黄土高原半干旱区天然锦鸡儿灌丛对土壤水分的影响

本文选择黄土高原半干旱区定西地区的一种地带性植被,天然甘蒙锦鸡儿灌丛,将其0～99m深的土壤水分含量与人工柠条锦鸡儿灌丛、人工杏树林、天然草地、放牧荒坡和农地的土壤水分含量进行了比较。结果发现,天然锦鸡儿灌丛在1m以下土壤各层的水分含量均高于人工柠条灌丛和人工杏树林,而与放牧荒坡和农地的土壤湿度接近,略低于农地。天然锦鸡儿灌丛4m以上土层的土壤湿度还明显高于天然草地;天然锦鸡儿灌丛形成的难效—无效水层深度在2m土层以上,而人工柠条灌丛形成的难效无效水层则深达56m,人工杏树林42m,天然草地、放牧荒坡分别为36m和33m,农地1m。

Effects of natural shrub of Caragana opulens Kom. on soil moisture in a semiarid area on the Loess Plateau

This study has chosen the shrubs of Caragana opulens Kom., a natural zonal vegetation in the semiarid area on northwest Loess Plateau, and compared its soil moisture from 0⁹.9m to those of re-vegetated shrubs of C.korshinskii Kom., re-vegetated almond forest, natural grassland （protected） dominated by Stipa breviflora, intensively grazed grassland and continuous cropland. Soil moistures were measured at the depth over 3m with an interval of 0.2m beneath and with an interval of 0.3m. The purpose was to testify the hypothesis that the zonal natural shrub vegetation consumes less soil water than re-vegetated shrub and forest vegetations. The results show that the soil moisture of natural shrub of C.opulens Kom. was largely higher than those of re-vegetated shrub of C.Korshinskii Kom. and almond forest beneath 1m in soil profile, close to those of intensively grazed grassland and cropland,but slightly lower than cropland. The average soil moisture in 0⁹.9m soil profiles of natural shrub of C.opulens, re-vegetated shrub of C.korshinskii, re-vegetated almond forest, natural grassland, intensively grazed grassland and cropland were 9.5%, 7.4%, 7.7%, 8.5%, 9.3% and 9.8%, respectively.and the average soil water moisture from 1⁹.9m are 10.2%, 7.6%, 8.1%, 9.0%, 10.6% and 10.0% respectively. The soil moisture of natural shrub land of C.opulens was higher than the soil moisture of natural grassland between the soil layer of 0⁴m, but beneath 4m, their soil moistures were essentially the same. All vegetation types have resulted in a continuous dry soil layer within which the soil moistures were hard or unavailable to vegetation. The thickness of hard or unavailable water moisture layers of natural shrub of C.opulens , re-vegetated shrub of C.korshinskii,re-vegetated almond forest, natural grassland, intensively grazed grassland and cropland were 2, 5.6, 4.2, 3.6, 3.3 and 1.0m, respectively. According to previous studies, the layer of unavailable soil moisture above 2m in soil profile is rechargeable by annual precipitation in the study area, but it hardly can be recharged by precipitation for unavailable soil water layers beneath 2m. From this initial study, we concluded that the natural shrubs of C.opulens consumes less soil water than re-vegetated shrubs of C.korshinskii, re-vegetated almond forest, underlining the importance of the role of zonal vegetation in the vegetation reconstruction in the study area.