Table of Content

10 June 2019, Volume 38 Issue 6

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Effects of slope position on phylogenetic diversity and structure of alpine shrub community.

XIAO Yuan-ming, YANG Lu-cun, NIE Xiu-qing,LI Chang-bin, XIONG Feng, WANG Ling-ling, ZHOU Guo-ying

2019, 38(6):  1611-1619. 

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Community phylogenetic information is one of the primary contents in biodiversity research. Slope position is an important topographic factor affecting species composition of plant community. It is important to examine the relationships between slope position and community phylogenetic diversity and structure for improving our understanding of distribution patterns of community phylogenetic diversity and assembly mechanisms. Here, we examined the distribution patterns of the community phylogenetic diversity and phylogenetic structure of alpine shrubs in the northeastern QinghaiTibet Plateau (Qinghai Province) along slope position at the herbaceousplant community level, woodyplant community level, and all-plant community level. We found that the phylogenetic diversity of the herbaceousplant and all-plant communities presented a unimodal pattern with the decreasing slope position with highest diversity on the middle slope. Neither the phylogenetic diversity of woodyplant communities nor the phylogenetic structure of the communities (herbalplant community, woodyplant community and allplant community) showed variation along slope position. Soil physicochemical factors (soil total nitrogen, total phosphorus, soil water content and pH) had higher ability to interpret phylogenetic diversity than phylogenetic structure. Especially, soil water content had significant effects on the phylogenetic diversity of herbaceousplant community and all-plant community. In conclusion, the slope position affected the phylogenetic diversity of the shrub community by changing species composition of the herbaceousplant communities rather than the woodyplant communities and had no significant effects on community phylogenetic structure.

Responses of stem anatomical structure of a lakeside dominant plant Hippuris vulgaristo simulated warming in Napahai wetland.

GUAN Dong-xu, FENG Chun-hui, TIAN Kun, WANG Zhi-bao, ZHANG Yi-nan, SUN Mei

2019, 38(6):  1620-1628. 

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Temperature is an important environmental factor affecting stem anatomical structure. It is less well understood how it affects the structure of wetland plants. In this study, we used opentop growth chambers (OTCs) to simulate climate warming, based on the prediction of future atmospheric warming by IPCC, to study the response of stem anatomical structure of the lakeside dominant species Hippuris vulgaris to the simulated warming in a typical plateau wetland in Northwestern Yunnan (Napahai basin). The results showed that warming significantly increased epidermal cell thickness and cuticle thickness of aboveground stem. The size of parenchyma cells and epidermal cells of the aboveground stem showed increasing trends. All the aboveground stem traits showed increasing trends with increasing temperature. Warming had a significant effect on cuticle thickness of belowground stem. All the belowground stem traits showed trends of decreasing first and then increasing with the increasing temperature. Among temperature variables, the annual mean temperature and daily mean temperature were the most significant factors positively affecting aboveground stem anatomical structure of H. vulgaris. The maximum temperature and annual mean temperature had most significantly negative impacts on the belowground stem anatomical structure of H. vulgaris. Our results suggest that warming significantly affects stem anatomical structure of H. vulgaris, reflecting its effective adaptation to warming, and thus reveal the response patterns and ecophysiological adaptive strategies of plant structure in plateau wetland to climate warming.

Effects of climate change on the distribution of wild population of Metasequoia glyptostroboides, an endangered and endemic species in China.

ZHU Ying-ying, XU Xiao-ting

2019, 38(6):  1629-1636. 

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The relict gymnosperm species, Metasequoia glyptostroboides Hu & Cheng (dawn redwoods), is a wellknown example of living fossil. It is an endangered, endemic and a national key protected species of China. Its wild populations survive only in the border region of Hunan, Hubei provinces and the Chongqing municipality in southcentral China. Although it has been widely cultivated worldwide, the cultivated populations are incapable of regenerating naturally. The wild populations are facing rapid population decline due to reduced natural regeneration. Therefore, the humaninduced climate change is likely to increase the extinction risk of M. glyptostroboides. To explore the effects of climate change on M.glyptostroboides, we established the species distribution models using its wild distribution records and current climatic data. Using these models, we predicted its future distributions based on the climate data simulated by three global circulation models (CCSM4, CNRM-CM5 and HadGEM2-ES). Our results show that the current potential suitable habitats for M. glyptostroboides are mainly the adjacent areas of Hubei, Chongqing, Hunan and Guizhou, which is consistent with its actual distribution area. The wild population of M. glyptostroboides will shift northwest to the present distribution area in the future (2070s) under both RCP2.6 and RCP8.5 scenarios, but with lower habitat suitability (<0.5). Our findings suggest a dramatic decline in the suitable habitats of M. glyptostroboides and this may likely wipe out its wild populations entirely in the near future. Our results suggest that climate change may threaten the wild populations ofM. glyptostroboides.

Community structure and environmental interpretation of Machilus thunbergii in Mountain Longchi, Jiangsu Province.

ZHANG Zhi-min, YANG Guo-dong, XIE Meng-meng, ZHONG Yu-qian, ZHAI Fei-fei, WANG Xian-rong, YI Xian-gui

2019, 38(6):  1637-1645. 

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To understand the effects of environmental factors on Machilus thunbergii community in Mountain Longchi Nature Reserve, the classification, ordination and vertical distribution pattern of species diversity in this community were investigated using the Multiple Regression Tree (MRT) and the Canonical Correspondence Analysis (CCA) method, with data from 64 plots. The results showed that: (1) The Mountain Longchi Nature Reserve consisted of 153 species, 129 genera and 72 families, which belonged to midtropical evergreen broad-leaved forest, with M. thunbergii being the predominant species. The arbor layer had an absolute advantage, and the seedlings of M. thunbergii were in a disadvantaged status. (2) According to MRT results, the community could be divided into four groups: Ⅰ. Quercus acutissima+Platycarya strobilacea-Ilex chinensis+Camellia oleifera-Ophiopogon bodinieri+Lophatherum gracile, Ⅱ.Machilus thunbergii+Nyssa sinensis-Litsea cubeba+Eurya muricata-Parathelypteris glanduligera+Lophatherum gracile, Ⅲ. Cyclobalanopsis glauca+Quercus variabilis-Eurya rubiginosa+Rubus swinhoei-Parathelypteris glanduligera+Woodwardia japonica, Ⅳ. Castanopsis carlesii+Sassafras tzumu-Symplocos lucida+Rhododendron ovatum-Ardisia japonica+Ophiopogon bodinieri. The classification results reflected the trend of succession of M. thunbergii community. (3) The CCA results verified the classification results of MRT, and showed that elevation and soil moisture content were the important factors affecting the distribution and development of the M. thunbergiicommunity. (4) The species diversity of M. thunbergii community showed a unimodal distribution pattern with elevation, with a maximum value at 150 m.

Effects of female cone development on the vegetative growth and biomass accumulation of shoots and needles of Pinus koraiensis.

ZHANG Jian-ying, YIN Dong-sheng

2019, 38(6):  1646-1652. 

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To clarify the effects of 2-year-old female cone’s development on vegetative growth and biomass accumulation of shoots and leaves in Pinus koraiensis, the differences of shoot growth and biomass accumulation in the current year were analyzed with reproductive branches and vegetative branches. The results showed that the 2-year-old female cones inhibited the development of 1-yearold female cones. The vegetative growth of the reproductive branches in the current year was more vigorous than that of the vegetative branches. The vegetative growth of the reproductive branches (excluding the terminal buds) in the current year was positively correlated with the length and basal diameter of the parent shoots (P<0.05). The biomass of the terminal and lateral shoots of the reproductive branches in the current year was positively related with the biomass of the parent shoots (P<0.05). The number of 2-year-old female cones was significantly positively correlated with the basal diameter of terminal shoot, length of lateral shoot, diameter of lateral shoot, number of lateral shoot buds, and number of lateral shoot of the reproductive branches in the current year (P<0.05). The biomass of 2-year-old female cones was significantly positively correlated with the biomass of terminal shoots, the biomass of lateral shoots, and the biomass of total shoots in the current year (P<0.05). These results indicated that the development of 2-year-old female cones could promote vegetative growth and biomass accumulation in the current year’s growth of the reproductive branches. The terminal shoots and needles, the lateral shoots and needles of the reproductive branches were allocated more biomass in the current year than the vegetative branch. More than 87% of the biomass in the reproductive branches was allocated to 2-year-old female cones, while only 0.22% was allocated to 1-year-old female cones. The development of 2-year-old female cones directly affected the biomass accumulation of the parent shoots of the reproductive branches, while the biomass of the parent shoots of the reproductive branches directly affected the biomass accumulation of the reproductive branches and vegetative branches in the current year.

