WATERSHED SCALE INVENTORY OF EXISTING RIPARIAN BUFFERS IN NORTHEAST MISSOURI USING GIS1

An observational study was conducted at the watershed scale using land cover (vegetation) data to assess the absence or presence of riparian buffers in three northeastern Missouri watersheds. Forests and grasslands lying within a 61 m (200 ft) parallel band directly adjacent to streams were considered “buffers” for improving or protecting water quality and were characterized according to their length, width, and vegetation type. Results indicated that riparian buffers were abundant throughout the watersheds but were typically narrow along first‐order and second‐order streams; in many cases they may not have been wide enough to provide adequate stream protection. At least 90 percent of all streams had buffer vegetation immediately adjacent to the streambanks, but as few as 31 percent of first‐order streams had buffers extending to 61 m from the stream on at least one side. On‐site evaluations are needed to determine the condition of these forests and grasslands and their ability to process nonpoint source pollutants. The results will be useful for providing natural resource managers with knowledge of current watershed conditions as well as in identifying specific locations for future conservation efforts within each watershed.     

1998年贵州省属长江流域地区洪涝灾害与森林植被的关系

１９９８年我国长江流域发生了历史上最严重的洪涝灾害．贵州地处长江上游,因此,本文对贵州省１９９８年长江流域地区雨情、灾情、森林植被在防灾、抗灾、减灾中的作用进行统计分析,并提出了洪涝灾害的防治对策措施。     

Adaptation of plant functional group composition to management changes in calcareous grassland

It is the aim of plant functional research to generate general rules of species assembly and species reactions based on plant functional traits. Here we determined plant functional groups that are important with regard to land use types (grazing, mowing, mulching, burning, abandonment) and looked for mechanisms leading to changes in species composition after management changes in calcareous grasslands.To filter out the set of traits which best described the variation in plant composition along the studied land use gradient and to identify functional groups we chose an iterative three-table ordination method. We included traits related to persistence as well as traits describing the germination niche of a plant. To gain insight into underlying mechanisms which led to differing importance of these plant functional groups at different management regimes we investigated shifts in dominance of the identified functional groups at eight management regimes using long-term vegetation data of a site which was grazed before the onset of different management regimes in 1974. Ongoing unidirectional changes in cover of the four determined functional groups at most of the treatments indicated that even after almost 30 years new equilibria of functional group composition were still not reached.The study showed that other management treatments but grazing and mowing led to changes in functional group composition, which were mainly driven by increasing dominance of a highly competitive species group.     

Development of plant communities on set-aside in England

A survey of land taken out of production from the early 1990s onwards under the European Union's set-aside policy in England was carried out in 2008, to record plant communities in set-aside of different ages, effects of distance from the field edge, sowing and soil type. Communities were classified using the Countryside Vegetation System (CVS), Ellenberg indicators and Grime CSR strategy. Species richness declined with distance from the field boundary. Annuals declined with age of set-aside. In older set-aside, perennials dominated, 40-50% of species were grasses, and grasses covered over 70% of the area. Sown areas had a higher proportion of grass species and a lower proportion of wind-dispersed species. Perennial forbs increased over time in naturally regenerated swards but decreased on sown swards. Annuals and grasses were more prevalent on light soils, with more bare ground on heavy soils. Most transects fell into CVS aggregate classes ‘tall grassland/herb’ and ‘fertile grassland’. Ellenberg fertility values decreased initially but then stabilised. Competitor scores increased, and ruderal scores declined, with age. In general, the rate of change declined with age. Although few sites had plant communities of significant conservation interest, the value of set-aside is likely to be primarily to maintain botanical diversity in intensively farmed areas, as well as providing food and habitat for fauna.     

考虑地形和土地覆盖影响的参数化台风风场模拟

现有参数化台风风场模型通常采用单一地表粗糙度假设,忽略地形和土地覆盖的影响,使得参数化台风风场模型不能真实反映台风风场。本文基于GTOPO30(Global Topographic Data of 30 arc seconds)全球数字高程数据和USGS(U.S.Geological Survey)全球土地覆盖数据,将地形地貌效应等效为地表粗糙长度,建立了受西北太平洋台风影响的东亚地区的地表粗糙长度空间分布;并对比验证了3个典型地貌的地表粗糙长度。然后,对参数化台风风场模型进行了适当修正,使其能耦合地形起伏对风场产生的抬升和沉降作用。以WRF(Weather Research and Forecasting)模式的模拟结果为基准,采用3个历史台风案例,考察了地形地貌对参数化台风风场模拟的影响。对比结果表明,考虑地形地貌效应可以显著提升参数化台风风场模型对台风空间结构的模拟能力。考虑地形地貌影响的参数化台风风场模型的模拟结果与实测结果吻合较好。     

Minimizing N2O fluxes from full-scale municipal solid waste landfill with properly selected cover soil

Municipal solid waste landfills emit nitrous oxide （N2O） gas. Assuming that the soil cover is the primary N2O source from landfills, this study tested, during a four-year project, the hypothesis that the proper use of chosen soils with fine texture minimizes N2O emissions. A full-scale sanitary landfill, a full-scale bioreactor landfill and a cell planted with Nerium indicum or Festuca arundinacea Schreb, at the Hangzhou Tianziling landfill in Hangzhou City were the test sites. The N2O emission rates from all test sites were considerably lower than those reported in the published reports. Specifically, the N2O emission rate was dependent on soil water content and nitrate concentrations in the cover soil. The effects of leachate recirculation and irrigation were minimal. Properly chosen cover soils applied to the landfills reduced N2O flux.     

