfall increased, the PM washoff efficiency increased logarithmically. The PM washoff efficiency increased rapidly within 30 minutes, and then increased in a very low speed.
    A short-term experiment on vegetation restoration in Baijianghe peatland of Changbai Mountains.
    LIU Yu, YANG Pan-pan, BU Zhao-jun, WANG Sheng-zhong, LIU Chao, LU Fan, CHEN Yong-da
    2019, 38(7):  2000-2006. 
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    Peatlands are one of the major carbon sinks in global terrestrial ecosystems, where Sphagnum is the most important contributor to carbon sequestration, but are faced with degradation over large parts of the world. In this study, an experimental restoration was performed in a drained and degraded part of Baijianghe peatland, Changbai Mountains, which had seen a recent dramatic loss of Sphagnum with the cover of Potentilla fruticosa reaching almost 100%. Experimental treatments included rewetting by ditch blocking (three water table depths), dwarf shrub removal (0, 50% or 90% removed) and Sphagnumpropagule spreading (three densities). The results showed that Sphagnum cover increased with increasing water table. When transplantation density (ratio of surface collected to surface restored) was no more than 1∶10, the cover of Sphagnum increased with transplantation density. Only at a high water table (5-30 cm), a high dwarf shrub cover led to an increase in Sphagnum cover. Results from this shortterm study suggests that the restoration efficiency of drained peatlands will be enhanced when sufficient amounts of Sphagnum propagule are transplanted and appropriate removal of dwarf shrubs are performed on the basis of raising water level.
    Species-specific growth responses to climatic factors in the eastern Qilian Mountains.
    ZHAN Si-min, WANG Ke-yi, ZHANG Ling-nan, RAN Yi-lin, LIU Xiao-hong
    2019, 38(7):  2007-2014. 
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    To understand the growth responses of different tree species to climatic factors in the eastern Qilian Mountains, we developed tree-ring width chronologies from two dominant tree species (Picea crassifolia and Juniperus przewalskii). The correlation coefficients between chronologies and climatic factors were calculated at 24 time scales. According to the parameters of chronologies, the residual chronology of P. crassifoliahad higher quality than the standard chronology, but the case was oppoiste forJ. przewalskii. The responses of J. przewalskii to temperature factors were stronger than that of P. crassifolia, which showed negative correlation with mean temperature from the previous June-July, the previous September and the current May-August. The responses of P. crassifolia to precipitation factors were stronger than that ofJ. przewalskii, which were positively correlated with total precipitation from the previous September and the current July-August. The radial growth of both species suffered from drought stress. In the context of global warming and intensified drought stress, enhanced protection and management should be carried out.
    Effects of different grassland use modes on spatial heterogeneity of vegetation in meadow steppe.
    YANG Yang, JIA Li-Xin, ZHANG Feng, QIAO Ji-Rong, ZHAO Tian-Qi, CHEN Da-ling, ZHAO Meng-Li
    2019, 38(7):  2015-2022. 
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    Understanding the spatial distribution of species in plant communities is important for explaining community succession under different use modes. Here, we investigated the spatial distribution of species and communities under three different use modes (grazing, mowing, and fence) in Hulun Buir meadow grassland in Inner Mongolia by using exponential function based on field survey data. The results showed that the patterns of species distribution well fitted the law of exponential function under all modes. Compared with control, grazing increased and mowing reduced community spatial heterogeneity. The number of species with higher species heterogeneity index than the community heterogeneity index increased under mowing and grazing. Mowing and grazing increased or decreased species frequency. For example, the frequency of Cleistogenes squarrosa was 0.010 in exclosure, 0.151 in mowing and 0.521 in grazing. The frequency of Artemisia dacunculu was 0.755 in exclosure, 0.132 in mowing and 0.028 in grazing.
    Effects of water saving and nitrogen reducing on annual yield and nitrogen use efficiency of ratoon rice and double rice.
    ZHENG Hua-bin, CHEN Qi-min, CHEN Yuan-wei, LI Bo, ZHANG Yan-sheng, TANG Qi-yuan
    2019, 38(7):  2023-2029. 
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    Simple and practical cultivation practice with water saving and nitrogenreducing is beneficial to promoting the development of rice cultivation technology with resourceconserving and environmentfriendly. Taking production model as object, we examined the effects of watersaving and nitrogenreducing on annual yield, the characteristics of population quality, and nitrogen use efficiency of double cropping rice. The results showed that watersaving did not decrease annual yield of ratoon rice and double rice, with highest yield of 8.42 and 12.71 t·hm-2  for both rice modes under the treatment of watersaving irrigation (W3). Compared with no nitrogen application (N0), annual yield under the treatment of nitrogenreducing (N2) and local nitrogen application level (N1) was significantly increased, with no significant difference between the treatments of N1 and N2. In addition, nitrogen agronomy efficiency, nitrogen partial factor productivity, and nitrogen use efficiency under the N2 treatment was higher than those under the N1 treatment. Therefore, to ascertain irrigating or not by the observation of the water layer in the soil layer using simple and homemade PVC tube, with reducing 24% and 20% nitrogen application respectively in the models of both ratoon rice and double rice, can achieve dual reduction of water and nitrogen use. It is a simple and practical cultivation technology with watersaving and nitrogenreducing in the rice production model.
    Ozone dry deposition in winter wheat field and the influence from rainfall.
    WEI Li, ZHENG You-fei, ZHAO Hui
    2019, 38(7):  2030-2040. 
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    An eddy-covariance system combined with rapid and slow ozone concentration analyzer was used to measure ozone (O3) dry deposition continuously in a winter wheat field in Zhengzhou. The aim of this study was to reveal the characteristics of O3 dry deposition in winter wheat field, and to examine the influence of rainfall. The results showed that the daily average value of O3 concentration was 42.7 nL·L-1 during the observation period. O3 concentration was mainly affected by solar radiation and humidity, with obvious daily and diurnal variations. The diurnal variation of O3 flux was singlevalley type, with daily mean value of -0.0073 μmol·m-2·s-1 (minus sign refers the direction towards the ground), which was greatly affected by the O3 concentration. The O3 deposition velocity was affected by atmospheric turbulence, vegetation growth characteristics, and meteorological conditions, with daily mean value of 0.38 cm·s-1. The diurnal variation was obvious single-peak type. The deposition velocity was mainly controlled by atmospheric dynamic process. The canopy resistance reached the daily minimum value at 9:30 a.m., which was the main factor leading to the maximum daily O3 deposition velocity in the morning. Rainfall affected the O3 deposition velocity of winter wheat field by increasing non-stomatal deposition and reducing atmospheric turbulence exchange. Therefore, the effects of rainfall on O3 dry deposition were dependent on background conditions.