The differentiation of plant functional traits in genus Lysimachia L.

CHEN Yan-song, LI Ling-ling, ZHOU Shou-biao, OU Zu-lan

2019, 38(6):  1653-1661. 

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Differentiation of the key functional traits among the species within the genus Lysimachia can help understand the mechanism of their ecological adaptation. We quantitatively analyzed the variation and co-variation relations regarding the root, stem and leaf functional traits of nine species from Lysimachia cultivated under the environmentally homogeneous potted conditions using the comparative method in plant functional ecology. The results showed that the variation degree of ten plant functional traits represented by the coefficient of variation (CV) was different at the generic level. Leaf size had the highest degree of variation (CV=75.0%), followed by specific root length (CV=60.7%) and specific stem length (CV=46.5%), and lowest for leaf carbon concentration (CV=3.6%), with the maximum value of CV being 21 fold of the minimum. The subgen. Lysimachia and subgen. Palladiawere significantly different in functional traits (P<0.05). Subgen. Lysimachia was characterized by a combination of plant functional traits dominated by specific root length, specific stem length, and specific leaf area. However, subgen. Palladia had greater root specific density and leaf size. The plant functional traits of Lysimachia were speciesspecific, with significant differences in leaf size, specific leaf area, leaf dry matter content, leaf carbon concentration, leaf nitrogen concentration, leaf C∶N ratio, specific root length, root specific density, specific stem length, and stem specific density (P<0.05). The root, stem and leaf functional traits worked in synergy as a whole plant for each of the nine Lysimachia species. Specifically, leaf size was negatively correlated with specific stem length (R²=0.484, P<0.01) and specific root length (R²=0.149, P<0.01), while specific stem length was positively correlated with specific root length (R²=0.348, P<0.01). Both the leaf economics spectrum and the plant economics spectrum were found for the nine Lysimachia species.

Variation in needle stoichiometric characters of Pinus thunbergiialong a coastalinland gradient.

SUN Yang, WANG Jing-yuan, ZHANG Hui, WANG Jian-nan, WU Tong-gui, ZHANG Peng

2019, 38(6):  1662-1668. 

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The effects of wind on the morphology, physiology and growth of trees have been a hot topic and difficulty in ecology. Previous studies examined response and adaptation of trees to wind through short-time wind simulation or mechanical stimulation, which cannot reflect the long-term adaptation mechanism of trees in the natural windy environment. To fill such knowledge gap, we measured the concentrations of carbon, nitrogen, phosphorus, potassium, calcium, sodium and magnesium in needles of a 60-year-old Pinus thunbergii forest along a coastalinland gradient, and analyzed the variations of element concentration and stoichiometric characteristics. The results showed that organic carbon concentration in needle on windward of P. thunbergii decreased from inland to coast, the concentrations of nitrogen, phosphorus, potassium, calcium, sodium and magnesium increased (P<0.05), and N∶P ratio remained stable. However, there were no significant differences for these variables on leeward along the coastal-inland gradient, except that calcium and sodium concentrations decreased. Needle stoichiometric characters were significantly different between windward and leeward within 500 m from coastline, and then kept stable over distance. The correlations among windward needle stoichiometry were pervasive, but on the leeward side, only significant relationships between nitrogen and phosphorus and between calcium and sodium existed. Standardized major axis (SMA) fitted between windward and leeward were not different in slope and intercept (P>0.05). In sum, the needle chemical composition of P. thunbergii was significantly affected by wind stress, but the ratio was relatively stable. The needle carbon assimilation function was significantly affected with the increases of sea wind stress. Meanwhile, P. thunbergii improved its tolerance to wind stress by increasing needle nitrogen, phosphorus, potassium, calcium, sodium and magnesium concentrations, which may be an adaptive strategy for P. thunbergii to long term wind stress in natural environment.

Ecological stoichiometry of various organs in the tree layer of subalpine forests in central Yunnan, China.

ZHANG Yu-jian, SONG Ya-li, WANG Ke-qin

2019, 38(6):  1669-1678. 

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Exploring ecological stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) in tree layer of forest is of great importance to understanding nutrient allocation and limitation status in the dominant layer of forest community. Different organs (leaf, branch, trunk, bark, and root) of five typical forests (Pinus yunnanensis forest, Pinus armandii forest, evergreen broadleaf forest,Quercus semicarpifolia forest,Keteleeria evelyniana forest) were sampled in subalpine area of central Yunnan. The concentrations of C, N and P were measured and C∶N∶P stoichiometry were analyzed. The results showed that the ranges of C concentrations in the leaves, branches, trunks, barks and roots of five forest types were 482.40-576.03, 472.50-566.47, 462.67-512.30, 465.10-542.30, 478.67-566.47 mg·g^-1, N concentrations 11.30-25.42, 4.20-7.47, 3.49-8.30, 6.18-9.71, 6.08-10.64 mg·g^-1, and P concentrations 0.84-2.36, 0.42-1.02, 0.25-0.81, 0.30-0.82, 0.55-1.63 mg·g^-1, respectively. The difference of C concentrations was not different among organs. The concentrations of N and P in leaf and root were higher than other organs. The C concentration, C/N, and C/P in the evergreen broad-leaved forest and Q. aquifolioides forest were ranked as: trunks > roots > leaves > branches > barks, the N concentration presented in the order of leaves > roots > barks > branches>trunks, while the C/P of the other three forest types were ranked as: trunks > barks > branches > roots > leaves. The P concentration in the organs of the five forest types followed the order of leaves>roots>branches>barks>trunks. The N/P in the four types of forests were between 10 and 20, and that in the evergreen broad-leaved forest was less than 10, indicating that the growth of the evergreen broadleaved forest was mainly limited by N and the other forest types were colimited by N and P. The results of twoway ANOVAs showed that the C concentration and N/P varied among forest types, while the N and P concentrations, C/N and C/P varied among organs.

Effects of different land use types on soil physicochemical properties and aggregate composition in Sanjiang Plain wetland.

ZHANG Hui-hui, WANG Shi-biao, WANG Jun-rui, WU Xu-ye, MA Song-liang, WU Yi-ning, LI Jin-bo, XU Nan

2019, 38(6):  1679-1687. 

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The aim of this study to clarify the effects of three land use types reclaimed from wetlands in Sanjiang Plain (upland, paddy field and artificial forest) on soil physicochemical properties and aggregate composition. The results showed that soil physicochemical properties significantly differed among different land use types. Compared with wetland, the three land use types significantly decreased soil water content and increased soil bulk density. Compared with wetland soil, soil available P in paddy field increased, while total N, total P, alkalihydrolyzable N and available P reduced in other land use types. There was a significantly higher reduction in upland and artificial forest than that in paddy field. The activities of soil urease, invertase and catalase under different land use types were significantly lower than those of wetland, with the reduction in paddy fields being significantly lower than that in upland and artificial forest. The activity of soil acid phosphatase in upland and artificial forest showed no significant different with wetland soil, whereas that in paddy field was lower. In addition, the concentrations of total organic C (TOC), microbial biomass C (MBC), dissolved organic C (DOC) and readily oxidized C (ROC) in soil under different land use types was lower than that in wetland soil. The decrease in TOC, MBC, DOC and ROC content was significantly higher in upland and artificial forest than that in paddy field. The soil aggregate composition with mechanical stability changed obviously under different land use types. The mean weight diameter (MWD) of soil in paddy field and upland was lower than that in wetland, with a significant decrease in uplands. However, soil MWD of artificial forest significantly increased compared to wetland. Our results indicated that the different land use types reclaimed from wetland significantly changed the soil physicochemical properties and aggregate composition. The damages of soil physicochemical properties, organic C stability and soil aggregate in paddy field were significantly lower than those in upland and artificial forest. Moreover, the destruction of soil physicochemical properties and structure in artificial forest was significantly lower than that in upland due to limited disturbance.

