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Table of Content

    10 January 2018, Volume 37 Issue 1
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    Relationships between the composition and diversity of understory vegetation and environmental factors in aerially seededPinus massoniana plantations.
    CAO Meng, PAN Ping, OUYANG Xun-zhi, ZANG Hao, NING Jin-kui, GUO Li-ling, LI Yang
    2018, 37(1):  1-8. 
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    We chose the aerially seeded Pinus massoniana plantations to study the relationships between the composition and diversity of understory vegetation and environmental factors using the redundancy analysis (RDA) and variation partitioning methods. Our results showed that: (1) A total of 54 understory species belonging to 29 families and 36 genera were recorded, and the importance values ofGlochidion puberumand Dicranopteris linearis were the highest in shrub and herb layers, respectively. Significant effects of average diameter at breast height (DBH), altitude and canopy density on species composition in shrub layer, and extremely significant effects of soil thickness on species composition in herb layer were found (P<0.01) using the forward selection and Monte Carlo analysis. (2) Nine factors selected by using Monte Carlo permutation test explained together 70.9% of species diversity variation, and average DBH, canopy density, soil thickness, available nitrogen and slope position were the important factors determining species diversity in understory vegetation. The biotic, abiotic factors and their interaction respectively explained 34.8%, 7.5% and 20.5% of the total variation in species diversity in understory vegetation, which indicated that biotic factors and their interactions with abiotic factors were the main factors affecting the species diversity in understory vegetation.
    Vegetation and soil characteristics of plant community micro-patches under different grazing intensities.
    HU Yan-yu, Wuyunna, HUO Guang-wei, SONG Yan-tao, WANG Xiao-guang, ZHANG Feng-jie
    2018, 37(1):  9-16. 
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    The co-existence of micro-patches in plant community is one of the basic characteristics of grazing pasture, which affects ecosystem structure and functioning. In this study, we investigated characteristics of plant communities, primary productivity, soil physical and chemical properties, plant nutrient content, and their correlations in different patches selected from plant communities under different grazing intensities. The results showed that with the increase of grazing intensity, species composition of plant community patches tended to be simplified, the species sensitive to grazing disappeared, and species richness decreased. High grazing intensity significantly decreased aboveground biomass of plant community. In addition, there was a significant relationship between aboveground biomass and total nitrogen concentration. The concentrations of soil total carbon, total nitrogen and total phosphorus showed increasing trends with the increase of grazing intensity. Influenced by the grazing intensity and patch structure, the spatial distribution of soil total carbon, nitrogen and phosphorus are heterogeneous. There were no significant correlations between plant and soil nutrient concentrations. The results suggested that community structure and ecosystem function would be changed by livestock grazing, with asynchronous dynamics between plant and soil nutrients.
    Evaluating natural restoration of vegetation on steep slopes in the Loess Plateau, Shanxi Province.
    CHEN Bao-qiang, ZHANG Jian-jun, ZHAO Rong-wei, SUN Ruo-xiu, LI Liang, RU Hao, WANG Ya-qiong
    2018, 37(1):  17-25. 
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    To understand the restoration status of vegetation on steep slopes above 35°, with the application of RS and GIS tools, 100 plots with different aspects on steep slopes of Caijiachuan watershed in Jixian County of Shanxi Province were selected. On the basis of division of site types, vegetation coverage, community restoration degree (RD) and restoration speed (RS) in different habitats of steep slope were analyzed by using the method of spatial sequence instead of time succession. The results showed that steep slopes could be divided into 3 groups of site types according to different slopes, i.e. group Ⅰ (35°-45°), group Ⅱ (45°-55°) and group Ⅲ(>55°). Coverage and biomass of groups Ⅰ and Ⅱ were obviously different from group Ⅲ(P<0.05). According to community RD and vegetation succession, recovery process was divided into early, middle and late stages. There were highest RS but lowest RD in the early stage; the moderate RD and RS in the middle stage; the slowest RS and the highest RD in the late stage. The natural restoration strategy was different for the three site types, and the RD was the highest in the early stage for both groups Ⅰ and Ⅱ, while the RD was the highest in late stage for group Ⅲ. The RD reached up to 0.8 for both groups Ⅰ and Ⅱ; for group Ⅲ, the maximum RD was only 0.5, and the effect of natural vegetation restoration was not obvious.
    Effect of slope aspect and terrain of sand dune on herbaceous diversity in Gurbantunggut desert.
    JIA Feng-qin, REN Juan-juan, ZHANG Yuan-ming
    2018, 37(1):  26-34. 
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    Spatial-temporal pattern of vegetation is determined by a variety of environmental factors on different scales. The influence of slope aspect and terrain on vegetation pattern has been increasingly reported in recent years. This study investigated the influence of slope location and terrain on vegetation distribution and their temporal structure on typical longitude sand dune in Gurbantunggut desert to provide scientific evidence for vegetation utilization and management, biodiversity conservation and ecosystem restoration and reconstruction. On each of three selected typical sand dunes, five parallel transects (west eastern direction) were established at 20 m intervals. Each transect covered six terrains: The base, lowslope, and upslope of the windward and leeward slopes of the sand dune. In midApril 2015, the aboveground vegetation was sampled in three 1 m × 1 m quadrats randomly placed along the transects. All plant species within each quadrat were identified and recorded. Among windward slope and leeward slope of sand dune, the main herbaceous species were from Compositae, and life form of ephemeral plants had the highest proportion; herbaceous density on windward slope was significantly lower than that on leeward slope, but showed a same trend of “V” pattern from April to September. On both slope aspects, the highest α diversity (richness index, Shannon index, Simpson index and Pielou index) was observed at up-slope and the lowest at base of slope; there was a decreasing trend or a “V” pattern in each terrain over investigation time. Cody index decreased but Sorenson index increased with the terrain rising on windward slope and leeward slope. The results suggested that habitat heterogeneity of sand dune terrain and slope should be considered to preserve and restore the desert plant diversity. Meanwhile, the temporal variation of plant diversity should be also considered to make scientific measures for desert management.
    Responses of leaf morphological and anatomical structure to elevation in an alpine plant Meconopsis integrifolia. 
    LIU Meng-Ying, LIU Guang-Li, KANG Yong-Xiang, ZHANG Shuo, WU Yun, WANG Yu
    2018, 37(1):  35-42. 
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    In order to reveal the adaptive mechanism of the alpine plantMeconopsis integrifolia, we compared foliar structure ofM. integrifolia in Mount Balang along an elevation gradient (3681, 3841, 4081, 4215, 4452 m)， using paraffin wax slices method and microimaging technique. We found that there existed differences in foliar traits along the altitudinal gradient. With the increase of altitudes, the patterns of foliar traits were as follows: (1) plant height and basal diameter decreased; (2) leaf length and width decreased, while length width ratio increased; (3) palisade mesophyll thickness, palisade-sponge mesophyll thickness ratio and leaf cell tense ratio showed an increase, while the thickness of leaf, epidermis, sponge mesophyll, the midrib diameter, sponge ratio decreased; (4) leaf trichome density, stomatal density as well as stomatal index showed a trend of increase. Besides, we analyzed the correlation between the anatomical characteristics of leaves, and investigated the response and ecological adaptability of plant characteristics to different altitudes. The results indicated the occurrence of a significant co-evolution between anatomical indexes in leaves. In particular, indexes such as plant height and leaf size exhibited high plastic responses to altitudes. All these suggested that differences in either morphological or anatomical structure ofM. integrifolia along the altitudinal gradient might result from its adaptation to complex alpine environment.
