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    10 November 2018, Volume 37 Issue 11
    Effects of intercropping with Alpinia oxyphylla in rubber plantation on soil water conservation function.
    WEN Zhi, ZHAO He, LIU Lei, LI Yan-min, MI Hong-xu, OUYANG Zhi-yun, ZHENG Hua
    2018, 37(11):  3179-3185. 
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    Rubber (Hevea brasiliensis)based agroforestry systems are regarded as an effective way to improve ecosystem functioning. However, few studies have examined soil water conservation function in this system. Here, we analyzed the direct and indirect factors affecting soil water conservation functions in two types of rubber plantations (pure rubber plantation and rubber Alpinia oxyphylla agroforestry system) in the central mountainous region of Hainan Island, based on structural equation model (SEM). The results showed that, compared to the rubber monoculture, soil water conservation function index of rubber-A. oxyphyllaagroforestry system increased by 1.09 times, indicating an increase of soil water conservation function in agroforestry system (P<0.05). The increases of litter quantity and fine root biomass accounted for the changes of soil bulk density and aggregate stability when A. oxyphylla was intercropped with rubber. Soil bulk density, soil aggregate stability and litter quantity accounted for 91% of the total variation of soil water conservation function. Those three variables can directly affect soil water conservation. Moreover, soil bulk density and litter quantity can also indirectly affect soil water conservation function through soil infiltration. We concluded that the species selected for intercropping in rubber plantations should have great fine root biomass and litter quantity so as to improve soil water conservation and enhance soil and water retention in the rubber plantations.  
    Composition of multi-year-old seedlings and their habitat interpretation in a mixed coniferousbroadleaf forest in Jiaohe, Jilin Province, China.
    QIN Jiang-huan, YAO Jie, MENG Ling-jun, CHEN Gui-lian, ZHAO Xiu-hai
    2018, 37(11):  3186-3193. 
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    We aimed to verify the density dependence effect in multi-year-old seedlings and explore the effects of biotic and abiotic factors on the composition and quantitative characteristics of the seedlings in a mixed coniferousbroadleaved forest in Jiaohe, Jilin Province, China. We installed 128 subplots (5 m × 5 m) in a 21.12hm2 dynamic plot. With multi-year-old seedlings of tree species (height H>30 cm, diameter at breast height (DBH) <1 cm) as the research objects, we examined the species composition and quantity characteristics. Multiple linear regression was used to quantify the relationship between seedlings and the neighboring trees with DBH of >1 cm within a radius of 10 m or 20 m and the abiotic factors. The results showed that: (1) A total of 871 seedlings were recorded, belonging to 13 families, 16 genera, and 25 species, all of which were the seedlings of the main tree species in the plot. The Simpson diversity index was 0.91. The top three species according to the importance value were Acer mono,Acer mandshuricum, and Pinus koraiensis. (2) Biotic factors affecting the number of seedlings varied among species at two scales (10 and 20 m). There was a significant positive correlation between the number of seedlings of A. mandshuricum and the number of its conspecific neighboring trees at both scales. The number of seedlings of P. koraiensis was positively correlated with the sum of basal area of its conspecific trees at both scales and was significantly negatively correlated with the relative basal area of its conspecific trees at the 20 m scale. There was a significant positive correlation between the number of seedlings of A. mono and the sum of basal area of its conspecific trees at the 20 m scale and a significant negative correlation with the relative basal area of its conspecific trees at the 20 m scale, while a significant positive correlation with the number of its conspecific trees at the 10 m scale. The conspecific trees did not show a significant density dependant effect on the number of the seedlings of the three species. (3) The results of regression analysis showed that the overall abundance of the seedlings of the three species were significantly positively correlated with the sum of basal area, leaf area index, and soil pH, but negatively correlated with soil moisture. There was a great difference in the correlation between 10 factors and A. mono, A. mandshuricum andP. koraiensis. The abundance of the seedlings of the three species had different relationships with 10 factors, indicating that there was a great difference in the selectivity of different species to different habitats.
    Changes of plant functional group in understory and environmental interpretation in the transformation of typical coniferous plantation to native broadleaved species plantation in south subtropical China.
    YOU Ye-ming, WU Xi-pin, MING An-gang, LIU Tong, CHEN Yong-kang, ZHU Hong-guang, WEN Yuan-guang, LIAO Shu-shou, HUANG Xue-man
    2018, 37(11):  3194-3201. 
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    Transforming typical coniferous plantation to native broadleaved species plantation is a major management for plantation in subtropical China. To explore the effects of transforming coniferous to native broadleaved species plantation on the plant functional groups in understory, we investigated the diversity and community composition of understory, and analyzed the role of environmental variables on understory functional groups by multivariable statistics in southern China. The richness of understory species (woody, gramineous, vern and vine groups) in the broadleaved plantations was lower than that in the coniferous plantations, especially for xylophyta and herb groups in the Castanopsis hystrix and Mytilaria laosenis plantations (P<0.05). The first principal component axis significantly separated the understory composition of plant functional groups between the coniferous and broadleaved plantations by Principal Component Analysis (PCA). Leaf area index, average leaf angle, soil C/N, soil total phosphorus content, litterfall C/N and light transmittance well explained the variations in the understory plant functional groups by redundancy analysis (RDA), with values of  33%, 13%, 6%, 5%, 2% and 2%, respectively. These results suggest that changes of canopy structure induced by forest transformation rather than soil physicochemical properties result in the variation of the understory plant functional groups.
    Effects of nitrogen addition on soil microbial community structure in a subtropical evergreen broadleaved forest.
    NI Zhuang, NIE Yan-xia, OUYANG Sheng-nan, SHEN Wei-jun
    2018, 37(11):  3202-3209. 
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    Soil microorganisms are key drivers of ecological processes such as nutrient cycling. However, our understanding of how soil microbes respond to elevated atmospheric nitrogen (N) deposition in Chinese subtropical evergreen broadleaved forests is still very limited. A field N addition experiment was conducted to study the responses and influencing factors of soil microbes to simulated N deposition in the Dinghushan Biosphere Reserve (DHSBR), Guangdong, China. Surface soil samples (0-10 cm) under four N treatment levels (0 (CK), 35 (LN), 70 (MN) and 105 (HN) kg-1·hm-2·a-1) were collected in the dry (January) and wet (July) seasons. Soil microbial community structure was analyzed using the phosphorous fatty acids (PLFAs) method. Our results showed that: (1) N addition significantly enhanced the PLFAs biomass of the dominant microbial groups including bacteria, actinomycetes and fungi, with bacteria being the most abundant group; (2) There were obvious seasonal differences in microbial responses to N addition. Although the PLFAs were always higher in the dry than wet season, the moderate N addition (MN) treatment had the largest impact on microbial biomass in the dry season while the high N addition (HN) had the largest impact in the wet season; (3) Both N addition and season imposed significant impacts on microbial community composition. Dissolved organic carbon content and soil water content were the most influencing factors regulating microbial community in the dry season, while soil pH and available N and P contents played the important role in the wet season. Our results indicate that elevated N deposition in the subtropical China may exert seasonally differentiated impacts on soil microbial communities, and thus key ecological processes. A comprehensive consideration of N deposition level, season, and soil microbial responses is critically important when studying the effects of atmospheric N deposition on the evergreen broadleaved forest in the region.
    Effects of warming and precipitation reduction on soil enzyme activity in a young Cunninghamia lanceolata plantation.
    JIANG Miao-hua, NI Meng-ying, ZHOU Jia-cong, CHEN Yueh-min, YANG Yu-sheng
    2018, 37(11):  3210-3219. 