Functional characteristics of soil microbial community of the typical artificial shelter forests in the windy-sandy region of northwest Liaoning Province, China.

ZHANG Yan, DENG Jiao-jiao, ZHU Wen-xu, YIN You, WEI Ya-wei, ZHOU Yong-bin

2019, 38(6):  1688-1696. 

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We analyzed functional characteristics of soil microbial community in three typical artificial shelter forests, including Pinus sylvestrisvar. mongolica, Pinus tabuliformis and Populus×canadensisin the windysandy region of northwest Liaoning Province, China, by Biolog-Eco method. Soil chemical properties were measured to explore their correlations with the metabolic activity and functional characteristics of soil microbial community. The results showed that compared with Pinus sylvestris var. ongolica and Pinus tabuliformis, Populus×canadensis had higher soil pH, dissolved organic C and available P concentrations, and lower C/N. There were significant differences in soil microbial community metabolic activities among different forests. The capacity of C source utilization by soil microbial communities (AWCD) was in the order of Populus×canadensisforest >Pinus sylvestrisvar. mongolica forest >Pinus tabuliformis forest. The Shannon diversity index, Simpson diversity index, and McIntosh diversity index of soil microbial community in the Populus×canadensis forest were 3.27, 0.96, and 8.13, respectively, and significantly higher than those ofPinus sylvestris var. mongolica and Pinus tabuliformisforests (P<0.05). There were significant differences in the utilization of the six types of carbon sources by soil microorganisms among different forests. The utilization rates of six carbon sources of Populus×canadensis forest were significantly higher than those of the other two forests (P<0.05). Results of principal component analysis and cluster analysis showed that soil microbial communities could be divided into two different functional groups, coniferous forests (Pinus) and broadleaf forest (Populus), characterized by different principal carbon sources including pyruvic acid methyl ester, i erythritol, and 2hydroxybenzoic acid. Soil pH, DOC, C/N and available P were the main factors affecting AWCD value, Shannon index, Simpson index and McIntosh index. In conclusion, the metabolic activities and functional diversity of soil microbial community in Populus×canadensis plantation were better than those in P. tabuliformis and P. sylvestris var.mongolica plantations. The plantation of Populus×canadensis is suitable for this region.

Community characteristics of soil ciliates in different modes of returning cropland to forest in Hui County, Gansu.

NING Ying-zhi, WAN Guan-hong, YANG Yuan-gang, WU Wei-ning, ZHOU Xiao-yan, WANG Yi-feng, LIU Na, CHENG Xiao, CHEN Ling-yun

2019, 38(6):  1697-1706. 

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The responses of soil ciliate communities to the returning of cropland to forest were investigated to examine whether ciliates can be used to evaluate the effects of ecological restoration. Four sampling sites were selected, with three different returned forest types and an abandoned land as control in Hui County of Longnan City, Gansu Province, China. At each site, the community characteristics of soil ciliates and vegetation, along with physical and chemical parameters of the soil, were analyzed. Ciliates were isolated from the soil using nonflooded Petri dish method and in vivo observation. Enumeration was carried out using direct-culture counting method. A total of 127 soil ciliate species belonging to 9 classes, 18 orders, 28 families, and 47 genera were identified. The species richness, density, and species diversity index of soil ciliates in the ecologically restored sites were significantly higher than those of the control site. The dominant group changed from Colpodida in control site to Sporadotrichida in ecologically restored sites, indicating that soil ciliate communities tended to complicate with the progress of the returning cropland to forest project. Soil ciliate community characteristics were closely related to vegetation type. Soil water content, organic matter content, total nitrogen content, and electrical conductivity were the dominant factors affecting soil ciliate community composition. After returning cropland to forest, the vegetation gradually recovered, soil physical-chemical factors changed, and soil ciliate communities showed positive response to the restoration of ecological environment. These findings suggest that ciliate community composition can be used as an indicator for the successful restoration of cropland to forest.

Long-term effects of natural restoration on C∶N∶P ecological stoichiometry in aggregates of red soil.

SONG Li-qun, WANG Yi-dong, LI Dong-chu, ZHANG Hui-min, LOU Yi-lai, DOU Bo-kai, SHANG Yun-tao, WANG Zhong-liang

2019, 38(6):  1707-1715. 

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It is not clear how long-term natural restoration affects soil aggregate distribution and C∶N∶P ecological stoichiometric characteristics in red soil. Soil samples (0-15 cm depth) were taken from two treatments, conventional farming (CF) and natural restoration (NR), in a 27-year field experiment in Hunan Red Soil Experimental Station. The aim of this study is to investigate the response of soil aggregate distribution and the contents and stoichiometric ratios of soil organic C (SOC), total N (TN) and total P (TP) to long-term natural restoration. Compared with CF, (1) The total soil waterstable macroaggregates (>0.25 mm) in NR significantly increased, and the proportion of microaggregates (0.053-0.25 mm) and mineral particles(<0.053 mm) significantly decreased; (2) The contents of SOC and TN in bulk soil of NR significantly increased. While the SOC content significantly increased in each aggregate size class, TN content in macroaggregates (>2 and 0.25-2 mm) and microaggregates (0.053-0.25 mm) significantly increased. In contrast, TP content significantly decreased in bulk soil and each aggregatesize fraction. The 0.25-2 mm aggregate size class contributed most of nutrients in the bulk soil. (3) The ratios of C∶N, C∶P and N∶P in bulk soil of NR significantly increased. The C∶N ratio of the four aggregates remained constant, while C∶P and N∶P showed greater variability and significantly increased in each aggregate size class. In conclusion, long-term natural restoration enhances soil aggregation effect, which results in more concentrated C, N and P in macroaggregates. While natural restoration can improve soil structure and aggregate quality, attention should be paid to the exacerbated phosphorus limitation in future.

Responses of Corydalis yanhusuo rhizosphere soil bacterial community diversity and structure to gap size in a moso bamboo forest.

LI Wei-cheng, SHENG Hai-yan, YANG Hui-min, LIU Yao-yao, ZHANG Rui

2019, 38(6):  1716-1724. 

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Under-forest economy has become an important way to increase forest output and promote forestry economic benefit. The objective of this study was to identify changes in soil bacterial community diversity and structure in Corydalis yanhusuo(an earlyspring medicinal plant) rhizosphere associated with moso bamboo forest gaps. We collected C. yanhusuo rhizosphere soil samples from plots located in large (400 m²), medium (100 m²), and small forest gaps (25 m²), as well as from the closed stands. Highthroughput sequencing combined with habitat parameters were used to analyze the variations of soil bacterial community diversity and structure among these plots. The results showed that the soil bacterial communities in the four plots contained 35 phyla, 104 classes, 195 orders, 321 families, and 523 genera. Although the specific rankings of the dominant groups in the soil bacterial communities of large and medium forest gaps were different, Acidobacteria and Proteobacteria were overall the most dominant taxa, followed by Chloroflexi and Actinobacteria. In small forest gaps and closed stands, Proteobacteria were dominant, followed by Actinobacteria and Bacteroidetes, while Acidobacteria was the least dominant. With the decrease of forest gap size, the relative light intensity dropped to 10.7%-22.5% of full light. The total number of taxa in bacterial communities tended to decrease, and species abundance and specificity, phylogenetic diversity, community diversity, and community evenness all decreased with the decreases of gap size. However, the closedstand habitat was better than the small forest gaps. The operational taxonomic unit (OTU) percentages of bacterial communities at the phylum and genus levels were significantly correlated with light intensity and air temperature, but showed opposite relationship with soil moisture content and air humidity, and had no correlation with forest gap size, altitude and border bamboo parameters. Therefore, large forest gaps were the best one favoring the development of C. yanhusuorhizosphere bacterial communities, while small forest gaps were not suitable for them. Forest gaps and closedstand habitats can provide growth opportunities for different bacterial communities under certain conditions. Consequently, soil microbiological indicators, such as representative communities, can be used as indicators of changes in the development of forest gaps. Relative light intensity and air temperature have great impacts on rhizosphere soil bacterial communities during the artificial creation of forest gaps and cultivation of C. yanhusuo, which are important in regulating soil bacterial community structure and promoting the stability of soil ecosystems.

Effects of the amount of corn stover return on plant-parasitic nematode communities.

