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    10 March 2019, Volume 38 Issue 3
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    Differentiation of vegetation types and biodiversity in the southern edge of Hulunbuir grassland.
    SHAN Dan, ZHU Yuan-jun, LIU Yan-shu, SHI Zhong-jie, YANG Xiao-hui
    2019, 38(3):  619-626. 
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    Plant communities in the southern edge of Hulunbuir grassland were investigated from east to west over a range of 200 km. The vegetation types and biodiversity in the study area were analyzed by quantitative ecological method. A total of 98 species were recorded, dominated by species from Compositae, Leguminosae, Gramineae, and Liliaceae, together accounting for 52.58% of the total species number. Xerophytes were the main water ecotype. Perennial grasses were the main life form of plants. The results of NMDS ordination showed that the distribution pattern of vegetation was influenced by the water and heat factors, with precipitation being the most important factor. The results of similarity analysis and similarity percentage analysis showed that species composition of desert steppe community was most different from meadow steppe community. There was a significant difference between desert steppe and typical steppe. The typical steppe and meadow steppe were distributed in a mosaic structure. The meadow steppe was in a trend of transition to typical steppe. This indicated that the aggravated arid climate and unreasonable human activities led to xerophytization of all vegetation types. The results of Rényi diversity ordination of three steppe types showed that the indices of species richness, Shannon diversity and Simpson diversity were the highest in meadow steppe, followed by typical steppe and the lowest in desert steppe, while the dominance showed an opposite trend. The biodiversity of the whole study area showed a general trend of decline. The trend of simplification and xerophytization from individual to community will seriously affect the protection, exploitation, and utilization of Hulunbuir grassland.
    Ecological benefits of different vegetation restoration modes along the Xining to Golmud section of Qinghai Tibet Railway.
    REN Kang, GUO Kun, ZHENG Jing-ming, ZHOU Jin-xing, WANG Jin-chang
    2019, 38(3):  627-636. 
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    Vegetation restoration along the Qinghai-Tibet Railway can not only improve soil physicochemical properties, but also plays an important role in the safety operation of the railway through the wind resistance and sand-fixing function of plants, with significant ecological and economic benefits. Through the investigation of soil and vegetation under five restoration modes along the Xining to Golmud section of Qinghai-Tibet Railway, we analyzed the effects of restoration modes on understory plant diversity and soil physicochemical properties. The results showed that the aboveground biomass and productivity of the plantations were different due to stand age and allocation. The highest productivity occurred in Populus simonii-Tamatix chinensisplantation (1.92 t·hm-2·a-1), followed by T. chinensisplantation (1.87 t·hm-2·a-1). All modes increased understory plant diversity, with eight species in theHippophaer hamnoides-Caragana korshinskii plantation and ten species in the T. chinensisplantation. The dominant species were different among different modes. Soil moisture increased in all the five restoration modes. The effects of shrub plantation on improving soil alkalinity were better than other modes. In the plantation of H. hamnoides-C. korshinskii and T. chinensis, the pH of surface soil (0-20 cm) decreased by 1.05 and 0.75, respectively. All the five restoration modes increased soil organic matter content (SOM), with more enhancement in surface than deep soil. The SOM in the T. chinensisplantation increased most obviously, with the surface SOM content of 12 g·kg-1, which was nearly doubled compared with that before restoration. Our results provide theoretical basis for desertification control and the selection of restoration modes along the QinghaiTibet Railway.
    Response of Larix olgensis at different elevations to climate change in the context of climate warming.
    ZHAO Xue-peng, BAI Xue-ping, LI Jun-xia, WANG Li-li, ZHANG Xian-liang, LU Xu, CHEN Zhen-ju
    2019, 38(3):  637-647. 
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    To examine the radial growth responses of Larix olgensis to climate factors under climate change in the north slope of Changbai Mountain, we sampled tree cores from two sites, located at different elevations (900 and 1400 m a.s.l.). The treering width chronologies of L. olgensis were established based on theories of dendrochronology. The relationship between L. olgensis and climate factors in two periods (1959-1993 and 1994-2009) was analyzed. Theresults showed that: (1) A sudden warming occurred during 1959-2009, with a breakpoint in 1993; (2) The response of radial growth of L. olgensis to climate factors varied between different elevations. Tree-ring width was significantly positively correlated with mean temperature of pre-growing season (April) and negatively correlated with precipitation of September at high elevation; while the significantly positive correlation between tree growth and the precipitation of September existed at low elevation; (3) With the rapid warming over the past ten years, the growth of L. olgensis showed significant variations in the response to climate factors. After warming accelerating, at high elevation, the positive correlation between tree growth and temperature of pregrowing season was significantly enhanced, and the negative correlation between treegrowth and mean temperature of the growing season as well as precipitation in September was enhanced. Radial growth ofL. olgensisshowed a decreasing positive response to precipitation in September and an increasing positive response to precipitation in April at low elevation; (4) The basal area increment (BAI) was significantly increased at high elevation, but that at low elevation was not obvious after the accelerating warming since 1993. Therefore, the situation of accelerating warming promoted tree growth at high elevation, but did not affect it at low elevation. It can be predicted that the natural distribution range of L. olgensis will expand with continuing climate warming.
    Nitrogen and phosphorus stoichiometric characteristics of new and old leaves in Pinus taiwanensis at different altitudes in Wuyi Mountain.
    FU Zuo-qin, LYU Mao-kui, LI Xiao-jie, REN Yin-bang, NIE Yang-yi, DENG Cui, ZENG Min, ZHANG Kang-jing, RUAN Chao-yue, XIE Jin-sheng
    2019, 38(3):  648-654. 
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    Foliar nitrogen to phosphorus ratio (N∶P) is widely used as an indicator of soil nutrient availability and nutrient limitation. Therefore, it is necessary to determine the most sensitive plant tissue as the indicator of soil nutrient status. Pinus taiwanensisoccupies a wide range of habitats in the Wuyi Mountain, China. Here, soil, new and old leaves of P. taiwanensis from three altitudes (1100, 1500, and 1900 m a.l.s.) were sampled in Wuyi Mountain. The concentrations of carbon (C), nitrogen (N) and phosphorus (P) as well as δ15N values of soil, new and old leaves were measured. The stoichiometric ratios of C, N and P (i.e. C∶N, C∶P, N∶P) in soil and leaves were calculated, respectively. Results showed that there was no significant difference in soil N availability among different altitudes, while the δ15N of soil and leaves increased with altitude, indicating that N availability for plants increased with elevations. Soil total P and available P concentrations, and P concentration of leaves at 1100 m altitude were lower than those at 1500 and 1900 m altitudes, indicating that the availability of soil N and P may serve as a limiting factor to the growth of P. taiwanensisat low altitude. There was no significant difference in the N and P concentrations and N∶P of the new leaves of P. taiwanensis among different altitudes. There was no correlation between N∶P in new leaves and soil nutrients. However, the variation patterns of N and P concentrations in old leaves were similar to those in soils, and the N∶P ratio in old leaves were closely related to soil nutrients. Our results indicated that old leaves of P. taiwanensis were more sensitive to soil nutrient status than the new leaves along the altitudinal gradient, which is beneficial to exploring the response of plant growth to variation in soil nutrients in the context of future climate change.
    The reproductive traits and invasiveness of Bidens pilosa var.radiata.
    LUO Ya-ting, WANG Ze-ming, CUI Xian-liang,ZHAO Li-kun, WANG Ju-hong, LUO Yin-ling
    2019, 38(3):  655-662. 