    Effect of alternative dry-wet shifting on eco-physiological characteristics ofCarex schmidtiitussocks.
    ZHANG Dong-jie, QI Qing, TONG Shou-zheng, ZHANG Zhong-sheng, WANG Xue-hong, AN Yu, PAN Yan-wen
    2018, 37(1):  43-49. 
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    Carex schmidtii tussocks, as a unique landscape in the Momoge National Nature Reserve, are governed by hydrological variations. In the present work, effects of alternative dry-wet shifting on height, biomass and chlorophyll content of  C. schmidtii were investigated based on laboratory simulation experiments so as to provide techniques and strategies for wetland restoration of C. schmidtiitussocks. Results showed that plant height, stem diameter and leaf width ofC. schmidtii under 30-day alternative dry-wet shifting had higher values than under other experimental scenarios in early growth period. At late growth stage, the growth of C. schmidtii was affected by the treatments implemented in different seasons. The-early group (group A, treated in May) had higher stem diameter and leaf width than the late group (group B, treated in June). Chlorophyll content of C. schmidtii from the group A was higher than that from the group B, but the chlorophyll a/b had an opposite trend. Overall, dry-wet alternation is conducive to improving morphology and chlorophyll content ofC. schmidtiiin early growth period. At late growth stage, rational irrigation and shortened dry-wet alternation are expected to increase biomass. Our results provide a scientific basis for wetland restoration and protection ofC. schmidtii tussocks.
    Distribution characteristics of basal diameter and internode length of Dinochloa orenuda in Ganshenling, Hainan Island.
    HU Xuan, QI Liang-hua, XU Rui-jing, PENG Chao, DING Xia, CHENG Chang-jin
    2018, 37(1):  50-56. 
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    Rattan-like bamboos are quite unique, which have scrambling-like stems and rattan-like shapes. In this study, the distribution characteristics of basal diameter and internode length of naturally distributedDinochloa orenudain Ganshenling, Hainan Island were analyzed using Kolmogorov-Smirnov algorithm, and its biological and ecological characteristics were further revealed. The results showed that the basal diameter ofD. orenudain Ganshenling, Hainan Island ranged 11.92-47.60 mm, and the distribution of basal diameter obeyed normal distribution, log-normal distribution and gamma distribution. The theoretical value of normal distribution was the most similar to the original value, followed by gamma distribution and log-normal distribution. The internode length ofD. orenuda ranged 23.33-43.33 cm. Its distribution obeyed normal distribution, Weibull distribution and gamma distribution. The theoretical value of normal distribution was the most similar to the original value, followed by Weibull distribution and gamma distribution. The basal diameter’s distribution ofD. orenuda in Ganshenling, Hainan Island was rational, and internode length ofD. orenudawas similar toAmpelocalamus saxatilis in Sichuan and Weixin of Yunnan.D. orenudacan be exploited as garden bamboo or bamboo corridor by molding, it can also be greening bamboo in mountainous regions.
    Effect of high humidity and high temperature interaction on photosynthetic characteristics of greenhouse tomato crops.
    YANG Shi-qiong, YANG Zai-qiang, WANG Lin, LI Jun, ZHANG Man-yi， LI Kai-wei
    2018, 37(1):  57-63. 
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    In order to reveal the effects of high temperature and high humidity interaction on photosynthetic characteristics of tomato leaves, a L9 (3-3) orthogonal test with tomato cv. ‘Jinfen 5’ was carried out in artificial climate chamber. To measure the photosynthetic parameters and fluorescence dynamic parameters of different treatments, three levels of influencing factors were set: Temperature of 35 ℃ (daytime)/18 ℃ (nighttime), 38 ℃/18 ℃, 41 ℃/18 ℃), relative air humidity of daytime (50%±5%, 70%±5%, 90%±5%), treatment days (3, 6, 9 d), and 28 ℃/18 ℃, 45%-55% as a control (CK). The results showed that the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), water use efficiency (WUE), PSII maximum quantum efficiency (Fv/Fm), photochemical quenching coefficient (qP) and electron transfer rate (ETR) were significantly lower than the CK, while the intercellular CO2 concentration (Ci) was the lowest in the 38 ℃/18 ℃, 70% air humidity treatment, stomatal limitation (Ls) was the lowest in the 38 ℃/18 ℃, 90% air humidity treatment. Compared to the CK, leafPn under temperatures of 38 ℃/18 ℃, 35 ℃/18 ℃, 41 ℃/18 ℃, and humidity of 70%, 50%, 90% decreased by 30.1%, 21.4%, 51.9%, 31.2%, 31.4% and 38.6%, respectively. No obvious differences in these indicators were observed among the treatment durations of 3 days, 6 days and 9 days. High temperature was the main stress factor affecting the Pn of tomato(P<0.05), and high humidity was a second stress factor; the interaction of high temperature and high humidity had a significant effect onPn (P<0.01). This study confirmed that when the maximum air temperature rises above 38 ℃, appropriate increase in air relative humidity to 65%-75% can effectively reduce the heat stress on tomato damage.
    Characteristics of soil nutrients and microbial activities of reed vegetation in the Huixian karst wetland, Guilin, China.
    LI Yan-qiong, HUANG Yu-qing, XU Guang-ping, SUN Ying-jie, ZHANG Zhong-feng, HE Cheng-xin, HUANG Ke-chao, HE Wen
    2018, 37(1):  64-74. 
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    In order to elucidate the vertical variation of soil nutrients and the characteristics of soil microbial activities of reed vegetation community in Huixian karst wetland, soil samples at0-80 cm depth were collected to analyze soil nutrient (C, N, P) concentrations, microbial biomass C, N, P (MBC, MBN, MBP) and microbial activity index (i.e.basal respiration (BR), potential respiration (PR), microbial quotient (qMB) and metabolic quotient (qCO2)). The correlations among soil nutrients and soil microbial activity indictors were examined. The results showed that: (1) The concentrations of total C (TC), soil organic C (SOC), soil inorganic C (SIC), total N (TN) and organic N (Org-N) decreased with soil depth, while the concentrations of soil available N (AN), ammonium N (NH4+-N), nitrate N (NO3--N), total P (TP), available P (AP), organic P (Org-P) and inorganic P (Inorg-P) in subsoil fluctuated. SOC and OrgN played a dominant role in the contents of TC and TN, respectively. Meanwhile, the concentration of Inorg-P was slightly higher than that of Org-P. (2) The MBC, MBN and MBP were much higher in the 0-30 cm soil layer, and also decreased with the soil depth. The MBC, MBN and MBP were positively correlated with the concentrations of SOC, TN and TP, respectively. (3) The soil BR and PR showed a decreasing trend with soil depth. However, with the increase of soil depth, theqMB decreased after an initial increase. TheqCO2 decreased in soil profiles, with small fluctuation in middle soil layers. (4) There were positive correlations among soil nutrients and microbial activity indexes. Soil microbial activities are important indicators for reflecting soil quality in the Huixian karst wetland.