ZHENG Hai-rui, LUO Jing-mei, LIU Xiao-tong, LIU Ya-jun, ZHAO Xiao-xia, XIE Hong-tu, ZHANG Xiao-ke

2019, 38(6):  1725-1731. 

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We investigated the effects of corn stover mulching amount on plant-parasitic nematode communities after 11-year stover mulching in the long-term Conservation Tillage Research and Development Station of the Chinese Academy of Sciences. Four treatments, including no corn stover mulching (NT0), 33% (NT33), 67% (NT67) and 100% (NT100) mulching amount of total corn stover harvest amount were set up. A total of 16 plant-parasitic nematode genera were identified, including four dominant genera, Basiria, Tylenchus, Pararotylenchus, and Pratylenchus. Our results showed that the total abundance of plant-parasitic nematodes firstly increased and then decreased in the 0-10 cm soil layer with the increases of corn stover mulching amount, while no obvious trend was found in the 10-20 cm soil layer. There was no significant variation in the total plant-parasites among different treatments in both soil layers. Among c-p (colonizers-persisters) groups, c-p3 of plant-parasitic nematodes was the dominant group. Corn stover mulching increased the total organic carbon content in the 0-10 cm soil layer, the abundance of dominant genera of Basiria and Tylenchus, the relative bundance of c-p2 group, and the biomass of c-p2 and c-p3 groups in the 0-10 cm soil layer. The increases of corn stover mulching amount did not enhance the possibility of harm from plant-parasitic nematodes. Stover return influenced the c-p groups of plant-parasitic nematodes through affecting soil organic carbon and pH.

Effects of organic amendments on soil bacterial community structure  with long-term tomato planting in greenhouse.

ZHAO Feng-yan, ZHANG Yong-yong, ZHANG Yue-qi, ZHANG Tian-shi, ZHANG Guo-xian, ZHANG Hui, YANG Li-juan

2019, 38(6):  1732-1740. 

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High-throughput sequencing technology was used to investigate the effects of rice straw, chicken manure compost, cow manure compost, and vermicompost on soil bacterial community structure with 20 years continuous tomato cropping. Meanwhile, soil chemical properties were measured to quantify their effects on the variation of bacterial community structure, to provide theoretical basis for scientific application of fertilizers in tomato cultivation in greenhouse. Results showed that: (1) Both vermicompost and chicken manure compost showed significant positive effect on soil bacterial diversity and richness, while cow manure compost significantly decreased bacterial diversity and richness. (2) Compared with control, organic amendments increased the relative abundance of dominant bacteria Proteobacteria and Actinobacteria by 36.40%-44.27% and 25.80%-29.35%, respectively, but significantly decreased that of Acidobacteria. The highest relative abundances of Proteobacteria and Actinobacteria were found in rice straw and vermicompost treatments, respectively, whereas the lowest relative abundance of Acidobacteria was found in cow manure compost treatment. Organic amendment applications promoted the growth of beneficial bacteria (such as Sphingomonas, Gemmatimonas, Bacillus, Streptomyces and Porphyrobacter) and suppressed pathogen bacteria (such as Gp6, Gp16 and Gp4). (3) Compared with control, all the treatments significantly decreased soil pH, but significantly increased EC value. Results of Pearson’s correlation analysis revealed that Vermicompost soil NH₄⁺ content, EC, pH value, and total C content were the most dominant factors affecting bacterial community composition. In summary, our results indicated that vermicompost was better than other organic amendments in improving soil bacterial community structure. More attention should be paid on the use of vemicompost in sustainable production of tomato in greenhouse.

Effects of nitrogen/potassium ratios on stem morphological and mechanical characteristics and grain yield of maize.

ZHANG Yi-fei, YU Song, YANG Ke-jun, XU Jing-yu, WU Qiong, WANG Huai-peng, YIN Xue-wei, YANG Li

2019, 38(6):  1741-1750. 

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To clarify the effects of the application ratio of nitrogen/potassium fertilizers on lodging resistance of maize stem and grain yield, a field experiment with split plot design was carried out in western Songnen Plain. The application level of nitrogen fertilizer was used as main factor, while that of potassium fertilizer was used as subsidiary factor. We measured the morphological and mechanical characteristics of maize stem at grain filling stage and grain yield under different combinations of nitrogen and potassium fertilizers (N: 195, 210, 225, 240 kg·hm^-2; K₂O: 70, 85, 100, 115 kg·hm^-2). The results showed that plant height was significantly affected by nitrogen application and the height of gravity center was significantly affected by the potassium fertilization. There were no significant interactive effects of nitrogen and potassium fertilization on plant height, ear height and height of gravity center. Nitrogen and potassium fertilization and their interactions had significant effects on internode length, stem diameter, area of cross section, internode plumpness, breaking resistance, puncture strength, section modulus, stem type index, bending moment, breaking moment, and bending stress. Among all the treatments, the lodging resistance index was the highest under 210 kg N·hm^-2 + 85 kg K₂O·hm^-2 treatment, followed by 225 kg N·hm^-2 + 100 kg K₂O·hm^-2 treatment, and 210 kg N·hm^-2 + 100 kg K₂O·hm^-2 treatment, which were 31.59%-80.86% higher than that of other treatments. Nitrogen and potassium fertilization had significant interactive effect on lodging resistance of maize (F_N×K=19.577^**). According to the morphological and mechanical characteristics of maize stem and grain yield levels, the optimum nitrogen and potassium application scheme for maize lodging resistance was 210-225 kg N·hm^-2 + 85-100 kg K₂O·hm^-2, with a nitrogen/potassium ratio of 1.75-1.88 : 0.71-0.83. Our results provide scientific basis and technical approach for the nutrient efficiency management of high yield, good quality and multiresistance maize population under close planting cultivation in Songnen Plain.

Response of dry matter accumulation parameters and yield of summer soybean to different amounts of drip irrigation under mulch film.

DU Xiao-jing, FU Xiao-wen, AN Chong-xiao, ZHANG Yong-jie, FANG Yan-fei, XU Wen-xiu

2019, 38(6):  1751-1759. 

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To alleviate the shortage of agricultural water and solve the water contradiction between summer soybeans and spring sowing crops, we examined the effect of different amounts of drip irrigation under film on dry matter accumulation of summer soybean variety Heihe 45. The results from this study would provide theoretical basis for highyield and watersaving cultivation techniques of summer soybean. An experiment with six amounts of drip irrigation under mulch film: 4200 (W₀), 3780 (W₁), 3360 (W₂), 2940 (W₃), 2520 (W₄), 2100 (W₅) m³·hm^-2, and one no mulch treatment 4200 m³·hm^-2 (CK) were conducted in 2016 and 2017. We measured dry matter accumulation and distribution, dry matter accumulation characteristics, yield and water use efficiency of summer soybean. The results showed that, with increasing irrigation volume, the variation of dry matter accumulation on various organs and per plant were all increased firstly and then decreased, which displayed a pattern of W₂>W₃>W₁>W₄>W₀>W₅≈CK. By fitting the Logistic equation, the dry matter accumulation characteristics of W₂ or W₃ treatment was better than other treatments in different years, with no significant difference between W₂ and W₃ treatments. Appropriate amount of drip irrigation could significantly increase dry matter accumulation and average dry matter accumulation rate, shorten the dry matter accumulation time, and accelerate the growth process. The average of the two years’ yields was the highest in W₂ treatment, being 3099.49 kg·hm^-2, which was 26.14%, 14.27%, 7.23%,7.20%, 20.40% and 34.17% higher than that of CK, W₀, W₁, W₃, W₄ and W₅. In the case of equivalent growth and yield of soybean, the plastic mulching saved 50% of drip irrigation than no mulching treatment. Therefore, 2940-3360 m³·hm^-2 would be the appropriate drip irrigation quota under mulch film for high yield and water saving of summer soybean.

Effects of combined application of vermicompost and chemical fertilizer on yield and quality of Lactuca sativa.

LIU Ming-da, WANG Qiu-ning, WEI Jia-lun, ZHANG Jing-ting, LIU Wen-e, WANG Yao-jing

2019, 38(6):  1760-1766. 

