以汾河上游环境生态重点治理县静乐、娄烦和岚县的近30年主要人工林杨树、杏树林为例,在14个采样点分别取0~600cm深度共820个土壤样品,测得各取样点土壤水分数据序列,分析不同林龄以及不同植被在不同地点生长期内的耗水情况。研究得出:娄烦10a龄杨树林200~400cm土壤平均含水量为9.89%,娄烦20a杨树林地200~400cm土壤平均含水量为7.88%,岚县18a龄杨树林200~400cm土壤平均含水量在7.27~8.83%之间,静乐30a龄杨树林阳坡200~570cm土壤平均含水量为9.02%、阴坡200~400cm为9.72%。表明:静乐、娄烦和岚县人工林各土壤剖面均存在干燥化现象,有中度或轻度干层发育。汾河流域上游人工林地干层发育具有普遍性,发育深度一般达到了600cm或更大深度。该区干层发育的自然现象,是降水量较少决定的。地形、植被等对干层发育有重要影响,梁峁地段人工林干层强于低洼冲沟地段,阳坡强于阴坡。从植被的适宜性角度提出汾河上游流域区作为生态建设重点地域,应遵循演替规律,科学实施退耕还林还草。在轻度干层发育区可以发展较为耐旱、低耗水的人工林;在中度干层发育区应先发展草灌为主的植被,水分条件改善后再恢复乔灌草相结合的植被。本研究为该地区的生态恢复提供了理论依据。

This article is a research report of soil desiccation based on our research of the soil in which the artificial poplar woods and the apricot woods have been growing for over 30 years in Jingle, Loufan, and Lanxian counties of Shanxi Province, which are the key sites of environmental ecological administration in the upper reaches of the Fenhe River.820 soil samples were separately taken from the depth of 0-600cm at 14 sampling points.The soil moisture data sequence in these sampling points was obtained. The different ages of the woods and the different water consumption of different vegetations in different places and vegetal periods were analyzed.The research results are: that in the soil 2-4m underneath the 10-year-old poplar woods was 9.89% in Loufan County, and in the soil 2-4m under the 20-year-old poplar forest was 7.88% in Loufan County, the average water content in the soil 2-4m beneath the 18-year-old poplars was between 7.27% and 8.83% in Lanxian County; the average water content in the soil 2-5.7m under the 30-year-old poplars growing on the sunny slopes was 9.02% and on the shaded slope 2-4m underneath the forest was 9.72% in Jingle County. All these indicated that the profiles of the soil reveal the features of light or medium development of dry layers.It is concluded that development of dry layers is universal in the soil under the artificial woods of the upper reaches of the Fenhe River.Terrain, climate and vegetation have exerted great impacts on the development of dry layers.Generally, soil desiccation in artificial forestlands on the ridges and loess hills are more intense than those on the low-lying and gulch locations.And soil desiccation on sunny slopes are more intense than those on shaded slopes.Scarce natural precipitation is an important factor accounting for the formation of the dry layers. It is proposed, from the perspective of vegetation suitability, that the law of vegetation development should be followed, grain-for-green programs be scientifically performed, ecological special zones be established, scientific eco-environmental programming in the upper reaches of the Fenhe River be conducted, and measures such as planting drought-enduring and low water-consuming sparse woods be taken in areas where light dry layer developed and served as source area to conserve water supply and provide drinking water for Taiyuan City.This research is expected to offer the theoretical basis for ecological recovery of this area.