    Effects of nitrogen application on yield and nitrogen use efficiency of winter wheat with different former crops.
    SHI Xiao-yan, WANG Zhi-qiang, GU Qing-hao, CHANG Ming-juan, HU Jun-jie, REN Yong-zhe, XIN Ze-yu, LIN Tong-bao
    2019, 38(7):  2041-2048. 
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    To explore the response of yield and nitrogen use efficiency of winter wheat to different former crops and nitrogen application levels, a split plot experiment with wheat ‘YN211’ was conducted. Factors in the main plots were three former crops, including sole maize (SM), maize intercropped with soybean (MS), and sole soybean (SS). In the subplots, there were four nitrogen levels, N0 (0 kg·hm-2), N180 (180 kg·hm-2), N240 (240 kg·hm-2), and N300 (300 kg·hm-2). The results showed that compared with SM, winter wheat yield significantly increased by 4.74%-10.01% and 5.12%-17.05% in MS and SS respectively under different nitrogen levels. Former crops had significant effects on spike number and kernel number per spike, but had no effect on 1000kernel weight. Compared with SM, winter wheat spike number increased by 10%-15% and 4%-19%, and kernel number per spike increased by 2%-21% and 4%-20% in SS and MS, respectively. Nitrogen application had a remarkable effect on spike number and 1000kernel weight, but had no effect on kernel number per spike. Former crops and nitrogen application interacted to affect grain number per spike and 1000kernel weight. Under same nitrogen application levels, the agronomic efficiency and partial factor productivity (PFP) of nitrogen fertilizer was the highest in SS, followed by MS and SM, which were significant at the nitrogen levels of N180 and N240. Based on the equation of N application level against yield, the yield of winter wheat was stable in SS and MS when the N application level was reduced, which has practical implications for guiding fertilization in wheat production under different former crops. The nitrogen application levels of optimum economic yield and maximum yield in winter wheat were 243 and 262 kg·hm-2 under SM, respectively. In SS and MS, the nitrogen application levels of optimum economic yield were 196 and 210 kg·hm-2, and those of maximum yield were 205 and 222 kg·hm-2, respectively.
    Responses of morphological structure and dry matter allocation of spring wheat to drought stress at different developmental stages in the irrigation district of Ningxia.
    WANG Chen, WANG Lian-xi, MA Guo-fei, ZHANG Xiao-yu, LI Qi
    2019, 38(7):  2049-2056. 
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    We examined the responses of morphological structure and dry matter distribution of spring wheat to drought stress in different developmental periods in 2018, with the mainly popularized variety of Yongchun No. 4 in Ningxia as the experimental material. There were six different irrigation treatments. The results showed that the treatment of no irrigation at all growth stages shortened the whole growth stage by 11 days. Drought in the tillering and jointing stages reduced lower stem segments of spring wheat spike, leaf area, and plant height, and advanced leaf yellowing. Water shortage at tillering stage had the strongest effect on leaf area, while water shortage at jointing stage had the most effect on plant height. Drought affected the accumulation and distribution of dry matter in spring wheat. When spring wheat was under drought stress at the tillering stage, the proportion of leaves in the total dry matter decreased by 6.6%, and the proportion of leaf sheath in the total dry matter increased by 9.0%. Compared with the control, when the spring wheat was under no irrigation at all growth stages, the spike length, spike number, spike grain number and thousand kernel weight were reduced by 5.9%, 43.4%, 9.6% and 7.6% respectively. Mild drought at tillering stage significantly decreased the wheat spike number, but increased the number of grains per spike and the thousand kernel weight by 9.2% and 4.7%. The drought during flowering to filling stage had the greatest effect on the thousand kernel weight, with a decrease of 17.4%.
    Daily photosynthesis dynamics of different degraded Zanthoxylum bungeanum in karst rocky desertification area and its relationship with environmental factors.
    TAN Dai-jun, XIONG Kang-ning, ZHANG Yu, HANG Hong-tao, QUAN Ming-ying, JI Chuan-ze, MA Xue-wei, ZHANG Shi-hao
    2019, 38(7):  2057-2064. 
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    Zanthoxylum bungeanum is an important ecological and economic tree species in karst rocky desertification area of China. We measured the photosynthetic productivity of Z. bungeanum in the fragile habitat with rocky desertification, including lightly degraded (LD), moderately degraded (MD) and severe degraded (SD) Z. bungeanum. Daily photosynthesis variations of Z. bungeanum and their relationships with environmental factors were examined. Moreover, the path analysis method was used to analyze the direct or indirect effects of environmental factors on the net photosynthetic rate (Pn) ofZ. bungeanum. Average daily Pn of LD, MD and SD were 3.53, 2.85 and 2.32 μmol·m-2·s-1, respectively. Diurnal photosynthesis assimilations of LD, MD and SD were 141.21, 113.44 and 94.97 mmol·m-2, with significantly lower value of SD than those of LD and MD. LD had higher water use efficiency and instantaneous carboxylation efficiency than MD and SD. Z. bungeanum with different degraded degrees showed no significant difference in average daily stomatal limiting value. Pn of LD was mainly influenced by CO2 concentration and photosynthetically available radiation (PAR). The interaction between air temperature (Ta) and relative humidity (RH) jointly restricted the value of Pn.PAR and RH were dominant factors influencing MD and SD respectively, with Ta as the major limiting factor. In conclusion, photosynthesis of different degraded Z. bungeanum was sensitive to the dynamics of physiological conditions and natural environment conditions, with relatively low photosynthetic productivity.
    The photosynthesis characteristics and instantaneous water use efficiency of Capsicum annuum under different light conditions.
    ZHONG Ping-an, SHAO Dong, HUANG Ying-jin, WANG Qiang, YANG Xiao-long, YE Zi-piao
    2019, 38(7):  2065-2071. 