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Understanding the effects of combined application of vermicompost and chemical fertilizer on yield and quality of vegetables is important for guiding the rational fertilization in cleaner vegetable production. We examined the effects of combined application of vermicompost and chemical fertilizer on yield, nitrate content, amino acid content and composition of Lactuca sativa in a pot experiment. The results showed that, compared with the single application of chemical fertilizer, combined application of appropriate amount vermicompost and chemical fertilizer increased the yield, while reduced the water content of L. sativa by 1.02%-2.46% and nitrate content by 20.78%-30.30%. The combined application of vermicompost and chemical fertilizer significantly increased the contents of total amino acids, essential amino acids, delicious amino acids, sweet amino acids, and pharmacodynamic amino acids. Under the conditions of equal amount of nitrogen, 30%-50% of nitrogen from vermicompost was the optimal. Therefore, the combined application of vermicompost and chemical fertilizer is feasible for the improvement of both yield and quality of L. sativa.

Hyperspectral monitoring of aboveground dry biomass of winter wheat under different irrigation treatments.

YANG Chen-bo, FENG Mei-chen, SUN Hui, WANG Chao, YANG Wu-de, XIE Yong-kai, JING Bing-han

2019, 38(6):  1767-1773. 

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Aboveground dry biomass is an important indicator for crop growth and yield. An experiment with different irrigation treatments was carried out to examine the changes of aboveground dry biomass of winter wheat. The predictive models for monitoring aboveground dry biomass were established using the methods of MLR and SPA-MLR. The results showed that irrigation at the jointing stage, booting stage, flowering stage and filling stages was a favorable method for aboveground biomass accumulation of winter wheat. The predictive models established with the method of SPA-MLR were more accurate than those built with the MLR method. Among them, the predictive model at the flowering stage of winter wheat performed best, with R²=0.96, RMSE=0.092 and R²=0.76, RMSE=0.18 for the calibration set and validation set, respectively. The predictive model covering all the growth stages from the jointing stage to filling stage of winter wheat achieved good prediction with R²=0.64, RMSE=0.30 and R²=0.54, RMSE=0.26 for the calibration set and validation set, respectively. Such a result indicated that this model could be potentially used to monitor the aboveground dry biomass in the winter wheat field as good predictive accuracy under extensive growth stages was achieved. Our results provide technical support for predicting the aboveground dry biomass of winter wheat using the hyperspectral technology.

Construction of the comprehensive impact index for wheat scab and its spatiotemporal variations in Jiangsu Province.

XU Min, GAO Ping, XU Jing-wei, WU Hong-yan, YI Hong-juan, WU Ding-bang, XU Dong-xiang

2019, 38(6):  1774-1782. 

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Based on the data of the spike rate of wheat scab, winter wheat phenology, and the daily weather data observed in 13 cities of Jiangsu Province, as well as in Tongzhou District (Nantong City) and Jianhu and Funing counties (Yancheng City), a comprehensive impact index and classification indicators for wheat scab were established by statistical methods, including grey correlation, synthetic analysis, census and percentile analysis. The proposed index and indicators were calibrated and validated using empirical data. Then, they were used to analyze the temporal and spatial patterns of wheat scab in Jiangsu Province. Cumulative rainy days, average relative humidity, and average temperature were key meteorological factors affecting wheat scab. Their weights were 0.348, 0.340, and 0.312, respectively. The proposed comprehensive impact index on the basis of these meteorological variables could indicate the situation of wheat scab occurrence in Jiangsu. The classification indicators according to the comprehensive impact index could retrieve the spatiotemporal variations of wheat scab. In recent 16 years from 2002 to 2017, the occurrence of wheat scab in Jiangsu decreased from south to north. However, areas with the most serious wheat scab shifted. The occurrence probability of serious wheat scab in the eastern coastal areas between the Yangtze and Huaihe rivers (mainly in Yancheng City) was significantly higher than that in other areas. Since 2010, serious wheat scab broke out more frequently in Jiangsu, probably due to climate warming. Our results can be used for the prediction and impact assessment of wheat scab, providing guidance for the effective prevention and control of the disease.

Risk assessment and division of wheat stripe rust based on GIS in Sichuan Basin.

GUO Xiang, MA Xian-ju, WANG Ming-tian, ZHANG Guo-zhi, WANG Ru-lin

2019, 38(6):  1783-1791. 

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With meteorological data from 1961 to 2017 in Sichuan Basin, monitoring data on wheat stripe rust from 1999 to 2016, and data on agricultural production and topography, we constructed risk assessment index system and evaluation model of wheat stripe rust in Sichuan Basin using the methods of aggregation, weighted comprehensive evaluation, and analytic hierarchy process, based on the natural disaster risk theory and the occurrence mechanism of wheat stripe rust in Sichuan Basin. We used GIS technology to evaluate the sensitivity of disaster environment, hazard of disaster-causing factors, vulnerability of disaster bodies, and capacity of drought disaster prevention and reduction. Finally, we assessed and partitioned the risk of wheat stripe rust in Sichuan Basin. The results showed that the overall meteorological environment of Sichuan Basin is suitable for wheat stripe rust in winter and spring. The areas with higher hazard index are mainly distributed in the western part of the basin, while 1the areas with higher vulnerability index are located in western basin and central basin. There are stronger capacity of drought disaster prevention and reduction in western basin, southern basin and the junction of the middle and northeast parts of the basin. The risk of wheat stripe rust could be divided into four levels: light, low, medium, and high. Highrisk areas are mostly concentrated in the west part of the basin. Lightrisk areas are scattered in the eastern and southern parts of the basin. The distribution areas of middle and low risk areas are similar, with the former being scattered and the latter mainly concentrated in the west and middle of the basin. The area with light-risk is the largest.

Screening differentially expressed proteins in response to mercury stress in rice roots by proteomic quantification based on stable isotope labeling and parallel reaction monitoring.

QI Zhong-da, WEI Yan, LONG Shui-ting, DAI You-gang, QIU Guang-le

2019, 38(6):  1792-1799. 

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Mercury (Hg) is highly toxic. Rice (Oryza sativaL.) is one of the most important pathways for Hg exposure to populations. To reveal the molecular mechanism of rice adaptation to Hg stress, the Jinyou 431 rice cultivar grown under supplementation of 0 mg·kg^-1 (CK), 50 mg·kg^-1 (low), 150 mg·kg^-1 (middle), and 300 mg·kg^-1 (high) HgCl₂ was selected to investigate root tips’ differentially expressed proteins in response to Hg stress using the isotope relative labeling and the absolute quantitative technique TMT (Tandem Mass Tag) combined with parallel reaction monitoring (PRM) quantitative proteomic technique. Bioinformatics analysis of the obtained differential proteins was performed to screen the target proteins responding significantly to Hg stress. A total of 20 differentially expressed proteins identified were selected for protein validation. The results showed that 5253 quantitative proteins and 364 differential proteins were identified (variation fold≥1.3, P<0.05), out of which 258 were up-regulated and 106 downregulated. The molecular function of gene ontology suggests that differential proteins are mainly involved in catalytic activity, binding transport activity, and antioxidant activity. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway significantly enriches in metabolic pathways, secondary metabolite biosynthesis, and phenylpropanoid biosynthesis (with false discovery rates of <0.05). The identified and validated differential proteins are related to antioxidant reductase, metal chelate peptide synthesis protein, and metallothioneinrelated proteins like. The expression levels of proteins involved in responding and signaling pathway to antioxidants and heavy metal stress defense were generally up-regulated, while the expression levels of those involved in metabolism, energy production and transport were generally down regulated.

Dynamics of phyllospheric fungal community in a wetland plant, Schoenoplectus tabernaemontani.

ZHAN Peng-fei, LI Hui, LIU Yun-shuo, YAN Peng-fei, XIAO De-rong, ZHANG Yun, WANG Hang

2019, 38(6):  1800-1809. 

