路域土壤重金属含量空间变异的影响因子

以纵向岭谷区景洪-思茅段公路沿线为研究区,通过公路不同地点样线布设,对不同土地类型、地形和公路距离下的98个样点进行了野外植被和环境因子调查及土壤采样,在土壤表层0～20cm重金属全量分析的基础上对影响其分布的环境因子做了相关分析,得出研究区路域土壤重金属污染的空间分异特征及其主要的影响因子.研究结果表明,公路沿线不同土地利用类型下土壤重金属元素的含量存在较大的差异,但不同类型下含量的变化趋势较为一致,草地重金属污染最为严重,而次生林,原始林重金属含量较低;土壤养分也受土地利用类型影响,但相关分析表明,除了pH值、总钾、总磷和重金属关系较为密切外,研究区其它土壤养分和重金属之间的含量相关不显著.重金属元素含量之间相关性显著,表明该段道路重金属污染具有同源性,即来自道路.距公路的距离对重金属含量影响较大,农田土壤重金属含量随距离公路增加逐渐降低,而自然土壤中,变化趋势呈波动趋势.进一步对自然土壤中重金属的影响因子做了分析,结果表明,地形影响重金属的含量垂直分异,而典范对应分析也显示研究区距离、地形、土地覆被和土壤特性共同作用于土壤污染的空间变异.影响程度为距离＞土地覆被＞地形＞土壤.     

Regional multiresource models in a national framework

The design and integration of models projecting the effects of management on environmental systems is one step in the environmental planning process. Interactions between resources produced on the same unit of land under current and future management can be examined only when assumptions and processes of these dynamic environmental systems are quantified. Multiresource interaction models have generally been large and cumbersome while also suffering from an inadequate amount of detail. This article presents a conceptual framework for integrating individual resource models to project multiresource interactions at a regional scale. Land management impact projections require common definitions of the total land base and common definitions of management activities applied to the same land unit. A case example focusing on the resources of timber, forage, wildlife, fish, and water for the southern United States is presented.     

Shrub Encroachment Impacts the Potential for Multiple Use Conflicts on Public Land

Public rangelands in North America are typically managed under a multiple use policy that includes livestock grazing and wildlife management. In this article we report on the landscape level extent of grassland loss to shrub encroachment in a portion of the Rocky Mountain Forest Reserve in southwestern Alberta, Canada, and review the associated implications for simultaneously supporting livestock and wildlife populations while maintaining range health on this diminishing vegetation type. Digitized aerial photographs of 12 km of valley bottom from 1958 and 1974 were co-registered to ortho-rectified digital imagery taken in 1998, and an un-supervised classification used to determine areas associated with grassland and shrubland in each year. Field data from 2002 were over-layed using GPS coordinates to refine the classification using a calibration-validation procedure. Over the 40-year study period, open grasslands declined from 1,111 ha in 1958 to 465 ha in 1998, representing a 58% decrease. Using mean production data for grass and shrub dominated areas we then quantified aggregate changes in grazing capacity of both primary (grassland) and secondary (shrubland) habitats for livestock and wildlife. Total declines in grazing capacity from 1958 to 1998 totaled 2,744 Animal Unit Months (AUMs) of forage (−39%), including a 58% decrease in primary (i.e., open grassland) range, which was only partly offset by the availability of 1,357 AUMs within less productive and less accessible shrubland habitats. Our results indicate shrub encroachment has been extensive and significantly reduced forage availability to domestic livestock and wildlife, and will increase the difficulty of conserving remaining grasslands. Although current grazing capacities remain marginally above those specified by regulated grazing policies, it is clear that continued habitat change and decreases in forage availability are likely to threaten the condition of remaining grasslands. Unless shrub encroachment is arrested or grassland restoration initiated, reductions in aggregate ungulate numbers may be necessary.

A TREE‐RING RECONSTRUCTION OF STREAMFLOW FOR THE COLORADO FRONT RANGE1

ABSTRACT: Water resource planning is based primarily on 20th century instrumental records of climate and streamflow. These records are limited in length to approximately 100 years, in the best cases, and can reflect only a portion of the range of natural variability. The instrumental record neither can be used to gage the unusualness of 20th Century extreme low flow events, nor does it allow the detection of low‐frequency variability that may underlie short‐term variations in flow. In this study, tree rings are used to reconstruct mean annual streamflow for Middle Boulder Creek in the Colorado Front Range, a semi‐arid region of rapid growth and development. The reconstruction is based on a stepwise regression equation that accounts for 70 percent of the variance in the instrumental record, and extends from 1703–1987. The reconstruction suggests that the instrumental record of streamflow for Middle Boulder Creek is not representative of flow in past centuries and that several low flow events in the 19th century were more persistent than any in the 20th century. The 1840s to early 1850s period of low flow is a particularly notable event and may have coincided with a period of low flow in the Upper Colorado River Basin.     

