喀斯特地区过度开发土地资源的环境变异

土地资源是有限的，我们在开发利用中必须重视科学，否则其将匮乏。过度开发利用土地资源所产生的环境变异主要表现为：大量使用化肥造成土壤板结，土壤逐渐丧失自组织能力和天然肥力；人们为在有限的土地上获得更侈的作物而在一年内多种植几季，从而加快土壤矿物和肌机质的枯竭和土壤结构的破坏，造成土壤退化。

THE DISCUSSION ON THE ENVIRONMENTAL VARIATION BY EXCESSIVE EXPLOITATION OF LAND RESOURCE IN KARST AREA

Land resource is limited. We must pay attention to science while exploiting it,otherwise,deficiency of land resource will be caused. The environmental variation which caused by excessive exploiting land resource are as follows: As chemical fertilizer is used vastly, soil is hardened and has gradually losed its capacity of self-organization and natural fertility; In order to gain more crop from limited land, man reap several crops in one year, that must quicken exhaustion of mineral and organic nutter and destruction of soil structure, and make soil degeneration; After forest is fellen, the soil erosion and drought and waterlogging will be aggravated; Because of industrial pollution, the organisms that live in soil will be restraines, crop will drop in production, and crop will assimilate harmful elements that will affect man's health directly, Drainage of tunnel and mine and recovering underground water nuke water table drop, that will cause subsidences.