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    Bidens pilosa var. radiata (Asteraceae) is an invasive plant species. Here, we examined its reproductive characteristics from aspects of flowering phenology of single inflorescence, breeding system, pollen ovule ratio, selfcompatibility, pollen vigor, pollinators, and seed germination. The effects of these aspects on its invasiveness were analyzed. The results showed that the flowering duration of a single inflorescence was 5-7 days. The pollen could maintain a high vigor (87.07%-93.41%) within 1-8 days. The pollen ovule ratio was 2508. Single inflorescence can be self-compatible or facultative heterosynthesis. B. pilosa var. radiata had a mixed mating system with high seed setting rate. The existence of edge flower (tongue flower) was beneficial to the increases of seed setting rate. The main pollinators were Phaeidae, Nymphalidae, Cochonidae, and Formicidae. By factors analysis and cluster analysis on germination percentage, germination rate, germination start time, and germination duration, the germination strategies of seeds of B. pilosa var.radiata could be classified into four types: outbreak type, transition type, slow budding type, and low sprouting type. Different germination types were selected by different environmental conditions. In conclusion, the self-compatibility, high seed setting rate, high seed germination percentage, fast germination rate, and diverse germinating strategies work together for the successful invasion of B. pilosa var.radiata.
    Quantitative dynamics of Cyclobalanopsis glauca population in Guilin karst mountainous areas.
    HUANG Dong-liu, LIANG Shi-chu, JIANG Yong
    2019, 38(3):  663-671. 
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    Cyclobalanopsis glauca is a dominant species in the evergreen and deciduous broadleaved mixed forest in Guilin karst mountainous areas. Little information is available about its population status. Here, we analyzed population structure and dynamics of C. glauca by using basic statistics including curves of survival rate, mortality rate, and disappearance rate as well as four survival function curves based on diameter size classes. We performed a time series model to predict the dynamics of C. glauca population in karst ecosystems. The results showed that the age structure was in an inverse-J shape, and mainly aggregated on age class Ⅰ (69.49%). The proportion of individuals successfully colonized in the next age class was very low. The population approximately belonged to the Deevey-Ⅱ  type and grew stably at present stage. Both the mortality and disappearance rate curves exhibited the same trend, with peaks in the first and sixth age classes. The survival rate of the population monotonically decreased, while the cumulative mortality rate increased, and mortality density and risk functional curves of the population varied in a similar trend. The C. glauca population sharply decreased in the young-aged period, stabilized in the middle-aged period, but declined in the old-aged period. The dynamic indices, Vpi and Vpi′, were greater than zero, and showed a stable-growth type population with a little increase butbeing sensitive to external disturbance. Time sequence model suggested that the oldaged individuals would increase in the age-classes of 2, 4, and 6 in the future, and that if the seedlings were not reared in time, the population would be unable to maintain stability.
    Clonal population plasticity of endangered plant species Thuja koraiensis and its response to soil factors.
    YIN Hang, JIN Hui, ZHAO Ying, LIU Li-jie, QIN Li-wu, JIA Xiang, WANG Chao, LI Bing-yan
    2019, 38(3):  672-679. 
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    Thuja koraiensis, an endemic tree species in the Changbai Mountain, is listed as the China’s national second-level protected plant species. In this study, we investigated the habitat conditions and morphological indices of the naturally distributed T. koraiensis population in Changbai Mountain, to analyze its clonal population characteristics. We used grey relational analysis and path analysis to examine the relationship between population modules and soil factors based on the module theory. The results showed that: (1) The clonal population of T. koraiensis had strong phenotypic plasticity. The clonal population with patches distributed under dark coniferous forests had longer spacer length, larger aboveground expansion domain, higher ramet spacing than the population in T. koraiensis pure forest. The population modules had higher variability. (2) The clonal growth pattern of T. koraiensis was between intensive and guerrilla type. It had rapid clonal expansion ability and obvious patch distribution. In the pure forest community with nutrientpoor soil, the clonal growth pattern was closer to the intensive distribution. Under the dark coniferous forest with better soil conditions, the clonal growth pattern tended to be guerrilla distribution. (3) The response of T. koraiensis clonal population growth to soil heterogeneity was specific. Soil moisture was the most important factor affecting the expansion of T. koraiensis population. Soil pH, soil humic acid, soil available phosphorus, and soil available potassium were important factors affecting the clonal population modules of T. koraiensis. (4) Soil nutrients directly affected the characteristics of clonal modules and ecological adaptation strategies. The soil nutrients affecting each clonal module were in order of soil available phosphorus > soil available potassium > soil organic matter > soil total nitrogen.
    Effects of fire disturbance on soil macroarthropod community in the karst region.
    YANG Da-xing, YANG Wen-jia, YE Ting, LI Can
    2019, 38(3):  680-688. 
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    Soil macroarthropods, an important component of ecosystems, play a key role in maintaining ecosystem structure and functioning. Here, we investigated soil macroarthropod community composition by hand sorting method to examine the effects of fire disturbance on soil macroarthropod at sites treated with burning and burning + reclamation, and a natural forest in karst of south Guizhou in October of 2015 and January, April and July of 2016. A total of 214 individuals were captured, belonging to five classes, 15 orders, 38 families and 54 groups. Scarabaeidae larvae were the dominant group of the soil macroarthropod community. The results from the principal component analysis showed that the community structure of soil macroarthropod differed obviously under different treatments. There were no significant differences in the group number, density, Shannon index and the density of each functional group of soil macroarthropod among the different treatments. Fire had significant impacts on seasonal variations of group number, density, Shannon index and the density of omnivore group. Seasonal variations of predator group were observed under different treatments. Soil available phosphorus concentration was significantly correlated with Shannon index of soil macroarthropod community. Our results indicated that different disturbances had different effects on seasonal variations of soil macroarthropod, which is possibly related to disturbance type and recovery time of burned areas.
     
    Stable carbon and nitrogen isotope characteristics and structure of the food chain in Lake Caohai.
    SONG Zheng-cheng, ZENG Ling-xia, HE Tian-rong, LI Zhen-ji
    2019, 38(3):  689-695. 
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    To clarify the trophic level of each biological group and examine the food chain in Caohai, a National Nature Reserve, the characteristics stable carbon (δ13C) and nitrogen (δ15N) isotope of aquatic organisms in Caohai were analyzed. The δ13C values in Caohai ecosystem ranged from -27.56‰ to -13.25‰ (Mean±SD: -21.52‰±3.61‰) and the δ15N varied from 0.32‰ to 15.14‰ (Mean±SD: 8.69‰±3.92‰). There was a significant negative correlation between δ13C and δ15N values (r=-0.423, P<0.01). The trophic levels in different biological groups ranged from 0.8 to3.7: fishes, 0.8-2.5; benthonic animals, 2.0-2.8; birds, 1.0-3.7. Moreover, the trophic levels in fishes and benthonic animals were different in different feeding habits, with an order of carnivorous>omnivorous>phytophagous. The food chain in Caohai had two transmitting carbon pathways: sediment/phytoplankton→zooplankton→ fish → birds, and hydrophyte→ fish → birds.
    Effects of elevated ozone concentrations on photosynthetic and resistant physiological characteristics of Monarda didymaL. leaves.
    WANG Yi-jing, LI Yan, XU Sheng, HE Xing-yuan, CHEN Wei, WU Xian
    2019, 38(3):  696-703. 
