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51.
52.
Delang CO 《Environmental management》2006,37(4):470-486
This article discusses the system of classification of forest types used by the Pwo Karen in Thung Yai Naresuan Wildlife Sanctuary
in western Thailand and the role of nontimber forest products (NTFPs), focusing on wild food plants, in Karen livelihoods.
The article argues that the Pwo Karen have two methods of forest classification, closely related to their swidden farming
practices. The first is used for forest land that has been, or can be, swiddened, and classifies forest types according to
growth conditions. The second system is used for land that is not suitable for cultivation and looks at soil properties and
slope. The article estimates the relative importance of each forest type in what concerns the collection of wild food plants.
A total of 134 wild food plant species were recorded in December 2004. They account for some 80–90% of the amount of edible
plants consumed by the Pwo Karen, and have a base value of Baht 11,505 per year, comparable to the cash incomes of many households.
The article argues that the Pwo Karen reliance on NTFPs has influenced their land-use and forest management practices. However,
by restricting the length of the fallow period, the Thai government has caused ecological changes that are challenging the
ability of the Karen to remain subsistence oriented. By ignoring shifting cultivators’ dependence on such products, the involvement
of governments in forest management, especially through restrictions imposed on swidden farming practices, is likely to have
a considerable impact on the livelihood strategies of these communities. 相似文献
53.
Measurement and Management of Human-Induced Patterns of Forest Fragmentation: A Case Study 总被引:1,自引:0,他引:1
Tole L 《Environmental management》2006,37(6):788-801
In many tropical developing countries, the twin pressures of population and poverty are resulting in substantial fragmentation
of forests, increasing the probability of extinction for many species, Forest fragmentation occurs when large contiguous forests
are perforated by small holes or broken up into edges and smaller patches to form a nonforested matrix of open spaces. Thus,
forest fragmentation refers not only to the area of forest cleared, but also to the pattern of this clearance, the resulting
forest’s spatial properties. Both characteristics are important for species survivability. Apart from opening up forests to
many abiotic and biotic influences, fragmentation can affect species dispersal and migration through its effects on forest
connectivity. Landscape ecology conceptualizes connectivity as a gradient of critical thresholds, ranging from the large intact
forest to the small unconnected forest patch. This article reports results from a multiple-scale analysis of forest fragmentation
in Jamaica’s Cockpit Country, an area of once contiguous forest now under threat from human encroachment. Spatial forest data
derived from classification of ETM+ satellite imagery are used to measure fragmentation patterns representing various degrees
of forest connectivity and density. The results suggest that, overall, 81% of the region is in forest. However, fragmentation
patterns also suggest that this forest is riven with extensive perforations indicative of an early stage in the decline of
contiguity. The results provided by the spatial fragmentation model are a first step in the design of effective conservation
and rehabilitation plans for the area. The article concludes with a discussion of possible multiscale management options for
the region. 相似文献
54.
55.
作为新兴生物燃料,大分子醇类燃料在低压下的火灾安全基础迫切需要得到深入研究。热解过程作为火灾过程的初始阶段直接控制着火过程,火灾中碳烟颗粒的产生也依赖于热解反应,因此可燃物的低压热解研究在其低压火灾基础研究中具有重要意义。利用同步辐射真空紫外光电离质谱方法研究了异戊醇在0.2atm下的流动反应器热解,探测到了20余种热解产物,包括烯丙基自由基和C_4H_8O、C_5H_8、C_6H_6等同分异构体,并测量了其摩尔分数。基于实验结果,对燃料分解路径和主要产物的生成及消耗路径进行了探讨。与本组之前正戊醇热解实验的对比表明,由于存在支链结构,异戊醇在热解中比正戊醇更容易产生戊烯、丁烯和丙烯,但更少地产生乙烯。此外,异戊醇在热解中能够生成更多的丙炔和丙二烯等环状化合物前驱体,令其苯和1,3-环戊二烯的生成量更高,表明异戊醇比正戊醇更易于生成多环芳烃和碳烟。 相似文献
56.
