利用方式对高寒牧区土壤有机碳含量及土壤结构性质的影响

在高山草原带选择了围栏草地、一年生人工草地(先围栏草地后开垦种植燕麦草)和多年生人工草地(先围栏草地后开垦种植多年生垂穗披碱草和无芒雀麦)三种利用方式,就人工草地利用方式对土壤有机碳含量和结构性质的影响进行了研究。研究结果表明,在高寒牧区,开垦自然植被分别种植一年生燕麦草20多年和种植多年生禾草7年以后与围栏草地相比较,0-30cm深度土壤有机碳密度分别平均降低了27.7% 和8.5%,土壤结构的稳定性(MWD)分别平均降低了46.9%和42.6%。同时土壤容重和土壤密度显著增加, 土壤孔隙度显著降低。在高寒牧区开垦自然植被建植人工草地情况下,土壤结构性质的恶化与有机碳(质)含量的降低密切相关。

EFFECTS OF LAND USE ON ORGANIC C CONCENTRATION AND STRUCTURAL PROPERTIES IN ALPINE GRASSLAND SOIL

Cultivating native pasture to plant oat or some other species of grasses is generally recommended as a way to alleviate grazing pressure on native grassland and to improve winter forage levels in high altitude regions,however, its effects on soil quality have not been well understood.This study selected three types of land use,fencing pasture (FP) .fencing pasture plus subsequent 25-year oat ( Arrhenatherum elatius) cultivating (FP SO) ,and fencing pasture plus subsequent 7-year perennial grasses ( Elymus nutans and Bromus inermis) cultivating (FP SPG) ,to investigate changes in soil organic C concentration and some soil physical properties caused by land use transition.The results show that compared with FP,FP SO and FP SPG significantly decreased soil organic C density in 0 - 30 cm depth by 27.7% and 8.5% ,and mean weight diameter ( MWD) by 46.9% and 42.6% , respectively. Meanwhile, FP SO and FP SPG significantly increased soil bulk density and particle density,and significantly decreased soil porosity. We concluded that decrease in aggregate stability and porosity, and increase in bulk density and particle density, were all related to reduction in soil organic C concentration by cultivation.