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A number of fungi inhabit the phyllosphere, which accompany plants during their whole life history. The habitats of plants at different stages regulate the structure, composition and diversity of fungal community, which has been widely concerned. In northwestern Yunnan Province, we collected plant samples from a typical emergent wetland plant, Schoenoplectus tabernaemontani, during the growth stage (A), standingdead stage (B), lodging stage (C), and submergence stage (D), and sediment samples (E) as a control. We extracted DNA after ultrasonic water bathing combined with vigorous shake methods, and sequenced ITS fragments using Illumina HiSeq platform to obtain the composition and abundance information of the phyllospheric fungi community. With the growth, withering and death of S. tabernaemontani, the α and β diversity of phyllospheric fungal community significantly increased, and the complexity of community structure enhanced. The heterogeneity among different samples increased and the difference in community composition gradually enlarged during the whole process. At the genus level, Alternaria and Cryptococcus were the dominant ones during growth stage and standingdead stage, while Gibberella and Phialophora gradually invaded into the phyllosphere and became the dominant one accompanied with plants in their lodging and submergence stages. Only 22 common OTUs were found in the samples A, B, C, and D, while 99 OTUs were shared by submergence stage and sediment, indicating that the phyllospheric fungal community tended to be consistent with the soil fungal community along with the plant death process. Our results reveal the succession of fungal community during plant life history, providing theoretical supports for further study on the underlying mechanisms shaping phyllospheric fungal community structure in wetland plants.

Diet of two passerine birds during breeding season in reed wetland of Hangzhou Bay.

ZHANG Xin-li, JIAO Sheng-wu, ZHAO E, WU Ming, SHAO Xue-xin, YE Xiao-qi, YAN Ya-nan

2019, 38(6):  1810-1816. 

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Information on the bird’s diet composition is essential to understand how wetland reclamation affects diversity of passerine birds. Samples of feathers of Reed Parrotbill (Paradoxornis heudei) and Oriental Reed Warbler (Acrocephalus orientalis) and samples of potential dietary insects were collected in the southern Hangzhou Bay (Shangyu, Shaoxing City), during the breeding season from July to August in 2017. Food sources were analyzed by measuring δ¹³C and δ¹⁵N values in bird feathers and insect samples. The results showed that the contribution of various diet composition of Reed Parrotbill ranked as: Noctuidae pupa > Lepidoptera > Arachnida > Hymenoptera > Homoptera. The contribution of various diet composition of Oriental Reed Warbler ranked as: Hymenoptera > Arachnida > Odonata > Lepidoptera > Coleoptera > Homoptera. The value of feeding niche breadths of Reed Parrotbill and Oriental Reed Warbler was 5.21 and 5.95, respectively. There was no significant difference in the δ^13C values between the two species, indicating an overlap between their feeding niches (P>0.05). However, there was a significant difference in the value of δ¹⁵N, with feeding niche overlap being 6.25, suggesting some differences of nutritional levels (P<0.01). Lepidoptera, Arachnida, Hymenoptera, and Homoptera were overlapping foodsource insects for the two passerine species. The narrower niche breadth of Reed Parrotbill was inferior, and the loss of reed habitat had greater impacts on Reed Parrotbill. Our results provide information for habitat establishment, conservation and management of passerine birds in the coastal reclamation area.

Ecological effects of coculture of macroalgae on water fleas Moina mongolica.

XIE Xi, WEI Jie, ZHANG Zhi-peng, ZHAO Wen

2019, 38(6):  1817-1823. 

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To clarify ecological effects of co-culture of macroalgae and saline cladocerans, two co-culture aquatic systems were established via addition of macroalgae, i.e.Ulva pertusa or Ulva intestinalis, into the static culture water with water fleas Moina mongolica. We investigated the impacts of those two macroalgae on the static water purification effect and the reproduction and population performance of the water fleas. The results showed thatthe two macroalgae had significant effects on the levels of ammonia, pH and DO in the co-cultured water (P<0.05). The water chemical parameters varied in a similar pattern for both systems. The levels of ammonia in both systems decreased to the minimum value (0.016 mg·L^-1) after 12 days, and then kept stable. Both pH value and DO level were elevated with increasing biomass of the two macroalgae. The pH values varied between 8.2 and 9.0 and DO levels between 4.2 and 6.4 mg·L^-1. The two macroalgae differentially affected the reproduction and population growth of M. mongolica in the coculture systems. The average neonates, intrinsic increase rate (r_m), finite increase rate (λ), and generation cycle (T) were increased with the increases of U. pertusa biomass. When U. pertusabiomass peaked at 2.5 g·L^-1, those parameters declined. In contrast, the average lifespan declined with the increasing biomass of U. pertusa. There were better ecological effects in the co-culture system based on U. pertusa than in the control. There was no significant difference between co-culture system based on U. intestinalisand the control (P>0.05). U. pertusa, with the biomass of 2.5 to 3.5 g·L^-1, played dual roles in both water purification and culture of aquatic animals in the co-culture system, beneficial to the purification of ammonia and DO in water and the growth and reproduction of M. mongolica. These findings provide useful insights into optimization of a large-scale culture technique and development of novel culture mode for M. mongolica.

Assessment of the population resources of Coregonus ussuriensis in the middle reaches of Amur River.

WANG Ji-long, LIU Wei, LU Wan-qiao, LI Pei-lun, TANG Fu-jiang

2019, 38(6):  1824-1829. 

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To obtain an understanding of the resource status of Coregonus ussuriensis, 953 samples were collected at seven stations located in the middle reaches of Amur River basin in 2013-2017. The range of fork length and body weight was 148-588 mm and 109.0-2854.9 g, respectively. Stock biomass was estimated by lengthbased cohort analysis (LCA), while population dynamics was evaluated by BevertonHolt dynamic model. The results showed that the natural mortality coefficient, total mortality coefficient, and fishing mortality coefficient was 0.284 a^-1,0.476 a^-1 and 0.192 a^-1, respectively. The current exploitation rate was 0.403. The average stock number and biomass of C. ussuriensis in the middle reaches of Amur River was 6.89×10⁶ individuals and 5463.89 t, respectively. The initial stock biomass was 6867.07 t. Results from the analysis of relative yield per recruit and biomass per recruit showed that the exploitation of C. ussuriensis resources is relatively sufficient, with no overfishing. Population decline of C. ussuriensis was mainly attributed to anthropogenic deterioration of habitat. To achieve sustainable utilization of C. ussuriensis resources and mitigate the impacts of human activities on fish stocks, regulation of harvest needs to be implemented, such as habitat restoration, increasing minimum length limits and so on.

Effects of manganese oxide on adsorption and transport of fluoroquinolone antibiotic in porous media.

LI Ye, SHI Ya-nan, CHEN Xi-juan, ZHUANG Jie

2019, 38(6):  1830-1838. 

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Metal oxides (such as manganese oxides) have received great concerns, due to its reactive surfaces which could affect the fate of fluoroquinolone antibiotics (FQs) in soil. In this study, batch and column experiments were conducted to investigate the effects of manganese oxides coated sand (MOCS, mimicking soil metal oxides) on transport of target compound ciprofloxacin (CIP, a widely prescribed fluoroquinolone). Batch experiments were carried out using Freundlich model to quantify the adsorption of CIP on manganese oxides. Column experiments were conducted at three levels of manganese oxides in sand (0, 55 and 109 μg Mn·g^-1 sand) to explore the effects of manganese oxides on CIP transport. Results showed that the K_F values were 1.63fold higher on MOCS than on sand, indicating that CIP had higher affinity in adsorption MOCS, due to the microporous structure of manganese oxides. It resulted in manganese oxides reducing the transport of CIP, as the content of manganese oxides increased from 0 to 109 μg Mn·g^-1 sand and C/C₀ decreased from 0.96 to 0.72. These were consistent with the twosite kinetic estimated parameters of k_att1 values, k_att2 values and S_max1 values, which with 109 μg Mn·g^-1 sand column were 2.04-2.33 and 4.21-12.69 times higher than the corresponding values with 55 μg Mn·g^-1 sand column and 0 μg Mn·g^-1 sand column, respectively. After eluting with a low surface tension solution (20% v/v ethanol in background solution), the total recovery rates reached up to 95%, illustrating that the adsorption of CIP on manganese oxides was reversible. Based on the transport behavior of CIP, our results showed that manganese oxides had higher affinity in adsorption cationic microorganic pollutants, which reduced the transport of cationic microorganic pollutants.

NDVI spatiotemporal variation in Yulin after grain for green project.

YANG Bo, WANG Quan-jiu, XU Xiao-ting, ZHOU Pei, LEI Jing-sen, WANG Yan, GUO Yong

2019, 38(6):  1839-1848. 