Johannes Kobler Walter J. Fitz Michael Mirtl 《Environmental pollution (Barking, Essex : 1987)》2010,158(3):849-854
Anthropogenic trace element emissions have declined. However, top soils all over the world remain enriched in trace elements. We investigated Pb and Cd migration in forest soils of a remote monitoring site in the Austrian limestone Alps between 1992 and 2004. Large spatial variability masked temporal changes in the mineral soil of Lithic Leptosols (Skeltic), whereas a significant reduction of Pb concentrations in their forest floors occurred. Reductions of concentrations in the less heterogeneous Cambisols (Chromic) were significant. In contrast, virtually no migration of Pb and Cd were found in Stagnosols due to their impeded drainage. Very low element concentrations (<1 μg l−1) in field-collected soil solutions using tension lysimeters (0.2 μm nylon filters) imply that migration largely occurred by preferential flow as particulate-bound species during intensive rainfall events. Our results indicate that the extent of Pb and Cd migration in soils is largely influenced by soil type. 相似文献
57.
虚拟耕地是指隐含在农产品贸易中,生产这些农产品过程中所必需占用的土地资源,有意识的在国际农产品贸易中实施虚拟耕地战略,对于平衡国内耕地赤字、保障粮食安全,发挥我国农产品在国际市场上的竞争优势具有重要的理论指导意义。首先介绍了虚拟耕地的定义及其量化方法,接着分析计算了我国谷物、油籽、棉花等几类主要农产品单位重量的虚拟耕地含量,在此基础上,对当前农产品进出口贸易中虚拟耕地的交易现状及未来发展趋势作了分析和预测。结果显示:近10 a来虚拟耕地净进口量出现持续增长,2006年,通过农产品国际贸易净进口虚拟耕地16602903.1 hm2,约占当年全国耕地总面积的12.77%。同时,虚拟耕地净进口量在今后若干年仍将保持增长态势。 相似文献
58.
We examined long-term data on water chemistry of Lake Rachelsee (Germany) following the changes in acidic depositions in central Europe since 1980s. Despite gradual chemical recovery of Rachelsee, its biological recovery was delayed. In 1999, lake recovery was abruptly reversed by a coincident forest die-back, which resulted in elevated terrestrial export of nitrate and ionic aluminum lasting ~5 years. This re-acidification episode provided unique opportunity to study plankton recovery in the rapidly recovering lake water after the abrupt decline in nitrate leaching from the catchment. There were sudden changes both in lake water chemistry and in plankton biomass structure, such as decreased bacterial filaments, increased phytoplankton biomass, and rotifer abundance. The shift from dominance of heterotrophic to autotrophic organisms suggested their substantial release from severe phosphorus stress. Such a rapid change in plankton structure in a lake recovering from acidity has, to the best of our knowledge, not been previously documented. 相似文献
59.
Amvrossios C. Bagtzoglou Eric D. Kenney April Hiscox David R. Miller 《Environmental Forensics》2014,15(2):147-158
This work applies optimization and an Eulerian inversion approach presented by Bagtzoglou and Baun in 2005 in order to reconstruct contaminant plume time histories and to identify the likely source of atmospheric contamination using data from a real test site for the first time. Present-day distribution of an atmospheric contaminant plume as well as data points reflecting the plume history allow the reconstruction and provide the plume velocity, distribution, and probable source. The method was tested to a hypothetical case and with data from the Forest Atmosphere Transfer and Storage (FACTS) experiment in the Duke experimental forest site. In the scenarios presented herein, as well as in numerous cases tested for verification purposes, the model conserved mass, successfully located the peak of the plume, and managed to capture the motion of the plume well but underestimated the contaminant peak. 相似文献
60.
Quantification of nitrate leaching from German forest ecosystems by use of a process oriented biogeochemical model 总被引:1,自引:0,他引:1
Kiese R Heinzeller C Werner C Wochele S Grote R Butterbach-Bahl K 《Environmental pollution (Barking, Essex : 1987)》2011,159(11):3204-3214
Simulations with the process oriented Forest-DNDC model showed reasonable to good agreement with observations of soil water contents of different soil layers, annual amounts of seepage water and approximated rates of nitrate leaching at 79 sites across Germany. Following site evaluation, Forest-DNDC was coupled to a GIS to assess nitrate leaching from German forest ecosystems for the year 2000. At national scale leaching rates varied in a range of 0–>80 kg NO3–N ha−1 yr−1 (mean 5.5 kg NO3–N ha−1 yr−1). A comparison of regional simulations with the results of a nitrate inventory study for Bavaria showed that measured and simulated percentages for different nitrate leaching classes (0–5 kg N ha−1 yr−1:66% vs. 74%, 5–15 kg N ha−1 yr−1:20% vs. 20%, >15 kg N ha−1 yr−1:14% vs. 6%) were in good agreement. Mean nitrate concentrations in seepage water ranged between 0 and 23 mg NO3–N l−1. 相似文献