自然恢复序列梯度上退耕地土壤容重变化及其蓄水性能效应

Soil Bulk Density Changes and Its Water-storage Capacity of Abandoned Farmland in Natural Restoration Series Gradient of Loess Hilly-gully Region

为了探索黄土丘陵区退耕地植被自然恢复对土壤水分环境的影响,以延安市安塞区5个植被自然恢复阶段(10,20,30,40,50年)退耕地为研究对象,采用空间代替时间法研究不同演替阶段土壤理性特征的变化、土壤蓄水性能及其影响。结果表明:陕北黄土丘陵区弃耕地在植被自然恢复过程中,同一演替阶段不同土层,其表层(0—20cm)土壤容重均小于下层(20—40cm)土壤容重。不同演替阶段表层土壤容重总体表现为先减少后增加的趋势,其土壤容重在30年的植被自然恢复期降到最低值,说明植被恢复导致表层土壤容重变小,表层土壤总毛管孔隙度、非毛管孔隙度均呈现先增大后减小的趋势,且在30年自然恢复期达到峰值,而土壤毛管孔隙度变化趋势为先减小后增大再减小再增大。不同演替阶段表层土壤饱和蓄水量、滞留蓄水量均表现为先增大后减小的趋势,且在30年自然恢复期其蓄水量达到峰值。土壤物理特征的变化趋势为土壤容重大,土壤粗砂粒含量增加,毛管孔隙度增大,非毛管孔隙度减小,土壤蓄水量降低;土壤容重减小,土壤细砂粒、粉黏粒含量增加,毛管孔隙度减小,非毛管孔隙度增大,土壤蓄水量增大。

For exploring the effect of natural vegetation restoration of abandoned farmland in the loess hilly region on soil water environment,this paper took five natural vegetation restoration(10,20,30,40 and 50 years)abandoned farmlands as the research object in Ansai County,Yanan.And the changes of soil characteristic in different natural restoration stages and its effects on soil water-storage capacity were studied using the method of substituting temporal serial with spatial serial.The results showed that:In the process of natural vegetation restoration of abandoned farmland,the soil bulk density of the surface layer(0-20 cm)was lower than that of the lower layer(20-40 cm)in different soil layers at the same natural recovery stage.At different stages of natural restoration,the soil bulk density of surface soil decreased first and then increased with a minimum at 30 years of natural restoration,indicating that natural vegetation restoration could lead to decrease soil bulk density of surface soil.Reaching the maximum at 30 years,the total capillary porosity and non-capillary porosity of surface soil increased first and then decreased,while capillary porosity decreased initially and increased afterwards.Reaching the maximum at 30 years,soil total water-storage capacity and non-capillary water-storage capacity increased first and then decreased at different stages of natural restoration.The changing trends of soil physical characteristic showed that with the increase of soil bulk,soil gravel content and capillary porosity,and with the decrease of non-capillary porosity,the soil water-storage capacity was reduced,and vice versa.