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    Soil enzyme plays an important role in soil processes, which drives soil nutrient and carbon cycling by participating in the decomposition process of litter and organic matter. However, there are many factors affecting the decomposition process, including temperature and soil moisture. In this study, we examined the effects of warming, precipitation exclusion, and their combined treatment on soil extracellular enzyme activity in a mid-subtropical young Cunninghamia lanceolata plantation. These extracellular enzymes included carbonacquisition enzymes (β-glucosidase, βG; cellulose hydrolase, CBH; phenol oxidase, PHO; peroxidase, PEO), nitrogen acquisition enzyme (β-N-acetylglucosaminidase, NAG), and phosphorus acquisition enzyme (acid phosphatase, AP). The results showed that the soil moisture, microbial biomass nitrogen, dissolved organic nitrogen, and dissolved organic carbon (DOC) were significantly decreased by warming, precipitation exclusion, and their interaction. Warming significantly increased the concentrations of ammonium (NH4+-N) and nitrate, and the activities of βG, CBH, and NAG (P<0.05). Precipitation exclusion enhanced the activities of βG, CBH and NAG to some extent. The activities of βG, CBH, NAG, PHO, and PEO increased slightly under the treatment of combined warming and precipitation exclusion (P>0.05). The activity of AP decreaseddramatically in all the treatments (P<0.05). Results from the redundancy analysis indicated that total nitrogen (P=0.002), NH4+-N (P=0.002), and DOC (P=0.03) concentrations were the main factors driving the changes in soil enzyme activity. Our results indicated that soil enzymes involved in carbon and nitrogen cycling positively responded to warming and precipitation exclusion. Increased enzyme activities accelerated soil carbon decomposition. However, the enzyme activities involved in phosphorus cycling significantly decreased, which could induce phosphorus limitation in this ecosystem in the future. Our results have implications for better understanding of carbon and nutrient cycling under the scenarios of increasing temperature and altering precipitation.  
    Seasonal dynamics of soil organic carbon in different forest types and its driving factors in mountainous region of eastern Liaoning.
    FAN Zhi-ping, WANG Qiong, LI Fa-yun
    2018, 37(11):  3220-3230. 
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    To address the seasonal dynamics of soil organic carbon and its driving factors in different vegetation types in mountainous region of eastern Liaoning, the concentration and dynamics of soil organic carbon (SOC), soil dissolved organic carbon (DOC) and soil microbial biomass carbon (MBC) were examined in different soil layers of Larix gemlinii plantation, Quercus mongolica-Juglans mandshurica secondary forest, and Acer secondary forest. The relationships between SOC, DOC, MBC and biomass, soil physicalchemical and climate factors were also analyzed. Our results showed that the concentrations of SOC, DOC, MBC in different forest types displayed a vertical distribution with decreasing order of 0-10 cm>10-20 cm>20-30 cm. In addition, the concentrations of SOC, DOC and MBC in the Q. mongolica-J. mandshurica forest were higher than those of Larixforests and Acer forests. The concentrations of SOC, DOC and MBC had significant seasonal dynamics, with the highest concentrations in summer. The SOC and MBC had positive correlations with soil water content, pH and soil temperature, and had negative correlations with soil bulk density and precipitation. The concentration of DOC had positive correlations with soil water content, pH and precipitation, and had a negative correlation with soil bulk density. The concentrations of SOC, DOC and MBC had negative correlations with the stem and root biomass of tree and decomposition layer of litter, and had positive correlations with belowground biomass of shrubherb layer and biomass of semidecomposed layer of litter. The relationships between SOC, DOC and MBC and their driving factors were remarkably different among forest types, indicating that the interactive effects of forest type and climate made a unique microenvironment for different forest types, which affected the content and seasonal changes of soil SOC, DOC and MBC. The SOC, DOC and MBC storage in Q. mongolica-J. mandshurica forest were higher than those in other two forest types, indicating that it was beneficial to nutrient accumulation. The Q. mongolica-J. mandshurica forest is a suitable model for the construction and reconstruction of forest structure adjustment and soil restoration in the mountain area of eastern Liaoning.
    Nitrogen gaseous loss in tropical forest soil and its responses to water addition.
    TANG Wen-guang, ZHOU Zhang, LIN Ming-xian, LI Yi-de, LUO Tu-shou, CHEN De-xiang
    2018, 37(11):  3231-3236. 
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    Quantifying gaseous loss of soil nitrogen (N) is important for understanding forest ecosystem N cycling. However, relatively few studies have investigated N gas loss, especially N2. In this study, using a soil incubation experiment in laboratory, we examined soil N gaseous loss and its responses to water addition in two tropical montane forests in Jianfengling, Hainan Island. The results showed that in ambient soil water contents, soil N gas emission rates were relatively low, and N2O and N2 emission rates were -0.004-0.03 and 0-0.022 nmol N·h-1·g-1, respectively. After water addition, N2O and N2 emission rates increased sharply by more than 70 and 40 times, respectively. Soil N gas emissions were affected by forest types and seasons. N gas emission rates in secondary forest were higher than those in primary forest, and were higher in wet season than in dry season, but with no significant difference. Our results indicated that tropical forest soil N gaseous losses were mainly controlled by soil water content. In order to accurately estimate soil N gas losses of tropical forest ecosystems, we should consider the influence of heavy precipitation.
    The response of radial growth and death of Populus davidiana to regional climate change in southern Greater Xing’an Mountains.
    HE Min, WEI Jiang-sheng, SHI Liang, ZHOU Mei, ZHAO Peng-wu
    2018, 37(11):  3237-3244. 
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    To assess the effects of global warming on tree  radial growth and massive mortality in semi-arid forests, the responses of radial growth and death of Populus davidiana to climate change were analyzed using annual climatology and correlation analysis in Saihanwula, southern Greater Xing’an Mountains, Inner Mongolia. The results showed that the radial growth of P. davidiana was significantly negatively correlated with the average temperature and minimum temperature (P<0.05). The radial growth of P. davidiana decreased when the temperature significantly increased after 1993. The radial growth had significant positive correlation (P<0.01) with precipitation in May but no such relationship with precipitation in other months. The rising temperature accelerated the reduction of radial growth and the death of P. davidiana.
    The regulating effects of coniferous plantation on temperature and humidity in Qianyanzhou.
    XU Ming-jie, ZHANG Tao, SUN Yi, LI Qing-kang, YANG Feng-ting, WANG Hui-min
    2018, 37(11):  3245-3254. 
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    Forests can regulate climate to some extent, which is an aspect of the ecological services of forests. Studies on forest microclimates can help us understand the regulations and mechanism of how the forests affect climate and provide theoretical guides to agricultural and forest production managements. We conducted tenyear parallel measurements of temperature and watervapor pressure both outside and inside a coniferous plantation in subtropical China from 2005 to 2014. To examine the effects of the coniferous plantation on microclimate, air temperature, soil temperature and water vapor pressure inside the forest were compared with those outside of the forest. The results showed that forest can significantly affect temperature and humidity in the forest. At annual scale, the multiyear mean air temperature inside the forest was 0.5 ℃ lower than that outside the forest. The multi year mean monthly maximum air temperature inside the forest was 2.0 ℃ lower than that outside the forest. Moreover, the multiyear mean monthly minimum air temperature inside the forest was 0.4 ℃ higher than that outside the forest. As the age of the forest increased from 20 years to 30 years, the cooling effects of the forest in summer significantly increased. In addition, the regulating effects on maximum and minimum air temperature were enhanced. The water vapor pressure inside the forest was generally higher than that outside the forest, which indicated a humidifying effect of forest. From 2005 to 2014, accompanying with the growth of the forest, water vapor pressure inside the forest significantly increased. The regulating effects of forest on soil temperature were greater than that on air temperature. The multiyear mean annual soil temperature at 5 cm depth inside the forest was 3.6 ℃ lower than that outside the forest. The forest showed significant cooling effects in the hot summers, while it showed heat preservation effects in winter. These effects did not show obvious increase or decrease trends with increasing forest age, but might be affected by soil water contents.
