基于改进突变级数法的典型喀斯特峰丛洼地生态安全预警评价——以贵州省平塘县19个乡镇为例

以喀斯特地貌发育典型的贵州省平塘县为研究对象,以乡镇为评价单元,根据自然-社会-经济(NSE)模型构建生态安全预警评价指标体系,采取熵权层次相结合法确定指标权重,运用改进突变级数法计算生态安全预警指数,旨在为平塘县生态可持续发展提供理论参考.结果表明:2011—2013年平塘县各乡镇生态安全预警指数为0.6~0.8,均属于中警,其中卡罗乡、新塘乡、西凉乡、四寨镇生态安全预警指数呈增大变化趋势,生态安全得到改善;大塘镇、掌布乡生态安全预警指数呈减小变化趋势,生态安全略显退化;平湖镇、苗二河乡、卡蒲乡等呈先减小再增大的变化趋势,生态安全呈波动变化.

Analysis of Grassland Productivity and Carrying Capacity of Natural Warm-temperature Tussock in the Central Region of Guizhou Province

[Objective] This study aimed to investigate the influences of grazing and fencing on grassland productivity and carrying capacity of subtropical natural warmtemperature tussock. [Method] With the natural warm temperature tussock in Longli County of Guizhou Province as study area, monthly, seasonal and annual dynamics of grassland productivity were investigate continuously during 2010 -2012, and the data were analyzed. [Result] Under grazing and fencing conditions, grassland present biomass and forage growth of warm temperature tussock in Longli County of Guizhou Province both increased first and decreased, reaching the maximum from August to October. Fencing significantly improved the productivity of natural grassland but had little effect on the vegetation composition. [Conclusion] From the perspective of grass-livestock balance, the suitable stocking capacity of warm-temperature tussock in the central region of Guizhou Province was 3.45 -4.66 sheep/hm2 , which has high ecological efficiency and can be borne by farmers and herdsmen.

Carbon Sequestration Effects of Shrublands in Three-North Shelterbelt Forest Region, China

Three-North Shelterbelt Forest （TSF） program, is one of six key forestry programs and has a 73-year construction period, from 1978 to 2050. Quantitative analysis of the carbon sequestration of shrubs in this region is important for understanding the overall function of carbon sequestration of the forest and other terrestrial ecosystems in China. This study investigated the distribution area of shrubland in the TSF region based on remote sensing images in 1978 and 2008, and calculated the carbon density of shrubland in combination with the field investigation and previous data from published papers. The carbon sequestration quantity and rate from 1978 to 2008 was analyzed for four sub-regions and different types of shrubs in the TSF region. The results revealed that： 1） The area of shrubland in the study area and its four sub-regions increased during the past thirty years. The area of shrubland for the whole region in 2008 was 1.2 × 10^7 ha, 72.8% larger than that in 1978. The Inner Mongolia-Xinjiang Sub-region was the largest shrubland distribution area, while the highest coverage rate was found in the North China Sub-region. 2） In decreasing order of their carbon sequestration, the four types of shrubs considered in this study were Hippophae rhamnoides, Caragana spp., Haloxylon ammodendron and Vitex negundo vat. heterophylla. The carbon sequestration of/-/, rhamnoides, with a maximum mean carbon density of 16.5 Mg C/ha, was significantly higher than that of the other three species. 3） The total carbon sequestration of shrubland in the study region was 4.5 x 107 Mg C with a mean annual carbon sequestration of 1.5× 10^6 Mg C. The carbon density in the four sub-regions decreased in the following order： the Loess Plateau Sub-region, the North China Sub-region, the Northeast China Sub-region and the Inner Mongolia-Xinjiang Sub-region. The paucity of studies and data availability on the large-scale carbon sequestration of shrub species suggests this study provides a baseline reference for future research in this area.

Roosting Territory of White Ear-Lobed Red Jungle Fowl （Gallus gallus gallus）

RJF （red jungle fowl） （Gallus gallus gallus） is territorial birds. Only males advertise and defend territory by metals of crows and combat fighting in severe cases. Crows are testosterone dependent and use up to 4-5% of their basal metabolic rate. Crows race individual voice signatures which differ in tone, duration and vibration. Crows together with radio-telemetry were used here to locate night roosts of dominant males. Between 2005 and 2009, 10 despots were intensively monitored. Outermost locations of individual＇s roosts were connected to form territory and a distance of 50 m was buffered to individual＇s territory to yield home range. Data indicated strong site fidelity of dominant males. The longest territory tenure was 31 months. The life time territory of males was on average 10.24 ha （±1.73 SE） and a home range was 17.59 ha （±2.15 SE）. Average yearly territory vmcied between 5.48 and 10.88 ha per individual and rarely overlapped. Some roosts were used repeatedly at the same point. In the night, RJF was relatively safe and difficult to approach both vertically and horizontally. Roost site selections were thus a trade-off between security and territory proclamation.