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    Gas exchange of Capsicum annuum L. under shading and greenhouse conditions was measured by LI6400 Portable Photosynthetic System. The lightresponse curves of photosynthesis and instantaneous wateruse efficiency were fitted by lightresponse models. The change tendency of the net photosynthetic rate and instantaneous wateruse efficiency of leaves were measured under different light conditions. The results showed that the maximum net photosynthetic rate (Pnmax) and transpiration rate (Tr) ofC. annuum leaves in greenhouse were lower than that under shading, whereas the maximum instantaneous wateruse efficiency (WUEinstmax) of C. annuum in greenhouse was higher than that under shading, and the corresponding saturating lightintensity (Iinstsat) was lower than that under shading. There was no significant difference of WUEinstmax and Iinstsat between the conditions in greenhouse and in shading (P>0.05). Furthermore, there was significant difference between Isat(corresponding to Pnmax) and Iinstsat(corresponding to WUEinstmax) (P<0.05), and the values of Isat  were greater than the values of Iinstsat. Our results indicate that both photosynthesis and instantaneous wateruse efficiency of C. annuum leaves are not synchronized for each of two different light conditions.
    Responses of the nosZdenitrifying bacterial communities to fertilization regimes in paddy soils.
    WANG Pei-xin, YANG Ya-dong, WANG Zhan-hai, ZENG Zhao-hai
    2019, 38(7):  2072-2079. 
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    The reduction of nitric oxide (N2O) to dinitrogen (N2) in denitrification is performed by the nosZtype denitrifying bacteria, which plays a key role in regulating N2O emission. To verify the effects of fertilization on the nosZtype denitrifying bacterial communities in paddy soils, realtime PCR and highthroughput sequencing approaches were applied to investigate the abundance and structure of the nosZtype denitrifying bacterial communities in a 30year fertilized paddy soil in Hunan Province, China. The abundances of nosZ gene ranged from 2.14×108 to6.09×108 copies·g-1 dry soil. ThenosZ gene abundances in the fertilized treatments (chemical fertilizer, 70% chemical fertilizer + 30% organic manure, and 40% chemical fertilizer + 60% organic manure) were 47.3%-64.8% lower than that of CK (P<0.01). Organic manure application rates rarely affected the nosZ gene abundance. Proteobacteria was the predominant phylum, accounting for 60.2%-77.5% of the total reads. Bacteria_unclassified, Proteobacteria_unclassified, Betaproteobacteria_unclassified, and Rhizobiales were the abundant order groups that represented 93.6%-95.9% of the total reads. Fertilization significantly decreased the Proteobacteria_unclassified abundances (P<0.01) and significantly increased the relative abundance of Rhizobiales, environmental_samples, and Rhodocyclales in the fertilized soils compared with CK (P<0.05). Fertilization altered the nosZtype denitrifying bacterial community structure. Organic manure application rates had minor effects on the community structure. All the examined soil properties, expect for C/N ratio, were significantly correlated with the abundance, relative abundance of some order groups and structure of the nosZtype denitrifying bacterial communities, with nitrate and soil pH were the most important factors affecting the nosZtype denitrifying bacterial community structure. These results indicated that fertilization significantly changed the abundance and structure of the nosZtype denitrifying bacterial communities, while organic manure application rates showed limited effect. Our results provided basis for further research on the effects of fertilization on the denitrifying bacterial community.
    Effects of root exudates of Cupressus funebris on soil nutrients and enzyme activities of potted Toona sinensis.
    YI Yan-ling, WU Li-ying, YANG Qian, REN Yong-sheng, LIU Hai, LI Xian-wei, FAN Chuan
    2019, 38(7):  2080-2086. 
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    We examined the effects of Cupressus funebris root exudates on soil nutrients and enzyme activities in the mixed plantation of C. funebris and Toona sinensis with a potculture method. The C. funebris root exudates were collected by soil culture method and added to the potted seedlings of T. sinensis every month. Four treatments of G1, G2, G3 and G4 were set up, corresponding to the treatments with rhizosphere soil extracts of 1, 2, 4, and 8 cypresses respectively. Meanwhile, a control was treated with distilled water. After one year, the nutrient concentrations and enzyme activities of soil in the five groups were measured. The results showed that C. funebris root exudates had no effect on the concentrations of soil total N, total P and total K (P>0.05), but significantly increased the concentrations of alkalihydrolysable N, available P and available K (P<0.05). The concentrations of alkalihydrolysable N, available P and available K increased with increasing concentration of the extracts, with no difference between G3 and G4 (P>0.05). The activities of urease, neutral phosphatase, catalase and invertase in soil were boosted after adding root exudates, which were increased with increasing concentrations of exudates. The results of correlation analysis showed that the activities of the four enzymes were remarkably correlated with the concentrations of soil alkalihydrolysable N, available P, available K and pH (P<0.01), but had no relationship with that of total N, total P, and total K (P>0.05). There was a positive correlation among the activities of the four enzymes (P<0.01). Our results indicated that increasing concentration of C. funebris root exudates could increase the concentrations of alkalihydrolysable N, available P and available K, and enhance the activities of soil urease, neutral phosphatase, catalase and invertase, which would directly or indirectly affect theavailability of soil nutrients. The root exudates of four cypresses had the strongest effects on soil available nutrients and soil enzyme activities. When the mixing ratio ofC. funebris and T. sinensis was 4∶1, the soil environment could be much improved.
    Soil labile organic carbon fractions and the differences of their concentrations in different types of wetlands in Yili valley.
    CUI Dong, YAN Jun-jie, LIU Hai-jun, CHEN Chen
    2019, 38(7):  2087-2093. 
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    Soil labile organic carbon is sensitive to environmental changes. We investigated the contents of labile organic carbon fractions in different types of wetland soils and its influencing factors in Yili Valley, including the longterm flooding reed (Phragmites australis) wetland, rarely flooding ditch millet (Paspalum orbiculare) wetland, and seasonal flooding chee reedgrass (Calamagrostis epigeios) wetland. The concentrations of easily oxidized organic carbon (EOC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC) in 0-40 cm soil layers of different types of wetlands were measured. The correlations between soil EOC, DOC and MBC, and their relationships with activities of soil enzymes (invertase, urease, catalase), soil nutrient concentrations (ammonium nitrogen, total phosphorus) and soil organic carbon (SOC) concentrations were analyzed. The vertical differentiation of the soil labile organic carbon contents in the 0-40 cm soil layer in the three different types of wetland was consistent, decreasing with soil depth across the soil profile. The contents of MBC, EOC and DOC were significantly different among the three wetlands (P<0.05), with lowest contents of MBC, EOC and DOC in reed wetland. Among the three types of wetlands, the proportions of MBC, EOC and DOC in SOC were 4.33%-18.02%, 28.85%-66.06%, and 0.73%-1.36% in the 0-40 cm soil layer, respectively. There was no consistent pattern of the proportions of MBC and EOC, except that the proportion of DOC in SOC increased first and then decreased. Among the three soil labile organic carbon fractions, the proportion of the EOC was the highest and that of the DOC was the lowest. The highest proportions of MBC and EOC in SOC were found in the ditch millet wetland. The highest proportion of DOC was found in the chee reedgrass wetland. The proportions of MBC, EOC and DOC in reed wetlands were relatively lower. The correlations between the MBC, EOC and DOC in the three types of wetlands were significantly correlated. The correlation between DOC and soil total phosphorus was not significant, while the three soil labile organic carbon fractions with soil nutrients and soil enzyme activities were significantly correlated. Our results indicated that soil enzyme activities and soil nutrients were important factors affecting soil labile organic carbon contents.