    Spatial structure of natural mixed coniferous-broadleaf secondary forest in Dahuofang Reservoir area, eastern Liaoning.
    GONG Wen-yan, CHEN Li-hua, YU Xin-xiao, ZHENG Xue-liang, ZHANG Xue-qi
    2018, 37(11):  3255-3261. 
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    To understand the merit of spatial structure of coniferous-broadleaf secondary forests in Dahuofang Reservoir area, eastern Liaoning, we measured four structure parameters, i.e., angular scale, neighborhood comparison, mixing degree and stand spatial structure index, to analyze the characteristics of stand spatial structure in upper slope and lower slope. The results showed that the horizontal distribution of the forest in the upper slope was randomly distributed, while that in the lower slope was characterized by a slight clustering distribution. In terms of individual plant size in the two positions, a subdominant state was found in the lower slope, while moderate neutral state was found in upper slope. The mixing degree was 0.29 and 0.56 for the upper and lower slope respectively, with the latter one being better. The spatial structure index was 54.81 and 68.04 for the upper and lower slope, respectively, so the integral structure in the lower slope was better. Our results suggested that the forest spatial structure in the lower slope was better than that in the upper slope, which provided a basis for managing the forest structure in this area.
    Responses of seed germination of Caragana korshinskii Kom. to light intensity and sand burial depth.
    ZHANG Jin-feng, YAN Xing-fu, SUN Yi, LUO Yong-hong
    2018, 37(11):  3262-3269. 
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    To reveal the responses of seed germination of C. korshinskii Kom. to light intensity and sand burial depth, an experiment was conducted to investigate the characteristics of seed germination of C. korshinskii under different light intensities (55.4% natural sunlight (NS), 18.9% NS, 5.5% NS, and 2.2% NS) and sand burial depths (0.0, 0.5 1.0, 2.0, and 4.5 cm) in a greenhouse. The results showed that light intensity had significant effects on germination percentage (GP), germination rate (GR), germination index (GI), and vigor index (VI) of C. korshinskii seeds while sand burial depth had significant impacts on GI and VI. Significant interactive effects of light intensity and sand burial depth on GP, GI and VI were also observed. The GP, GR, and GI of C. korshinskii seeds decreased with the decline of light intensity at all burial depths except 0 cm. With the decreasing light intensity, VI showed an increasing trend at 0 cm sand burial depth, while it continually or undulately decreased at other depths. Under the light intensities of 55.4% NS, 18.9% NS, and 5.5% NS, the maximums of GP were detected at the depth of 1.0 cm sand burial (45.0%, 30.6%, and 27.5% respectively) and the minimums were observed at 0 cm sand burial depth (22.2%, 22.1%, and 20.0% respectively). GR, GI, and VI all increased and then decreased with increasing sand burial depth, all of which maximized at 0.5-2.0 cm sand burial depth. Under 2.2% NS, all germination parameters decreased with increasing sand burial depth. At 1.0, 2.0, and 4.5 cm sand burial depths, GP, GR and GI were significantly lower than that at 0 cm sand burial depth (P<0.05). The differences in VI between 0 cm and other sand burial depths were significant (P<0.05). In summary, both light intensity and sand burial depth were important factors driving the germination of C. korshinskii seeds. Sand burial could strengthen the dependence of seed germination on light. Seed germination could be facilitated by moderate depths of sand burial under high light intensity but be restrained by sand burial under low light intensity.
    Effects of drought on photosynthesis and resistance physiology of Excentrodendron hsienmu seedlings in karst habitat.
    OU Zhi-yang, CAO Yan-yun, TAN Zhang-qiang, ZHENG Wei, PANG Shi-long, SHEN Wen-hui
    2018, 37(11):  3270-3276. 
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    To understand the physiological adaptability of Excentrodendron hsienmu to arid habitat of karst mountains, a moisture control experiment was conducted with 2-year-old E. hsienmu seedlings in a water supply device, which was set up with a simulated karst structure comprising soil, limestone, and epikarst layer. A twofactor design, soil layer and epikarst layer water gradient condition, was performed to examine leaf photosynthetic and resistance physiological characteristics of E. hsienmu seedlings. The results showed that the photosynthesislight response curve of the seedlings well fitted the nonrectangular hyperbola model. Light response curve under different treatments in epikarst layer showed the similar variation. Results of twoway analysis of variance showed soil layer water significantly affected the maximum net photosynthetic rate (Pmax) and dark respiration rate. Both factors and their interaction had markedly significant effects on relative chlorophyll value. The Pmax and dark respiration rate decreased, while relative chlorophyll value increased with the increases of soil drought stress. Soil layer water very significantly affected free proline, and had significant impact on both malondialdehyde content (MDA) and peroxidase (POD) activity. Content of free proline in drought stress groups was significantly higher than that in control, while MDA content under severe drought stress was significantly higher than that in control. Peroxidase activity increased firstly, and then decreased with the increases of soil drought stress, with the peak occurring in moderate drought stress. Our results demonstrate that E. hsienmu has strong tolerance to drought stress, with the active adaptation of osmotic adjustment as the main reason.
    Effects of different forms and ratios of nitrogen on physiological characteristics of Perilla frutescens (L.) Britt under salt stress.
    SUI Li, YI Jia-ning, WANG Kang-cai, LI Yu-qing
    2018, 37(11):  3277-3283. 
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    To investigate the effects of nitrogen nutrition on the growth of P. frutescens in salted stress and provide a theoretical basis for rational regulation of nitrogen fertilizer in production, we examined the effects of different forms and ratios of nitrogen on the growth, antioxidant enzyme system, soluble protein content and nitrogen metabolism of Perilla frutescens under 60 mmol·L-1 salt stress. The results showed that under the treatment of no NaCl supplied, the total fresh and dry weights of aboveground part, total chlorophyll content, nitrate reductase (NR) and glutamine synthetase (GS) activities, soluble protein content and antioxidant enzyme activity of P. frutescensat NH4+-N/NO3--N ratio of 25∶75 were higher than those in other treatments. Under the NaCl stress, P. frutescens biomass was inhibited, chlorophyll content was decreased, soluble protein and MDA content was increased, antioxidant enzyme activity was enhanced, and NR and GS activities were also increased. At NH4+-N/NO3--N ratio of 25∶75, P. frutescens leaves had the highest chlorophyll content, SOD activity, CAT activity and soluble protein content, and with the lowest MDA content. The activity of POD was the highest at the NH4+-N/NO3--N ratio of50∶50. Under the salt stress, with the increased proportion of NO3--N, the activities of NR and GS showed an upward trend, and the highest activity at the NH4+-N/NO3--N ratio of 0∶100. The activities of NR and GS in the amido nitrogen treatment were lower than those in the purenitrate treatment but higher than those in the pure ammonium treatment. Under the salt stress, different nitrogen forms and ratios had significant effects on chlorophyll content, nitrogen metabolism, anti retrogradation regulation and yield of P. frutescens. All the results indicated that under the salt stress, the combined applications of ammonium and nitrate were more effective than pure nitrate, pure ammonium, and amidenitrogen applications. Furthermore, the NH4+-N/NO3--N ratio of 25∶75 was more favorable to maintain the activities of antioxidase and nitrogen metabolism enzyme, alleviate the salt stress on seedling growth, and increase seedling weight, and thus could achieve high salt tolerance.
    Crop yield and soil nutrients under paddy-upland multiple cropping rotation systems. #br# -
    WANG Lan, HUANG Guo-qin, SUN Dan-ping, WANG Shu-bin
    2018, 37(11):  3284-3290. 