     
    Effects of nitrogen addition and litter manipulation on soil nitrogen in a mixed Pinus tabuliformis andQuercus wutaishanicaforest.
    TANG Zuo-xin, ZHAO Jing, SUN Xiao-lu, YOU Ye-ming
    2018, 37(1):  75-81. 
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    With a randomized block design by changing above-ground litter and nitrogen addition rate, we studied the main effects and interactive effects of nitrogen addition and litter manipulation on soil nitrogen in a mixedPinus tabuliformis andQuercus wutaishanica forest. Litter manipulation included complete removal of all litter (Littnil), double of fine woody litter (Littwoody), double of leaf litter (Littleaf), and double of mixed leaf and fine woody litter (Littmix), and the nitrogen addition rates were 0 (N0), 5 (N5) and 10 g·m-2·a-1 (N10). We collected the surface soil from 0-5 cm in growing season (August) after 5 years of treatment, analyzed the soil and microbial variables correlated with soil N, including soil water content (SWC), soil pH, soil organic carbon (SOC), soil total nitrogen (TN), NH4+-N, NO3--N, microbial biomass nitrogen (MBN), N-acetyl glucosaminidase (NAG), protease and urease activities. The results showed that NH4+-N was the main form of soil inorganic nitrogen, ranging from 64.53% to 87.02%. Nitrogen addition and litter manipulation did not change soil pH, and significantly higher SWC, TN, SOC, NH4+-N, soil inorganic nitrogen, MBN, and NAG were found in the plots of Littleaf and Littmixcompared to those in the plots of Littwoody and Littnil. The protease and urease activities were not influenced by litter manipulation. Furthermore, TN, NO3--N contents and urease activity were significantly influenced by nitrogen addition, and TN decreased with increasing nitrogen rate. NO3--N content increased and then decreased in Littnil and Littwoody treatment, but increased with increasing nitrogen rate in Littleaf and Littmix treatment. The urease activity showed a trend of descending after ascending with increasing nitrogen rate. Moreover, there were no interactive effects between litter manipulation and nitrogen addition on any of the variables. This study also indicated that leaf litter input improved soil quality.
    Effects of simulated sulfur deposition on soil organic carbon fractions inLarix principis ruppechtii plantation in North China.
    LI Bin, CHENG Xiao-qin, YANG Jin-fang, WANG Luo-xin, HAN Hai-rong, KANG Feng-feng, GUI Zhi-hong
    2018, 37(1):  82-88. 
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    Determining the effects of atmospheric sulfur (S) deposition on soil organic carbon (SOC) dynamics can provide useful information for understanding the process of carbon cycling of forest ecosystem and its response to global change. Therefore, a simulated S deposition experiment was conducted in a 34-year-oldLarix principis rupprechtii plantation at the Taiyue Mountain of Shanxi Province in 2015. Sulfur deposition treatments included control (CK, 0 kg S·hm-2·a-1), low S (LS, 50 kg S·hm-2·a-1), medium S (MS, 100 kg S·hm-2·a-1) and high S (HS, 150 kg S·hm-2·a-1) with three replicates. The experiment was initiated in April 2015. In this study, SOC and its fractions including coarse particulate organic carbon (CPOC, >250  μm), fine particulate organic carbon (FPOC, 53-250  μm) and mineral associated organic carbon (MOC, <53  μm) as well as POC/MOC ratios in surface layer (0-10 cm) and subsurface layer (10-20 cm) were determined in June, August and October of 2015, respectively. Soil temperature, humidity, pH were also measured, and the relationships between three fractions of SOC and soil environmental factors were studied through path analysis. The results showed that the contents of POC, MOC, and the ratios of POC/MOC in the surface layer were higher than those in the subsurface layer. The POC and MOC in August were significantly lower than those in June and October. In the control, the value of POC/MOC in June was lower than that in August and October in the surface soil; however, there was an opposite pattern in the subsurface soil. Sulfur deposition significantly changed the MOC but not the POC. In the surface layer, the MOC was significantly lower in the low and medium S treatments than that in the control (P<0.01). However, in the subsurface soil, the MOC was significantly greater in the high S treatment than that in the control (P<0.01). The CPOC, FPOC and MOC had a significant negative correlation with soil temperature, humidity and pH. In addition, by analyzing the responses of soil organic carbon to environment, we found that soil temperature had strong direct effects on these soil organic fractions. However, soil humidity was not the main factor affecting the POC. These results indicated that the shortterm S deposition depressed the stability of SOC in theL. principisrupprechtii plantation. More attention should be paid on the effect of temperature on SOC dynamics in longe-term study.
    Cadmium accumulation and translocation efficiency of rice under different cadmium polluted soils.
    ZHOU Jing, YANG Yang, MENG Gui-yuan, MA Guo-hui, CHEN Yan-yan
    2018, 37(1):  89-94. 
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    A pot experiment was carried out in mildly and severely cadmiumpolluted soil with 48 rice varieties suitable for planting in Hunan. Based on the analysis of grain yield, the enrichment coefficient of each organ, the transfer coefficient and purification ability of plants, the effects of different cadmium pollution levels on the cadmium accumulation, translocation and purification efficiency of rice were studied. The results showed that the cadmium content and grain yield of brown rice were 0.010-0.048 mg·kg-1 and 96.63-152.55 g·pot-1 for mildly cadmium-polluted soil, and 0.105-0.476 mg·kg-1 and 101.10-165.12 g·pot-1 for severely cadmium-polluted soil, respectively. Severely cadmiumpolluted soil significantly increased cadmium content in brown rice, but had little effect on grain yield. There was no significant correlation between yield and cadmium enrichment efficiency of brown rice in mildly and severely cadmium polluted soil. Based on the analysis of the yield and the concentration of cadmium in brown rice, all the varieties were divided into low cadmium-low yield group and low cadmium-high yield group under mildly cadmium-polluted soil, and high cadmium low yield group and high cadmium high yield group in severely cadmium polluted soil. The cadmium accumulation and translocation efficiency in organs of rice were in the order of brown rice<leaf<stem<root and soil-root>stem-leaf>stem-brown rice>root-stem, respectively. Soil cadmium was transported to roots and enriched in roots. The cadmium accumulation and translocation efficiency of rice were less affected by yield factors, but greatly affected by soil cadmium enrichment. Severely cadmium polluted soil significantly enhanced the cadmium enrichment of each organ and the translocation efficiency of root brown rice, compared to mildly cadmium polluted soil. The purification efficiency of rice roots was much higher than that of the aboveground parts.
    The influence of hummock microtopography on plant litter decomposition in Carex peat mire.
    LIU Shuang-shuang, WANG Ming, DONG Yan-min, WANG Sheng-zhong, HAN Yuan-yuan, CAO Yi-wen, XU Zhi-wei
    2018, 37(1):  95-102. 