    Heavy metal tolerance, accumulation and distribution in five clones of Casuarina equisetifolia.
    LI Xiao-gang, KANG Xi-rui, CAI Ze-yu, ZHANG Han-dan, ZHANG Jian-feng, HE Gui-ping, CHEN Guang-cai
    2019, 38(7):  2094-2101. 
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    To compare the phytoremediation potential of Casuarina equisetifolia cultivated in an artificially contaminated soil with copper (Cu), cadmium (Cd), lead (Pb) and manganese (Mn), we evaluated the tolerance of heavy metals (HMs) and accumulation capacity of one-year-old cutting seedlings of five clones (S13, S44, S48, S60 and S80) ofC. equisetifolia. There were four HMs levels (CK, low (T1), medium (T2) and high (T3)) in this experiment. The plant growth, HMs accumulation and distribution characteristics were measured. The results showed that all clones could survive on the polluted substrate and maintain the normal growth. The five clones showed different tolerance levels to the HMs treatments. Compared to CK, HMs treatments significantly promoted the growth of S13 and S44. The growth of S48, S60 and S80 showed no significant difference in the HMs treatments compared to CK. The HMs concentrations in tissues were increased with increasing HMs concentrations in soil. Furthermore, the HMs concentrations in tissues showed variation depending on metal speciation. For example, the concentrations of Mn in tissues were in the order of twig > stem > root. Moreover, the translocation factor (TF) values of Mn were greater than 1 in all clones and HMs treatments. The amounts of Mn in aboveground part of C. equisetifolia account for 86%, suggesting that C. equisetifolia had the higher Mn transfer capability. The concentrations of Cu, Cd and Pb in the roots were higher than in the stems and twigs. The amounts of HMs in the aboveground part were more than 50% of the total accumulation. Under the T3 treatment with the highest HMs concentration, there was no significant difference in comprehensive bioconcentration index (CBCI) of heavy metals among the five clones, indicating that they had similar accumulation capacity to heavy metals. According to the biomass and CBCI, clones S13 and S44 had a greater potential in phytoremediation. Taken together, C. equisetifolia had high tolerance, good accumulation and translocation capabilities for Cu, Cd and Mn. Therefore, C. equisetifolia could be a promising species for phytoremediation application on HMs pollution soil, especially for Mn pollution.
    Characteristics and source identification of heavy metal pollution in agricultural soils and vegetables in Wuqing District, Tianjin City, China.
    PENG Hao, MA Jie, MA Yu-ling, CHEN Ya-li
    2019, 38(7):  2102-2112. 
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    To evaluate heavy metal pollution in agricultural soils and vegetables in North China, 45 surface agricultural soil samples and corresponding vegetable samples, 32 livestock manure samples, and four soil profiles were collected in Wuqing District, Tianjin City. For all samples, heavy metal (Cd, Cr, Cu, Ni, Pb, Zn) concentrations and their fractions were analyzed. The correlation analysis and principal component analysis were used to determine the potential pollution sources. The results showed that the accumulation (relative to soil background value) of heavy metals in surface soils decreased in the order of Cd>Cr>Cu>Zn>Pb>Ni. The concentration of Cd in 26.7% of samples exceeded the Second Standards of Soil Environment (GB 15618-2018). Heavy metal concentrations in vegetable roots were relatively enriched (especially for Cd), while those in leaves did not exceed the standards (GB 2762-2017). In the study area, 16% of samples for Cd in applied livestock manures exceeded the industry standards of organic fertilizer of China (NY 525-2012), which could lead to the accumulation of heavy metals in surface soils after longterm application. Relatively high proportion of exchangeable Cd, Cu and Zn in the surface soil might increase the potential risk of heavy metals absorbed by crops and lead to the accumulation of heavy metals in roots and leaves of vegetables. Results from the principal component analysis showed that Cr and Ni may derive from soil parent material, Zn from agricultural activities (such as the application of livestock manures), Cd and Pb from industrial activities, and Cu from both agricultural and industrial activities. In summary, Cd in some soil and livestock manure samples exceeded the standard in this area. More attention should be paid to control or reduce the impacts of agricultural and industrial pollution on metal concentrations in soils and vegetables, although no heavy metal concentrations in leaves exceed the limit of stan dards at present.
    Spawning habitats of two sympatric species of Urodela.
    WANG Heng, HAN Lei, ZHAO Wen-Ge, LIU Peng
    2019, 38(7):  2113-2119. 
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    The spawning time, egg bag attachment, spawning site, and oviposition site habitat of the Siberian salamander (Salamandrella keyserlingii) and the Northeastern China salamander (Hynobius leechii) in Changbai Mountain were measured from April to May 2018. The results showed that there were overlaps in the spawning time and the spawning sites between the two sympatric species, with the altitude being an important factor driving their separation or coexistence. Aquatic vegetation was the dominant attachment of egg bags in Salamandrella keyserlingii, accounting for 66.15% of the total, while dead branches were the dominant attachment of egg bags in Hynobius leechii, accounting for 71.60%. There was no significant difference in the spawning sites, but with significant differences in the microhabitat of oviposition sites such as depth of oviposition, water temperature and coverage ratio of sundries. Oviposition sites of Salamandrella keyserlingiiwere shallower, higher in water temperature and coverage ratio of sundries than that of Hynobius leechii. It is concluded that the habitat separation of the spawning sites is the main reason for the coexistence of the two sympatric species.
    Acoustic characteristics and daily circadian rhythms of Fejervarya cancrivora (Anura:Dicroglossidae).
    WANG Tong-liang, JIA Le-le, ZHAI Xiao-fei, WANG Ji-chao
    2019, 38(7):  2120-2125. 