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    In order to screen a continuous cropping pattern of water and drought replanting rotation, which is sustainable and suitable for rice fields in southern China, we carried out an experiment with five treatments from 2014-2016. The “winter fallowearly ricelate rice” model was control (A), and there were four types of paddy field irrigation and drought multiple cropping rotation modes, including potatomaize ‖ soybeanlate rice→vegetablespeanut ‖ corn late rice→milk vetchearly ricelate rice (B), vegetablespeanut ‖ corn-late rice→milk vetchearly rice-late rice→rapepeanutlate rice (C), milk vetchearly ricelate rice→oil rapepeanutlate rice→potatomaize ‖ soybeanlate rice (D), oil rapepeanutlate rice→potatomaize ‖ soybeanlate rice→vegetablespeanut ‖ cornlate rice (E). We analyzed crop yield with mainly for late rice yield and the changes of soil nutrients under different planting patterns. The results showed that paddyupland multiple cropping rotation systems had advantages in yield, with the yield of late rice being higher than that of winter fallow cropping pattern. Compared with control, the paddyupland multiple cropping rotation systems increased soil organic matter and available nutrient content, being more conducive to organic carbon fixation. Paddyupland multiple cropping rotation patterns are planting patterns of increasing yield and improving soil fertility, with better performance for treatments C and E.
    Effects of root depth on compensatory growth of corn seedlings during post-drought re-watering.
    QIN Rong-rong, WANG Xiao-ling
    2018, 37(11):  3291-3297. 
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    We explored the relationship between root depth and compensatory growth of corn seedlings during post-drought re-watering from April 20 to June 3, on the basis of leaf cytokinin induced by roots. Four treatments including wetness, wetness with root cutting, re-watering, and re-watering with root cutting were set up. At the end of drought stress period (28 days after seedling emergence), root cutting was conducted to remove deep roots as cutting root system into two halves by horizontal cross in the middle position of pot longitudinal section with a thin knife. Compared with wetness treatment, drought stress inhibited corn growth by decreasing biomass of the whole plant. Rewatering induced roots to produce cytokinin in the absence of root cutting, which was then transported to leaves through the xylem sap. The enhanced cytokinin in leaves increasednet photosynthetic rate and biomass of the whole plant. As a result, faster growth occurred in corns during post-drought re-watering without root cutting. Under root cutting, although stimulated by re-watering, the shallow roots could not induce high-level production of cytokinin. We found no changes of cytokinin content and net photosynthetic rate in leaves under root cutting treatments. The biomass of whole plant did not increase rapidly, and no rapid growth occurred in corn with root cutting. In summary, rootinduced cytokinin is a key factor in corn compensatory growth during postdrought rewatering. Root cutting leads to the loss of deep roots, and shallow roots of corn hardly produce cytokinin, which cannot result in compensatory growth. Our results showed that deep roots play a key role in the compensatory growth of corn during post-drought re-watering.
    Relationships among vegetation types, biomass and soil environmental factors in the wetlands of Yellow Sea and Bohai coastal areas.
    2018, 37(11):  3298-3304. 
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    Understanding the relationships among wetland types, biomass and environmental factors is fundamental for wetland vegetation restoration. Based on field investigation in coastal areas of Yellow Sea and Bohai, TWINSPAN was used to categorize wetland types, and redundancy analysis was used to determine the major environmental factors affecting the spatial distribution and biomass variation of wetland types, aiming to provide scientific basis for wetland restoration. Results showed that wetland vegetation in coastal areas of Yellow Sea and Bohai could be classified into eleven types. Soil total carbon content and electrical conductivity significantly influenced the spatial distribution of wetland types. The wetlands in coastal areas of yellow Sea and Bohai had high biomass, with the highest (48512 kg·hm-2) occurring in Spartina alternifloracommunity, followed by Suaeda salsa, Phragmites australis, and Tamarix chinensis communities(>5000kg·hm-2), and the lower (<5000 kg·hm-2) in other communities. Soil organic carbon and total nitrogen contents were the major factors influencing the spatial variation of wetland biomass. Under climatic warming and increased nitrogen deposition, the biomass of wetland vegetation can be enhanced. Therefore, it is an effective way to strengthen wetland conservation and to restore the degraded wetland ecosystems for enhancing coastal wetland carbon sink and coping with climatic change.
    Interaction of vegetationsoil system and their response to spatial differentiation of sedimentation in coastal wetlands.
    LI Cheng-wei, ZHAO Meng, TAO Yan-dong, ZHONG Sheng-cai, YU Ke-feng, FANG Shu-bo
    2018, 37(11):  3305-3314. 
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    Understanding vegetation soil interaction in costal wetland is essential for coastal vegetation rehabilitation. In this study, we analyzed the response of Scirpus mariqueter to the spatial variation of coastal sedimentation and to establish the relationship between vegetation index and soil physicochemical parameters. We collected the data of soil physicochemical parameters and elevation of 32 soil samples in 2015 and 2017 and spectral reflectance of S. mariqueterin seven sampling locations with highdensity vegetation cover in the east tidal flat of Nanhui coastal area in Shanghai. The interaction between vegetation index and soil physicochemical properties and their response to tidal flat elevation were analyzed using correlation analysis, regression analysis, and spatial analysis by ArcGIS. Amplitude of elevation and NDVI variations was classified into 12 grades, with median 6 as the threshold for analysis. Results showed that the proportion of area with both NDVI and elevation variation amplitudes of no less than 6 was 51.45%. Most of these areas were located at the eastern part of the study site. 80.45% of area with NDVI variation amplitude of greater than 6 was included in the area with elevation variation amplitude of greater than 6. Moreover, both elevation and NDVI synchronously increased year by year after reclamation. Soil salinity and soil moisture were spatially correlated with tidal flat elevation, and both of them were the controlling factors for the spatial distribution of S. mariqueter. Our results suggested that the variation of tidal elevation caused by sedimentary environmental differentiation was the key factor controlling S. mariqueter spatial expansion. NDVIbased vegetation analysis could provide a holistic approach to understand the overall dynamics of vegetation change and dispersal.
    Diurnal dynamics and constraints of soil CO2 concentration in a limestone site during summer.
    FU Yu-cong, LANG Yun-chao, WANG Zhong-jun, LI Si-liang, DING Hu
    2018, 37(11):  3315-3322. 
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    Soil respiration is the process of soil releasing CO2. It is important to explore the dynamics of soil CO2 and its controls for mechanistic understanding of the terrestrial carbon budget and global climate change. Using infrared sensors (Vaisala GMP252) and an automatic device, we monitored CO2 concentration and apparent respiration rate (i.e., soil surface CO2 flux) of a limestone soil profile with high frequency, aiming to capture the diurnal dynamics of soil CO2 and its relationship with soil temperature, soil moisture and intense rainfall during summar. The results showed that the diurnal dynamics of soil CO2 concentration generally exhibited singlepeak curves, with a maximum during 12:00-13:00  each day. Moreover, soil CO2 concentration showed a V-shaped response to intense rainfall. Soil CO2 had a positive correlation with soil temperature, but had a negative correlation with soil moisture. The equilibrium of HCO3-, CO32- and CO2 in the water filling in soil porespace during rainfall may have impacts on the CO2 concentration dynamics in limestone soil due to its alkaline property. The apparent soil respiration rate had a similar diurnal variation trend as soil temperature and CO2 concentration, showing significant correlation with temperature, while the poor correlation with soil CO2 concentration. Soil temperature and moisture explained 45% of the variation of apparent soil respiration rate. Our results indicated that with the impacts of intense rainfall events, short-term apparent soil respiration of limestone was mainly controlled by CO2 exchange between soil and atmosphere, which was largely dependent on environmental factors such as rainfall, soil temperature and moisture.
    Effects of continuous subsoiling on temperature, water content, enzyme activity and bacterial community in black soil.
    ZHANG Bo-wen, YANG Yan-ming, LI Jin-long, CHEN Xin-yu, ZHANG Xing-long, XU Zhong-shan, LIU Jing-hui
    2018, 37(11):  3323-3332. 