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    Carex peat mire is widespread in high latitude regions of northern hemisphere. Hummock microtopography is a pervasive feature ofCarex peat mire and the difference of microenvironment inside and outside tussocks created byCarex may lead to spatial heterogeneity in litter decomposition. A litter decomposition experiment through litterbag method was conducted to study the spatial heterogeneity of litter decomposition inside and outside tussocks in aCarex schmidtii peat mire in Changbai Mountain, Northeast China. Results showed that patterns of litter dry weight loss inside and outside tussocks were consistent throughout the study. The total litter dry weight loss and decomposition rate inside tussocks were lower than that outside tussocks (21.70%±2.25% vs. 40.20%±4.22%; 0.0012±0.0001 d-1 vs. 0.0021±0.0001 d-1). Litter dry weight loss from the litterbags with large mesh inside and outside tussocks was 1.81%±0.32% and 2.91%±0.30% higher than that from the small mesh litterbags, respectively. The contribution of soil microorganisms to the litter decomposition rates inside and outside tussocks were 6.37 times and5.65 times that of soil fauna, respectively. However, the contributions of soil fauna and soil microorganisms to the litter decomposition rates outside the tussocks were 1.79 times and 1.59 times that inside the tussocks, respectively. Correlation analysis demonstrated that the dry weight loss of litter was significantly positively related with the accumulated temperature (P<0.05). The litter dry weight loss was negatively related with the water level inside tussocks (P<0.05), but positively related with the water level outside tussocks (P<0.05). The results suggested that soil temperature and soil water content were different between positions inside and outside tussocks, which affected the distribution and structure of fauna and microorganisms, and further affected litter decomposition rate. The water regime outside tussocks was a key environmental factor affecting litter decomposition inCarex peat mire.
    Effects of highway from Inner Mongolia to Xinjiang on habitat suitability of ungulates in Alashan desert.
    LI Shuai, ZHANG Xiang-feng, SHI Jian-bin, DONG Shi-kui, GAO Xiao-xia
    2018, 37(1):  103-110. 
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    Alashan desert area is one of the 8 biodiversity protection centers in China, which is passed by the expressway from Inner Mongolia to Xinjiang. The passages for ungulate species have been designed along the highway during the construction. It is of great importance to evaluate the suitability of animal passages for the ungulates. Based on the niche theory, we used fuzzy comprehensive evaluation method combined with GIS spatial data presentation to evaluate the habitat suitability of ungulate species along the highway in this study. The results show that the suitability index of animal passages declines along the highway from east to west. In the section K46-K168, the suitability index changes greatly, the change of suitability index is the second among the sections of K295-K620, and the change of suitability index is smaller between the sections of K641-K891. The distance between the drinking water, the distance from the residential area and the number of drinking water points are the main causes of such changes. There is a significant difference in suitability index from the highway. Except for the influence of highway elements on suitability, other factors and their superimposed effects on the suitability index are not significant.
    Winter and spring diet composition ofMoschus chrysogaster in the Helan Mountains, China.
    XU Jia, BAO Xu, LIU Zheng-sheng, GAO Hui, ZHAO Chang, SUN Yu-jiao, WANG Ji-fei, TENG Li-wei
    2018, 37(1):  111-118. 
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    The faeces of alpine musk deer (Moschus chrysogaster) were collected in the Helan Mountains, and the feeding habits of winter and spring were studied by the fecal microhistological analysis. The fecal and plant samples were collected from the habitats of alpine musk deer. The diet proportion of alpine musk deer in winter and spring was processed by frequency conversion method. The results showed that alpine musk deer’s diets in winter belonged to 30 species of 19 families, including 17.16% of Rosaceae, 16.64% of Caprifoliaceae, 15.64% of Fabaceae, 10.93% of Cyperaceae, being the main food of alpine musk deer in winter. Alpine musk deer’s diets in spring belonged to 31 species of 20 families, including 27.37% of Rosaceae, 13.28% of Salicaceae, 12.84% of Fabaceae, being the main food of alpine musk deer in spring. Among them,Astragalus chingianus was the main species common to winter and spring, accounting for 11.33% and 11.04% of spring and winter food, respectively. In addition, alpine musk deer also feed arbors, with food intake from 9.53% in winter to 18.67% in spring. Analyses of the food composition and diversity of alpine musk deer showed that Shannon diversity index, Shannon evenness index and niche width index were higher in winter than in spring.
    Response of morphology and germinability of heteromorphic seeds of four Chenopodiaceae species to sheep rumen digestion.
    WANG Shu-lin, Wu Fei, CHEN Yi-shi, JING Peng-cheng, LU Wei-hua， SUN Hai-yong, LI Na-na, JIN Sheng-fei
    2018, 37(1):  119-127. 
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    The objectives of this experiment were to study the response of seeds to digestion in the rumen of sheep and to discuss the significance of seed heteromorphism phenomenon of Chenopodiaceae plants. The seeds were from the following species: Ceratocarpus arenarius L.,Halogeton glomeratus C. A. Mey.,Atriplex aucheri Moq. and Salsola affinisC. A. Mey.; each plant can produce two different types of seeds. After determining their morphological characteristics, the seeds were put into nylon bags which were then placed in the rumen of sheep through a fistula. The bags were removed at different times and then the seed length, width and thickness and germination rates were determined. The results showed that the seeds became dark after digestion, the seed appendix structures (such as bracts, seed trichomes and seed wings) of all four species were digested by rumen fluid of sheep and the internal annular embryos were exposed. Digestion time had significant effect on the seed length, width, thickness and 1000seed weight of the four plant species (P<0.05). The relationships between seed length, width, thickness, weight of 1000 seeds and digestion time were described by the equationsY=1.00+7.92e-0.04X(R2=0.92, P<0.0001), Y=1.28+4.63e-0.11X(R2=0.91, P<0.0001),Y=0.70+1.36e-0.09X(R2=0.92, P<0.0001) and Y=1.48+9.57e-0.20X(R2=0.36, P<0.0001) respectively, whereX is time in hours. Sheep rumen digestion could break the seed dormancy of  Chenopodiaceae plants, significantly improving seed germination rates (P<0.05). In addition to the gradually increased germination rate of A. aucheri smallbract seeds with the extension of rumen digestion time, the seed germination rates of the rest seeds decreased after an initial increase. The seed germination rates were all >40% when digestion time was >12 h, which increased significantly compared with seeds that were not digested (P<0.05). These eight kinds of Chenopodiaceae seeds all can disperse by sheep digestive tract. This study indicates that different types of seeds produced by the same species can respond to sheep rumen digestion in convergence. Chenopodiaceae plants not only can reproduce by “bet hedging” strategy to adapt to the harsh desert environment, but also can spread by grazing sheep digestive tract to increase the opportunity of population dispersal. This is a survival way of plants to adapt to changing environment in desert.
    Effects of alpine meadow degradation on epigeic arthropod communities in Zoigê.
    LONG Wei, GAO Yan-mei, WU Peng-fei
    2018, 37(1):  128-138. 