论现有环境质量综合指数的可能虚假性

通过各种例子,利用数学分析方法,得出如下结论:①现有的许多环境质量综合指数都存在着可能的虚假性,而这种虚假性是由数学模式本身的性质所决定的;②对于一个数学模式来说,当综合指数一定时,单项指数的值域也是一定的。      

Glacier Variability (1967‐2006) in the Teton Range,Wyoming, United States1

Edmunds, Jake, Glenn Tootle, Greg Kerr, Ramesh Sivanpillai, and Larry Pochop, 2011. Glacier Variability (1967‐2006) in the Teton Range, Wyoming, United States. Journal of the American Water Resources Association (JAWRA) 48(1): 187‐196. DOI: 10.1111/j.1752‐1688.2011.00607.x Abstract: Glacier area and volume changes were quantified through the use of historical aerial photographs in Wyoming’s Teton Range. Glacier area changes in the Teton Range were estimated for three glaciers using unrectified aerial photography from 1967 to 2006. The total surface area of the three glaciers was 0.53 km² in 1967 and 0.40 km² in 2006, a decrease of 25% during the 39‐year period. The smallest glacier, Teepe, experienced the greatest area loss (60 ± 3%), whereas the largest glacier, Teton Glacier, lost 17 ± 3% of the 1967 area. For the current research, aerial photography from 1967 to 2002 was used to estimate glacier volume loss using stereoscopy techniques. The aerial photographs provide a finer resolution when compared with other datasets including satellite imagery (e.g., Landsat). Volume loss for the three glaciers was estimated to be 3.20 ± 0.46 million cubic meters over the period of 1967 to 2002. In assessing the primary climatic driver of the glacier ice loss, observed summer (June, July, and August) temperature data showed a statistically significant increase in temperatures when comparing the period of study (1968 to 2006) with historical temperatures from 1911 to 1967. When comparing spring (April 1st Snow Water Equivalent) snowpack for the period of study with historical records beginning in 1931, a significant difference in snowpack was not observed.     

念青唐古拉山西段小冰期以来冰川变化

小冰期是指15世纪到20世纪早期之间一系列相对寒冷的气候波动阶段,研究小冰期以来的冰川规模变化,对于了解百年尺度上冰川变化及其气候指示意义具有重要意义。利用Google Earth和Arc GIS10.3研究了念青唐古拉山西段的现代冰川和小冰期冰川,统计了冰川的基本信息和小冰期以来的变化情况,分析了面积、高程、坡度和坡向因素对冰川变化的影响,探讨了平衡线高度变化的气候指示意义。结果表明:念青唐古拉山西段共发育现代冰川847条,总面积约689.71 km~2,共识别出小冰期冰川306条,总面积约746.12 km~2。小冰期以来冰川面积减少约31%,平衡线高度平均上升约58 m,冰川的面积、坡度和高程对冰川面积变化的解释率为71%,平衡线高度变化与印度季风关系密切。     

Assessment of the rangelands of southwestern Santiago del Estero, Argentina, for grazing management and research

Native rangelands of the southwest part of the province of Santiago del Estero, Argentina, are a key source of forage for cow-calf operations. The objectives of this study were to delineate the ecosystem units of the area, to describe the associated plant communities and to interpret the role that physical factors and disturbances such as fire and grazing have had in the changes of the structure of these plant communities. This information is needed for developing recommendations for grazing management, for prescribing appropriate improvement practices (e.g. shrub control, prescribed fire) and as guidelines for future research. The ecosystem was divided into smaller units using a hierarchical method, the categories of practical importance being 'range unit' and 'range site'. They represent the catchment and hillslope scale of the water runoff-runon phenomenon, respectively. Vegetation was sampled using a block and cluster sampling design, registering tree, shrub, forb and grass species frequency, and the standing aerial biomass of the herbaceous layer in a sampling unit=1 ha. Environmental data (topographic position, fire frequency, current and past use, and tree and shrub cover) were also registered for each sampling unit. Indirect ordination of sampling units classified according to range units and range sites, and correlation with environmental variables were performed using multidimensional scaling (MDS) as well as the vector fitting technique. Standing forage and stocking rate were estimated from biomass data. Results indicate that 'range site' is the ecosystem unit that should be considered for management purposes since it correlates well with plant communities: tall, hardwood forests are located on upland sites, woodlands are located on midland sites and savannas are located on lowland sites. Dense shrub thickets dominate in areas rated in poor condition, irrespective of range site. Disturbances such as fire and current and past use have a significant positive and negative correlation with range condition, respectively, suggesting that a state and transition model would explain vegetation dynamics better than the succession model. The estimated stocking rate in lowland sites in good condition was 2 ha UG(-1), while in upland sites in poor condition the stocking rate was 90 ha UG(-1). Active (fire, mechanical treatments) rather than passive (grazing management) methods should be used for range improvement in order to achieve the full potential of the ecosystem.