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    To clarify the effects of subsoiling on the dynamics of soil hydrothermal conditions, soil enzyme activity and bacterial community diversity in black soil, seven treatments were set up from 2016 to 2017, including rotary tillage (CK), one year of surface tillage (QS1), two years of surface tillage (QS2), one year of deep subsoiling (SS1), two years of deep subsoiling (SS2), one year of extradeep subsoiling (CS1), and two years of extradeep subsoiling (CS2). The variations of soil water content, temperature, catalase activity, saccharase activity, urease activity and bacterial community structure among different treatments were assessed. The results showed that subsoiling significantly reduced soil water content of 0-20 cm layer, with SS1 and SS2 showing the lowest reduction, and improved soil water content of 20-40 cm layer, with the highest enhancement in QS2. Soil water content in subsoiling for two years was higher than that in subsoiling for one year. The soil temperature of subsoiling treatments was significantly lower than that of CK at the flowering stage, while soil temperature at jointing stage, tasseling stage, mature stage was significantly higher compared to CK. Soil temperature declined significantly with the increases of subsoiling depth. Subsoiling could maintain longterm soil enzyme activity in 0-20 cm soil layer, and increase soil enzyme activity in 20-40 cm soil layer. Subsoiling improved the richness and diversity of bacterial communities in the rhizosphere soil of 0-20 cm layers. The richness of bacterial communities in subsoiling for two years was higher than that for one year, with SS2 being the best. Subsoiling increased the relative abundance of Acidobacteria, Gemmatimonadetes, Planctomycetes and Thaumarchaeota, but reduced that of Actinobacteria and Firmicutes. Our results indicated that subsoiling can optimize soil hydrothermal environment, maintain high and stable soil enzyme activity, coordinate the structure of bacterial community, and promote the sustainable use of black soil.
    Population viability analysis of Sichuan golden snub-nosed monkey in context of climate change in Hubei Province, China.
    ZHANG Yu, LI Jia, XUE Ya-dong, LI Li, LI Di-qiang
    2018, 37(11):  3333-3341. 
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    Climate change is anticipated to alter habitat area, distribution and configuration of wildlife, exacerbating the extinction risk for endangered species. Sichuan golden snubnosed monkey (Rhinopithecus roxellana) in Hubei Province is vulnerable to environmental changebecause it is genetically distinct and has a small population size with low genetic diversity. Simulations of habitat shifts and population dynamics under climate change can assist in recommending effective adaptive strategies for its conservation. Here, we built a species distribution model based on monkey occurrences associated with bioclimatic and environmental variables. We assessed the extent to which climate change would impact monkey habitat distribution and carrying capacity from the current to the 2050s. Using Vortex model combined with population parameters, we predicted the monkey population’s viability in the period of 100 years in existence of extreme weather disaster and climate change. Our results showed a potential habitat loss of 64.45% due to climate change by the 2050s, resulting in a decrease in the carrying capacity of 93.48%, 72.86% and 13.96% for the Dalongtan, Jinhoulin and Qianjiaping subpopulations, respectively. Without the influence of climate change, the Sichuan golden snubnosed monkey population size in Hubei Province would gradually increase, indicating that the population has certain fecundity. The greatest impact on reduction in population size occurs when extreme weather disasters and climate change happen simultaneously. However, sensitivity to extreme weather disaster and climate change varied among different subpopulations. The protection of current suitable habitat and connectivity between habitats as well as the provision of interventional protection for extreme weather disasters are fundamental ways to conserve the species.
    Effects of feeding of insects with three types of mouthparts on the activities of polyphenols oxidase (PPO) and phenylalnine ammonialyase (PAL) in leaves of kidney bean plant.
    YUE Wen-bo, ZHI Jun-rui, ZHANG Tao, YE Mao, HOU Xiao-lin
    2018, 37(11):  3342-3350. 
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    To clarify the effects of feedingmodes of different insects on systematic defenses in kidney bean plant, we examined the impacts of damages by tobacco cutworm Spodoptera litura(chewing), spider mite Tetranychus urticae (piercingsucking), and western flower thrips Frankliniella occidentalis (raspingsucking) after 6, 24, 48, and 96 h of feeding middle leaves on activities of polyphenols oxidase (PPO) and phenylalnine ammonialyase (PAL) in the damaged middle leaves and undamaged upper and lower leaves of kidney bean plant. The results showed that PAL and PPO activities were significantly influenced by treatment types, periods of time and leaf position (P<0.01), with significant interactions among the three factors. The activities of PPO in middle leaves increased significantly at 6 h in all different treatments (P<0.05), and changed in different patterns with time extension. The PAL activity in middle leaves was not significantly activated until 48 h after mechanical damage (CK). The activities of PAL in middle leave fed by S. litura, T. urticae and F. occidentalis increased obviously at 6, 6 and 24 h, and reached the maximum, being 2.66, 1.75 and 2.79 times of the control, respectively. The responses of the PAL and PPO in undamaged upper and lower leaves by herbivore feeding were faster than that by mechanical damage. T. urticae feeding caused the fastest changes of PAL activity. The activities of PAL in the upper and lower leaves by T. urticaefeeding reached the maximum at 6 h, which were 2.72 and 5.07 times of the control, respectively. Our results indicated that herbivore feeding could induce the systematic defenses of kidney bean plant, with the effects of temporal and spatial defenses  related to the types of pests.
    Salinity tolerance of Palaemonetes sinensis and effects of salinity on its respiratory metabolism.
    BAO Jie, JIANG Hong-bo, Fu Pei-pei, JIANG Qiu-yue, YU Ye-hui, LI Xiao-dong
    2018, 37(11):  3351-3356. 
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    To investigate the salinity tolerance and respiratory metabolism of Palaemonetes sinensis, we examined the effects of salinity (0, 5, 10, 15, 20, 25, 30) on survival, oxygen consumption rate (OCR), ammonia excretion rate (AER), and asphyxiation point (AP) ofP. sinensis which were exposed for 0 or 3 days in laboratory. The results showed that P. sinensis had strong salinity tolerance. The semilethal salinities were 37.07, 35.86, 35.04 and 34.31 at 24, 48, 72 and 96 h respectively, with a safe salinity concentration of 10.07. Salinity had significant effects on OCR, AER, AP and O/N ratio for P. sinensis (P<0.05). For the 0 dayexposure group, the OCR was lowest at salinity of 5 and highest at salinity of 10 when the salinity ranged from 0 to 30. For the 3 dayexposure group, the lowest OCR was at the salinity of 10, 25 and 30 while the highest OCR was salinity of 0. For the 0dayexposure group, the lowest AER was at salinity of 30, and the highest was at salinity of 10 and 15. For the 3 day exposure group, the lowest AER was at salinity of 25 and 30, and the highest was at salinity of 10. There was no significant difference of AP between 0 day exposure and 3 dayexposure groups. The lowest O/N ratio was at salinity of 5 for the 0dayexposure group and was at salinity of 10 for the 3dayexposure group, while the O/N ratio was highest at salinity of 30 for both groups. The OCR in the 3dayexposure group was lower than that in the 0dayexposure group at salinity of 10, 15 and 25. The AER in the 3dayexposure group was lower than that in the 0dayexposure group at salinity of 25. The O/N ratio in the 3dayexposure group was significantly lower than that of the 0dayexposure group at salinity 30. Overall, P. sinensis had a high tolerance to salinity and could be cultured in water with a certain salinity. However, different salinities and treatment methods may change its respiratory metabolism and energy utilization.
    Community structure and secondary production of macrobenthos in intertidal zone of Jiangsu.
    YUAN Jian-mei, ZHANG Hu, TANG Xiao-hong, YU Wen-wen, BEN Cheng-kai, GAO Ji-xian, LIU Pei-ting, HU Hai-sheng, XIAO Yue-yue, XU hai-hua
    2018, 37(11):  3357-3363. 