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    An experiment was conducted to examine the variations of the physiological characters in leaves of Monarda didyma L. exposed to different ozone concentrations (40 (CK), 80, 120 and 160 nmol·mol-1) in open top chambers (OTCs). The results were as follows: (1) An obviously visible leaf injury was observed under 120 and 160 nmol·mol-1 O3 with fumigation of 14 days, and a large number of yellowbrown patches appeared on the leaves, while no visible injury was observed under 80 nmol·mol-1 O3. (2) After 14-days fumigation, elevated O3 (160 nmol·mol-1) decreased net photosynthetic rate (Pn), stomatal conductance (Gs), PSⅡ electron transfer quantum yield (ΦPSⅡ) and PSⅡ maximum photochemical efficient (Fv/Fm) by 30.2%, 53.1%, 25.7% and 3.6%, respectively. (3) Elevated O3 (160 nmol·mol-1) increased malondialdehyde (MDA) content (74.6%) and the production rate of superoxide radical (O2-·) (31.0%) after fumigation of 14 days, while significantly deceased superoxide dismutase (SOD) activity (19.5%) and soluble protein content (20.9%), indicating that elevated O3 led to serious lipid peroxidation and oxidative stress and destroyed the function of antioxidant system in plants. The content of abscisic acid (ABA) significantly increased (31.0%), suggesting the acceleration of the aging and abscission of plant leaves (the proportion of yellow leaves increased). Consequently, O3 pollution may have adverse effects on the growth of Monarda didyma and its edible and medicinal values.
    Physiological responses of different whitefly resistant peppers to exogenous methyl jasmonate.
    WU Xiao-xia, HE Jing, ZHOU Fu-cai, CHEN Xue-hao, YANG Ai-min, ZHANG Hai-bo
    2019, 38(3):  704-709. 
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    In this study, we examined the physiological responses of two pepper varieties with different whitefly resistance, Sujiao 13 (susceptible variety) and Xinyidai Shanyingjiao (resistant variety), to the exogenous methyl jasmonate treatment. We measured the dynamic changes of chlorophyll content, soluble sugar content, soluble protein content, phenolic compound content, and peroxidase and polyphenol oxidase activity. Our results showed that chlorophyll content, soluble sugar content, phenolic compound content, and the activities of peroxidase and polyphenol oxidase in leaves of two cultivars all exhibited a trend of first increase and then decrease with the increasing concentration of methyl jasmonate. The peak response concentrations were among 10-100 μmol·L-1. All physiological indices in 1000 μmol·L-1 treated groups were significantly lower than those in the control. Under the treatment of appropriate concentration of methyl jasmonate, the contents of soluble sugar and phenolic compounds in the resistant variety were significantly higher than those in the susceptible variety. The soluble protein content showed no significant difference in treated groups of different concentrations of methyl jasmonate. The peroxidase and the polyphenol oxidase activities in the susceptible variety were substantially stimulated by exogenous methyl jasmonate, and were higher than that in the resistant variety. The soluble protein content showed a downward trend, but with no significant difference among different treatments. Our results indicate that an appropriate concentration of exogenous methyl jasmonate can induce the adjustment of insect-resistant substances in peppers and improve the insect resistance of pepper. The responses of different resistant varieties to the exogenous methyl jasmonate are different.
    Effects of soil nitrogen and phosphorus levels on leaf nitrogen and phosphorus contents and photosynthesis of Tamarindus indica L. in Yuanjiang and Yuanmou dryhot valley.
    WANG Chun-xue, HE Guang-xiong, SONG Zi-bo, FAN Bo, ZHANG Meng-yin, FANG Hai-dong, WANG Yan-dan, SHI Liang-tao
    2019, 38(3):  710-718. 
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    Field experiments were carried out to examine the effects of different soil nitrogen and phosphorus concentrations on leaf nitrogen and phosphorus concentrations and photosynthesis of tamarind (Tamarindus indica L.) in the Yuanjiang and Yuanmou dry-hot valleys. Soil nitrogen and phosphorus concentrations, leaf nitrogen and phosphorus concentrations, and the photosynthetic parameters were measured. We used four kinds of common light response curve fitting models, including rectangular hyperbola model, non-rectangular hyperbola model, modified rectangular hyperbola model, and quadratic regression model. The results showed that soil nitrogen and phosphorus concentrations, and ratio of nitrogen to phosphorus were significantly different between Yuanjiang and Yuanmou dry-hot valleys. Soil nitrogen concentrations were 1.205 and 0.881 g·kg-1, soil phosphorus concentrations were 0.481 and 0.177 g·kg-1, soil nitrogen to phosphorus ratios were 2.61 and 5.49, respectively in Yuanjing and Yuanmou dry-hot valleys. Leaf nitrogen concentrations of tamarinds were 17.28 and 13.51 g·kg-1 in Yuanjing and Yuanmou dry-hot valleys, respectively, being significantly different. There was no significant difference in leaf phosphorus concentrations (1.51 vs. 1.81 g·kg-1) between Yuanjiang and Yuanmou valleys. The ratio of nitrogen to phosphorus in leaf had no significant difference between the two sites (11.80 vs. 11.66). The four light response curve fitting models all had a high degree of fitting for the light response curves of the tamarind in the two sites. The modified rectangular hyperbola model under the condition of low photosynthetically active radiation (PAR) was the best one, while the quadratic regression model under the condition of high PAR fitting degree was the most suitable model. The apparent quantum efficiency (α), light compensation point (LCP), dark respiration rate (Rd) were calculated with the modified rectangular hyperbola model, with corresponding values of 0.055, 38.921 μmol·m-2·s-1 and 1.377 μmol·m-2·s-1 in Yuanjiang valley, and 0.060, 8.019 μmol·m-2·s-1 and 0.404 μmol·m-2·s-1 in Yuanmou valley, respectively. The maximum net photosynthetic rate (Pnmax) and light saturation point (LSP) were calculated with the quadratic regression model, with corresponding values of 11.073  and 3223.2 μmol CO2·m-2·s-1 in Yuanjiang valley, and 6.331  and 2532.4 μmol CO2·m-2·s-1 in Yuanmou valley, respectively. In conclusion, photosynthetic rate of tamarind in Yuanjiang dry-hot valley was significantly higher than that in Yuanmou dry-hot valley. Soil phosphorus and leaf phosphorus concentrations were the key influencing factors for the photosynthesis of tamarind.
    Effects of straw mulching and biochar addition on soil temperature and maize yield.
    DAI Wan-ning, WANG Li-xue, Ismail KHAN, WANG Xiao-fan, LI Zhen-hua
    2019, 38(3):  719-725. 
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    To explore the effects of straw mulching and biochar addition on soil temperature and maize yield, a field experiment was conducted following two-factor split-plot design, with two types of mulching (non-mulching, straw mulching) as main plots and three levels of biochar application (0, 4 and 12 t·hm-2) as sub-plots. Maize grain yield, yield omponents, and soil temperature in different soil depths were measured. The results showed that straw mulching decreased soil temperature, with such effect decreased with increasing soil depth. Soil temperature showed a large change in the early growth period and a small change in the later period. Under different cover conditions, biochar addition had different effects on soil temperature. Under the nonmulching condition, biochar addition increased soil temperature, with the magnitude of such effect positively depending on application rates. Under straw mulching condition, biochar amendment resulted in a lower soil temperature in the 0-10 cm soil layer but an increase in 15-25 cm soil layer in vertical dimension. Straw mulching and biochar treatments significantly increased maize yield, yield composition and economic coefficient. The highest yield was achieved at the treatment of straw mulching incorporating with 12 t·hm-2 biochar; this treatment increased grain yield, its components and economic coefficient by 24.2%, 6.4%-15.7% and 15% respectively, compared to the non-mulching and biochar-free treatment. Among all yield components, spike length and grain number had the greatest impacts on yield. Grain yield was negatively correlated with spike length and positively correlated with grain number.