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Since the start of returning cropland to forest and grassland project, vegetation in the Loess Plateau has grown rapidly. To clarify the vegetation variation and change trends in this region, trend analysis, standard deviation analysis, and Hurst index were applied to analyze the MODIS 250 m resolution NDVI in Yulin from 2000 to 2017. The NDVI was increased by 88.56% from 2000 to 2017, with an annual rate of 4.92%. The NDVI of cultivated land, woodland, grassland and unused land were all obviously increased. The NDVI in different elevations and slope ranges also increased significantly. NDVI was positively correlated with rainfall but not with temperature. Increased grain yield, the total number of domestic animals, and the total area of returning cropland to forest and grassland had a significant correlation with NDVI, suggesting that after the transformation and upgrading of agricultural production, ecological environment governance and rural economy had achieved coordinated development. According to the forecast results of Hurst index, the returning cropland to forest and grassland project in this area was close to its carrying potential, but NDVI index had about 10% growth potential. In the extreme drought years of future, vegetation would experience the threat of droughtinduced death and the risk of NDVI index reduction, mainly concentrated in the hilly and gully areas with better NDVI recovery. In the period of after returning cropland to forest and grassland, it is an important task to coordinate the rational allocation of soil and water resources for realizing ecological construction in this area.

Agricultural drought characteristics and its influencing factors in Gansu Province based on TVDI.

PANG Su-fei, WEI Wei, GUO Ze-cheng, ZHANG Jing, XIE Bin-bin

2019, 38(6):  1849-1860. 

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To understand the agricultural drought situation and its influencing factors in Gansu Province, the feature space was constructed by Normalized Difference Vegetation Index and Land Surface Temperature. Temperature Vegetation Dryness Index (TVDI) was calculated to evaluate the drought event during 2001-2016, and its influencing factors were quantitatively analyzed. Drought occurred every year in Gansu, with the proportion of lightly and moderately dry acreage being largest. Drought had obvious regional differentiation in space, gradually increased from southeast to northwest. The drought was heavy in most parts of Hexi Corridor and rarely occurred in Qilian Mountains and Gannan plateau. The formation of drought and non-drought occurrence regions was the result of a combination of many factors such as altitude, temperature, precipitation, underlying surface, and human disturbance. Large acreage of drought usually occurred in regions with lower altitude, higher temperature, less precipitation, sparse vegetation and land types dominated by sand and Gobi. Temperature, precipitation, altitude, slope, vegetation types and land cover types were the major factors influencing agricultural drought. Other factors were superimposed together with major factors, resulting in the overall pattern of “southeast wet and northwest drought” in Gansu. Using TVDI index based on the combination of vegetation and temperature to reflect agricultural drought situation, it is simple in calculation and its results are scientific and accurate. This method is worth to be tried and used in drought monitoring of meteorological department in the future. Our results provide scientific reference for preventing drought and formulating agricultural production policies.

Simulation and spatio-temporal pattern of vegetation NPP in northwest China.

ZHU Ying-ying, HAN Lei, ZHAO Yong-hua, AO Yong, LI Jun-jun, XU Kai-bo, LIU Bing, GE Yuan-yuan

2019, 38(6):  1861-1871. 

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The data production of MOD17A3 NPP in northwest China is seriously deficient, with consequences on further research on vegetation net primary productivity (NPP) in this region. Based on the meteorological data, DEM, NDVI, and MOD17A3 NPP with high quality, the BP neural network model was constructed to simulate vegetation NPP and fill the areas without NPP data in northwest China from 2000 to 2014. Its spatio-temporal variations and relationships with meteorological factors were analyzed using unitary linear regression, R/S analysis, and partial correlation analysis. The results showed that: (1) Coefficients of determination (R²), mean absolute error (MAE), mean relative error (MRE) and root mean square error (RMSE) between MODIS NPP and simulated NPP were 0.833-0.906, 25.84-40.1, 0.16-0.23, 34.57-59.36, respectively, which well met the accuracy requirements. The BP neural network model was suitable for vegetation NPP simulation in northwest China. (2) The annual mean NPP had a strong spatial variation, showing a gradual decline from southeast to northwest and a high-value block area in the northwest of Xinjiang. (3) The annual mean NPP ranged between 106.64 and 156.17 g C·m^-2·a^-1 from 2000 to 2014, with a slightly fluctuating downward trend in the interannual variation. (4) From 2000 to 2014, the change of NPP in northwest China had spatial heterogeneity, which was mainly reduced. Only 10.79% of the areas passed the significance test. NPP change was weakly persistent. The future change trend of NPP is mainly uncertain, supplemented by improved and declined areas, with the improved area being larger than the declined area. (5) Responses of vegetation NPP to temperature and precipitation varied spatially, which were generally more closely related to precipitation.

Spatiotemporal change and its driving factors of built-up land sprawl in Yangzhou City.

CHE Tong, LUO Yun-jian, LI Cheng

2019, 38(6):  1872-1880. 

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Built-up land sprawl is the most drastic and visual manifestation of urban land-use change. Understanding spatiotemporal change of built-up land sprawl and its driving forces can reveal the inherent laws of urban sprawl, and thus scientifically regulate urban land use. In this study, we used multisource data (e.g., 30 m resolution Landsat images in 1995, 2000, 2005, 2010, and 2015) and socioeconomic data to analyze spatiotemporal changes of built-up land sprawl in Yangzhou City. Further, we employed the boosted regression tree method to quantify the effects of geographic, social and economic factors on such sprawl. Results showed that the built-up land area gradually increased from 725.4 km² in 1995 to 1076.5 km² in 2015. With the increasing urbanization, the spatial form of built-up land tended to be compact and regular, and the gravity coordinates also migrated accordingly, showing local attraction and linkage of municipal districts (e.g., Hanjiang and Guangling). Among geographic, social, and economic factors, geographic factors (e.g., altitude, the distance from the county core, the distance from built-up land) had the greatest influence on built-up land sprawl, with the relative influence gradually decreasing from 73.9% in 1995-2000 to 60.2% in 2010-2015. The influence of social and economic factors gradually increased from 5.2% and 20.9% in 1995-2000 to 7.9% and 31.9% in 2010-2015. Geographic factors (e.g., the distance from the county core and the distance from built-up land) generally had negative effect on built-up land sprawl, but the effects of social and economic factors were inconsistent. For example, population density, GDP per capita and fiscal revenue promoted built-up land sprawl, gross population inhibited it, and secondary industry first inhibited built-up land sprawl and then promoted it.

Dynamics of resource and environment carrying capacity of Guangdong Province based on catastrophe progression method.

SUN Duan, CHEN Ying-biao, CAO Zhen, HU Ying-long

2019, 38(6):  1881-1889. 

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The carrying capacity of resources and environment is important basis for sustainable development. Effective evaluation of carrying capacity of resources and environment is of great significance to the construction of ecological civilization society. Based on catastrophe progression method in catastrophe theory, we used 14 evaluation indices from four aspects of economy, society, resources and environment to evaluate the carrying capacity of urban comprehensive resources and environment of 21 prefecturelevel cities in Guangdong Province from 2000 to 2015. The results showed that in the 15 years, the index of comprehensive resources and environmental carrying capacity of Guangdong Province slightly decreased on the whole. Guangdong gradually changed from a high bearingcapacity province in most areas to a relatively high comprehensive bearing capacity index in the Pearl River Delta region and relatively weak comprehensive bearing capacity in Dongguan and Shenzhen. Each subsystem had different influence on the comprehensive carrying capacity of the city. The composite system of resources and environment is the supporting foundation of carrying capacity, while the composite system of economy and society is the powerful guarantee of carrying capacity. Among all cities, Jiangmen, Shantou, Huizhou and Foshan had the highest comprehensive carrying capacity index of resources and environment, indicating that the more balanced the economic level and resources and environment, the higher the comprehensive carrying capacity of cities. The bearing capacity index of each subsystem changed with different forms. The economic subsystem highlighted the status of urban economic development. The higher the economic level, the higher the carrying capacity, the smaller the overall growth pattern. Due to the aggravation of floating population, the carrying capacity index of the social subsystem declined slightly. Based on the premise of relative stability of resources, the carrying capacity index of resource subsystem was relatively stable. The carrying capacity index of environmental subsystem showed a downward trend due to environmental pollution. Spatially, the differences of bearing capacity index of the subsystems in Guangdong were significant. The index of carrying capacity of economic and social composite system was basically matched with the economic development level of each city. Meanwhile, the index of carrying capacity of the composite system of resources and environment was roughly consistent with the topography of Guangdong, with the index being high in eastern and western Guangdong, and gradual decline in the Pearl River Delta in Dongguan and Shenzhen.