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    Calls are an important medium for acoustic communication among animals. Analysis of acoustic characteristics is beneficial to understand acoustic communication in frogs. Calling patterns in frogs are speciesspecific and influenced by selection pressures from local environment. From June to October in 2017, the acoustic structure and daily circadian rhythms of calling activity were recorded for 24 individuals of Fejervarya cancrivora that inhabited brackish water and semisaline water. The results showed that F. cancrivora calls were composed of basic syllables, combination calls with the basic syllables, and multisyllabic calls. Furthermore, the calls were frequency modulated. Male individuals called from 20:00-21:00 to 5:00-6:00, with a peak at 2:00-4:00. The numbers of hourly calls of males were not significantly correlated with air temperature or relative humidity (P>0.05). However, the calling behavior ended (5:00-6:00) with rising temperature. F. cancrivora communicated more efficiently via frequency modulation and changes in calling types. The calling behavior of F. cancrivora followed daily circadian rhythms, occurring throughout the night. The beginning and ending time of calling activity was influenced by air temperature. The high relative humidity facilitated the transmission of calls.
    The dominant shrimp species and its niche in the coastal area of southern Zhejiang.
    CHEN Wei-feng, YE Shen, YU Yue, PENG Xin, CHEN Shao-bo
    2019, 38(7):  2126-2132. 
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    Based on the fishery resource data from the bottom trawl surveys conducted in the Zhejiang coastal area in November 2015 (autumn), February 2016 (winter), May 2016 (spring) and August 2016 (summer), we analyzed the ecological niche of dominant shrimp species using index of relative importance (IRI), niche breadth and niche overlap and canonical correspondence analysis (CCA). The results showed that there were 12 dominant shrimp species, belonging to 5 families and 9 genera. The spatial, temporal and spatiotemporal niche breadth of dominant shrimps ranged from 0.98-6.16, 0.16-1.34 and 0.45-7.64, respectively. Solenocera crassicornishad the strongest capacity to use resources, whereas Alpheus digitalis was the least. The niche overlap value between Alpheus japonicusand Alpheus digitaliswas the highest, indicating that these species were highly similar in resource utilization. Acetes chinensis (a pelagic and middle planktonic species) and Metapenaeus joyneri (a migratory shrimp in estuaries) had niche differentiation with other species in spatial and temporal dimensions. Organic matter, chlorophyll a, and suspended matter in water were the main factors driving the distribution of dominant species, which was associated with food habits. Temperature had slight effects on shrimp community due to the great dominance of eurythermal and euryhaline species. Salinity had substantial impacts on the eurythermal and hypohaline species, Acetes chinensis and Alpheus digitalis.
    Effects of constant and diel-fluctuating temperature on thermal tolerance of zebrafish at different life-history stages.
    WANG Guo-qiang, XIA Ji-gang
    2019, 38(7):  2133-2137. 
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    To examine the effects of constant and diel-fluctuating temperature on thermal tolerance of zebrafish (Danio rerio) at different lifehistory stages, the newly hatched fry, juvenile fish, and sexually mature females and males were acclimated to constant temperature (28 ℃) and diel-fluctuating temperature (26-30 ℃) for two weeks. Then, the critical thermal maxima (CTmax), lethal thermal maxima (LTmax), critical thermal minima (CTmin), and lethal thermal minima (LTmin) of zebrafish at different life-history stages were measured using the critical thermal methodology of Becker and Genoway. Acclimation temperature, life-history stage, and their interactions had significant effects on thermal tolerance of zebrafish (P<0.05), whereas acclimation temperature and gender had no significant effect on thermal tolerance of adult zebrafish (P>0.05). The thermal tolerance of larvae was weaker than that of juvenile and adult fish, with lowerCTmax and LTmax and higher CTmin and LTmin. These characteristics might be related to the living habits and habitat environment of fishes at different life-history stages. The diel-fluctuating temperature had no effect on the thermal tolerance of juvenile and adult fish, but it increased body length and decreased thermal endurance scope in larvae, suggesting a tradeoff between growth and thermal tolerance.
    Ecosystem pattern change and its influencing factors of “two barriers and three belts”.
    WANG Xiao-feng, LESImu-chu, ZHANG Ming-ming
    2019, 38(7):  2138-2148. 
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    The “two barriers and three belts” is an important part of China’s national ecological security strategic pattern. Understanding the spatialtemporal distribution and transformation of ecosystem types in the barrier is important for the sustainable development of the barrier and the construction of ecological civilization. Based on the land use data of 30m resolution in 2000, 2005, 2010 and 2015, the spatial and temporal changes of ecosystem types in barrier areas from 2000 to 2015 were analyzed by the methods of ecosystem pattern change analysis, land transfer matrix, PNTIL model and geographical detectors model. Furthermore, the influencing factors of forward/reverse transformation of ecosystems were discussed. Urban expansion and agricultural land change were the most significant phenomena in the process of ecosystem change from 2000 to 2015. The negative conversion rate of ecosystems in barrier was slightly higher than the positive conversion rate. The negative transformation of ecosystems in barrier had obvious directions of population development, economic development and industrial development. The impacts of natural environmental factors on the positive transformation of ecosystems were significantly greater than those of socio-economic factors. There was a significantly positive correlation between socio-economic factors and the reverse transformation of ecosystems, but no significant correlation between socio-economic factors and the positive transformation of ecosystems. As the “natural constraining force” of ecosystem changes, the natural environmental factors had a significant correlation with the reverse or positive transformation of ecosystems.
    The differences of thermal environment effect of urban green space evolution: A case study of Fuzhou.
    CHEN Yan-hong, CAI Yuan-bin
    2019, 38(7):  2149-2158. 
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    We quantified the land surface thermal environment during urbanization of the main urban area of Fuzhou by extracting the land use/land cover (LULC) based on Landsat series remote sensing data and retrieving the land surface temperature (LST). The results showed that there were dramatic changes in LULC of Fuzhou from 1993 to 2013, with the reduction of urban green space (UGS) including forest/grass, water and wetland and the significant increase of builtup land. The LST of different LULC had significant differences. The buildup land and bare land had positive contribution to the LST, while the UGS had negative effect on LST, with the order of water > wetland > forest/grass. During the evolution process of different types of UGS, there was a diversified temperature pattern. The ΔLST caused by UGS loss was the most obvious, followed by the UGS exchange and the UGS extension regions. The relationship between evolution direction of different UGS types and temperature effect was quantified by TVX. Our results might help understand the mitigation effect of different UGS types on urban heat island effect and provide useful reference to the conservation of green space in coastal cities.
    The impacts of hydropower development in Zhangye section of Qilian Mountains on regional eco-environment.
    GUI Juan, GAO Hai-ning, LI Zong-xing, ZOU Hai-ming, YUAN Rui-feng
    2019, 38(7):  2159-2166. 
