喀斯特石漠化过程中土壤的空间分布

Spatial Distribution of Soils during the Process of Karst Rocky Desertification

本文对贵州花江1.2km2小流域内樵采和开垦石漠化过程土壤的空间分布进行了调查研究。结果显示:喀斯特土壤分布极不均匀,土被极度破碎,土壤分布面积分别在5.4%～20.1%和11.1%～48.5%,樵采石漠化过程的土壤分布特点与开垦过程既有相似的方面也存在明显的差异,差异表现在樵采作用下土壤分布面积小、每种小生境的面积也小、土壤块数量少;相似性表现在随着喀斯特石漠化进程的演化,潜在石漠化土壤主要分布在石沟、土面、石土面3种小生境类型,轻度石漠化土壤则主要存在于石沟、土面小生境中,发展到中度和重度石漠化类型时,土壤主要分布在石沟、土面、石坑中;土壤厚薄分布不均,厚土主要分布在潜在石漠化区域,石漠化过程中土壤厚度的变化趋势为随着石漠化的进行土层变薄但并不是完全符合这一规律的变化,土壤分布面积与土壤厚度之间没有关联,对喀斯特土壤厚度的作用需要认真对待;尽管喀斯特土壤土层极薄,但潜在石漠化区域能够生长高大乔木林且植被盖度可达70%以上,说明喀斯特土壤厚度的认识存在一定的缺陷。土壤的空间分布特点表现出石土面小生境土层从有变无,土壤存在的小生境演变为石坑,样地土壤总面积缩小,土层变薄,土块小生境数量增加,而土块的面积缩小,显示出土壤侵蚀以渐进形式进行。樵采石漠化进程中土壤的侵蚀主要在樵采时就已经大量发生,石漠化过程中的侵蚀变化较小;开垦石漠化进程中发生剧烈土壤侵蚀,人为开垦种地过程促进了土壤侵蚀的发生。

The spatial distribution characteristics of soils in karst rocky desertification during cultivated and wood-cutting processes were broadly investigated in a 1.2 kmz watershed in Huajiang, Guizhou Province, China. Results showed that the spatial distribution soils during karst rocky desertification was extremely asymmetrical; soil cover was extremely fragmental and the distribution areas account for about 5.4%- 20.1% and 11.1% - 48.5% ,respectively. There are significant similarity and discrepancy between cultivated and wood-cutting processes of karst rocky desertification. Discrepancy involved smaller soil dis- tribution area, the number of soil fragments in plot, smaller soil area of each microhabitat during wood-cutting process com- pared with cultivated process with respect to karst rocky desertification. Simultaneously, similarity is shown in the distribution of soils mainly in gully, soil and rock-soil microhabitats in the area of potential rocky desertification, but gully, soil microhabi- tats in the area of weak rocky desertification, and gully, soil, and stone pit microhabitats in the area of medium and strong rocky desertification. There are some differences in soil thicknesses in the area. Thick soil was mainly distributed in potential rocky desertification plot. Soil became thinner in the process of karst rocky desertification, but at some stages there were no rules. There is not any relationship between soil cover area and thickness , which means that more attention must be paid to soil thickness. High forest can grow well and the vegetation coverage can reach about 70% in a very thin soil layer, implying some misunderstanding of soil thickness. From soil distribution characteristics of karst rocky desertification, soil erosion happened step by step, soil cover area and soil thickness were reduced, soil distribution microhabitat changed from rock to stone pit, pieces of microhabitats increased, and the area of each piece of soil decreased during the process of karst rock desertifica- tion. More soil erosion happened during the process of wood-cutting but less in the process of wood-cutting rock desertification, and heavily in the process of cultivated rock desertification , which means that artificial reclamation enhanced soil erosion.