金沙江干热河谷坡改梯及生物地埂对土壤可蚀性的影响

Effect of Terracing Slope cropland and Bio-bank on Soil Erodibility in Dry-hot Valley of Jinsha River Basin,Southwest China

以金沙江干热河谷试验区不同土壤类型、修建年限及生物地埂类型的梯田为研究对象,系统分析梯田和地埂土壤基本物理性质、团聚体分布特征及其抗冲、抗蚀性指标,研究了坡改梯和生物地埂对土壤可蚀性的影响。结果表明:(1)与坡耕地相比,新修梯田土壤物理性质和抗冲性及抗蚀性无显著变化,甚至有所退化,可能与土壤结构破坏、原表土搬离和坡改梯初期土壤侵蚀加剧等有关,随修建时间延长,老梯田土壤容重和孔隙度分别显著减小和增大,粒径>0.25 mm水稳性大团聚体、水稳性团聚体几何平均直径(GMD)和有机质含量较坡耕地分别呈显著或极显著增加;(2)新修红壤和黄红壤梯田生物地埂土壤容重、孔隙度和抗蚀性与裸土地埂基本无显著差异,而红壤老梯田生物埂土壤紧实度和粒径>2mm水稳性大团聚体显著增加,抗冲性和抗蚀性整体上较裸土地埂显著改善,说明生物地埂的长期利用可以有效增强土壤抗冲和抗蚀能力,加强地埂稳定性,有利于梯田水土保持效应的持续性;(3)地埂长期生物利用的老梯田水土保持功能最强。

Terraces of different soil type at different ages and bio-banks with different vegetation were investigated to understand effect of terracing slope cropland and bio-bank utilization on soil erodibility,revealed by major physical properties,distribution pattern of aggregates and anti-scourability and anti-erodibility of soils in dry-hot valley of Jinsha River basin.The results showed that：（1）The physical properties,anti-scourability and anti-erodibility of soils in the newly-built terraces did not vary significantly or even degraded compared with the control（i.e.slope cropland）,possibly caused by soil structure destruction,removing of original topsoil and soil erosion intensification during initial stage of terrace.However,with terracing age increase,soil bulk density decreased and soil porosity rose,while the content of water stable aggregates（diameter〉0.25 mm in size）,soil organic matter and geometric mean diameter（GMD）of water stable aggregates increased significantly compared with the control.（2）No significant difference in soil physical properties and indexes of anti-erodibility was found between the bio-banks and the bare ridge from newly-built terraces,while soil anti-scourability and anti-erodibility indexes of bio-bank from terraces built over 10 years improved significantly,which indicated that long-term utilization of bio-bank should make a significant contribution to the stability of terrace ridge and sustainability of terrace soil conservation.（3）Soil conservation function of terraces with long-term bio-bank utilization was the best among all treatments.