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    Four typical habitats, including swampy meadow, grassland meadow, moderately degraded meadow and seriously degraded meadow, were selected in Zoigê wetland, and epigeic arthropod communities were investigated using pitfall traps in May, July, and September 2014, to reveal the effects of alpine meadow degradation on the epigeic arthropod community structure and diversity. A total of 8364 epigeic arthropod individuals were collected during the research periods and classified into 4 classes, 17 orders, and 123 taxonomic groups (family or genus). GeneraEntomobryaand Sphaeridia were the dominant groups in epigeic arthropod communities, andEntomobrya only appeared in the grassland meadow. The diversity index of epigeic arthropods in seriously degraded meadow was significantly lower than in the other habitats, which indicated that the degradation of alpine meadow had a significant effect on the composition of epigeic arthropods. Furthermore, the monthly dynamics in individual number and diversity indices of the epigeic arthropod communities differed among the four habitats. The individual number and richness index of epigeic arthropods in swampy meadow were higher in September than in May and July, but were higher in July for the other habitats. The Shannon diversity index for moderately and seriously degraded meadows varied significantly in different months, and Simpson’s diversity indexamong the four months varied significantly only in seriously degraded meadow. Regression analysis showed that the individual number and diversity of epigeic arthropod communities were affected by the factors of plant communities and soil properties. The results indicated that the degradation of alpine meadow affected the composition and diversity of the epigeic arthropod communities by altering plant communities and soil properties.
    Impact of straw returning on cropland soil mesofauna community in the western part of black soil area.
    LIU Peng-fei, HONG Mei, CHANG Fei, GAO Hai-yan, LI Zhi-xin, MA Xi
    2018, 37(1):  139-146. 
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    In order to understand the effect of straw returning on cropland soil mesofauna community in the black soil, an experiment with five different amounts of maize straw returning,e.g.，0 (CK), 4500 (JG1), 9000 (JG2), 13500 (JG3), and 18000 kg·hm-2 (JG4), was carried out in Zhalaid Banner of Inner Mongolia from June to September in 2016. The results showed that totaling 3350657 individuals of soil mesofauna were captured and they were classified into 53 taxonomic groups. Straw returning significantly increased soil mesofauna density (F=12.040, P<0.05), and taxonomic groups. The soil mesofauna density (933030 ind·m-2) and taxonomic groups (34) were the highest in JG4 treatment. The sampling month had a significant influence on soil mesofauna community, with highest density and taxonomic groups of soil mesofauna in July. The richness and dominance indexes were the highest in JG4, with the values of 0.98 and0.34, respectively. The diversity and evenness indexes were the highest in CK, with the values of 1.72 and 1.73, respectively. Correlation analysis showed soil mesofauna density and dominance index were correlated positively with soil humidity (P<0.05), while negatively with soil bulk density (P<0.05). There was significant positive correction between soil mesofauna density and soil temperature (P<0.05). Soil mesofauna taxonomic group number and richness index were significantly correlated with soil organic matter content (P<0.01). Soil mesofauna community had no correlation with soil pH (P>0.05).
     
    Bird diversity and its correlation with the habitat structure in Dashanbao Black-necked Cranes Nature Reserve.
    YANG Yong-xia, BAI Hao-tian, FU Wei, PENG Ming-chun, ZHAO Zi-jiao, WU Tai-ping, RAN Qiu-yue, WU Zhao-lu
    2018, 37(1):  147-156. 
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    Nine sampling sites with an area of 1 km2 each were selected to study bird diversity and its relation with habitat structure by using line transect and point count surveys method and remote image-based habitat structure analysis for four seasons from 2015 to 2016. It was found that there were a total of 127 species of birds in Dashanbao Nature Reserve, which belong to 41 families and 16 orders, including 14 of key state protected species. Of the 127 species, the 3 main orders, Passeriformes,  Anseriformes, and Charadriiformes, take up a total of 27 families and 80 species. The number of 3 species,Anser indicus, Alauda gulgula andGrus nigricollis was the greatest, accounting for 50.09% of the total. The resident birds and songbirds were dominant species, accounting for 49.61% and 51.97% of the total species, respectively. In terms of number, winter resident birds and water birds were dominant, accounting for 58.13% and 60.28% of the total, respectively. Moreover, birds preferring waters and wetlands accounted for 40.94% of the total species and 60.28% of the total number, respectively. Pearson’s correlation coefficient showed a significant relationship (P<0.05) between the percentage of water area and number of birds in winter and spring, and between the percentage of forest shrub area and species of birds in summer and autumn. Dashanbao Nature Reserve is an important bird habitat and wintering site, and its habitat structure has a great effect on bird species and number. Constructing a habitat mosaic of waters, forests, shrubs, and wetlands is an important way to protect bird diversity of the reserve.
    Phylogeographical analysis ofEpisyrphus balteatus(Diptera: Syrphidae) in Yanshan-Taihang Mountains Area.
    BAI Qian-qian, PAN Zhao, REN Guo-dong
    2018, 37(1):  157-163. 
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    In order to understand the genetic differentiation and the phylogeographical structure ofEpisyrphus balteatus in Yanshan Taihang Mountains Area, a fragment with 658 bp from the mitochondria COI gene was extracted, expanded and sequenced for the specimens ofE. balteatus from Hebei, Inner Mongolia, Shanxi, Henan and adjacent places. In total, 36 sequences were obtained, the average content of A+T (69.9%) was obviously higher than C+G content (30.1%), and there were no insertions or deletions. The results showed that the Wuling Mountain population had the highest genetic diversity. The analysis of molecular variance revealed the significant genetic subdivision among the individuals within populations. The result of Mantel test indicated that there was no significant correlation between the genetic distance and geographic distance (P=0.639), so it did not conform to the inference of geographical isolation model. Phylogenetic analysis was constructed by using the maximum likelihood method, and results showed that the haplotype 3 from the Wuling Mountain population was well separated from others. The current study estimated the divergence time of populations, which was in the Pleistocene (0.02-0.94 Ma) and part of populations was without differentiation. We supposed that the reasons of differentiation ofE. balteatus in Yanshan-Taihang Mountains Area are the repeated changes of Quaternary glacial climate, and the Wuling Mountain should be one of the important refuges forE. balteatus in the last ice age of the Quaternary.
    Suitability evaluation of potential geographic distribution forRana zhenhaiensis based on MaxEnt.
    ZHANG Kai-long, YANG Kun, WO Yu-bin, TONG Hao-jie, JIN Yuan-ting
    2018, 37(1):  164-170. 
