南京城郊麻栎林坡面土壤体积含水率与侧向流对降雨响应

Lateral water flow and volumetric water content with rainfall for soils in a suburban Quercus acutissima forest in Nanjing

为了研究森林涵养水源机制，选择南京城郊麻栎Quercus acutissima林，采用ECH20土壤含水率检测系统在坡面0M00CHI深土壤5，15，30，40，60，100CHI等6个深度层次进行土壤水分定位监测，分析了小雨、中雨、大雨条件下南京城郊麻栎林地各层次土壤水分变异过程，分析各土壤层次体积含水率的变化过程对降雨强度响应曲线，得到5cm和15cm层次土壤水分变化与降雨量变化有良好的同步性，在降雨量6．8mm，11．8mm和36．8mm时5cm和15cm层次的土壤体积含水量变化量分别是1．48％和2．10％，5．21％和5．72％，7．55％和7．85％；随着土壤层次的加深土壤含水率变化趋势与降雨量同步性逐渐下降，在中雨和大雨中土壤含水量的峰值会延迟1～2小时，在小雨下无变化。在降雨强度0-4．0mm·h^-1，土壤含水率自表层到30cm变异幅度增大，5cm，15cm和30cm层次土壤体积含水量变化量分别是1．48％，2．10％和2．90％；降雨强度12～30mm·h^-1，土壤含水率自表层到60cm层次变异幅度降低特征，5，15，30，40和60C[II的土壤体积含水量变化量分别是8．01％，7．85％，6．39％，5．96％和2．63％，而100cm层次土壤含水率却变异幅度显著土壤体积含水量变化量达到8．97％。在2011-2012年中研究的3场降雨量为6．8cm，16．2cm和36cm中，在降雨强度0～60．0mm·h^-1。区间，0～60cm层次土壤水含水率的增加量显著高于降雨量，无地表径流发生，最大侧向流分别为2．1mm·h^-1，2．4mm·h^-1。和28．7mm·h^-1，呈非饱和下渗现象。研究了在小、中、大降雨强度下，0～1．00m深度土壤垂直坡面上各层次侧向流对降雨强度响应的变化曲线，揭示了林地侧向流对各层土壤含水率变化的影响规律。

Infiltration in forest which is not well understand till now may be quite different from that on the bare land. In order to study water conservation mechanisms and soil water infiltration law for a forest, an ECH20 soil moisture content detection system was used to measure the volumetric soil water content （VSWC） at six soil depths： 5, 15, 30, 40, 60, and 100 cm, for a Ouercus acutissima forest in the suburbs of Nanjing, China. VSWC with light, moderate, and heavy rainfall conditions was analyzed along with the VSWC curves of different soil depths. Also, the response of the VSWC increasing rate and its peak value as well as the peak value time to rainfall were analyzed. The response curve of lateral flow to precipitation intensity at each soil depth level between 0-100 cm was studied and the affect for the law of lateral flow on variation of VSWC at each soil depth was determined. Results showed that the VSWC at 5 cm and 15 cm levels changed syn- chronously with rainfall, at rainfall of 6.8 mm, 11.8 mm, 36.8 mm whose variation of VSWC are 1.48% and 2.10%, 5.21% and 5.72%, 7.55% and 7.85% respectively. And as the soil level deepened, the changing syn- chronicity between the VSWC and rainfall declined gradually because peak VSWC was 1-2 h lateral at middle rainfall to storm while showing no change at small rainfall. At a rainfall intensity of 0-4.0 mm. h^-1 the varying amplitude for VSWC increased from the surface to 30 cm soil depth, with the variation of VSWC at 5cm, 10cm, 30 cm soil depth being 1.48%, 2.10%, 2.90% respectively; at 12.0-30.0 mm.h^-1 varying amplitude for VSWC decreased from the surface to 60 cm soil depth, whose variation of VSWC are 8.01%, 7.85%, 6.39%, 5.96%, 2.63% respectively, but greatly increased at 100 cm soil depth, that is 8.97%. For selected 3 precipi- tation events of 6.8 mm, 16.2 mm, 36.0 mm, from 2011 to 2012, when rainfall intensity was less than 60 mm. h^-1, the precipitation needed to increase soil water content during precipitation was much higher than actual rainfall without any happening of surface runoff , of which the biggest lateral water flow was 2.1 mm. h^-1, 2.4 mm.h^-1 and 28.7 mm.h^-1 respectively. Thus, a phenomena of non-saturated water infiltration in forest soil oc- curred. [Ch, 6 fig. 1 tab. 19 ref.]