    Spatial pattern of soil moisture and vegetation coverage in Cao Lake wetland.
    DUAN Kai-xiang, ZHANG Song-lin, ZHAO Cheng-zhang, PENG Xin-bo, JUAN Wei-chao, YANG Peng, YANG Ye, JIANG You-jin, LUO Yan
    2019, 38(3):  726-734. 
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    Soil moisture is a major factor driving the formation and evolution of vegetation patterns. The exploration of spatial heterogeneity of soil moisture in salt marsh wetland in arid area is helpful for revealing the environmental adaptation of wetland plants and the interaction mechanism between soil moisture and wetland plants. In this study, the variogram models of soil moisture content (0-90 cm) and vegetation coverage were established according to the vegetation cover conditions (high, medium, and low) of three Calamagrostis pseudophragmitesdominated population patches in the wetland of Cao Lake, Jiayuguan City, using the geostatistical method. The spatial distributions of soil moisture and vegetation coverage were mapped with the Kriging interpolation method, and the spatial autocorrelation properties of soil moisture and vegetation coverage in the wetland were determined by the Moran’s I coefficients. Finally, the spatial heterogeneity of soil moisture and vegetation cover in wetland and their interaction relationships was analyzed. Results showed that soil water contents in different sites of the Cao Lake wetland were in order of lakeside>dry lake>flat land between dunes, and salt content was in order of dry lake>lakeside>flat land between dunes. On the patch scale, soil moisture and vegetation cover were in line with the normal distribution model. The spatial structure of soil water content in each layer and vegetation cover of C. pseudophragmites in the three sites all had an obvious patch-like distribution and exhibited high degrees of spatial heterogeneity. The spatial distribution of soil moisture contents and vegetation coverage in all three plots had positive correlations and agglomeration characteristics. The spatial agglomeration intensity of soil moisture content for the 60-90 cm soil layer was larger than those of 0-30 and 30-60 cm soil layers, and the spatial clustering characteristics of vegetation cover was more obvious in the lakeside plot. Therefore, C. pseudophragmites maximized the use of soil water resources, and thus improved its adaptability to drought habitats, which, to a certain extent, affected the spatial distribution of soil moisture on small scale.
    Differences of soil enzyme activities and their driving factors under different flooding conditions in the Bird Island area, Qinghai Lake.
    CHEN Yan-xin, GENG Yu-qing, HUANG Jin, CUI Xue-qing, HOU Meng
    2019, 38(3):  735-743. 
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    Wetland is characterized by permanent or seasonal inundation, whose structure and function are directly influenced by the changes of flooding conditions. To investigate the effects of flooding conditions on soil enzyme activities and identify the driving factors, we used three kinds of plots with different flooding conditions (longterm flooded wetlands, periodically flooded wetlands and seldom flooded wetlands) in the Bird Island of Qinghai Lake. Soil chemical properties, soil microbial biomass carbon and nitrogen, and soil enzyme activities were analyzed. The results showed that, compared to the long-term flooded wetland, the activities of β-glucosidase, cellobiase, and glycine aminopeptidase in the periodically flooded wetland decreased by 24.01%, 18.80% and 2.96%, respectively. The activities of those enzymes decreased by 33.65%, 18.84%, and 63.47% in the seldom flooded wetlands, compared with the periodically flooded wetland, respectively. The activities of N-acetylglucosaminidase and leucine aminopeptidase were significantly higher in periodically flooded wetland and long-flooded wetland than in the seldom flooded wetlands. However, the activities of alkaline phosphatase and phenol oxidase were the highest in the seldom flooded wetlands. Results of redundancy analysis showed that readily oxidizable carbon, total nitrogen, organic carbon, microbial biomass carbon and nitrogen, and dissolved organic nitrogen were significantly correlated with the changes of soil enzyme activities. Among them, soil organic carbon was responsible for the variability in cellobiase activity, whereas the activities of β-glucosidase, N-acetylglucosaminidase and glycine aminopeptidase were well explained by readily oxidizable carbon. Our results indicate that imposing flood was more conducive to the accumulation of carbon and nitrogen, and thus increased the activities of several hydrolases.
    Distribution pattern of liverwort community in relation to environmental factors of caves in karst Tiankeng: A case study of Monkey-Ear Tiankeng of Guizou Province.
    LI Cheng-yi, ZHANG Zhao-hui, WU Jin, LI Xiao-fang
    2019, 38(3):  744-752. 
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    Revealing the relationship between distribution pattern of liverworts community and environmental factors is an important step for biodiversity conservation in Tiankeng cave. Multivariate regression trees analysis, α and β-diversity analysis, and canonical correspondence analysis were conducted to analyze the distribution patterns of liverwort communities in four caves with different depths in Monkey-Ear Tiankeng, Guizhou Province and their relationships with environmental factors. The results showed that the community composition of liverworts was simple in Tiankeng caves, mainly consisting of one or two dominant species. Species richness of liverwort community increased with the increasing depth of cave location, showing a gradient pattern. The liverwort communities could be divided into three types from four caves using cross-validation: (Ⅰ) Communities of middle-depth cave, mainly consisting of Cyathodium smaragdinum+Pellia endiviifolia+Riccia fluitans; (Ⅱ) Communities of lower middle depth cave, mainly consisting of Cyathodium smaragdinum+Riccia fluitans; (Ⅲ) Communities of bottom cave, mainly including Pelliaendiviifolia+Conocephalum japonicum+Dumortiera hirsuta. In horizontal direction, the diversity of liverwort community changed with community composition (species, genera, and families) in the Wanmutitian cave, which was first increased and then declined. However, the environmental heterogeneity of communities showed a contrasting pattern. The diversity of liverworts was consistent with the environmental heterogeneity in the Tianletang cave, which was first decreased and then increased. The distributions of liverwort community in both vertical and horizontal directions were affected by the gradient variations of temperature, humidity, and illumination. The diversity of liverwort community was a result of the combinations of three environmental factors. The interpretation of axis 1 and axis 2 was 45.89% and 79.28% from canonical correspondence analysis, respectively.
    Screening, identification and efficacy of combined biocontrol actinomycete strains against root rot disease of Astragalus membranaceus.
    ZHENG Dou-dou, NIU Shi-quan, ZHOU Xuan, WANG Yan, ZHU Xue-tai, KONG Wei-bao, ZHANG Ai-mei
    2019, 38(3):  753-761. 
