金沙江头塘小流域人工林有机碳及其剖面分布特征

采用野外调查、室内分析并结合相关的方法,研究探讨了金沙江头塘小流域7种不同植被恢复人工林土壤剖面层次有机碳(SOC)含量、有机碳密度(SOCD)和有机碳储量及分布特征。结果表明,不同林分类型及土层间土壤SOC含量存在明显差异:就整个土层(0~100 cm)而言,7种林分土壤SOC平均含量介于6.46±1.67~24.95±2.32 g·kg–1,大小依次为柳杉林旱冬瓜林圆柏林栓皮栎林圣诞树林墨西哥林藏柏林,且差异显著(p0.05);7种林分土壤SOC含量均出现表聚现象,从表层到深层都呈现递减趋势,且具有一定的规律性;7种林分土壤容重总体上均表现为随土层深度的增加逐渐增加,土壤容重表现为:柳杉林栓皮栎林圣诞树林圆柏林旱冬瓜林墨西哥柏林、藏柏林;7种林分土壤有机碳密度垂直分布和土壤有机碳含量垂直分布特征一致,随土层深度增加土壤有机碳密度减少,以表土10 cm的土壤有机碳密度最大;有机碳储量均随着土层加深所占比例逐渐降低,同时土壤有机碳主要集中于土层0~40 cm内,分别占总有机碳的65.60%(圣诞树林)、63.16%(旱冬瓜林)、54.41%(墨西哥柏林)、58.56%(圆柏林)、62.96%(藏柏林)、61.70%(栓皮栎林)和56.37%(柳杉林),0~40 cm土层土壤有机碳占总有机碳的百分比均达到50%以上。     

2008-2009年中国北方干旱遥感动态监测

干旱是威胁我国及世界农业发展的自然灾害之一,利用遥感技术进行干旱监测与评估已成为一种重要而有效的手段。2008年10月至2009年2月,我国北方地区出现了大面积的持续干旱,给冬小麦的生长造成了严重的影响。基于2000年至2009年Terra卫星MODIS传感器8天合成的地表反射率数据,结合地面实测土壤水分和实地调研数据,利用距平植被指数(AVI)和距平水分指数(AWI)对我国北方冬小麦主产区的干旱程度进行了分级,对干旱的发生、发展和时空变化情况进行了连续监测,得到了该时期的旱情分布结果:2008年10月份以后旱情逐渐加重,2009年1月下旬各地旱情达到了最严重的程度。研究表明,AWI对干旱的反应比AVI敏感而且准确。     

城市绿地生态综合评价研究进展

以"四川省地震灾后置建社会满意度调查"数据为依据,通过因子分析,找到影响社会满意度的关键因素,确立低碳模式为灾后和谐社会建设的最佳模式.通过对低碳社会的特征分析,结合社会学理论,认为:低碳社会的发展是低碳价值理念、低碳准则、低碳行为互相作用的过程.低碳社会模式的发展路径是基于综合集成与统筹优选的方法,从价值理念、低碳行为、规范体系三个方面对低碳社会的各项要素进行集成:低碳社会的推行模式分为低碳农村模式和低碳城市模式.低碳农村可以与灾区社会主义新农村建设同步进行,发展生态经济,探索生态发展模式和生态补偿政策;低碳城市相对于一般社会发展模式和农村发展模式,更集中体现在建筑、交通、文化、消费行为等某些特定领域.建议:从国家到灾区的各级政府必须多管齐下,从制度创新入手,实施一系列相互配套、切实有效的对策及措施,如转变单纯追求GDP的政策目标,制定法律法规,促进新能源开发,建立低碳技术支撑体系等来保障低碳社会模式的推行.     

