金沙江流域退耕还草对土壤物理性质的影响*

 在金沙江流域云南省昭通市彝良县海拔2000m的半山区进行，在坡耕地建立了不同组合模式的退耕还草试验,通过持续两年的试验，实地观测和分析了不同混播牧草组合草地的土壤物理性质。结果表明，多年生黑麦草和白三叶混播组合的植被覆盖度和生物量均高于其它混播组合。人工混播草地与撂荒坡地相比较，土壤含水量增加4.07%～13.13%，毛管孔隙度增加3.84%～28.35%，土壤容重减小0.3～0.46g/cm³,土壤渗透速率提高0.83～2.64mm/cm，土壤完全崩解时间延长219～583h。容重和总孔隙度间的相关性最强，R²=0.5795；毛管最大持水量与毛管孔隙度间相关系数为R²=0.8909，土壤饱和持水量与总孔隙度之间的相关系数为R²=0.6075。退耕草地具有良好的水土保持作用。

Soil Physical Properties of Artificial Grassland on Sloping Fields of the Jinsha River Basin

From the year of 2002 to 2004, the experiment of artificial grassland were established on sloping fields of the Jinsha River Basin at Yiliang county in Yunnan Province, which was on the half mountain area with elevation of above 2 000 metres. From two years analyze of physical property of mixed sow pasture, we know that the total vegetation coverage, total biomass combination of perennial Ryegrass and white clover was higher than others, some indexes of soil physical property superiored to others combination; Comparing with control, the soil water content of artificial mixed grassland increased with 4.07% - 13.1% , capillary porosity increased with 3.84% -28.35% , soil bulk density reduced with 0.3 - 0.46 g/cm^3, permeability index raise in 0.83 - 2.64 mm/cm, index resistant of soil erosion such as complete collapse time lengthened with 219 - 583 h , the physical and chemical properties of the soil attained improvement in various degree ; there was positive the remarkable correlation between total vegetation coverage and total biomass;the correlation between soil bulk density and total porosity was the bigest, the correlation coefficient was R^2 = 0. 579 5 ; correlation coefficient between soil capillary porosity maximum capillary suppporting water is R^2 = 0. 890 9, correlation coefficient between soil total porosity and soil and saturated water content is R^2 = 0. 607 5.