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    From July 26 to August 13, 2017, by the methods of on thespot investigation, plot survey, and the analysis of river water and soil samples, we assessed the impacts of construction time, site area of hydropower stations, and hydropower development on water quality, soil and ecological flow in Zhangye section of Qilian Mountains Nature Reserve. The results showed that the construction of hydropower stations was mainly concentrated from 2000 to 2008. The total area for 26 hydropower stations was 798.35 hm2, accounting for 0.042% of total area in study region (1.88 million hm2), which indicated that hydropower projects covered a small area. The vegetation coverage and biomass in the construction areas of the hydropower stations were 27.14% and 236.8 g·m-2 lower than those of the original vegetation, respectively. The water quality and soil of the areas around hydropower stations were in good conditions, indicating that the water and soil were seldom affected by hydropower development. The hydropower development had led to the decrease of ecological water quantity, causing a waterreduction river section with a length of 156.76 km.
    Spatiotemporal variation and landscape pattern of soil erosion in Qinling Mountains.
    GUO Si-qi, HAN Lei, ZHAO Yong-hua, YUAN Xue-feng, WANG Da, LI Yun-qi
    2019, 38(7):  2167-2176. 
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    Soil erosion is an important factor restricting the sustainable development of Qinling Mountains region. This study aims to explore the soil erosion status and landscape pattern change in Qinling Mountains. Based on the results of remote sensing interpretation in 2005, 2010 and 2015, the general soil erosion equation (RUSLE) was used to calculate the soil erosion in those three years. After that, soil erosion status of the five major watersheds in Qinling Mountains was quantified. The relationships among soil erosion, land use, and topographic factors were analyzed, and the changes of soil erosion landscape pattern in the study area were clarified. Intensity and area of the soil erosion in Qinling Mountains significantly decreased from 2005 to 2015. The total erosion amounts in 2005 and 2015 were 0.90×108 and 0.33×108 t respectively, with a reduction of 63.33%. Soil erosion decreased from west to east and from south to north. Soil erosion was the most serious in the Jialing River basin, situated in the western part of the study area. The soil erosion modulus in 2005, 2010 and 2015 were 3872.80, 1454.31 and 1461.91 t·km-2·a-1, respectively. The soil erosion modulus was positively correlated with topographic factors such as slope and elevation, and showed obvious temporal and spatial variations. Soil erosion showed a weakening trend in different land use types in the region, with the most obvious reduction for the unused land. The fragmentation degree of the overall erosion landscape and the total number of patches in Qinling Mountains reduced, and the fragmentation index and the landscape heterogeneity decreased. The anthropogenic disturbance on the landscape of Qinling Mountains weakened over time, and the ecological environment was developing in a benign direction.
    Dynamic evaluation of natural capital in Zhejiang Province based on the three-dimensional ecological footprint extension model.
    JIN Xue-ru, LI Xiao-xian, ZHANG Hong-ming, ZHANG Nan-yu, FENG Zhe
    2019, 38(7):  2177-2183. 
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    Natural capital is the basis for human survival and sustainable development, which has received wide attention. In this study, the threedimensional ecological footprint extension model was used to estimate footprint size, footprint depth, and ecological carrying capacity in 2000, 2004, 2008, 2012 and 2016 in Zhejiang Province, to reflect the temporal dynamics of natural capital. From 2000 to 2016, the per capita ecological footprint of Zhejiang Province increased first and then decreased. In 2012, it reached a peak of 2.7950 hm2·cap-1. Zhejiang Province was in a state of serious ecological deficit. Under the trend of increasing contradiction between supply and demand of natural resources, footprint depth in Zhejiang Province dropped from 8.2144 in 2012 to 8.1696 in 2016, providing a development strategy for mitigating ecological pressure by exploring energysaving technologies and seeking alternative energy sources. The overdraft of natural capital in Zhejiang Province was mainly on cropland and grassland, and the consumption of whose stocks continued to increase. Our results can enrich the evaluation method of natural capital and provide reference for accelerating ecological civilization system reform and building a Beautiful China.
    Spatiotemporal differentiation of forest land conversion on township scale of the loess hilly region in central Gansu: Effectiveness of ecological construction project.
    GONG Jie, LI Hong-ying, CAO Er-jia, ZHANG Jin-xi, LIU Dong-qing, MA Xue-cheng
    2019, 38(7):  2184-2190. 
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    Based on GIS techniques and Landsat images, the transformation source, extent and speed of forest land use, and the spatiotemporal differentiation characteristics of forest land transformation were obtained on the township scale for Anding District, Dingxi City in 1995, 2000, 2005, 2010 and 2015. From 1995 to 2015, the total area of forest land transformation was increasing, with the grassland and cultivated land being the main sources. The forest land transformation extent and transition speed showed a tendency of decrease first and then increase from 1995 to 2015. The spatial distribution of forest land transformation differed, and the transformation area of forest land in each town was also different. The change of forest land transformation differed with the increasing slope. Both the net conversion and transformation extent of forest land showed a trend of increase first and then decease, but with opposite transformation speed. The major transformation of forest land occurred in the area with slope larger than 15°.
    A review on hydrological mediating functions and mechanisms in forest ecosystems.
    HAN Chun, CHEN Ning, SUN Shan, ZHAO Chang-ming
    2019, 38(7):  2191-2199. 
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    With the ecohydrological processes of forest ecosystems as the research focus, we introduced the relevant concepts and development to give a review on the topic. We discussed the ecohydrological processes, influencing factors and ecohydrological models of different interface layers (canopy, litter layer and soil layer) in forest ecosystems. We also reviewed the evapotranspiration process, soil and water conservation, water quality purification and material cycling process. Future studies should address the following issues: (1) The effects of functional traits and environmental factors in different interface layers on water saving, circulation, infiltration and runoff process, and the underlying mechanisms. (2) The coupling mechanisms of soil and water conservation, water quality purification, and element cycling. (3) The relationship between ecohydrological processes and energy flow and material cycling. (4) The ecohydrological processes should be studied on temporal and/or watershed scale(s). Overall, the future research should strengthen the multi-disciplinary, multi-field and multi-scale integrated research on forest ecosystems. Combining the modern hightech approaches to examine the effects of the functional traits of different vegetation types on ecohydrological processes and mechanisms will provide a scientific support for the management of forest ecosystems.
    Application of modern molecular biotechnology in studying ancient DNA of lake sediments.
    YAN Dong-na, XU Hai, HOU Wei-guo
    2019, 38(7):  2200-2209. 