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    To understand the status of macrobenthos in intertidal zone of Jiangsu Province, nine sections of intertidal zone in Jiangsu were deployed for macrobenthos sampling in May, August, October, 2014 and March, 2015. In total, 78 species of macrobenthos were identified, including 39 species of Annelida, 23 species of Mollusca, 12 species of Crustacea and four species of other animals. The mean density was 78.64 ind·m-2, and annual mean biomass (ash-free) was 13.01 g·m-2. The mean secondary productivity of macrobenthos was 8.57 g·m-2·a-1 and P/B ratio was 0.66. Compared with the survey in the 1980s and of the “908” special project, the main groups of macrobenthos in intertidal zone of Jiangsu did not change, but species richness decreased. The difference in secondary productivity between the middle tidal zone, the high and low tide zones was significant (P<0.05) but there was no significant difference among seasons (P>0.05).
    Prediction of potential geographic distribution of Anoplolepis gracilipes (Homoptera: Formicinae) in China using MaxEnt model.
    ZHANG Yan-jing, MA Fang-zhou, XU Hai-gen, FAN Jing-yu, SUN Hong-ying, DING hui
    2018, 37(11):  3364-3370. 
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    Yellow crazy ant, Anoplolepis gracilipes, a newly recorded invasive species in southern China, poses serious threats to native biodiversity. In order to reveal the potential risk of its expansion and adaptive distribution, the occurrence points were divided into two parts: the native points and the global points, with local and global prediction models being constructed, respectively. Seven climatic environmental factors, which strongly influence the survival of A. gracilipes, were selected for model analysis. The maximum entropy (MaxEnt) model was adjusted by using the ENMeval data package in R software. The prediction of the niche area of A. gracilipes in China was constructed using the local and global prediction models with the default and refined parameter settings. The pROC protocol was used to test the reliability of the models. The results showed that under the same setting, there was an obvious difference in the potential geographic distribution of A. gracilipes, based on the global model and the native model, while the influence of the refined parameter settings on the model’s prediction was minimal. Overall, the potential distribution of A. gracilipes with high suitability was Yunnan, Guangxi, Guangdong, Fujian, Hainan and Taiwan, whereas Hunan, Guizhou, Jiangxi and parts of Sichuan were areas of intermediate suitability. Moreover, for the native model, central Africa and northcentral America were the potential distributions of the highly adaptive A. gracilipes. The definition of the local scope of A. gracilipes has a considerable impact on the accuracy of the prediction results of the model.
    Analysis and risk prediction of pinewood nematodes based on landscape patterns: A case study from Yichang, China.
    HONG Cheng-hao, ZHANG Zi-yi, CAI San-shan, CHEN Jing-yuan, SONG De-wen, LI Yong-xia, ZHANG Xing-yao
    2018, 37(11):  3371-3380. 
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    The incidence of pine wilt disease (pinewood nematode) is severe around the Three Gorges area, which puts huge pressure on local environment. The conventional tactics of management for this pest costs too much resource but is not effective. Under the framework of patchcorridormatrix model, the relationships between annual incidence area of pinewood nematodes and landscape patch and landscape pattern were analyzed, and then outbreak risk was assessed. The interpolation risk analysis was carried out based on the Pearson correlation coefficients between the disease situation and pattern indices (CA, PD, LSI, PRD, and SHDI) on both levels of landscape (Yichang City) and patch (Yiling District, Yidu City, and Central District of Yichang City). The results showed that the incidence of pinewood nematodes was quite serious in Yiling District and Yidu City. The disease incidence area was positively correlated to the area of the host patches and their shape indices, with correlation coefficients of 0.826 and 0.818 respectively. There was no significant correlation between disease incidence area and human activity affected patches. The results of interpolation risk analysis showed that the fragmental large host patches and those with high shape index should be the key points of management to reduce expenditure on material and financial resources.
    Responses of landscape ecological pattern to the expansion of urban construction land in river valley city under different scenarios: A case study of Lanzhou.
    CHEN Xi-dong, SHI Pei-ji, WANG Chuan, YUE Xiao-xin, LIU Xiao-xiao, ZHANG Wen-min
    2018, 37(11):  3381-3389. 
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    We used land use data of the main urban area of Lanzhou, a city developed in the river valley, in 1995, 2005, and 2015 to analyze the spatial and temporal characteristics of construction land expansion. The CLUE-S model and Markov model were integrated to simulate the growth and spatial distribution of construction land under three different scenarios in 2025. The landscape ecological pattern characteristics were analyzed through landscape principles. The results showed that, from 1995 to 2015, the expansion of construction land was mainly based on the internal filling of urban groups and supplemented by external expansion, and the expansion was significantly affected by the terrain and policies. During 2015 and 2025, the growth rate of construction land under three scenarios in a descent order would be baseline scenario, comprehensive development scenario, ecoconservation scenario. The expansion area mainly includes the north of the Yellow River in Chengguan District, the north of Anning District urban area, and the southern edge of Qilihe District urban area. Because of the intensive expansion of the construction land, the unstable landscape pattern with the simple landscape patch shape and enhanced vulnerability is formed under the baseline scenario and comprehensive development scenario, while the landscape pattern with reasonable patch components, and rich diversity and uniform distribution is formed under the ecoprotection scenario in which the expansion speed of construction land is effectively controlled.
    Design of the continuous rainfall days index insurance of peanut in Henan Province.
    WANG Xin-wei, DU Ming-zhe, WANG Li, LI Meng-xia, XU Yan-yan, LIU Xiao-ying, LI Ning
    2018, 37(11):  3390-3395. 
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    To provide technical support for effectively improving the insurance company’s compensation for meteorological disasters, we employed longsequence meteorological dataset, planting area, total production, and yield per unit area of peanut to quantify the threshold for disaster indices of the continuous rain days corresponding to different yieldreduction rates, established continuous rain weather index insurance models, and designed insurance products of continuous rain weather index suitable to the study area. According to the continuous rain disaster index, the deductible amount was 0% in Lankao, Yucheng and Tongxu counties, 10% in six counties such as Kaifeng, 15% in four counties such as Suixian, and 20% in six counties such as Huaiyang. The pure insurance rates and insurance expenses in different regions were determined, and an agrometeorological insurance index contract was designed. The weather index insurance products adopt objective meteorological data to fix the loss and are very maneuverable, which can effectively transfer the risk of meteorological disasters during peanut growth and help agricultural insurance companies to provide economic compensation for meteorological disasters objectively and quickly.
     
    Spatial and temporal characteristics of climatic potential productivity of maize in Liaoning Province from 1966 to 2015.
    LIU Jiang, Pan Yu-hong, WANG Ping-hua, LI Yi-ming, JIN Lei, WEN Yong-jing, GAO Shu-xin
    2018, 37(11):  3396-3406. 
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    Based on daily meteorological observation data of 46 stations in Liaoning Province from 1966 to 2015, we analyzed the interannual trends of climate factors in the growing season of maize. The photosynthetic, lighttemperature, and climate potential productivity were estimated by mechanical method. The temporal and spatial distribution characteristics of climate potential productivity of maize were analyzed by empirical orthogonal function (EOF) and rotated EOF (REOF) decomposition methods. The results showed that: (1) The mean temperature during the growth period of maize increased, solar radiation declined, and the precipitation showed a fluctuating decline trend in Liaoning Province from 1966 to 2015. The trend of photosynthetic potential productivity of maize was decreased by phases, light temperature potential productivity and climate potential productivity of maize showed a fluctuating upward trend, but the trends of those changes were not significant. Compared with the 1970s and 1980s, climate potential productivity of maize increased substantially in the early 21st century. (2) The photosynthetic potential productivity was gradually decreased from southwest to northeast, and light temperature potential productivity showed a belt typed distribution. The first two modes of EOF analysis explained 86.47% of the total variation. The results revealed the spatial distribution of climate potential productivity of maize characterized by an overall consistency, with the midland region being a center. Among them, southern coastal area and eastern region showed a reverse trend in Liaoning Province. (3) The spatial distribution of the climate potential productivity of maize in Liaoning Province could be divided into four typical distribution types. The high value area was located in the middle and southern coastal areas, while the low value area was located in the eastern part and the semi-arid western part of Liaoning.