Shrub Communities and Environmental Variables Responsible for Species Distribution Patterns in an Alpine Zone of the Qilian Mountains, Northwest China

Understanding the factors that drive variation in species distribution is a central theme of ecological research. Although several studies focused on alpine vegetation, few efforts have been made to identify the environmental factors that are responsible for the variations in species composition and richness of alpine shrublands using numerical methods. In the present study, we investigated vegetation and associated environmental variables from 45 sample plots in the middle Qilian Mountains of the northwestern China to classify different community types and to elucidate the species- environment relationships. We also estimated the relative contributions of topography and site conditions to spatial distribution patterns of the shrub communities using the variation partitioning. The results showed that four shrub community types were identified and striking differences in fioristic composition were found among them. Species composition greatly depended on elevation, slope, shrub cover, soil pH and organic carbon. The important determinants of species richness were soil bulk density and slope. No significant differences in species richness were detected among the community types. Topography and site conditions had almost equal effects on compositional variation. Nonetheless,a large amount of the variation in species composition remained unexplained.

Integration of remotely sensed indices for land cover changes caused by the 2009 Victorian bushfires using Landsat TM imagery

In order to minimise the bushfires negative impacts on society, an efficient andreliable bushfire detection system was proposed to assess the devastated effects of the2009 Victorian bushfires.It is possible to utilise the repetitive capability of satellite remotesensing imagery to identify the location of change to the Earth's surface and integrate thedifferent remotely sensed indices.The results confirm that the procedure can offer essentialspatial information for bushfire assessment.

Competition and abiotic stress affect the size of mangroves near their geographic range limit

Studies of competition in mangroves are mostly limited to seedlings and artificial settings like forestry projects.We conducted the first experimental study of intraspecific competition among adult mangroves in a natural mangrove forest to examine how important competition is in determining tree size compared with abiotic conditions.We conducted a study near Port Aransas,TX,USA,which is near the geographical limit of mangroves and dominated by monospecific stands of‘scrub’form black mangroves,Avicennia germinans.We thinned 10 plots to create a gradient of mangrove cover,and quantified the effects of mangrove cover on the growth of tagged mangroves from 2013 to 2019,and the mangrove canopy height in 2019.The relative growth rate of tagged mangroves declined as mangrove cover increased,and plants in the plot with 100%mangrove cover did not grow,indicating that they had attained their maximum size.In plots with reduced mangrove cover,plant height increased sharply,with plants in the plot with 11%mangrove cover growing~52%taller over 6 years.Canopy height was~30%taller in the plot fringe than in the interior,and canopy height in both fringe and interior declined as mangrove cover increased.Measures of leaf chlorophyll concentration and light interception suggested that plants were primarily limited by nitrogen.Our results showed that scrub mangroves compete strongly despite being limited by abiotic conditions,and that the importance of competition was greater in magnitude than that of abiotic differences between the fringe and interior.

Dynamic Changes of the Bush Encroachment in Low Altitude Area of Ethiopia

Bush encroachment is widely distributed in arid and semi-arid regions, and it has a serious impact on livestock production, especially in Africa where livestock is a primary source for the livelihoods of many people. In this study, methods of supervised classification and decision tree classification, and indexes of a land use change significance index（Ci） and a single land use dynamic degree, were applied to remote sensing imagery of Ethiopia for 1986–2016. The results show the dynamic characteristics of grassland bush encroachment in low altitude areas（pastures 1500 m above sea level） of Ethiopia in the 30 year period studied. The results revealed several interesting features of this phenomenon.（1） The area of bush encroachment showed an increasing trend, with a maximum of 3.74×10^3 km^2 in 2003, which represented 68.97% of the total area, and declined slightly from 2003~2016.（2） Among classification types, the area of severe shrub grassland was the largest, accounting for 28.36–49.10% of the total area, while the area of moderate bush encroachment accounted for 9.77–16.68%, and slight bush encroachment accounted for 5.52–7.57%.（3） The expansion rate of shrubby grassland was 0.74% for the 30 year period, while the average annual expansion rate was 2.16% for the 8 years from 1995–2003.（4） Forest land and grassland were the two main land use types of shrub grassland transformation in low altitude areas and bush encroachment changed large amounts of forest land into grassland due to shrub grassland management. The results of this study provide basic data for revealing the impacts of development processes on subsequent bush encroachment and can inform better management for the sustainable development of grasslands in low altitude systems.

Arbuscular Mycorrhizal Fungi in Wetland Habitats and Their Application in Constructed Wetland: A Review

Over the last three decades, the presence and functional roles of arbuscular mycorrhizal （AM） fungi in wetland habitats have received increasing attention. This review summarized the mycorrhizal status in wetlands and the effect of flooding on AM fungal colonization. Plants of 99 families living in 31 different habitats have been found to be associated with AM fungi, even including submerged aquatic plants and several plant species that were thought to be nonmycorrhizal （Cyperaceae, Chenopodiaceae, and Plumbaginaceac）. The functions of AM fungi in wetland ecological systems could be concluded as their influences on the composition, succession, and diversity of the wetland plant community, and the growth and nutrition of wetland plants. Affecting the composition, succession, and diversity of the wetland plant community, AM fungi have positive, negative, or neutral effects on the performance of different wetland species under different conditions. The factors that affect the application effect of AM fungi in constructed wetland （CW） include flooding, phosphorus, plant species, aerenchyma, salinity, CW types, operation modes of CW, and wastewater quality. The generalist AM fungi strains can be established spontaneously, rapidly, and extensively in wastewater bioremediation technical installations; therefore, AM fungi can be considered ideal inhabitants of technical installations for the plant-based bioremediation of groundwater contaminated by organic pollutants or other contaminants. In the future, roles of AM fungi and factors that affect the purifying capacity of AM-CW system must be understood to optimize CW ecosystem.