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    In recent years, the development of new techniques in molecular biology offers a new way for understanding the evolution of lake ecosystem. Ancient DNA could well record the migration and evolution of animals, plants, algae and even microbes, and thus has become an effective tool to reconstruct paleoclimate and paleoenvironment. Studies on the ancient DNA preserved in lake sediments have provided abundant information and high-resolution data that are needed for reconstruction of ancient microbial, plant, or animal community, as well as the ancient environmental conditions. Here, we firstly introduced the preservation characteristics of the ancient DNA and DNA extraction methods from lake sediments, and then reviewed the latest molecular biology techniques for studying ancient DNA preserved in lake sediments. We also discussed the application of ancient DNA in lake sediments including reconstruction of paleoclimate, paleoecology and the impacts of human activities on paleoenvironment. Finally, some problems and possible trends on the research of ancient DNA in lake sediments were summarized.
    Research advances in plant ecological adaptability in karst area.
    NI Long-kang, GU Da-xing, HE Wen, HUANG Yu-qing, CHEN Zhong-yi
    2019, 38(7):  2210-2217. 
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    We reviewed the research progress on ecological adaptability of plants to karst environments, including high light and temperature, soil drought, soil nutrient and habitat heterogeneity. High light and temperature, geological drought force plants to change their physiological and morphological characters to cope with the damage caused by karst environment. Special soil properties also enable karst plants to evolve strong biochemical regulatory functions. The relationship between spatial heterogeneity and plant functional traits is a hot topic in recent years. At present, there has been great progress in the study of karst plants adapting to the special habitat, with some shortcomings in the scope of research. It is necessary to strengthen the study on the relationship between community succession and different functional traits, to provide scientific basis for the ecological restoration of karst area.
    A brief introduction to ecological problems and the research progress of soil remediation in the northern foot of Qinling Mountains.
    ZHOU Yu-jie, ZHAO Yong-hua, LI Wan-ying
    2019, 38(7):  2218-2227. 
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    Qinling Mountains is one of the key areas of ecological conservation in China. As an important part of the Qinling Mountains, the northern foot of the Qinling Mountains (Xi’an section) is related to the ecological environment and economic development quality of Xi’an City. The special location, over exploitation of mineral resources, illegal construction of private villas, free discharge of domestic waste,  have led to a series of soil pollution problems, with serious environmental damage in the northern foot of Qinling Mountains. In view of the ecological problems such as diverse pollution types and varying pollution levels in the northern foot of Qinling Mountains, it is necessary to use remote sensing monitoring to carry out indepth investigation, with the aim to promote the restoration and evaluation of contaminated land and realize the rational utilization of land resources and further improvement of soil quality. According to different soil properties and pollution conditions, physicochemical, biological and new soil remediation techniques are used to establish effective remediation system in the aspects of pollution source and pollution degree, and to carry out longterm dynamic monitoring. In addition, through land science and technology innovation, the research in microbes and trace elements, the theoretical study of land science and engineering, we will establish ecological protection standard system and ecological redline in the northern root of Qinling Mountains, which will help the government to be selfregulated and improved, thus realizing the land resource classification management, soil quality improvement, and environment management optimization and providing guidance and operable strategies for ecological restoration in the northern foot of Qinling Mountains.
    Eco-environmental problems and their solution strategy for large-scale land consolidation and development in Mu Us Sandy Land of Yulin in North Shaanxi.
    SHI Hui, LIU Xiu-hua, CHEN Zhan-fei, SU Hong-yu
    2019, 38(7):  2228-2235. 
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    Land consolidation and development is a key way to achieve the balance of cultivated land occupation and compensation in China. The land consolidation and development of the Mu Us Sandy Land in Yulin region has contributed to the dynamic balance of total cultivated land in Shaanxi Province. Given that the Mu Us Sandy Land is located in an ecologically fragile area, large-scale land consolidation and development may lead to serious environmental problems. Through the investigation of land development projects in Mu Us Sandy Land of Yulin, we found that the sandy land development area in Yulin was nearly 10000 hm2. This largescale sandy land development had led to the decline of groundwater level in some areas, and the concentrations of NH4+-N, NO3--N and NO2--N in groundwater exceeded water quality standard. There is risk of resandification for those cultivated lands developed on sandy lands due to lack of the protection from shelter forests and effective coverage. In connection with the natural characteristics and land consolidation and development status of the Mu Us Sandy Land in Yulin, we suggest reduce intensity of land development and increase the intensity of land consolidation. Strategies include: implementing environmental impact assessment of land consolidation planning, understanding the potential of land development and consolidation in the region from the planning aspect, providing solutions to the environmental problems from a macroperspective; postevaluation of the environmental impacts of the developed lands to summarize lessons. Moreover, in the process of land consolidation and development, it is necessary to optimize land consolidation and development model, to enhance the overall service function of the regional ecosystem, and rationally extract groundwater to maintain ecohydrological security.
    Application of the actual 3D model from multi-source data fusion in land consolidation.
    TIAN Ge, HAN Lei, ZHAO Yong-hua
    2019, 38(7):  2236-2242. 
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    Since the beginning of 21st century, land consolidation projects have rapidly developed under the background of ecological civilization construction in China. With the rapid development of unmanned aerial vehicle (UAV), the technology of the oblique photography measurement comes into the public’s vision and has been widely used in the land consolidation projects. Based on the method of multisource data fusion, using multi-len cameras, UAV takes pictures for the buildings from different angles and regain the forms of the tops and sides of the buildings efficiently. More accurate details of models can be achieved. This technology can provide basic geographic data for land consolidation projects. Such data can be applied to many areas, such as planning, design and construction of land consolidation projects. Here, we introduce the use of actual 3D model technology from multi-source data fusion into land consolidation projects, and propose related solutions and technical processes.
    Effect of technical parameters of vertical tube emitter on soil water infiltration characteristics.
    HE Jing, BAI Dan
    2019, 38(7):  2243-2248. 