Land Area Eligible for Afforestation and Reforestation within the Clean Development Mechanism: A Global Analysis of the Impact of Forest Definition

Within the United Nations Framework Convention on Climate Change (UNFCCC) Kyoto Protocol, countries have significant latitude to define a forest. The most important parameter affecting area designated as forest is the minimum crown cover which can be set between 10 and 30%. The choice will have implications for the amount of land available in a country for afforestation and reforestation activities within the Clean Development Mechanism (CDM-AR). In this paper, we present an analysis of the regional differences in land availability for CDM-AR projects. We then examine how the choice of a high or low threshold value for crown cover will affect the area available for CDM activities and how the limitations imposed by this element of the definition compares to other factors that are likely to limit CDM activities. Results represent a global analysis that included all countries not included in Annex I of the Kyoto Protocol, and examined the effect on land availability of a range of crown cover thresholds ranging from 10–30%. Of the 140 Non-Annex One countries, 107 countries were found to have a potential for CDM-AR projects. Asia had the largest amount of combined area suitable for CDM-AR at the 10% crown cover threshold level. However, at 30%, South America had the greatest amount of land available, and a large change in available land area, which increased by almost five times compared to what was available at the 10% threshold. The area available in Africa increased by a factor of 5.5. Central America showed the largest increase, to almost 10 times more at the 30% threshold. By contrast, within Asia, the area increase was comparatively less, but still the area nearly doubled. Globally, a low threshold of 10% crown cover excluded almost 2/3 of the land identified that was eligible at 30%, over 5 million km². The spatial analyses showed not only the effects of the choice of the crown cover criterion, but also where the land was available for CDM activities within each country at different thresholds. Protected areas account for 10–20% of the CDM-AR eligible area in most countries.     

甲烷胁迫下不同填埋场覆盖土的氧化活性及其菌群结构

对比研究了常规填埋场覆盖材料(粘土)和甲烷胁迫下垃圾生物处理后的材料(垃圾土)的甲烷氧化活性及其菌群结构.结果表明,粘土由于持水能力弱,其含水量较低,随着环境温度、降水等条件的变化,极易结块,从而影响其中甲烷氧化菌的生长;而垃圾土富含有机物,持水力强,空隙率高,有利于甲烷氧化菌的生长和繁殖.暴露于甲烷气流120 d后,垃圾土柱中下层土壤的甲烷氧化潜力达到了11.25～13.48 μmol/(g·h),是相应粘土层甲烷氧化潜力的10.4～24.5倍.土柱上层土壤由于水分蒸发、变干,抑制了其甲烷氧化活性.试验结束时,垃圾土柱甲烷氧化去除率达到了48.3%,是粘土柱的5～6倍.甲烷氧化菌TypeⅠ和TypeⅡ的生物标记物 PLFAs 16：1ω8c和18：1ω8c分析表明,土样的PLFA18：1ω8c含量与其甲烷氧化潜力具有很好的线性相关性.     

植被覆盖对沙尘天气滞后性影响的机制分析

1982～2000年卫星和335个气象台站沙尘天气观测资料相关分析显示,中国区域沙尘天气年发生频次与植被覆盖率存在非线性关系.在沙尘天气主要发生源地,夏季植被的覆盖状况会直接影响后期冬春两季各类沙尘天气的发生次数,而这种影响机制却不清楚.本研究通过准地转正压模式,从3个摩擦量级分析了上述现象的物理机制.结果表明,在大气与水面摩擦系数量级,最高可在72 h内使边界层大气风速平均下降90%;在大气与裸土摩擦量级,18 h内边界层大气平均风速最高可下降100%;在大气与植被摩擦量级,1 h内边界层大气平均风速就可以下降100%.观测事实和模拟结果证实,地表植被残存的根茎,是影响冬春两季沙尘天气发生频次的重要因素之一.残留根茎对大气的摩擦阻挡作用,是夏季植被对沙尘天气产生滞后性作用的主要机制.     

遥感技术在全球变化研究中的应用

全球变化是当今地球科学研究的热点。具有快速、多波段、周期性、大面积覆盖等观测能力的空间遥感技术,是全球环境变化研究中不可替代的重要手段。本文对全球变化研究的主要内容进行了简要回顾,对遥感技术在全球变化研究当中的地位和作用进行了论述。遥感技术在中国全球变化研究中的应用主要体现在土地覆盖、森林与草场、海洋调查与灾害监测等方面。这些研究为遥感技术在全球环境变化研究中的深入应用奠定了基础。