Research progress of pond ecosystem structure and function.

LU Hong-yu, YUAN Xing-zhong, WANG Xiao-feng, WU Shuai-kai

2019, 38(6):  1890-1899. 

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Pond is small hydrostatic water body commonly seen on land, with the characteristics of small area, shallow water body, large quantity and wide distribution. Pond is an important type of terrestrial freshwater ecosystem. However, the functions of ponds are often ignored due to the difficulty in spatial identification. Here, we reviewed the research progress of pond systems at home and abroad, clarified the basic concept related with pond, and discussed the abiotic factors, biological factors and environmental relations of pond systems. Based on the discussion of the ecological function of the pond, we propose that: (1) The material circulation rate of the pond system is high, and the water body is often purified by oxidation pond, with consequences on carbon and nitrogen cycling in the global terrestrial system; (2) Pond group system is an important habitat for sustaining regional biodiversity. Species area relationship, habitat heterogeneity, and adjacent ecosystem characteristics are the main factors driving biodiversity in pond ecosystems; (3) As a surface depression system, pond has the function of water and soil conservation, with remarkable effect on sediment and rainwater harvesting. We propose three aspectsdeserved more attention in the future research: biogeochemical cycle characteristics of pond system under changing environment; background data accumulation and maintenance mechanism of biodiversity, and the application of water and soil conservation in ecological restoration project. Pond ecosystem is an important ecosystem to respond to future environmental changes.

Soil acidification and its ecological effects.

ZHANG Ling-yu, ZHAO Xue-qiang, SHEN Ren-fang

2019, 38(6):  1900-1908. 

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Soil acidification is a slow process under natural conditions, but it has been accelerated to some extent in the recent decades by anthropogenic activities, with a series of negative effects. We should pay more attention to the accelerated soil acidification. Here, we first reviewed the processes of soil acidification under both natural and anthropogenic conditions, and explored their driving factors such as soil base saturation percentage, acid buffering capability, acid deposit, fertilizers, plants, and land use management. Then, we summarized the ecological effects of soil acidification, including inhibited plant growth, altered soil biological community, increased soil heavy metal availability, and decreased water quality. Finally, sustainable strategies for acidic soil use were discussed from the two aspects, acid soil amendment and plant genetic modification. We proposed the future research trends in soil acidification.

Research advances in the effects of rainfall on soil selenium migration and transformation.

CHEN Jin-ping, LIU Yong-xian, ZENG Cheng-cheng, PAN Li-ping, XING Ying, LIAO Qing, LIANG Pan-xia, JIANG Ze-pu

2019, 38(6):  1909-1915. 

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As one of the important reservoirs of selenium (Se), soil is an important material basis for Se to enter the food chain through plants. The content of soil Se is therefore the key factor affecting the Se level of edible crops. Rainfall plays an important role in driving soil Se input and output. Elucidating the influence of rainfall on soil Se is essential to better understand the spatial distribution of soil Se at a national scale. Based on analysis of the latest researches in China and abroad, we found that rainfall is an important route for soil Se input, by comparing the Se input from wet deposition between the Se-rich area of Southeast China and the low-Se belt stretching from Northeast China to Southwest China. The role of rainfall in the formation of low-Se belt and endemic diseases was revealed by summarizing the impacts of rainfall on soil Se leaching loss and its bioavailability. Finally, we discussed the natural and artificial factors that influence the effects of rainfall on soil Se, such as climate, soil, plant and human activities. To better forecast the variation trend of soil Se in the future, it is necessary to synthetically study the multiple processes that govern soil Se migrations.

Comparison of two compatible biomass models: A case study from three broadleaved tree species in Guangdong.

CAO Lei, LI Hai-kui

2019, 38(6):  1916-1925. 

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Based on biomass data of 270 individuals of three broadleaved tree species in Guangdong, Cinnamomum camphora,Schima superba, and Liquidambar formosana, a multiple nonlinear joint estimation was adopted with components addition and total control methods to separately establish onevariable (diameter at breast height, DBH) and bivariate (DBH and tree height or DBH and canopy width) compatible biomass equations. The fitting goodness and estimated accuracy of compatible equations derived from these two methods were evaluated. The results showed that: (1) The compatible equations separately established by components addition and total control methods performed well, with no significant difference in estimated accuracy between them. The model of components addition performed slightly better. (2) Binary equations generally performed better than the unitary equation. Adding the second variable could produce different impacts for tree components. With tree height as the second variable, the binary model improved the fitting effect of stemwood and stem-bark biomass. With the canopy width as the second variable, the model improved the fitting effect of branch, foliage, and aboveground biomass. For the compatible equation of broadleaved species, using the DBH and canopy width of trees could get better accuracy. (3) Compatible model based on the second variable respectively from components model performed better, even with higher accuracy for total biomass estimation than individual model. The components addition was slightly better than total control in constructing compatible model. For the selection of second explanatory variable of broadleaved tree species, the binary model accuracy with canopy width factor was higher than that with tree height factor.

Quantitative classification of Kanas taiga communities along the pyrogenic succession using multivariate regression trees.

GUO Ke1, PAN Cun-de, LI Gui-hua, YU Ge-bi, ZHANG Fan, LIU Bo, ZOU Zhuo-ying, LIU Xiao-ju

2019, 38(6):  1926-1936. 

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To understand the mechanism and process of taiga along the pyrogenic succession in Kanas, Xinjiang, we investigated topography, soil, fire disturbance and species importance value by typical sampling method. The types and characteristics of taiga communities, as well as the factors influencing species distribution pattern, were analyzed using canonical correspondence analysis (CCA) and multivariate regression trees (MRT). The results showed that there are 172 species, 125 genera and 43 families of vascular plant species in Kanas taiga. Based on life form, these species can be divided into 7 tree, 19 shrub and 146 herbaceous species. Elevation, total potassium concentration, fire severity and posfire time were the main factors affecting species distribution in Taiga forest along the pyrogenic succession. Communities can be classified into six categories using MRT in Kanas taiga: (1) Betula pendula+Picea obovate Vaccinium hirtum-Carex atrata+Elymus sibiricus community, (2) B. pendula+P. obovate-V. hirtum+Spiraea chamaedryfolia-C. atrata community, (3)Larix sibirica+B. pendula-V. hirtum+Rosa spinosissima-C. atrata+Eremosyne pectinata community, (4)Pinus sibirica+L. sibirica-V. hirtum+Linnaes borealis-E. sibiricus+E. pectinatacommunity, (5)L. sibirica-V. hirtum+Lonicera caerulea-Vicia tenuifolia+E. sibiricus community, and (6) L. sibirica+P. obovate-V. hirtum-E. sibiricus+C. atratacommunity. In conclusion, variation in species distribution of taiga along the pyrogenic succession was mainly determined by topography, soil and fire disturbance. Within the factors -related to topography, soil and fire disturbance, altitude, fire severity and postfire time were the key factors driving the formation and persistence of communities in Kanas taiga.

Construction of an index system for green cities based on urban classification.

DOU Pan-feng, ZUO Shu-di, REN Yin, HUANG Wei

2019, 38(6):  1937-1948. 

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A comprehensive evaluation index system is of significant importance for the planning, construction, evaluation and management of green cities. The formulation of region differentiated index systems is fundamental for promoting the development of green cities in accordance with the local conditions, and is crucial for the Chinese cities with substantial economic, lifestyle and environmental differences. Firstly, we classified cities with three perspectives, including urban production development, living status, and environmental background. Next, a self-organizing feature map (SOFM) neural network was constructed to classify 288 cities into 26 types. Then, the SMART principle was applied to build a green city index system with three first-level indicators, including green production, green lifestyle, and green environment, 11 secondary indicators, and 70 third-level indicators. The third-level indicators were further sub-classified into basic and characteristic indicators. Finally, we provided the detailed applicable indicator classification for each of the 288 selected cities. The index system described here fully considers the construction foundation and development needs of different cities, and provided new ideas and methods for the establishment of green city index system, with both theoretical innovation and practical value.