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    Subsurface irrigation is a type of water saving technology. Current subsurface irrigation emitters have poor anti-clogging abilities and consume a lot of energy. Considering the disadvantages of old subsurface irrigation emitters, a new type of subsurface irrigation emitter-a vertical tube emitter-was proposed based on energyefficient by decreasing pressure head and improving anticlogging characteristics. In this study, the characteristics of cumulative infiltration of vertical tube emitter were examined. The hydraulic head and infiltration time were considered as factors affecting infiltration of the vertical tube emitter. The experimental scheme was established with different pressure levels (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 m) and different tube diameters (4, 8, 12, and 16 mm). A Mariotte bottle was used to regulate the hydraulic head. The total infiltration time was 5 h for each trial, with the time intervals of 1, 2, 3, and 5 min during 0-50 min, respectively. Then, the time interval was 10 min for every record. During 100-180 min, the time interval was 20 min, and the last interval was 30 min from 180 to 300 min. The cumulative infiltration was observed and recorded with different pressure heads. The results showed that at the first infiltration stage, the value of cumulative infiltration was remarkably fluctuated. As the infiltration time went on, the fluctuation of the value decreased slightly and then tended to be stable. Pressure head had a significant influence on cumulative infiltration. Such effect was weakened with the infiltration time. There was a significantly positive correlation between tube diameter and cumulative infiltration, but this influence decreased with the increasing tube diameters. The correlation coefficients between observed values of cumulative infiltration and predicted values using pressure head and tube diameter as predictor variables were 0.997 and 0.998, respectively, indicating a good relationship between cumulative infiltration and influencing factors. Our results are important for further study on infiltration performance of vertical tube emitters in subsurface irrigation and the application of vertical tube emitters.
    Spatiotemporal distribution of drought in Shanxi Province based on modified relative moisture index.
    LI Na, HUO Zhi-guo, QIAN Jin-xia, XIAO Jing-jing, ZHOU Xiao-yu
    2019, 38(7):  2249-2257. 
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    Based on 57 years (from 1960 to 2016) data of daily precipitation, temperature, sunshine hours, relative humidity, wind speed and vapor pressure from 70 meteorological stations in Shanxi, we calculated modified relative moisture index (M10i) using the relative moisture index (M). The spatial distribution of drought frequency and intensity in Shanxi was analyzed at annual and seasonal scales. The results showed that drought years were well expressed by M10i. In the study period, annual drought intensity tended to be more serious. Drought was light in the 1960s, and became serious in the 1980s and 1990s, then continuously decreased. Spatially, drought intensities were higher in the north and lower in the south, with the most severe drought in the north and the middle part of Taiyuan. Drought was more serious in winter and spring than in summer and autumn. Specially, heavily severe drought occurred with the highest frequency, followed by severe drought, light drought, and moderate drought. Drought happened most frequently in winter, followed by spring, autumn and summer in Shanxi.
    Estimation of winter wheat yield based on coupling remote sensing information and WheatSM model.
    LI Ying, CHEN Huai-liang, TIAN Hong-wei, YU Wei-dong
    2019, 38(7):  2258-2264. 
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    WheatSM, a wheat growth model developed for different types of winter wheat in China, is applied in scientific research and public service. The coupling of remote sensing information with crop growth model has important application value in crop growth monitoring and yield estimation in large area. Hebi City in Henan Province is a main winter wheat producing area of China. With Hebi as the study area, the optimized reconstructed time series MODIS LAI data from 2013 to 2017 was coupled with WheatSM model with both SCE-UA optimal assimilation and EnKF assimilation methods to estimate the yield of winter wheat at both site and regional scales. The results showed that the introduction of remote sensing data with uncertainties did not improve the simulation accuracy of the crop model on the premise of strictly calibrating the parameters of WheatSM at site scale. The quality of remote sensing observation data had greater effects on the results of EnKF assimilation method than that of SCE-UA optimal assimilation method. At regional scale, the accuracy of data assimilation results with both SCE-UA and EnKF methods were higher than that without data assimilation. RMSE between simulated yield and statistical yield decreased from 2036.0 kg·hm-2 to 1641 kg·hm-2  with SCE-UA method and to 1587.7 kg·hm-2  with EnKF method, with a reduction of 19.4% and 22.0%, respectively. The efficiency of EnKF assimilation method was higher than that of SCE-UA optimal assimilation method. Our results could provide a basis for the selection of data assimilation strategies coupling WheatSM with remote sensing data.
    Climate quality evaluation model for navel orange in Ganzhou.
    XIE Yuan-yu, WANG Pei-juan, ZHU Ling-jin, CHEN Xing, HUANG Ying
    2019, 38(7):  2265-2274. 
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    The quality of navel orange is closely related to meteorological conditions. In this study, six indicators for the quality of navel orange, including total soluble solids (TSS), titratable acid (TA), the ratio of TSS to TA (RTT), vitamin C content (VC), edible rate (ER), and single fruit weight (SW), and daily meteorological data at corresponding meteorological stations in 11 counties in Ganzhou City were analyzed in 2008-2011. The key meteorological factors affecting six quality indicators of navel orange were quantified with correlation analysis and stepwise regression. Six climate quality evaluation models for navel orange were constructed by using principal component regression. The results showed that temperature, sunshine, and precipitation from June to November were critical factors affecting the quality of navel orange. TSS was significantly positively correlated with the average temperature from September to October, diurnal temperature variation, and sunshine in October, while it was significantly negatively correlated with the precipitation in October. VC was positively correlated with the maximum temperature, sunshine, and diurnal temperature variation in October. ER was negatively correlated with diurnal temperature variation in October, maximum temperature in July-October, and sunshine in August-October. TA was negatively correlated with average temperature from October to November, minimum temperature in October, and precipitation during July-October. SW was positively correlated with average temperature in June-November, maximum temperature in June-July, and precipitation in October. Models of six quality indices for navel orange were built based on meteorological factors during critical period. The validation results with insitu observed qualities of navel orange in 2017 showed that the average relative errors for simulated qualities of navel orange were all within 12%, with the errors of both TSS and ER being less than 5%.
    Forecast technique for meteorological grade of rice false smut.
    WANG Zhi-hai, MENG Zhong, JIN Zhi-feng, XIE Zi-zheng, HUANG Shi-wen, YANG Bo, JI Dan-dan
    2019, 38(7):  2275-2282. 
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    Research on meteorological grade prediction for rice false smut is critical to the prevention of rice disease. Based on the meteorological data from 71 basic weather stations and 2259 regional automatic stations in Zhejiang Province, Optimized Consensus Forecast fine grid numerical prediction products, as well as field investigation of rice false smut, the diseasepromoting meteorological index model and dynamic forecast method for rice false smut grade were established by GIS and weighted index sum method. Results showed that the disease-promoting meteorological index model performed well, with a validation accuracy rate of 87.5%. The meteorological grade of rice false smut could be predicted eight days in advance, with resolution at township. The forecast result of 21 August, 2018 was consistent with the actual situation, with a test accuracy rate of 90.9% in 11 cities across the province. Our results provide scientific meteorological technique support for fine and quantitative monitoring and forecasting services of crop disease.