    Adsorption of copper ions in acidic mine drainage by β-FeOOH modified montmorillonite.
    ZHOU Hua-feng, ZHANG Xiao-xiao, LI Xiang
    2018, 37(11):  3407-3412. 
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    In this study, β-FeOOH-Mt was prepared by montmorillonite modified with beta hdroxy iron oxide. N2TPD was used to identify the structure of β-FeOOH-Mt. The adsorption of copper ions in acidic mine drainage by β-FeOOH-Mt (3.5) was examined. It was found that the specific surface area and the pore volume of montmorillonite increased after modification. β-FeOOH-Mt (3.5) had strong adsorption capacity for Cu2+. When the initial concentration of Cu2+ was 5-25 mg·L-1, the application amount of β-FeOOH-Mt (3.5) was 2-9 g·L-1, and the concentration of Cu2+ was lower than 0.5 mg·L-1 after 20 min. The Langmuir isotherm model better fitted with the experimental data than Freundlich isotherm model. The adsorption process is in accordance with the single molecule adsorption model. The kinetic study showed that the adsorption followed the quasi second adsorption kinetic equation with a good correlation.
    Evaluation on water eutrophication and retention effect in wetland landscape of Hani Rice Terraces.
    ZHA Zhi-qin, JIAO Yuan-mei, LIU Zhi-lin, LIU Cheng-jing, GAO Xuan, DING Yin-ping, ZHAO Dong-mei
    2018, 37(11):  3413-3421. 
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    Agricultural non-point source pollution is the main factor of surface water eutrophication. Wetland landscape could retain pollutants or nutrients. Taking region as research object, we collected 36 samples of the surface water in the terraced wetland landscape of Dayutang village in Hani Rice Terraces in June (rainy season) and December (dry season) of 2017. We measured total nitrogen (TN) and total phosphorus (TP) concentrations, analyzed their temporal and spatial characteristics, and evaluated their eutrophication level and retention function by eutrophication composite index (PI) and retention capability, respectively. The results showed that the mean concentrations of TN and TP in all samples in the rainy season were higher than those in the dry season, with such values in ditch being the highest among the four wetland types. In terms of landscape types, the TN and TP concentrations in water from village and rice terraces were higher than those in forests and rivers. The PI value of all water samples in rainy season was higher than that in dry season. The ditch water was moderately eutrophic (with a PI value of 2.01) among the four water types, while the water in the landscape type of village was heavily eutrophic (PI 5.09). Furthermore, ditches (1.38 vs. 0.07 mg·L-1), rice terraces (0.25 vs. 0.08 mg·L-1), rice terraces area (2.04 vs. 0.17 mg·L-1) and rivers (0.05 vs. 0.00 mg·L-1) were of significant purification function, which kept the downstream river free of non-point source pollution and the entire landscape presenting obvious retention effects. Our results provide a basis for the ecological conservation of Hani Rice Terraces.
    Vertical distribution of nitrogen species and nitrate isotopic composition in wet deposition in karst depression.
    ZENG Jie, WANG Zhong-jun, YUE Fu-jun, LI Si-liang, WU Qi-xin, LIU Tao-ze, SI Xia-li
    2018, 37(11):  3422-3429. 
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    To understand the vertical distribution of nitrogen species and nitrate isotopic composition in wet deposition in karst depression, we collected wet deposition samples within a typical karst agricultural depression in the rainy season (May to August 2015) in Puding County, Guizhou Province. The concentration of nitrogen species and nitrate isotopic composition were examined. The results showed that there was a stronger capture effect on the ammonium released from the depression in wet deposition. The source of dissolved organic nitrogen was closely related to agricultural activities. There was no obvious vertical variation of nitrate concentration, but its isotopic composition presented high contribution of NOx released from soil. The main nitrogen species in wet deposition of karst depression was NH4+-N during the rainy season. There was vertical variation of nitrogen species, in that the NH4+-N and DTN in depression were generally higher than that in the mountain top. DON concentration of depression was higher than that from the mountain top from May to July, but lower than that from the mountain top in August. The δ15N-NO3-and δ18O-NO3- values were -4.8‰±2.3‰ and 58.1‰±7.6‰ in the mountain top, respectively, and were -7.3‰±3.3‰ and 57.3‰±6.6‰ in depression. Nitrate isotopic composition in mountain top was relatively higher than that in depression, which was related to both the contribution of NOx released from cropland and the possible fractionation in the diffusion process. Monthly variation of δ15N-NO3-value indicated that the contribution of each NOX source to the nitrate in rainwater was changed monthly.
    Research progresses in treeline dynamics and driving forces in the Northern Hemisphere.
    ZHANG Yu, LU Xiao-ming, WANG Ya-feng
    2018, 37(11):  3430-3439. 
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    Treeline is an ideal ecotone to monitor the responses of forests to climate change. However, it is still unclear how treeline respond and adapt to climate change, which is one of key topics in evaluating relationships between climate and alpine forests. We reviewed current understanding of the responses of treeline position and regeneration to climate change. Since the 20th century, treelines showed diverse responses to climatic change in the Northern Hemisphere. However, tree regeneration at treelines showed an overall increasing trend. Simultaneously, tree morality occurred due to warminginduced drought in some regions. In Europe and North America, about 56% studied treelines showed upward shifts, while 44% were stable. In Asia, 64% studied treelines moved upward significantly, while 36% showed little change in treeline elevation or kept stable. We discussed the driving factors for the diverse responses of treeline shifts in the Northern Hemisphere. As indicated by recent studies, treeline shifts in different areas were driven by various climatic and non-climatic factors. Such an understanding is crucial to predict spatio-temporal dynamics of treelines in response to future climate change.
    Effects of nitrogen regime on nitrogen metabolism of rice and nitrogen transformation and translocation in paddy soils.
    BAI Zhi-gang, ZHANG Jun-hua, HUANG Jie, ZHU Lian-feng, CAO Xiao-chuang, ZHU Chun-quan, ZHONG Chu, JIN Qian-yu
    2018, 37(11):  3440-3448. 
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    Nitrogen (N) fertilizer management is an important procedure in high-yield cultivation for rice. Identifying the effects of N management strategies on N metabolism in rice and N transformation and translocation in paddy soils will be of great significance in improving N use efficiency (NUE) of rice and increasing benefits of rice planting. We reviewed the effects of N management strategies on the expression of N transporters and the activity of key enzymes in N metabolism of rice, and analyzed the interaction between N metabolism and carbon metabolism. We summarized the effects of N application strategies and methods on the transformation and translocation of different N forms in paddy soils. The regular patterns of N loss affected by the N application strategies and methods and the possible regulation approaches for reducing N loss were also concluded. We argued that although the influence of N management on the N metabolism in rice at the physiological level is clear, the research at the genetic and molecular level is limited. Although it is certain that the improvement of N management in rice fields has made an obvious contribution to the enhancement of NUE, there are many problems in practical application, which need further improvement. Further studies should focus on deeply exploiting the potential of N metabolism in rice, thereby increasing the NUE combined with more efficient N application strategies in paddy soils.
    Advances in the research on microbial degradation of sulfonylurea herbicides.
    WANG Xin, SUN Shi-yu, ZHANG Hui-wen
    2018, 37(11):  3449-3457. 