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    Rana zhenhaiensis is a newly named species endemic to China; its potential geographic distribution is still unclear due to lack of field investigation. Thirtyfive distribution localities ofR. zhenhaiensiswere collected from field investigations and literatures. The MaxEnt ecological niche model was used to predict the potential distribution of R. zhenhaiensis by importing corresponding data of 20 biological and environmental variables downloaded from WorldClim database between 1950 and 2000 corresponding to the above 35 localities. The predicted habitats with suitability probabilities of 0.5-1.0 forR. zhenhaiensis mainly included Zhejiang, Jiangsu, Shanghai, Anhui, Hunan, eastern Hubei, central, western and northern parts of Jiangxi, coastal regions of Fujian, western Tianjin, and several other parts in Sichuan, Chongqing, Shandong, Hebei, Guangxi and Guangdong. Besides, Beijing, Shandong, Henan, Chongqing, Guizhou, Guangxi, Fujian, Guangdong, southern Liaoning, eastern Tianjin, southern Hebei, southern Shanxi, eastern Sichuan, western Hubei, southern Hunan, northern and southwestern parts of Jiangxi as well as northern Taiwan were relatively lower suitable habitats (suitability probabilities, 0.09-0.5) forR. zhenhaiensis. The average AUC values for both training and test data predicted by MaxEnt were 0.993, indicating high accuracy and reliability of our predicted model. Jackknife test in MaxEnt ecological niche model showed that the contributions of different environmental variables to models were different, and precipitation in the warmest quarter (contribution rate, 44.6%) and standard deviation of temperature seasonal change (contribution rate, 20.4%) were the primary factors that affect the distribution ofR. zhenhaiensis.
    Microbial community structure and physicochemical factors in the water of upland pond of Litopenaeus vannamei during the middle and late stage of culture.
    HU Xiao-juan, WEN Guo-liang, LI Zhuo-jia, SUN Zhi-wei, YANG Keng, ZHANG Jia-song, HAN Ning, CAO Yu-cheng
    2018, 37(1):  171-178. 
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    For the culture mode of over-winter sheds (OWS), water samples were collected fromLitopenaeus vannamei culture ponds aiming to investigate the variation of microbial community structure, dominant bacterial species and environmental factors in the pond water in the middle and late stage of culture. The results showed that the water temperature increased from 20.6   ℃ to 26.5   ℃ after building OWS, which was suitable for the growth of shrimp. The amount of heterotrophic bacteria in the water was between 5.1×104 and 2.95×105 cfu·mL-1 in the middle and late stage of culture. The structure of microbial community was relatively stable, and the number of dominant bacteria increased.Psychrobacter andSulfitobacter were the dominant bacteria, whileFlavobacteria andHyphomicrobium appeared after building OWS. Additionally, the RDA analysis showed that nitrite nitrogen, nitrate nitrogen and temperature were the major physical and chemical factors influencing the abundance and distribution of microbial communities. The results indicate that aquaculture environment could be kept relatively stable after OWS building, and the regulation of nitrogen concentration is very important in the middle and late stage of culture. Therefore, we suggested that probiotics should be used before and after building OWS in order to promote and stabilize ecological advantage of beneficial bacteria, and regulate bacterial community structure and ecological function.
    Effects of different types of artificial seagrass on reproduction of Oryzias melastigma.
    SONG Jing-jing, LIU Ying, YU Chao-yong, LIU Hong-jun, XU Zhi-guang, ZHAO Wen-xi, GUAN Shu-guang, YU Dao-de
    2018, 37(1):  179-186. 
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    This study was undertaken to evaluate the effects of four different types of artificial seagrass onOryzias melastigmareproduction. The results indicated that daily egg production ofO. melastigma was significantly affected by artificial seagrass. When every two types of seagrass were added together, more eggs were found on globular artificial seagrass or artificial seagrass shaped like sea anemone than on other types of artificial seagrass (P<0.01). When the four types of artificial seagrass were added together, the number of eggs pooled from globular artificial seagrass (176±47 eggs·d-1) and artificial seagrass shaped like sea anemone (89±32 eggs·d-1) were significantly higher than that from the others. Besides, the number of eggs presented a reciprocal dynamic trend on different types of seagrass. The number of eggs on artificial seagrass shaped like sea anemone was increased, and eventually exceeded the number of eggs on globular artificial seagrass. It is speculated that marine fish is obviously selective to physical structure of seagrass during the process of laying eggs. Our study provides certain basis for the restoration of fishery resources.
     
    Regression analysis betweenPlanktothricoides spp. biomass and environmental factors in urban rivers from Shanghai, China.
    WANG Meng-meng, ZHANG Wei, YANG Li, XU Xiao-ying, WANG Li-qing
    2018, 37(1):  187-193. 
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    Field investigation data in summer from 36 urban rivers in Shanghai  were used to explore the relationship betweenPlanktothricoidesspp., which can form  cyanobacteria bloom, and its environmental factors. The generalized additive model (GAM) results showed that the biomass ofPlanktothricoides spp. significantly increased when the water temperature ranged between 25 and 35 ℃ and the pH values ranged between 6.5 and 9.5. Contrarily, Planktothricoides spp. didn’t show significant correlation with total nitrogen and total phosphorus (P>0.05) when their concentrations ranged from 0.04 to 7.33 mg·L-1 and from 0.04 to 4.10 mg·L-1, respectively. It was indicated that the high concentrations of nutrients in Shanghai rivers were no longer the limitation factors for the growth of Planktothricoides spp. Furthermore, significantly positive correlations were observed between the biomass of rotifer, protozoan and cladocera andPlanktothricoidesspp., while the latter showed a negative correlation with copepod biomass. This correlation pattern between zooplankton andplanktothricoidesspp. may be explained by the abundance of small sized edible algae in the water column and the tolerance capability of different sized zooplankton to filamentous cyanobacteria.
    Trophic spectrum of fishery species from the Pearl River Estuary by stable isotope analysis.
    ZENG Yan-yi, LAI Zi-ni, YANG Wan-ling, LI Hai-yan, PENG Song-yao, LI Jie, DAI Shou-hui
    2018, 37(1):  194-202. 
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    Totaling 39 major fishery species including 30 species of fish, 5 species of shrimps and 4 species of mollusks were collected in the Pearl River Estuary in August 2015. The stable carbon and nitrogen composition (δ13C and δ15N) of the organisms were analyzed using StableIsotope Ratio Mass Spectrometry. The results showed that fishery community in east and west parts of the Pearl River Estuary had statistically different stable isotopes values (δ13C: P<0.001, δ15N:P=0.036). The δ13C values of fishery community ranged from -31.92‰ to -19.34‰ (with an average of -23.65‰) in the east estuary and from -26.75‰ to -16.36‰ (with anaverage of -21.19‰) in the west estuary. The δ15N values of fishery community ranged from9.57‰ to17.14‰ (with an average of 13.48‰) in the east estuary and from 9.01‰ to 16.49‰ (with an average of 12.72‰) in the west estuary. Trophic levels of fishery organisms in the east and west estuary were calculated based on different baseline organisms; the trophic levels of communities in the two areas were similar, with a range of approximately 2.0 to 4.7, including herbivores, omnivorous, low, middle and high classes of carnivores. Among the organisms, a smallamount of species were at the bottom and top trophic positions, while large amount of species were at the medium trophic positions. The average trophic levels of about 43% of fish species were within the record ranges, 33% of fish species were lower than the low threshold, and 23% of fish species higher than the high threshold when compared with the trophic level of the same fish from the Fishbase. By preliminarily establishing trophic spectrum of primary fishery species in the Pearl River Estuary, this study provides a basis for utilization and management of the fishery resources in the study region.