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    To develop effective biocontrol products for controlling the root rot of Astragalus membranaceus, actinomycete strains with excellent prevention and controlling effects to pathogenic bacteria were isolated from the saline-alkali soil of Shule River basin, which were further combined into compound agents to improve the antibacterial effect on root rot of A. membranaceus. The plate tolimulus method and growth rate method were used to screen high-efficiency biocontrol actinomycete strains. Morphological characteristics, physiological and biochemical characteristics, and 16S rRNA DNA sequence analysis were used to identify strains. After that, a pot experiment was conducted to test the controlling effect on root rot of A. membranaceus. The results showed that among the total 244 tested strains of actinomycetes, 11 strains had inhibitory rates of more than 50% against the root rot disease. After rescreening, the inhibitory rate was 7%-57%. Combined with the screening effect and the inter-strain affinity test, the strains DA4-3-12, DA8-4-10 and 221 were used as the research targets for the compound strains. The strains DA4-3-12 and 221 were identified asStreptomyces alboflavus and strain DA8-4-10 as Streptomyces alanosinicus. Single strains DA4-3-12, DA8-4-10 and 221 and their compound strains in different combinations (DA4-3-12 + DA8-4-10, DA4-3-12 + 221, DA8-4-10 + 221, DA4-3-12 + DA8-4-10 + 221) all had controlling effects on root rot of A. membranaceus, and their control efficiencies were 60%, 46%, 70%, 55%, 70%, 64%, and 72% respectively. Among them, the compound DA4-3-12+DA8-4-10+221 had the best controlling effect. The synergistic effects of various strains in the mixed strains were fully expressed, with wide antimicrobial spectrum.
    Effects of light intensity and nitrate level on growth and photosynthetic characteristics of Sargassum horneri.
    LIU Ting, MA Zeng-ling, LI Hui, XU Zhi-guang
    2019, 38(3):  762-769. 
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    The effects of light intensity on the growth and photosynthetic characteristics of Sargassum horneri, a golden tide causing species, were investigated under different nitrate (NO3--N) levels to reveal the physiological mechanism underlying the outbreak of golden tide. There were two NO3--N levels and three light intensities: i.e. high N (100 μmol·L-1), low N (50 μmol·L-1, the normal NO3- concentration in natural seawater), high-light (150 μmol photons·m-2·s-1), medium-light (60 μmol photons·m-2·s-1) and low-light (10 μmol photons·m-2·s-1). The growth, pigment concentration, soluble sugar concentration, soluble protein concentration, nitrogen absorption rate and the maximum photosynthetic oxygen evolution rate (Pmax) of S. horneri thalli were measured after they had acclimated to different NO3--N and light levels for seven days. The results showed that the growth rate, soluble sugar concentration, soluble protein concentration, nitrogen absorption rate, and Pmax ofS. horneri thalli all increased with increased light intensities, while the pigment concentration decreased with the increasing light intensities. For the lowN acclimated S. horneri thalli, except for carotenoids, all the above mentioned indicators under the high light treatment were significantly higher than those under the low light treatment (P<0.05). For the highN acclimatedones, except for the soluble sugar, all the indicators under high light treatment were significantly higher than those under the low light treatment (P<0.05). For the S. horneri thalli acclimated under same light intensities, pigment concentration, soluble protein concentration, nitrogen absorption rate andPmax increased with the increasing NO3--N level, while the soluble sugar concentration decreased with the increasing NO3--N level. For the S. horneri thalli acclimated to the three light conditions, the Pmax under the highN treatment was significantly higher than that under the lowN treatment. In conclusion, after seven days acclimation to different light intensities and NO3--N levels, S. horneri thalli showed higher potentials in growth and photosynthesis under the condition of high light intensity and high nitrogen level. Therefore, eutrophication in seawater would aggravate the occurrence of golden tide in that S. horneri thalli can obtain higher light intensities when they break from the stems and drift on the sea surface, which would stimulate the potentials of growth and photosynthesis.
    Effects of succinic acid, an allelopathic substance of Pontederi cordata, on the growth and competition of Microcystis aeruginosa and Scenedesmus obliquus.
    XU Lan-xin, TIAN Ru-nan
    2019, 38(3):  770-777. 
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    To understand the impacts of organic acids released by roots of Pontederia cordata on growth and competition of Microcystis aeruginosa and Scenedesmus obliquus, single culture and mix-culture of the two species were treated with succinic acid at different concentrations in a laboratory control environment. The initial ratio of M. aeruginosa toS. obliquus in BG11 medium was 1∶0 (100% M), 1∶1 (50% M+50% S), 2∶3 (40% M+60% S), 3∶2 (60% M + 40% S) and 0∶1 (100% S). Succinic acid exhibited a strong inhibitory effect on growth of M. aeruginosa and S. obliquus, and the magnitude of such effect was positively correlated with the concentration of succinic acid. In the absence of succinic acid, M. aeruginosa cultured with or without S. obliquushad a faster growth rate than S. obliquus.With the addition of 60 mg·L-1 succinic acid, β (an inhibitory parameter of S. obliquus toM. aeruginosa) was more than 0 when the ratio of M. aeruginosa to S. obliquus was 2∶3 or 1∶1 and less than 0 when the ratio ofM. aeruginosa toS. obliquus was 3∶2, indicating that the inhibitory effect of one to another varied with the initial proportion of the two species. The succinic acid could change the competition between M. aeruginosa and S. obliquus. Under low concentrations (20, 40 mg·L-1), M. aeruginosa inhibited S. obliquus, butS. obliquus promoted M. aeruginosa. Under high concentrations (60, 80 mg·L-1), the performance of both species was mutually inhibited, indicating an intensified competition.
    Salt tolerance and growth of submerged macrophyte Myriophyllum spicatum.
    LIU Meng-meng, LIU Qiao, YANG Na, BAO Yan-lin, ZHANG Qi, YU Ke-feng, HUO Yuan-zi, HE Pei-min
    2019, 38(3):  778-784. 
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    Salt tolerance and growth properties of Myriophyllum spicatum were investigated by both artificial seawater culture and cultivation in Hangzhou Bay. Results from the indoor cultivation showed that the branch of M. spicatum could grow normally in artificial seawater with salinity less than 12. Low salinity treatment promoted the growth of adventitious roots. When salinity reached 15, the chlorophyll content and maximum photosynthetic efficiency (Fv/Fm) of M. spicatum decreased, the growth was stagnant, and most plants died gradually. Results from field cultivation showed that M. spicatum could survive in the salinity of 6.06-9.03 in Hangzhou Bay from June 2017 to May 2018, with water temperature of 3.85-33.37 ℃. The rapid growth period of M. spicatum was from August to October. M. spicatum can carry on sexual reproduction and vegetative reproduction in the low salinity water of Hangzhou Bay, mainly by vegetative reproduction. These results provide basis for the establishment of M. spicatum in waters with low salinity.
    Energy expenditure and foraging behavior of wintering Tundra Swan and Swan Goose in a lotus pond reclamation area in Poyang Lake.
    ZHANG Cong-min, ZHI Yi-jin, LU Ping, SHAO Ming-qin, DAI Nian-hua
    2019, 38(3):  785-790. 
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    From December 2016 to February 2017 and from December 2017 to March 2018, the scan-sampling technique and focus animal method were used to study energy expenditure and foraging behavior of wintering Tundra Swan (Cygnus columbianus) and Swan Goose (Anser cygnoides) in a lotus habitat near Poyang Lake during the daytime. The results showed that both Tundra Swan and Swan Goose spent their daytime on resting (36.01% vs. 28.02%), foraging (32.71% vs. 17.44%), and locomotion (17.26% vs. 30.61%). Correspondingly, they mainly expended energy for foraging (354.1 vs. 144.88 kJ·d-1), resting (275.22 vs. 164.35 kJ·d-1) and locomotion (219.79 vs. 299.22 kJ·d-1) in daytime. The energy expenditure of foraging behavior and total energy expenditure of Tundra Swan were significantly higher than those of Swan Goose. There was no significant difference in daily energy expenditure between Tundra Swan and Swan Goose. Tundra Swan mainly adopted feeding way from the water surface and dipping with headneck submersed, while Swan Goose used feeding way from the water surface and digging food. This is related to the water depth, food composition, and their own morphology. Tundra Swan and Swan Goose have different foraging methods and foraging water depth to decrease interspecific competition.
