青藏高原沼泽草甸区植被退化对浅层寒冻土壤环境的影响

Influences of the vegetaion degradation on the shallow cryic soil environment in the wet meadow areas on the Qinghai-Tibetan plateau

在青藏高原风火山地区对未退化和已退化沼泽草甸下垫面浅层寒冻土壤理化性质及其水热变化进行了研究,同时对土壤环境变化引起的生态效应进行了探讨.结果表明:植被退化引起下垫面浅层土壤中氮、磷、钾、有机质质量分数严重下降而pH值、容重增加,导致土壤贫瘠化和土壤碳库流失;退化还导致浅层土壤冻结和融化时间提前,植被暖季制冷、冷季保温效能降低,导致植被产生"生理干旱"和根系发生冻害,使草地退化加剧;植被退化后草毡层变薄,持水和保水功能下降,使浅层土壤水热状况发生显著改变,导致多年冻土稳定性降低,且随着上层水分和养分迅速下渗流失,进一步促使植被发生退化.

The changes in the physical and chemical properties of the shallow cryic soil and its water and heat regimes in the wet meadow areas with non- or degraded vegetation were studied at the Fenghuoshan region on the Qinghai-Tibetan plateau. The corresponding eco-environmental effects resulting from the changes of the soil environment were discussed. The results showed that the vegetation degradation has led to the contents of nitrogen, phosphorus, kalium and that organic matter decreased significantly, but the soil pH and volume weight increased, causing the soil to become impoverished and the loss of the soil carbon pool. The vegetation degradation also led to the shallow soil began to freeze and thaw to on earlier dates, the efficiency of cooling in warm seasons and heat insulating in cold seasons degraded. This resulted in the vegetation suffering from a physiological drought and a freezing damage, and the degradation of the wet meadow was intensified. The sod layer became thinner with the vegetation degradation, causing the water-holding and water-retention functions to decrease and the stability of the permafrost to decline. With the upper soil moisture and nutrients being infiltrated and lost rapidly, the vegetation would degrade further due to water shortage and malnutrition.