     
    Evolution pattern of ecosystem and its driving mechanism in Urban Agglomeration in Fujian Delta Region.
    LIN Jin-huang, CHEN Wen-hui, QI Xin-hua, CHENG Rui-tong, CHEN Zeng-wen
    2018, 37(1):  203-210. 
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    Ecological security is one of the fundamental guarantees for the social and economic sustainable development of urban agglomeration. However, nowadays the ecological security of urban agglomeration is greatly threatened. According to land cover/ecosystem types extracted from Landsat TM/ETM+OLI in 2000, 2005 and 2010, combined with analysis of social and economic factors, the evolution pattern and driving mechanism of ecosystems in Urban Agglomeration in Fujian Delta Region were analyzed from the dimensions of area change, type shift and spatial pattern of ecosystems in this study. The results showed that the area of urban ecosystem presented positive growth from 2000 to 2015, while the forest and farmland ecosystem were in negative growth, and the shrub, wetland, grassland and other ecosystems remained relatively stable. The area proportion of ecosystems was in the order of forest > farmland > urban > shrub > wetland > grassland > other ecosystems. The intensity of mutual transfer of ecosystem was weak from 2000 to 2005, but strong from 2005 to 2010 with the input of urban ecosystem and the output of otherecosystems being the largest during this period. The intensity was still strong from 2010 to 2015 with both the largest output of other ecosystem and the largest input of forest ecosystem. From 2000 to 2015, the forest ecosystem was distributed unevenly in different regions, while the farmland and urban ecosystems were mainly distributed in the central and eastern Urban Agglomeration in Fujian Delta Region, and the distribution of wetlands was consistent with that of rivers; the grassland, shrub and other ecosystems were in scatted distribution. At the same time, the landscape pattern was basically stable without significant changes in patch number, patch density and clustering characteristics, but there were significant differences among different ecosystems. The spatial pattern of ecosystems in the Urban Agglomeration in Fujian Delta Region was basically stable from 2000 to 2015, while the different ecosystems were in unbalanced changes, and the transfer intensity of various ecosystems in different periods was significantly distinct from each other. The economic and industrial development, urbanization, and urban pattern change significantly affected the pattern evolution of the ecosystems, especially forest, farmland and urban ecosystems.
    The spatiotemporal change of NDVI in Yulin, Shaanxi Province, China from 2000 to 2014.
    SHI Yu-qiong, ZHENG Ya-yun, LI Tuan-sheng
    2018, 37(1):  211-218. 
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    In order to evaluate the implementation effect of the Grain for Green Project (conversion of degraded farmland into forest or grass Land) and the eco-environment variation of Yulin, MODIS NDVI data was used to examine the spatial and temporal change of vegetation cover by applying maximum value composite (MVC) method based on the GIS. NDVI was higher in hilly loess region than that in blown sand region from 2000 to 2014. In general, the vegetation had improved during the past 15 years. In whole Yulin, the area of the improved vegetation accounted for90.7%, the area of degradation constituted only 1.0%, and the area of no variation was 8.3%. In hilly loess region, the area of improved vegetation accounted for 94.2%, mainly with moderate improvement. The area of vegetation improvement on slopes accounted for more than 80%. The obvious improvement at 7°-35° slopes constituted more than 51%. Therefore, the effect of the Grain for Green Project was obvious.
     
    The characteristics of actual evapotranspiration and influencing factors of paddy field in low hilly red soil region.
    LI Qian, JING Yuan-shu, MA Mei-juan, WANG Han, LI Gen
    2018, 37(1):  219-226. 
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    In this study, we used the data of field meteorological observation of late rice in low hilly red soil region and analyzed the distribution characteristics with typical diurnal and monthly variation of the actual evapotranspiration of rice field at different growth stages. At the same time, the influences of meteorological factors on the actual evapotranspiration were studied by using the path analysis method and Beven’s sensitivity formula. The results indicated that the actual value of evapotranspiration during the whole growth period was 290.61 mm and the measured evapotranspiration value was the largest at transplantingtillering stage, which was 96.91 mm, accounting for 33.3% of the whole growth period. The evapotranspiration of paddy field in the whole growth period showed a tendency to increase first and then decrease gradually. The peak appeared in the later stage of rice tillering. The change of rice field evapotranspiration in one day showed the low intensity in the morning and evening but high at the noon, which just liked a ‘reverse’ U. Weather conditions and the duration of growth period also had some influences on evapotranspiration. Path analysis and sensitivity analysis showed that net radiation and relative humidity had higher total contribution coefficient and sensitivity coefficient, which means these two factors were the main meteorological factors that affected the evapotranspiration of paddy field. The three temperature factors (the highest temperature, lowest temperature, average temperature) were in the next place, and the wind speed’s effects on evapotranspiration were little. There was a significant time scale difference for the relationship between evapotranspiration and meteorological factors. The effect of each meteorological factor on the actual evapotranspiration was more significant at daily scale than at hourly scale.
    Simulation on the impacts of future climate change on rice production in Fujian Province.
    ZHOU Tong-yu, JIANG Min, SUN Wang-liang, SUN Bin
    2018, 37(1):  227-236. 
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    To evaluate the impacts of future climate change on rice yields in Fujian Province, this study classified Fujian Province into three rice regions, and chose 66 sites and 7 representative rice varieties as study subject. Based on BCC_CSM (Beijing Climate Center Climate System Model) climate model under 2 Representative Concentration Pathway (RCP) scenarios: Stable emission path RCP4.5 and high emission path RCP8.5, we simulated the rice yields with CERES-Rice model under rainfed and irrigated conditions. The results showed that under the future climate change scenarios, with the increase of average temperature in growth period to some extent, the growth period of rice in Fujian Province would be shortened obviously. Without direct effect of CO2 elevation, the simulated rice yields would decrease by no more than 12% as compared to the baseline, and the rainfed rice was slightly worse than irrigated rice. In the meantime, different scenarios have different results, and higher yield decrease was simulated under high emission path RCP8.5 than under RCP4.5 climate scenarios. When the fertilization effect of CO2 was considered, the simulated yields were more optimistic with an increase by 15.2% at most of the study sites.
    Effect of dissolved silicate on the stability of scorodite.
    2018, 37(1):  237-244. 
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    The adsorption and polymerization of dissolved silicate on minerals affect its stability in the aquatic environment. The study of silicate chemistry on mineral surfaces is theoretically and practically important to understand the polymerization behavior and effect on its stability. In this work, the adsorption kinetics of dissolved silicates on scorodite was investigated, their polymerization behavior was characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and the stability of the silicate adsorbed scorodite was analyzed. The results showed that the adsorption of silicates by scorodite could be attributed to chemical adsorption and replacement reaction. Higher amount of silicate absorbed by scorodite at pH 3 and 4 and the ATRFTIR results also indicated that the adsorbed polymeric silicates on scorodite surface showed a structure similar to silicic acid (SiO2·xH2O). In addition, the leaching stability test showed that the amount of arsenic leached out from silicate absorbed scorodite was decreased by 68.1%, 52.5% and 15.5% at pH 4, 6 and 8 respectively, compared with that from scorodite. The findings in this work may have important implications for further stabilizing and reserving the arsenic containing residue from the metallurgical industry to reduce their environmental risk.