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    Sulfonylurea herbicides are featured by high efficiency, broad spectrum, and high selectivity. They have caused serious damage to the environment after widely used in long term. The elimination of environmental problems caused by the use of sulfonylurea herbicides is one of the important issues in modern agriculture. The main degradation methods of sulfonylurea herbicide include chemical degradation and biological degradation. Biological degradation is a natural way to degrade pollutants with high feasibility and low side effects. In recent years, many studies have examined the role of fungi, bacteria and other microorganisms in degrading sulfonylurea herbicides, with many important results being achieved. We summarized the properties, structure and degradation mechanism of sulfonylurea herbicides, and the variety of microorganisms capable of degrading herbicides, and the factors affecting the efficiency of microbial degradation. Finally, we proposed the problems and the development trend of sulfonylurea herbicides in the future.
    Issues on fish behaviors in the design of fish passage facilities.
    CAI Lu, JIN Yao, PAN Lei, ZHAO Ping, HE Da, HOU Yi-qun, CHEN Xiao-juan, ZHANG Peng
    2018, 37(11):  3458-3466. 
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    Hydropower projects obstruct fish migration and prevent gene exchange. Fish passage facilities are the primary means of mitigating such adverse impacts. Understanding fish behaviors, including swimming performance and tropism, is important for the design of fish passage facilities. We reviewed the concepts of swimming performance and tropism, research approaches and influencing factors (such as flow velocity, flow field, and temperature). Key research results on swimming performance and tropism are summarized and the application of fish swimming behaviors to fish passage facility design is discussed. Four critical issues are addressed: (1) Fish behaviors in complex flow fields should be considered in depth because of the complexity of flow fields in fish passages. (2) Exercise training can improve fish swimming performance and thus could be used to increase the success rate of fish passage. (3) Swimming performance variesamong species. New and innovative designs are required to increase the number of species able to utilize a fish passage facility. (4) Different methods have been used to study fish behaviors, with results being difficult to compare. Hence, research administrators, with input from experts, should formulate criteria and guidance for standardizing fish behavior research.
    Reconstruction of stand-replacement disturbance and stand age of Chinese fir plantation based on a Landsat time series in Huitong County, Hunan.
    ZHANG Wen-qiu, FANG Lei, YANG Jian, ZHANG Wei-dong, YAN Yan, YAN Qiao-ling
    2018, 37(11):  3467-3479. 
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    We constructed a relatively complete annual time series of Landsat archived data of Huitong County, Hunan Province from 1986 to 2016, and detected the dynamics of each forest pixel by calculating and analyzing the annual Integrated Forest Z-cores in order to obtain historical disturbance information. We mapped stand age in the study area by establishing a statistical relationship between historical disturbance information and fieldmeasured stand ages. The results showed that: (1) The area of Chinese fir plantations was 7.67×104 hectares, which was mainly distributed in the regions with the slope steepness less than 25°; (2) The disturbance of Chinese fir plantations mostly occurred before 1996. The highest loss of Chinese fir plantation area caused by the disturbance occurred mainly during 1987-1992, accounting for 17.54% of the total area. The area of disturbed Chinese fir plantation gradually declined after 2000, while the area of forest recovered from disturbance increased rapidly during the same period. About 42% of Chinese fir plantations were recovered from disturbances during the past 15 years, which were mostly located along the major transportation routes and the rivers; (3) Mature and intermediateaged Chinese fir plantations occupied the majority of forest landscape, covering about 47% and 15% respectively. In contrast, young, nearmature, and overmature Chinese fir plantations covered 15%, 3%, and 6%, respectively. Our results suggested that remote sensing timeseries data could be used to effectively retrieve stand age distribution of regional plantation forest. Our results provide critical information for the management of local forest resources.
    Monitoring of Enteromorpha prolifera in the Yellow Sea with MODIS image based on linear mixing model and NDVI threshold.
    DING Yi, CAO Cong-hua, CHENG Liang-xiao, WANG Ning, WEN Lian-Jie
    2018, 37(11):  3480-3486. 
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    Due to eutrophication,E. prolifera disasters have frequently occurred in China’s Yellow Sea since 2007, which have become the most serious ecological disaster in the Yellow Sea. Satellite remote sensing has the advantages of largescale monitoring and instantaneous monitoring, and is one of the most important monitoring means of E. prolifera disaster. Moderateresolution imaging spectroradiometer (MODIS) image is the main data source of E. prolifera operational monitoring because of its large size, high temporal resolution and free distribution. There are many errors in E. prolifera area derived from NDVI threshold, because of mixed pixels in the coarse resolution (250 m) MODIS images. In order to solve this problem, we extracted the E. prolifera area from the MODIS image with the spatial resolution of 250 m by combining the linear spectral mixture decomposition method and NDVI threshold method. A large area and its threeinner subareas were selected for the accuracy evaluation based on the data of E. prolifera extracted from quasisynchronous ZY-3 satellite with 5.8 m spatial resolution. We found that the error of E. prolifera area, extracted from the linear mixed model with a NDVI threshold of 0.04, was the smallest, and the errors of the large area and its three subareas were 7.86%, 14.59%, -7.65% and -0.15% respectively. Hence, we provide a method that can effectively eliminate interference from the E. prolifera mixed pixel and non E. prolifera pixel, and greatly improve the inversion precision which is stable in different regions. This method can provide support for the management decision and evaluation of E. prolifera ecological disaster.
    Sampling method and sample size for studying soil physical property: A case of alpine meadow in eastern Qilian Mountain.
    CHU Bin, ZHANG Zhen-fen, ZHOU Jian-wei, WANG Ting, HUA Li-min
    2018, 37(11):  3487-3492. 
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    Soil heterogeneity is one of the major factors that influence vegetation heterogeneity and habitat selection of soil fauna and rodents. Rational soil sample size and distribution is very important for reflecting the useful information of soil. In this study, we investigated soil compaction, soil bulk density, and soil moisture in alpine meadow of the eastern Qilian Mountain, by setting up 121 sampling points within a 110 m × 110 m plot. We compared the results of different sampling sizes (3-36 sampling points) and three sampling methods (random sampling, grid sampling, and diagonal sampling) with entire sampling method (121 sampling points). We found that: (1) The standard errors of sampling decreased with increasing the sampling sizes using different sampling methods. (2) Among the three sampling methods, the random sampling method was the best one. Sampling size of >18 points could meet accuracy requirement under 90% and 95% confidence level. We suggest that the sampling effects should be considered according to the study purpose and grassland type.
    Fungal communities in twigs of three bamboo species based on high-throughput sequencing technology.
    GENG Xian-sheng, SHU Jin-ping, PENG Han, ZHANG Wei
    2018, 37(11):  3493-3498. 
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    To understand the characteristics of fungal communities of bamboo infected with witches’ broom disease and explore the correlation between witches’ broom pathogen and other bambusicolous fungi, species composition and diversity in fungal communities associated with witches’ broom diseased twigs of three bamboo species (Phyllostachys bambusoides f.lacrimadeae, Ph. edulis and Ph. praecox) were analyzed using highthroughput sequencing technology, DNA barcode technology, and bioinformatics technology. The results showed that: (1) A total of 706 OTUs were obtained, with 48 OTUs being shared by all samples. Aciculosporium, Shiraia, Myrothecium, Pyrenochaeta, Colletotrichum, Fusarium, CamptophoraandPseudozyma were the dominant genera of bambusicolous fungal communities. (2) Chao1 index and Shannon index were not significantly different among fungal communities (P>0.05). (3) The causal agent of witches’ broom disease of the three bamboo species was Aciculosporium take, which was negatively correlated with other 13 species of bambusicolous fungi, and nine of them were significantly correlated (P<0.05). This pathogen showed a weak positive correlation with other two species of bambusicolous fungi. (4) Trichoderma virens, Cladosporiumsp.,Shiraiasp.,Curvulariasp., Penicilliumsp. and Acremoniumsp. were important components of the fungal communities, which were the potential biocontrol agents of bamboo diseases.