    Concentrations and emissions of dissolved CH4 and N2O in the Yarlung Tsangpo River.
    YE Run-cheng, WU Qi-xin, ZHAO Zhi-qi, HU Jian, CUI Li-feng, DING Hu
    2019, 38(3):  791-798. 
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    Rivers release large quantities of greenhouse gases into the atmosphere, which is an important link in the material cycling and energy flow of terrestrial ecosystems. Mountainous rivers are ‘hotspots’ for greenhouse gas emission, but the release of CH4 and N2O from those rivers has been less documented. To explore the spatiotemporal distributions and related controls of CH4 and N2O in middle-large plateau rivers, the seasonal variations of CH4 and N2O in tributary and main stream of the Yarlung Tsangpo River were examined. The results showed that the ranges of CH4 and N2O concentrations in the Yarlung Tsangpo were 2.3-864.9 and 8.2-23.7 nmol·L-1, respectively. There was no significant difference in CH4 concentrations between low-flow and high-flow periods (P=0.112), but the N2O contents were higher in low-flow months than in high-flow months (P=0.017). River water discharge and water temperature were the major factors controlling the dynamics of CH4 and N2O emission, respectively. The release rates of CH4 and N2O in the Yarlung Tsangpo River ranged 4.3-11.1 mg C·m-2·d-1 and 0.16-0.37 mg N·m-2·d-1, respectively. The emission amounts of CH4 and N2O in Yarlung Tsangpo River system were 1.88-4.59 Gg C·a-1 and 0.07-0.16 Gg N·a-1, accounting for 1.25‰-3.06‰ and 2.17‰-4.96‰ of global river estimations, respectively. The evasion of CH4 and N2O in mountainous rivers need further detailed studies, which may revise the global estimation of greenhouse gas emission.
    Evaluation and source analysis of heavy metal pollution in sediments of Hongfeng Reservoir in Guizhou Province, China.
    HE Ying, LI Qiu-hua, TANG Li, WANG Long, MA Xin-yang, LIU Yong-xia, MENG Fan-li, ZHANG Hua-jun
    2019, 38(3):  799-809. 
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    To understand the status of heavy metal pollution in sediments in Hongfeng Reservoir, a total of 80 sediment samples were collected from eight sites. The concentrations of Hg, As, Zn, Pb, Cd, Cr, Cu and Ni were analyzed using atomic fluorescence spectrometer and atomic absorption spectrometer. The pollution status was evaluated by geoaccumulation index (Igeo) and potential ecological risk index (RI). Meanwhile, correlation analysis was carried out and the sources of pollution were discussed. The results showed that the concentrations of heavy metals in the sediments of the North Lake of Hongfeng Reservoir were significantly higher than those in South Lake. The average concentrations of Hg, As, Pb, Cd, Cr, Cu, Zn and Ni were 0.56, 35.76, 43.66, 0.50, 91.03, 89.14, 152.44 and 109.30 mg·kg-1, respectively. Based on the soil background value of Guizhou Province, the results of Igeo evaluation showed that Hg was in a moderate pollution, and the pollution order was Hg>Ni>Cu>As>Zn>Pb>Cr>Cd. The RI evaluation results showed that Hongfeng Reservoir was in a medium ecological risk. There were three sources for the heavy metal pollution of Hongfeng Reservoir. Industrial emissions were the main source of Pb, Zn and Cd for North Lake and Central Lake. Urban emissions and the remaining of pesticides and chemical fertilizers surrounding the reservoir were the main source of Cr, Ni, As and Cu for North Lake. The Hg and As mainly came from mining activity for the whole reservoir.
    Effects of mixed compost of sewage sludge and green waste on growth and heavy metal accumulation of Cosmos bipinnatus.
    ZHAO Xia, HU Zi-hang, ZHENG Jing-ming, SI Li-qing
    2019, 38(3):  810-817. 
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    With urban population growth and rapid urbanization, a large amount of sewage sludge and green waste are produced every day. The application of mixed composting products from anaerobic digested sludge and green waste for soil amendment in woodland is an economical and effective way for the re-use of urban waste. In this study, an experiment was conducted in Beijing Plain afforestation area to explore the effects of mixed compost application on the growth of Cosmos bipinnatus and its absorption of heavy metal elements. Results showed that application of compost had no significant effect on the contents of total soil N and organic matter. Meanwhile, three heavy metals, i.e., Cu, Zn, and Cd, were mainly present as residual form in the soil. Although compost application increased the Cu and Zn contents in soil, total Zn content did not exceed the pollution risk screening value of 300 mg·kg-1 by the Soil Environmental Quality Standard of China (GB 15618-2018), while total Cu content exceeded the pollution risk screening value of 100 mg·kg-1 only when the dosage of compost was high. Cd content in the ambient soil had exceeded the value of soil pollution risk control value of 4.0 mg·kg-1. There was no effect of compost application on the Cd content. Plant height, biomass, and flower number of C. bipinnatus increased with the increasing compost dosage. The enrichment capacities of C. bipinnatus to the three heavy metals were in order of Cu>Cd>Zn. Our results demonstrated that plantation ecosystems in Beijing plain region could tolerate certain concentration of heavy metals from the mixed compost, and utilize other nutrients to improve the soil fertility with positive effect on plant growth.
    Spatial distribution of crop climatic potential productivity and its response to climate change in agro-pastural ecotone in northern Shanxi Province.
    MA Ya-li, GUO Jian-ping, ZHAO Jun-fang
    2019, 38(3):  818-827. 
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    Based on the daily meteorological data of 19 meteorological stations in agropastural ecotone of northern Shanxi Province from 1961 to 2016 and the observational data of five grain crops during growth period from 1981 to 2016, the potential productivity of crops were calculated through a stepbystep correction method. The spatial distributions in climatic potential productivity of five grain crops at different levels were analyzed. The impacts of changes in climatic elements, such as radiation, temperature and precipitation on climatic potential productivity were analyzed by a statistical model based on the propensity to change in potential productivity at all levels. The results showed that the light/temperature potential productivity of maize, millet, sorghum and soybean in the northern Shanxi Province during the period 1961-2016 decreased from the east to the west. The spatial difference of photosynthetic potential productivity of potato was minor. The climate potential productivity of maize, millet and sorghum decreased from the southeast  to the northeast. The distribution of climatic potential productivity of potato was higher in the west and the east and lower in the middle. The spatial difference in photosynthetic potential productivity of soybeans was slight. The impact of climate change on the climatic potential productivity differed among crop species. The effects of radiation changes on the climate potential productivity of five crops were negative. The effects of temperature changes on the climatic potential productivity were positive for thermophilic crops (maize, soybean, millet and sorghum) in most regions, but negative for chimonophilous crops (potato). Climate warming was beneficial to improving heat shortage in northern Shanxi. Precipitation was the dominant climatic factor affecting the spatial change of climatic potential productivity. Reduced precipitation had a negative effect in the northern part with less precipitation, and no effect in the south part with more precipitation. To adapt to the climate change, it is necessary to strengthen the selection of high photosynthetic efficiency and drought-resistant crop varieties, rationalize planting density, adjust sowing date, optimize agricultural distribution, and promote agricultural rainwater harvesting and agricultural water-saving irrigation technologies in accordance with local conditions, in order to enhance the utilization of agricultural climate resources and promote stable and high yield of food crops.
