黄土高原水蚀风蚀交错区植被间土壤水分竞争

通过对黄土高原水蚀风蚀交错区4 种相邻植被条带（撂荒地、柠条地、苜蓿地、农地）0~4m土壤剖面含水量和地上生物特征的测定分析，研究不同植被之间的水分竞争关系。结果表明：水平方向上，撂荒地和农地土壤含水量随着靠近柠条地和苜蓿地呈下降趋势，且柠条对临近撂荒地土壤水分影响的水平距离至少有6 m。而深根性植物柠条和苜蓿相邻处测点的土壤含水量在所有测点中最低。此外，通过对地上生物特征分析，临近农地的苜蓿和临近撂荒地的柠条有较高的生物指标，证明这两种深根系植物吸收利用了相邻地块的土壤水分。因此，柠条和苜蓿对土壤水分竞争激烈，不宜搭配种植，而深根-浅根植物搭配扩大了深根系植物根系吸水空间，有利于其生长。

Competition for Soil Moisture between Different Vegetation Types in the Water and Wind Crisscross Region of the Loess Plateau

Below ground interactions for water among neighboring vegetation were studied in the water and wind erosion crisscross region of the Loess Plateau by field survey. The purpose of the study is to investigate water competition among vegetation types by contrast analysis of soil moisture and aboveground biological characteristics. The experiment included four land use types (abandoned land, caragana land, alfalfa land and farmland) and three replications. Soil samples were collected from 0 to 400 cm in summer, 2012. The aboveground biological characteristics (height, canopy diameter and biomass) were measured at the same time. The results showed that soil moisture content in the abandoned land and farmland decreased close to the caragana land and alfalfa land. The total soil water storage of the abandoned land decreased 75.3 mm from the first measured point (573.7 mm) to the fourth measured point (498.4 mm), and the total soil water storage of farmland decreased 71.6 mm from the second measured point (685.8 mm) to the first measured point (614.2 mm). Caragana affected soil moisture in adjacent abandoned land by at least 6 m in the horizontal direction. Soil water storage from the fourth measured point of caragana land to the fourth measured point of alfalfa land were all smaller than 400 mm, and soil water storage (360.3 mm) of the second measured point of alfalfa land affected by caragana and alfalfa was the lowest among all measured points. Moreover, caragana near abandoned land and alfalfa near farmland have a higher biological index than the other measured points. This means that these two deep root plants absorbed soil water from neighboring land. So, planting caragana and alfalfa together would lead to intensive competition for soil water. Plants with shallow roots and deep roots should be arranged together when vegetation restoration is conducted in arid or semi-arid regions in order to delay soil water depletion.