Flora and Vegetation of Tasiilaq,Formerly Angmagssalik,Southeast Greenland: A Comparison of Data Between Around 1900 and 2007

The changes in the vascular plant flora of Tasiilaq, low arctic Southeast Greenland, between around 1900 and 2007 were studied by comparing the data from historical literature with those of the field observations performed between the late 1960s and 2007. Since 1900, the percentage of widely distributed arctic species distinctly decreased, whereas that of the low arctic species somewhat increased, and boreal species hardly increased. Vegetation monitoring revealed minor changes and showed that several thermophilous and xerophilous species increased between 1968/1969 and 2007, whereas some hygrophilous species decreased. Repeated vegetation mapping of a shallow pond revealed conspicuous changes suggesting increased evaporation/precipitation ratios associated with environmental warming up and decreasing snow accumulation in winter, in line with results of previous investigations. In spite of climate warming, expansion of the town and increasing human impact, flora and vegetation on the whole appeared rather stable during the last 40 years without invading species or introductions.     

Rainfall Runoff Relationships for a Cloud Forest Watershed in Central America: Implications for Water Resource Engineering1

Caballero, Luis A., Alon Rimmer, Zachary M. Easton, and Tammo S. Steenhuis, 2012. Rainfall Runoff Relationships for a Cloud Forest Watershed in Central America: Implications for Water Resource Engineering. Journal of the American Water Resources Association (JAWRA) 48(5): 1022‐1031. DOI: 10.1111/j.1752‐1688.2012.00668.x Abstract: Understanding the basic relationships between rainfall and runoff is vital for effective management and utilization of scarce water resources. Especially, this is important in Central America with widespread potable water shortage during the dry months of the monsoon. Potential good water sources are cloud forests, but little information concerning its potential is available to water supply engineers. Our objective is to define rainfall‐runoff‐base flow relationships for a cloud forest catchment. Flumes were installed for measuring river flow in four subwatersheds in La Tigra National Park, Honduras. One of the four watersheds was a 636‐ha subwatershed (WS1) with 60% cloud forest coverage. Precipitation averaged 1,130 mm/yr over the entire basin. About half of the total rainfall became runoff for the cloud forest watershed whereas, for the adjacent undisturbed forested watershed, the total discharge was <20% of the amount of precipitation. Infiltration rates were generally greater than rainfall rates. Therefore, most rainfall infiltrated into the soil, especially in the upper, steep, and well‐drained portions of the watershed. Direct runoff was generated from saturated areas near the river and exposed bedrock. This research provides compelling evidence that base flow is the primary contributor to streamflow during both wet and dry seasons in cloud forest catchments. Protecting these flow processes over time is critical for the sustained provision of potable water.     

Multi-decadal changes in tundra environments and ecosystems: synthesis of the International Polar Year-Back to the Future project (IPY-BTF)

Understanding the responses of tundra systems to global change has global implications. Most tundra regions lack sustained environmental monitoring and one of the only ways to document multi-decadal change is to resample historic research sites. The International Polar Year (IPY) provided a unique opportunity for such research through the Back to the Future (BTF) project (IPY project #512). This article synthesizes the results from 13 papers within this Ambio Special Issue. Abiotic changes include glacial recession in the Altai Mountains, Russia; increased snow depth and hardness, permafrost warming, and increased growing season length in sub-arctic Sweden; drying of ponds in Greenland; increased nutrient availability in Alaskan tundra ponds, and warming at most locations studied. Biotic changes ranged from relatively minor plant community change at two sites in Greenland to moderate change in the Yukon, and to dramatic increases in shrub and tree density on Herschel Island, and in subarctic Sweden. The population of geese tripled at one site in northeast Greenland where biomass in non-grazed plots doubled. A model parameterized using results from a BTF study forecasts substantial declines in all snowbeds and increases in shrub tundra on Niwot Ridge, Colorado over the next century. In general, results support and provide improved capacities for validating experimental manipulation, remote sensing, and modeling studies.     

