紫色土成土速率的估算与田间测定

MODEL-BASED ESTIMATION AND FIELD MEASUREMENT OF PURPLE SOIL FORMATION RATE

成土速率是确定容许侵蚀量的基础之一。本研究应用以物质循环理论为基础的Barth模型,估算了不同母质类型、不同种植植被和不同土层厚度下紫色土的成土速率,并在田间定位试验点测定了这三种不同处理条件下的成土速率,取得了以下结果:(1)用Barth模型估算的成土速率,与田间测定值比较,总体上明显偏小;且估算的成土速率主要与径流量显著相关;不同土壤母质下成土速率的估算差异显著,但不同植被类型和土层厚度下的差异不显著。(2)田间测定的成土速率,由于土壤母质特性和水热条件的差异,在不同条件下的成土速率差异明显,且均反映出一定的变化规律。不同类型紫色土的成土速率大小次序为沙溪庙组>蓬莱镇组>遂宁组;不同植被下的成土速率大小次序为作物>果树>牧草;不同土层厚度下的成土速率,总的趋势是母岩上覆盖的土层愈薄,成土速率愈大。(3)综合考虑田间不同试验条件下的成土速率并分析转换,四川丘陵区沙溪庙组和蓬莱镇组紫色土的成土速率确定为1 200 t km-2a-1,遂宁组的成土速率为800 t km-2a-1。

Soil formation is the basis for determinantion of soil permissible erosion rate. In this study, soil formation rates （SR） of the purple soils （Regosols） different in parent material, vegetation and thickness in hilly areas of Sichuan, China were calculated using the Barth model that is based on the material recycling theory, and measured at the stationary experiment sites in the field. Results show that estimated-SRs were generally, smaller than measured-SRs, and varied significantly with parent material, but not with vegetation or soil depth. Moreover, they were closely related to runoff volume. Measured-SRs varied substantially between the treatments, owing to different characteristics of soil parent materials and different temperature and soil moisture at the interface between soil and parent materials. In terms of measured-SR the three types of soils showed an order of J2s 〉 J3P 〉 J3s, and the three vegetations did an order of crop 〉 trees 〉 grass. The general trend of soil formation rate in relation to soil depth was that the thinner the soil layer was; the higher the rate was. Based on the measured-SR, the SR was determined to be 800 t km^ -2 a^-1 for J3s purple soils, and 1 200 t km^-2 a^-1 for J2s purple soils and for J3P purple soils in the study region.