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11.
南、北盘江流域(贵州部分)土地退化类型及机理 总被引:1,自引:0,他引:1
在对珠江上游南、北盘江流域(贵州部分)调查的基础上,分析了该流域土地退化成因,原生生态系统的脆弱性只是导致土地退化的一个方面。而人为活动才是土地退化的主要因素。根据土地退化的成因、结果,将珠江上游南、北盘江流域(贵州部分)土地退化划分为:土壤侵蚀、石漠化、土地贫瘠、土壤污染、土壤破坏五种类型,并提出了退化土地的管理及恢复措施。 相似文献
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履带式拖拉机和轮式拖拉机由于其走行机构的不同,其集材道土壤压实也存在差异,特别衡量土壤压实的两个重要指标——土壤硬度和孔隙度——两种机型不一致。通过对调查测定数据进行计算处理以及用灰色系统理论进行动态分析,结果表明:与轮式拖拉机相比,履带式拖拉机对苗木生长是有利的。 相似文献
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Abstract. Current tillage erosion models account for the influence of tillage direction in the magnitude of the soil (tillage) transport coefficient. It is argued here that this is counter-intuitive and causes significant problems in modelling tillage erosion in areas of complex terrain. This article examines whether a re-modelling of tillage erosion is possible that separates tillage direction (an interaction with the landform) from the soil transport coefficient (a measure of tillage intensity representing the combination of implement erosivity and soil erodibility). Experimental data for mouldboard ploughing upslope, downslope and cross-slope at Coombe Barton Farm, Devon are examined. Integration of data for all directions into a single relationship, which relates translocation in the direction of tillage to slope in the direction of tillage and translocation perpendicular to tillage to slope perpendicular to tillage, is not possible using previously published methods of analysis. However, when total translocation distance is regressed against the tangent of the slope at 45° to the tillage direction (bisecting the tillage direction and the direction of overturning) it is found that a single relationship can be used to describe tillage in all three directions. Therefore, this relationship is used to determine a single value of the soil transport coefficient ( k fTa ) for constant soil and implement conditions but different tillage directions. This redefinition of tillage is important both for true estimation of tillage erosion severity, the adirectional coefficient being 40% larger than the directional coefficient, and for modelling of tillage erosion in complex terrain. These improvements are vital when tillage erosion simulation is used to direct soil conservation strategies. 相似文献
15.
A method developed to evaluate the cumulative effect of wetland mosaics on water quality was applied to 33 lake watersheds in the seven-county region surrounding Minneapolis-St. Paul, Minnesota. A geographic information system (GIS) was used to record and measure landscape variables derived from aerial photos. Twenty-seven watershed land-use and land-cover variables were reduced to eight principal components which described 85% of the variance among watersheds. Relationships between lake water quality variables and the first six principal components plus an index of lake mixis were analyzed through stepwise multiple regression analysis. A combination of three landscape components (wetland/watershed area, agriculture/wetlands, and forest/soils components) explained 49% of the variance in a trophic state index, even though most of the lakes examined were already highly eutrophic, and thus were influenced by internal loading. The regression equations explained a range of 14 to 76% of the variation in individual water quality variables. Forested land-use was associated with lower lake trophic state, chloride, and lead. High lake trophic state was associated with agricultural land-use and with wetland distance from the lake of interest. The extent of wetlands was associated with low total lead and high color in lakes downstream. Wet meadows or herbaceous, seasonally-flooded wetlands contributed more to lake water color than did cattail marshes. 相似文献
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退化草地土壤生化活性研究 总被引:3,自引:0,他引:3
通过对三种不同退化程度的退化草地土壤生化活性进行测定和相关性分析,结果表明草地退化后其土壤生化活性受到不同程度的影响,表现为土壤生化活性随着退化程度增高而减小,但差异并非都达到统计学上的显著性,而土壤生化活性间的相关性则显著地与草地退化程度有关,说明退化草地土壤微生物间的协调作用受到显著影响,从而影响土壤氮素和碳素代谢途径。 相似文献
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Change in spatial characteristics of forest openings in the Klamath Mountains of northwestern California,USA 总被引:4,自引:0,他引:4
Carl N. Skinner 《Landscape Ecology》1995,10(4):219-228
Change in the spatial characteristics of forest openings was investigated in three forested watersheds in north-western Siskiyou County, California totalling approximately 24,600 hectares. Watersheds with minimal human disturbance were chosen for study. However, fire suppression has been pervasive throughout. Characteristics of forest openings (area, perimeter, distance between neighboring openings) were measured on aerial photographs taken 41 years apart. An index of regional form was determined for the landscape. Shape complexity for each opening was calculated using two indices based upon fractals. Significant differences were found using the Kolmogorov-Smirnov two-sample test between the perimeters, areas, distance from sample point to nearest opening, and distance between neighboring openings. The perimeters and areas became smaller, and the distances from the sample point to the nearest opening and between neighboring openings became greater over the 41 years between aerial photo sets. The estimated area occupied by openings decreased from 25.8 % to 15.6 % of the study area. No significant difference was found in the shape of the openings except as the shape indices were influenced by changes in size of the openings.This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright. 相似文献
20.
Landscape-ecological mapping of the Netherlands 总被引:1,自引:0,他引:1
Kees J. Canters Cees P. den Herder Aart A. de Veer Paul W. M. Veelenturf Rein W. de Waal 《Landscape Ecology》1991,5(3):145-162
The Landscape-ecological Mapping of the Netherlands project (LMN project) started in 1983 with the aim of establishing a landscape-ecological database for use in developing and evaluating national land-use plans. The project, working with grid cells of 1 km2, has four working objectives: a) development of mapping potential for basic landscape-ecological data, b) assessment of susceptibility to interventions, c) evaluation of significance for nature conservation and d) production of vulnerability maps, as a combination of susceptibility and significance. In addition to information on soil, groundwater, ecotopes, flora and fauna, the database also incorporates information on physiographical features and entire landscapes. The resulting database is a geographic information system (GIS). This article describes the second phase of the project (1985–1989), covering the Randstad area, and focusses on the methods and the applications potential of the database. 相似文献