    Construction and optimization of ecological network under the stress of road landscape in coastal beach area: A case study of Dafeng District, Yancheng City.
    LIU Rui-cheng, SHEN Chun-zhu, JIA Zhen-yi, WANG Jun-xiao, LU Chun-feng, ZHOU Sheng-lu
    2019, 38(3):  828-837. 
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    Under the background of rapid economic and social development, the disorderly expansion of road landscape has aggravated habitat fragmentation, hindered biological circulation and impaired ecosystem services in coastal beach areas. Simulation of ecological network based on multiple resistance scenarios considering road construction stress is helpful to revealing the impacts of road network on key ecological processes and optimizing regional ecological security pattern. In this study, Dafeng District of Yancheng City was taken as a case study area and analyses were processed based on GIS, Conefor Sensinode, and other software platforms. Three kinds of resistance scenarios were established, which were based on landscape type assignment, modified according to the buffer zone on both sides of the road, and modified according to the high density zone of the road network, respectively. Lastly, ecological networks were simulated and quantitative evaluation on the structure and spatial pattern were conducted. The results showed that the ratio of high density areas of roads was about 8.21%, including central urban area and port area, in which the habitats faced with higher risk of road landscape stress. Under the stress of road network, the area of green land composition of corridors decreased by 7.40%, and the mean curvature increased by 12.82%, which implied that energy consumption of biological migration was significantly increased. The coastal wetland exerted the strongest effects on the other ecological sources in the ecological network, which could provide natural passages for biological migration. Furthermore, it is of great benefit to quantify the impacts of important sensitive factors, e.g. road density, on resistance surface assignment and component structure of ecological network, which can not only help understand the change and underlying mechanism of key ecological processes, but also provide effective support for the construction of regional ecological security pattern.
    The effects of “ecological-production-living” land use transformation on associated ecological service value: A case study of Yingkou City.
    ZHANG Lei, LIU Ge-ge, WEI Jun-qing, LIU Yan-fang
    2019, 38(3):  838-846. 
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    Understanding land use transformation and its ecological effects based on “ecological-production-living” functions is an important issue of land use/land cover change, which can provide support for the optimization of “ecological-production-living” land use. We constructed a classification system of “ecological-production-living” land use mainly oriented by dominant functions of land use for Yingkou City. A modified quantitative and spatial analysis model was used to analyze the dynamics and regional types of “ecological-production-living” land use transformation, and adopted the improved equivalent factor method to analyze the profit and loss of ecological service value. The results showed that, during 2000-2015, the transferred area of ecological land was the largest, with the active types of ecological land being distributed in the southwest and central north of the city. The living land significantly increased with a high speed, being mainly transformed from ecological land and agricultural producing land. The total value of ecological service in Yingkou experienced a decreasing-increasing-decreasing process, and was higher in the southeast and lower in the west. The change of ecological service value presented a spatial pattern of “three regions”. During 2000-2005 and 2010-2015, the decreasing trend in southeastern and north central area was significant, consistent with the spatial distribution of newly added active type of living land.
    Ecological security evaluation of wetlands in Qingdao based on the comprehensive weighting method.
    LI Yue, YUAN Ruo-yu, LIU Yang, XI Min, KONG Fan-long
    2019, 38(3):  847-855. 
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    Based on the pressure-state-response model, we constructed an index system and assessed the ecological security of wetlands in Qingdao using a composite index. The comprehensive weighting method was used to quantify the weight of each index.The results showed that the ecological security comprehensive index of wetlands in Qingdao was 61.63, suggesting a low level of security. Population growth, regional development, and increased water consumption were the major pressure on wetlands. The overall condition of wetlands was good, with relatively good landscape and strong resistance and selfregulation ability. The investments in the technology and environmental protection were relatively low, and the industry optimization and upgrade was slow. The ecological security comprehensive index of wetlands in Qingdao decreased in the order of Jiaozhou > Huangdao > Pingdu > Urban > Jimo > Laixi > Laoshan > Chengyang. The wetlands in Jiaozhou, Huangdao and Pingdu were at a safe state, whereas wetlands in other areas were at a state of threshold safety. The urban ecological function regionalization represented by national wetland parks was helpful to the management and protection of wetlands, which was an important factor affecting ecological security of wetlands. The high population, development pressure, and high water consumption directly reduced the ecological security of wetlands. Therefore, we suggest to improve the ecological safety of wetlands in Qingdao by delimiting red line of wetland conservation, accelerating transformation and upgrading of traditional industries, and increasing the investment in the technology and environmental protection.
    Research progress on alpine wetland changes and driving forces in Qinghai-Tibet Plateau during the last three decades.
    LIU Zhi-wei, LI Sheng-nan, WEI Wei, SONG Xiang-jing
    2019, 38(3):  856-862. 
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    Qinghai-Tibet Plateau has unique and large-scale alpine wetlands in the world, which plays an important role in climate regulation and water supply. Due to its unique geographical environment, Qinghai-Tibet Plateau is a sensitive zone and an early warning zone for global climate change, which has attracted worldwide attention. Here, we reviewed the changes of wetland area, wetland soil, wetland hydrology, wetland plants and animals and their driving factors in Qinghai-Tibet Plateau in recent three decades, and put forward the key directions of wetland research in Qinghai-Tibet Plateau. The basic characteristics of climate change in the QinghaiTibet Plateau were warming and humidifying. Wetland area decreased from 1970 to 2000. After the year of 2000, the degradation of wetland slowed down and the wetland area increased to a certain extent. The surface soil moisture of wetland decreased, carbon emission increased, and vegetation coverage decreased on the whole. The rising temperature, surface evapotranspiration, precipitation and rodent damage were the major driving forces for wetland changes. Meanwhile, wetland changes were affected by human activities, such as the increases of livestock quantity, resource exploitation, and road engineering. Due to the special geographical location and the constraint of the natural conditions of the Qinghai-Tibet Plateau, we lack basic data of alpine wetlands. Further research should mainly focus on the application of remote sensing technology and long-term positioning monitoring means to collect basic data and carry out relevant mechanism research.
    Responses of forest soil nutrient cycling to nutrient input modes: A review.
    NI Hui-jing, SU Wen-hui, FAN Shao-hui, ZENG Xian-li, JIN Yi
    2019, 38(3):  863-872. 
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    Soil nutrient cycling is of great significance to the maintenance of forest ecosystem stability, selection and renewal of tree species, and forest sustainable management. Learning the sources and processes of nutrient inputs can facilitate the analysis of matter cycling and energy flow and the evaluation of ecosystem functions. Leaf litter, root turnover, and root exudates are the main sources of nutrients in forest soils and important components of soil nutrient cycling. In this paper, the three major nutrient input processes and their influencing factors were analyzed. The effects of litter composition and physicochemical properties, biotic factors, and environmental factors on litter decomposition and soil nutrient cycling were summarized. The effects of fine root substrate properties, tree species composition, soil biology, and environmental factor changes on fine root turnover and soil nutrient cycling were reviewed. The role of root exudates in the soil nutrient cycling process was explored. Finally, important directions that need urgent research in this filed are proposed to provide reference for related research and nutrient management of forest ecosystems.