Arsenic and mercury bioaccumulation in the aquatic plant, Vallisneria neotropicalis

Arsenic (As) and mercury (Hg) are among the most toxic metals/metalloids. The overall goal of this study was to investigate the bioaccumulation of these trace elements in Vallisneria neotropicalis, a key trophic species in aquatic environments. For this purpose, As and Hg concentrations were determined in sediments and natural populations of V. neotropicalis in sub-estuaries of Mobile Bay (Alabama, USA), differing with respect to past and present anthropogenic impact. Analyses indicate that the Fish River is the most contaminated among the sub-estuaries investigated; levels of As found in Fish River sediments fall within a range that could potentially cause adverse effects in biota. Sediment As concentrations were only moderately correlated with those in V. neotropicalis; no correlation was found between sediment and plant Hg levels. However, several parameters could have masked such potential relationships (e.g., differences in sediment characteristics and “biological dilution” phenomena). Results presented herein highlight the numerous parameters that can influence metal/metalloids accumulation in aquatic plants as well as species-specific responses to trace element contamination. Finally, this study underscores the need for further investigation into contaminant bioaccumulation in ecologically and economically important coastal environments.     

Carbon exchange between ecosystems and atmosphere in the Czech Republic is affected by climate factors

By comparing five ecosystem types in the Czech Republic over several years, we recorded the highest carbon sequestration potential in an evergreen Norway spruce forest (100%) and an agroecosystem (65%), followed by European beech forest (25%) and a wetland ecosystem (20%). Because of a massive ecosystem respiration, the final carbon gain of the grassland was negative. Climate was shown to be an important factor of carbon uptake by ecosystems: by varying the growing season length (a 22-d longer season in 2005 than in 2007 increased carbon sink by 13%) or by the effect of short- term synoptic situations (e.g. summer hot and dry days reduced net carbon storage by 58% relative to hot and wet days). Carbon uptake is strongly affected by the ontogeny and a production strategy which is demonstrated by the comparison of seasonal course of carbon uptake between coniferous (Norway spruce) and deciduous (European beech) stands.     

昆阳磷矿植被恢复地土壤肥力状况分析及评价

采用野外调查、室内分析并结合相关的方法,对昆阳磷矿人工林植被恢复样地土壤养分指标进行研究,以对矿区植被恢复地土壤肥力现状进行科学合理的评价。结果表明：矿区植被恢复地土壤的容重均小于18 g/cm,孔隙多,结构性较好,有益于植物的生长;植被恢复地土壤样本的有机质含量缺乏,全氮和碱解氮含量属于中等和较缺乏水平,全磷和有效磷、全钾和速效钾含量极为丰富。土壤有机质、有效磷,变异系数较大,分布不均匀,碱解氮、全氮、全磷、速效钾为中等变异的养分指标,变异系数相对小些,土壤中全钾呈弱变异,在土壤中的含量相对分布比较均匀。通过灰色关联度分析,得出研究区不同植被类型或不同年代组合恢复模式土壤肥力顺序为：2005年恢复的旱冬瓜+藏柏+麻栎林＞2006年恢复的旱冬瓜+藏柏+麻栎林＞2007年恢复的旱冬瓜+藏柏林＞平台覆土＞2005年恢复的旱冬瓜+藏柏林＞2005年恢复的旱冬瓜+藏柏+墨西哥柏林     

Effect of Coal Mine Soil Contamination on the Elemental Uptake and Distribution in Two Edible Amaranthus Species,A. dubius and A. hybridus

The impact of coal mine dump contaminated soil on the elemental uptake by two edible plants, namely, Amaranthus dubius (red herbs) and Amaranthus hybridus (green herbs), was studied by investigating their response and ability to tolerate and accumulate varying levels of elements in their roots and shoots. The vegetation was grown on varying amounts of contaminated soil, viz. 0%, 5%, 15%, 25% w/w using coal mine dump soil. The soil was analyzed for soil pH, cation exchange capacity (CEC), soil organic matter (SOM), moisture content, and selected heavy metals. The distribution of six metals, namely, Pb, Cd, Hg, Ni, Mn, and Fe, in roots, stem, and leaves of the plants was determined in two stages of growth after 5 weeks and 10 weeks. All soil and plant samples were microwave digested and subjected to heavy metal analysis using the ICP-OES, GFAAS, and CVAAS. The pH of the coal mine dump contaminated soil decreased with an increase in contamination. Both the SOM and CEC values decreased, which increases the availability of elements, by providing more binding sites in the soil. Relatively, the red herbs had higher elemental concentrations than the green herbs. Both plants recorded high manganese accumulation. No mercury was detected in the soils or plants.