黄土丘陵区典型人工幼林土壤水分特征

为明确黄土丘陵区典型人工幼林土壤水分时空变化特征，采用ECH₂O土壤水分监测系统，基于标准径流小区坡面土壤水分观测方法，收集土壤水分及气象数据，分析了撂荒地与不同类型人工幼林土壤水分状况及时间稳定性。结果表明：(1)与撂荒地相比，人工幼林土壤含水量整体较低，且具有明显的季节性变化特征，变化趋势基本一致，均随降水量的增加(减少)而升高(降低);(2)不同类型人工林土壤水分垂直分布差异较大，相较于撂荒地，刺槐和油松在50 cm深度土层土壤含水量较低，在80—120 cm深度土层土壤含水量较高，丁香幼林土壤水分整体偏低；(3)油松和撂荒地土壤水分代表深度分别为：120 cm和80 cm,决定系数(R²≥0.9)和纳什系数(NSE≥-0.1)对该结果的评价显示土壤水分代表深度的选择均是可接受的，刺槐和丁香不同深度土层土壤水分差异较大。研究认为，在黄土丘陵区，人工幼林显著影响土壤水分垂直分布规律，土壤含水量整体呈低态势，相较于撂荒地，刺槐和丁香土壤水分变异性较大，油松较为稳定。

Characteristics of Soil Moisture in Typical Young Plantations in Loess Hilly Region

In order to clarify the temporal and spatial changes of soil moisture in typical young plantations in loess hilly areas, soil moisture and meteorological data were collected through using the ECH₂O soil moisture monitoring system and the standard runoff plot slope surface soil moisture observation method, and the soil moisture status and time stability of abandoned land and different types of young plantations were analyzed. The results show that:(1)compared with abandoned land, the soil moisture content of young plantation is generally lower, and has obvious seasonal change characteristics, and the change trend is basically the same, all of which increase or decrease with the increase or decrease of precipitation;(2)the vertical distribution of soil moisture in different types of plantations is quite different; compared with abandoned land, Robinia pseudoacacia and Pinus tabulaeformis forests have lower soil moisture at a depth of 50 cm, and high soil moisture at a depth of 80—120 cm; the soil moisture of young lilac forest is relatively low as a whole;(3)the representative depths of soil moisture of Pinus tabulaeformis and abandoned land are 120 cm and 80 cm, respectively; the evaluation of the results based on the coefficient of determination(R²≥0.9)and the Nash coefficient(NSE≥-0.1)show that the selection of the representative depth of soil moisture is acceptable, and the soil moisture of different depths of Robinia pseudoacacia and Syzygium aromaticum is quite different. These research results suggest that in loess hilly areas, young plantations significantly affect the vertical distribution of soil moisture, and the overall soil moisture content is low. Compared with abandoned land, the soil moisture variability of Robinia pseudoacacia and Syzygium aromaticum is greater, whereas the soil moisture variability of Pinus tabulaeformis is more stable.