    Advances on photosynthesis characteristics of alpine plants.
    CAI Jin-huan, XUE Li
    2018, 37(1):  245-254. 
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    Photosynthesis of alpine plants is affected by intense irradiance, low temperature and drought. Moreover, rising atmospheric CO2 concentration and global warming exert a profound influence on photosynthesis of alpine plants in recent years. This paper reviewed the effects of intense radiation, low temperature, drought, elevated atmospheric CO2 concentration and global warming on photosynthetic characteristics of alpine plants. Future researches should focus on photosynthetic characteristics of main plants in different alpine regions, interactive effects of environmental factors on photosynthetic characteristics of alpine plants, the effects of simulated soil available nutrient content on photosynthetic characteristics of alpine plants, the impact of global climate change on photosynthetic characteristics of alpine plants using mathematical models, and photosynthetic characteristics of alpine plants at different growth stages by longterm positioning study.
    Advances in study on organic carbon characteristics in the riverine systems.
    ZHOU Miao, LI Siliang, DING Hu, QIN Cai qing, YUE Fujun
    2018, 37(1):  255-264. 
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    The interfaces of the Earth’s critical zones are the place where organic carbon is dramatically decomposed and transformed. The dynamics and fate of organic carbon serve as an important foundation of revealing the material transportation and energy transfer in the critical zones, which is of great significance to support the ecological system. The geochemical characteristics of organic carbon in riverine system is reviewed in this study, including the research methods, sources, storage, dynamics and turnover process of organic carbon. It is suggested that the the dynamics of organic carbon in the critical zones should be studied well for understanding carbon cycling in the riverine systems. Various technical methods, short-term high-frequency observation, long-term observation research in the multiinterface with multitime scales should be conducted in typical critical zones, in order to reveal the key factors and its mechanisms of organic carbon dynamics and processes in the riverine systems. Furthermore, the response and feedback mechanism of organic carbon cycle to global change and human activities on longtime scales should be studied. Besides, the carbon exchange between interfaces of atmosphere-plant-litter-soil-river and the dynamics of organic carbon in watersheds should be further analyzed under different disturbance intensities of human activities. Understanding the impacts of environmental changes and human activities on the geochemical cycling of organic carbon in critical zones would benefit the optimization of carbon cycling model and climate change predictions.
    Characterization of dicarboxylic acids, oxocarboxylic acids, and α-dicarbonyls in atmospheric aerosols: A review.
    ZHAO Wan-yu, FU Ping-qing
    2018, 37(1):  265-277. 
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    In this study, we summarized the seasonal variation, molecular distribution of low molecular weight (LMW) dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls in atmospheric aerosols, and also discussed the experimental methods, photochemical aging, size distributions, sources, and transformation processes as well as diagnostic ratios of these organic acids. Based on the analyses and comparisons of dicarboxylic acids and related compounds in urban, marine and polar areas, we suggested that continental aerosols were mainly associated with anthropogenic emissions, such as fossil fuel combustion, biomass burning, meal cooking and plastic waste burning; whereas marine aerosols were not only affected by outflows from continental areas, biogenic unsaturated fatty acids and biogenic semi-volatile organics emitted from the surface ocean, but also attributed to the photochemical oxidation of related precursors during the long-range atmospheric transport. In addition, we discussed the compound specific stable carbon isotopic analyses of diacids, oxoacids and α-dicarbonyls. The isotopic composition of diacids was a powerful tool to investigate the photochemical aging processes of atmospheric aerosols. At last, the relationship between the longdistance transport of aerosol and the stable carbon isotope composition of diacids and related compounds was also illustrated in this paper.
    Prediction of  potential geographical distribution pattern change forMelliodendron xylocarpum HandelMazzetti since the Last Glacial Maximum.
    WANG Lu, XU Xiao-gang, LI Yao
    2018, 37(1):  278-286. 
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    Melliodendron xylocarpum HandelMazzetti, a tree species endemic to China, is of extremely high ornamental value. To understand its response of potential geographical distribution pattern to climate change can shed light on effective protection and reasonable utilization of the species. In this study, we used ENMeval to optimize parameters of Maxent model. The potential distributions during different ages,e.g. the Last Glacial Maximum, midHolocene, present, and year 2070 under the scenario of representative concentration pathway 8.5 were simulated by the model based on 137 modern geographical distribution records and 8 bioclimatic variables. Also, the multivariate environmental similarity surface analysis and the most dissimilar variable analysis were used to evaluate the climate anomaly and its key influencing factors, while the percent contribution, permutation importance and Jackknife test were applied to assess the importance of each bioclimatic variable. The results showed that: (1) when the feature combination was linear, quadratic, hinge, product, and threshold, and regularization multiplier being 2, the complexity and degree of overfitting of the model were relatively low. As a result, the accuracy of the model was very high as indicated by the area under the receiver operator characteristic curve for test data up to 0.9853±0.0055. (2) The highly suitable region for the present distribution was at the junction of Guangxi, Guangdong, and Hunan provinces. During the Last Glacial Maximum, the area of the suitable region was significantly reduced and the suitable region in south China moved southward. In the midHolocene, the area of suitable region was increased but no obvious movement occurred. In 2070, the annual mean temperature and maximum temperature of warmest month were the most abnormal variables in low altitude regions, and highly and moderately suitable areas may remain in high altitude regions. (3) Both the temperature and precipitation factors restricted the potential geographical distribution of M. xylocarpum, but the former was more likely to lead to the change of geographical distribution.
    Evaluation of key nodes and corridors of river and canal network in Hani Rice Terraces based on graph theory.
    LIU Xin, JIAO Yuan-mei, WANG Mei, ZHANG Kan-feng
    2018, 37(1):  287-294. 
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    Landscape connectivity is an essential indicator for ecological processes and functions of habitat landscape, which plays an important role in the research of ecological processes such as biological migration and dispersal, interference diffusion, and gene flow. In this study, we used the Quickbird image of Yuanyang County, Yunnan Province in 2010 to study river and ditch corridors in Quanfuzhuang watershed of Yuanyang County. By means of graph theory, two calculating units (node and corridor) were selected to calculate landscape connectivity and importance index with five distance thresholds of 500, 1000, 2000, 4000 and 6000 m. With the graph of Hani terraced landscape corridor structure, the importance index of connectivity and corridor were analyzed, with further analysis and planning of landscape pattern. The results showed that the degree of connectivity indicated the importance of corridors to a greater extent, and reflected their connection situations. Meanwhile, connectivity degree increased with the increase of threshold value. Besides, the analysis of importance index showed that the importance index was higher for the corridors connected with different blocks in intensive river network, while the importance index of the longer corridors was higher in sparse river network. The study provides ideas for the ecological conservation and planning of Hani Rice Terraces, and also new insights for landscape connectivity research.