苏南丘陵区毛竹林坡面土壤水分对降雨的响应

目的]研究苏南丘陵区毛竹林涵养水源机制,降低由于毛竹集约经营而导致水土流失的影响。方法]选取南京市铜山林场的毛竹林,采用ECH2O土壤含水率检测系统于2012年6月5号至2013年8月28号以每0.5h监测1次的频率在坡面土壤深度为10,15,40,60cm的4个深度层次进行土壤水分定位监测,分析了不同降雨强度条件下苏南丘陵区毛竹林地各土壤层次水分变异过程,得到各土壤层次体积含水率变化过程对降雨强度的响应曲线,并提出侧向流以及分析其对不同雨强的响应特征。结果]10,15cm层次土壤含水率变化趋势与降雨量变化趋势具有一致性,40,60cm层次土壤含水率的峰值相对延迟0.5~1.5h;小雨条件下,土壤含水率的变化幅度自表层到40cm土层呈现逐渐减小的趋势,中雨和大雨条件下,15—60cm层次土壤含水率的变化幅度表现出随深度增加而增大的趋势,大雨条件下此趋势更加明显;小雨、中雨和大雨条件下最大侧向流分别为10.17,60.26和95.92mm。结论]随着深度的增加,土壤含水率与降雨量的同步性呈现下降趋势;不同雨强条件下各层土壤含水率的变化幅度存在明显差异;降雨入渗表现为非饱和入渗,每场降雨垂直面上都有不同程度的侧向流存在,主要集中在40—60cm层次,其主要受土壤结构和降雨强度的影响。

Response of Soil Moisture Content to Rainfall in Phyllostachy Pubescens Forest in Hilly Areas of Southern Jiangsu Province

Objective] The objective of this study is to analyze the mechanism of water conservation in Phyllostachy pubescens forest in the hilly areas of Southern Jiangsu Province, and reduce the influences of intensive bamboo management on soil and water loss . Methods] ECH₂O soil moisture content detection system was used to measure the volumetric soil water content (VSWC) at four soil depths (10, 15, 40, 60 cm) in P. pubescens forest in Nanjing Tongshan forest farm. The observed VSWC data (from June 2012 to August 2013) was used to analyze the variability of VSWC under different precipitation intensity. The VSWC curve at different soil depths under different precipitation intensity was made, and lateral flow was proposed to analyze its response to different rainfall conditions (light, moderate and heavy rain). Results] The VSWC at the depth of 10 and 15 cm changed consistently with the variation of rainfall. The peak value of soil moisture content in the soil depth of 40 and 60 cm was delayed by 0.5 to 1.5 h, The variation amplitude of VSWC decreased from the surface to 40 cm of soil depth under light rainfall condition. The variation amplitude of VSWC increased from the 15 to 60 cm of soil depth under moderate rain and heavy rain conditions, and this trend was more obvious under the heavy rainfall condition. The maximum lateral flow under light, moderate and heavy rainfall condition was 10.17, 60.26 and 95.92 mm, respectively. Conclusion] As the increase of soil depth, the synchronicity between the VSWC and rainfall declined. Obvious differences in the amplitude of VSWC were existed among different soil layer with different rainfall intensity. Rainfall infiltration was unsaturated infiltration. Lateral flow existed in vertical plane under each rainfall, and they mainly concentrated at 40-60 cm soil depths, and influenced by soil structure and precipitation intensity.