    Traditional subak irrigation system and its eco-hydrological effects in Bali rice terraces, Indonesia.
    GAO Xuan, JIAO Yuan-mei, LIU Cheng-jing, ZHA Zhi-qin, LI Rong
    2019, 38(3):  873-881. 
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    Irrigation system could regulate eco-hydrological pattern and process of agricultural landscape to maintain its sustainability through management of water resources. In Bali of Indonesia, a traditional Indonesian Subak Irrigation System (SIS) is the wisdom of local people to effectively regulate eco-hydrological pattern and process of terraced landscapes, which is the key mechanism underlying the sustainability of Rice Terraces Landscapes (RTL). We used the published literatures on SIS as a data source to review its mechanisms in ensuring the sustainable development of RTL and the reasonable exploitation of agricultural water resources at basin and irrigation-unit scales respectively, and further analyzed its eco-hydrological effects. At basin scale, the dynamic multi-level temple structure of management in SIS enhances stability and adaptability of RTL. At irrigation-unit scale, the rules of tek-tek water distribution and awig awig-management in each subak organization increase water use efficiency and alleviate community conflicts. Due to the irrigation facilities and spatio-temporal management activities, SIS has eco-hydrological effects, namely increasing hydrological connectivity, controlling pests and improving ecosystem services. The existing researches on SIS are mainly based on the qualitative and static research of social sciences such as sociology, anthropology, and history, with few on the natural sciences such as ecology and hydrology. In future, we should strengthen the quantitative and dynamic research of natural sciences and multi-discipline, which would provide inspiration for the protection and management of other terraces systems globally.
    Advance in study on effects of soil fauna on soil carbon cycling.
    NIE Li-kai, YU Zheng-da, KONG Fan-long, LI Yue, XI Min
    2019, 38(3):  882-890. 
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    As an important component of belowground ecosystem, soil fauna plays a vital role in regulating soil carbon cycling. However, previous studies provided limited scope for the effects of soil fauna on soil carbon cycling. Based on the analysis of recent literatures, we presented an integrated overview to summarize the effects of soil fauna on litter decomposition, soil carbon stock, the regulation of plants and microorganisms, and soil respiration. To better understand theimpacts of soil fauna on soil carbon cycling, future research should be strengthened in the following aspects: more attention to the lower-latitude areas; the combination of field experiment and lab simulation test should be strengthened as for the research methods; the mechanism such as soil fauna respiration and the effects of fauna on net carbon sequestration should be deepened regarding the research contents; and global hot issues should be combined regarding the research fields.
    Progress in the study of soil salt accumulation in arid region.
    LIU Li-juan, LI Xiao-yu
    2019, 38(3):  891-898. 
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    Soil salinization land is widely distributed in the dry regions of China. Salinization, as one of the main aspects of soil degradation, has important impact on the sustainable development of agriculture. As one of the countries most seriously threatened by salinization, China needs to pay more attention to the prevention and control of soil salinization. We summarized the technologies and methods of soil salinization monitoring, and analyzed the effects of land use, irrigation, and natural environmental factors on soil salt accumulation and migration processes. In the aspect of prevention and control of soil salinization, we should comprehensively consider the different factors in each irrigation basin and explore the best combination model to improve salinized soil at the balance of environmental protection and economic cost. Furthermore, we should strengthen screening and cultivation of more suitable and efficient salttolerant plants. We proposed the future research directions of salt transport processes at river basin or landscape scale, to provide reference for the prevention and management of soil salinization in arid regions.
    Research advances about magnesium isotope in forest ecosystems.
    LIU Jin-ke, HAN Gui-lin
    2019, 38(3):  899-907. 
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    Magnesium, one of the major elements, is important substance for life-sustainingactivities. The weathering products of magnesium-containing minerals are transported by river to the ocean, in which magnesium participates in ecosystem material cycling, and finally undergo re-diagenesis as carbonate precipitation. This process is closely related to global carbon cycle. Recently, with the improvement of non-traditional metal isotope systems and the use of MC-ICP-MS (multi-receiver inductively coupled plasma mass spectrometer), the accuracy and convenience of magnesium isotope analysis have been substantially improved. Magnesium plays an important role in the chemical weathering process and life activities and becomes an effective tool for tracing the material sources and various geochemical processes in the surficial environment. Therefore, studying the characteristics and fractionation mechanism of magnesium isotope can help us understand different geochemical processes occurring in the surficial ecosystem and explore the global element cycle and climate changes. This review systematically expounds the magnesium isotopes composition of various components and the controlling factors of fractionation in forest ecosystems. We also summarized the problems existing in the current forest ecosystem research and proposed the future research directions of magnesium isotope in forest ecosystems.
    Basin land use intensity based on panel data of irrigation district and the identification of spatiotemporal difference of influencing factors.
    MA Li-bang, LI Xiao-yang, CHENG Wen-juan, BO Jie
    2019, 38(3):  908-918. 
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    We analyzed the land use intensity in the middle and lower reaches of Shule River Basin and the temporal and spatial variation of influencing factors between 1987 and 2015 by using the comprehensive index of land use intensity and the model of SFA (Stochastic Frontier Analysis). The results showed that there was no obvious change in the land use structure of the middle and lower reaches of the Shule River Basin between 1987 and 2015. Non-vegetative area still dominated over 80%, followed by grassland, and construction land was the least (<1%). The comprehensive index land use intensity showed an increase trend, with significant spatiotemporal differences. The index raised by 35.36 during 1987-2015, with a sharp increase during 1996-2007, reaching 24.17, which accounted for 68.35% of the total increment value. After 2007, the increase became steadier than the previous stage, and the spatial pattern of land use intensity showed a trend from “low in east and west, and high in middle” to “high in east and middle, and low in west”. The spatiotemporal difference of influencing factors of land use intensity was significant at irrigation district level. Land use intensity change in the three irrigation districts was related to agricultural production structure and immigrants during 1987-1996, and was affected by land use change and immigrants during 1996-2007, and by agricultural production structure and land use change between 2007 and 2015.
    Suitability evaluation and corridor design of habitats for Green Peafowl based on MaxEnt Model.
    LI Rong, JIAO Yuan-mei, LIU Xin, LIU Zhi-lin, GAO Xuan
    2019, 38(3):  919-926. 
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    Green Peafowl (Pavo muticus) is inscribed in the Chinese First-Class National Protected Animals list for its rarity and preciousness. Anthropogenic habitat fragmentation threatens its survival. Based on 15 occurrence records of Green Peafowl and eight environmental parameters in Konglong River nature reserve of Yunnan Province in southwestern China, we evaluated the habitat suitability using MaxEnt Model and designed habitat corridors using Minimum Cost Model. The results showed that the area under ROC curve (AUC) of MaxEnt Model was 0.951, indicating an excellent assessment result of the model. The distance to river bank and the elevation were dominant environmental variables for the suitability of Green Peafowl habitats, with a contribution rate of 59.2% and 30.1%, respectively. The habitats with very high (44.47 km2) and high (76.91 km2) suitability were elongated and fragmented on both sides of the Konglong River, which together accounted for 15% of the total area of the nature reserve. Furthermore, 28 habitat corridors with a width of 1000 m were designed in the river valley between the elevation of 500-1000 m a.s.l., of which the total length is 232.08 km and the area is 241.97 km2. Our results provided a scientific basis for the protection of Green Peafowl in China.