宁南山区不同乔木林地土壤干层分布及干燥化特征

以宁南山区典型坡面不同人工林地为研究对象,分层采集0~600 cm土样,分析杏树(Armeniaca vulgaris)、杨树(Populus simonii)、榆树(Ulmus pumila)、刺槐(Robinia pseudoacacia)和松树(Pinus sylvestris var.mongolica)及农田(对照)土壤含水量垂直剖面分布特征,采用干燥化指数(SID)、土壤水分相对亏缺指数(CSWDI)、干层起始深度(DSLFD)、干层厚度(DSLT)和干层内平均含水量(DSL-SWC)等指标对土壤干燥化强度和干层分布特征进行分析,利用冗余分析(RDA)确定相关环境因子对土壤干燥化和干层的影响,为黄土高原山区植被合理利用水土资源和生态恢复等提供数据支撑。结果表明:(1)杏树、杨树、榆树、刺槐、松树土壤水分均属中等变异,且0~600 cm平均土壤含水量与对照农田相比分别降低了31.17%、24.15%、23.19%、29.67%和18.35%。(2)不同人工林地干层起始深度、干层厚度及垂直剖面土壤水分分布明显不同,杏树、杨树、榆树、刺槐、松树和农田土壤干层起始深度分别为90、160、140、140、160和600 cm,干层厚度分别为510、460、480、480、460和0 cm。(3)杏树、杨树、榆树、刺槐和松树0~600 cm平均土壤干燥化指数分别为63.48%、91.88%、95.17%、73.97%和111.91%,土壤水分相对亏缺指数分别为0.68、0.59、0.52、0.63和0.41,其土壤水分干燥化强度及亏缺程度由高到低依次为杏树>刺槐>杨树>榆树>松树。(4)RDA分析结果表明,乔木类型、黏粒含量和地形条件是影响土壤干燥化的重要因素。

Distribution and Desiccation Characteristics of Dried Soil Layer in Different Forest Lands in the Mountain Area of Southern Ningxia

Different artificial forest lands under typical slopes in southern Ningxia mountainous region were selected as research objects.We collected soil samplings from 0-600 cm different profiles to analyze vertical profile characteristics of soil moisture in apricot,poplar,elm,locust,pine,and with farmland as control group.Soil desiccation index,compared soil water deficit index,dry layer initial depth,thicknesses of desiccated soil layer and average water content in the dry layer were used to evaluate soil desiccation intensity and distribution characteristics,and used redundant analysis to determine the effects of relevant environmental factors on soil desiccation and dry layers.The results showed that:(1)the soil moisture of apricot,poplar,elm,locust and pine trees were moderately variable,and the average soil water content of 0-600 cm was 31.17%,24.15%,23.19%,29.67%and 18.35%,respectively,which were lower than that of farmland.(2)The initial depth of soil dry layer,the thickness of soil dry layer and the distribution of soil moisture in vertical profile were obviously different in different lands.The initial depths of apricot,poplar,elm,locust,pine and farmland trunk layers were 90,160,140,140,160 and 600 cm,respectively.The thickness of dry layer was 510 cm,460 cm,480 cm,480 cm,460 cm and 0 cm,respectively.(3)The soil drying index of 0-600 cm profile of apricot,poplar,elm,locust and pine were 63.48%,91.88%,95.17%,73.97%and 111.91%,respectively.The relative deficit index of soil moisture was 0.68,0.59,0.52,0.63 and 0.41,respectively.The order of soil moisture desiccation intensity and deficit degree from high to low was apricot>locust>poplar>elm>pine.(4)RDA analysis showed that the arbor types,clay content and topographic conditions were important factors affecting soil dry layer.