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1.
Selamyihun?Kidanu Tekalign?Mamo L.?StroosnijderEmail author 《Agroforestry Systems》2005,63(3):281-290
In recent years, Eucalyptus globulus planted along field boundaries has come to dominate the central highland landscape of Ethiopia. Although evidence is scanty,
there is a perception that this practice adversely affects crop productivity. An on-farm trial was conducted on Pellic Vertisol
at Ginchi to determine the production potential of eucalypt boundaries and their effect on the productivity of adjacent crops
of tef (Eragrostis tef) and wheat (Triticum sp.). The experiment comprised three stand ages, four field aspects and six distances from the tree-crop interface, using
a split-split plot design with three replicates. Wood production rates ranged between 168 kg ha−1 y−1 (four years old) and 2901 kg ha−1 y−1 (twelve years). Thus eucalypt boundaries planted on a hectare of land would satisfy 50 to 75% of the annual biomass energy
requirement of a rural household of five persons. Significant depression of tef and wheat yields occurred over the first 12m
from the tree line: the reduction was 20 to 73% for tef and 20 to 51% for wheat, equivalent to yield losses of 4.4 to 26%
and 4.5 to 10% per hectare respectively. Nevertheless, in financial terms, the tree component adequately compensated for crop
yield reduction and even generated additional income. Therefore, eucalypt boundaries have great potential to satisfy the rising
demand for wood, without requiring a major change in land use on the highland Vertisols. The greater availability of wood
will reduce the demand for dung and crop residues for fuel, and thus may contribute to improved soil management on croplands
while relieving the increasing pressure on indigenous forest and woodlands. 相似文献
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《国际水土保持研究(英文)》2020,8(2):164-172
Watershed development programmes carried out in different agroclimatic conditions in India resulted in beneficial impact in terms of productivity enhancement and natural resources conservation, but less attention paid to institutional and participatory aspects. This paper explored the performance of various institutions regarding execution of watershed development programmes in semi-arid region of India. Recorded observations from documents maintained at watershed level and information collected through primary survey as well as focus group discussion with different types of stakeholders were used for analysis. The results indicated lacunae in participatory aspects during programme implementation process like monitoring activities, management of common property resources and equity. Gap in linkages and differential level of performance of various watershed level functionaries indicates the necessity for corrections in the structures and linkages pattern for sustainability of the infrastructure and institutions. The study also showed unequal priorities by the implementing agencies towards institutions, land and water resources development, production enhancement activities and fodder resources development as well as rationalities of technical, economic, financial, political and social aspects among the watersheds. 相似文献
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在GIS环境下采用美国ESRI提供的水文模块,利用美国联邦地质调查局(USGS)提供的SRTM 90m DEM原始数据.以三江平原挠力河流域为例,进行了相关的流域分析,包括水流方向模拟、河网提取、流域界线划定及子流域划分等多项内容,为三江平原挠力河流域研究提供了基础的数据平台. 相似文献
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Human development of freshwater ecosystems has lead to drastic changes in freshwater fish faunas, including the loss of many native species and the gain of non-natives. Typically conservation ecologists view these two opposing forces as contributing to biological homogenization, and consider homogenization as one of the principle negative consequences of urbanization. However, homogenization is only one outcome out of many that can result from the loss and gain of species. In particular, it is possible for invasions and extinctions to lead to differentiation; a process whereby two (or more) regions become less similar to one another through time. Using the freshwater fishes of California, we show that urbanization is highly positively correlated to both the endangerment of native fish and the invasion of non-native fish within watersheds. Despite this, the fish faunas of California’s watersheds have differentiated from one another through time. Furthermore, the degree of differentiation is positively correlated with measures of urbanization, which is contrary to expectation. We suggest that this result reflects: (1) the haphazard manner in which non-native fishes have been introduced into California watersheds, (2) the difficulty that both native and non-native fishes have in expanding their geographical ranges, and (3) the continued presence of vestiges of formerly distinct regional faunas. This pattern of differentiation among watersheds is likely a matter of scale, as previous work on freshwater fishes has demonstrated homogenization at both larger and smaller spatial scales. In addition the observed pattern is probably a short-term (temporal) phenomena and will disappear with continued invasion and extinction. We suggest that similar patterns may occur for other taxa that have limited natural dispersal abilities and that are idiosyncratically released as non-natives via human activities (e.g. herptiles). 相似文献
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浙西山区上梧溪小流域生态恢复工程效益评价研究 总被引:4,自引:0,他引:4
研究分析了浙西上梧溪小流域生态恢复工程措施,采用层次分析及模糊综合分析相结合方法,建立了该小流域生态恢复工程效益综合评价指标体系,并用欧式距离模型结合模糊聚类分析法对生态恢复工程效益进行评估。 相似文献
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吴旗柴沟流域植被物种多样性研究 总被引:1,自引:0,他引:1
为了解吴旗县植被自然恢复的基本过程及其物种多样性变化,对该县柴沟流域封禁多年的植物群落进行了研究,结果表明:柴沟流域植物种主要以猪毛蒿、达乌里胡枝子、赖草、铁杆蒿为主,阳坡的植被演替规律为猪毛蒿+狗尾草+华虫实→赖草+猪毛蒿(达乌里胡枝子、铁杆蒿、隐子草)→达乌里胡枝子+赖草(百里香、冷蒿、角蒿、铁杆蒿),阴坡植被恢复的演替规律为猪毛蒿(达乌里胡枝子、赖草)→铁杆蒿(冷蒿)。柴沟流域阴坡群落的物种丰富度、多样性、均匀度都较高,阳坡较低,混交林地的丰富度最大、均匀度最小。 相似文献