黄土高原北部人工灌草植被土壤干燥化过程研究

黄土高原北部水蚀风蚀交错区是典型的生态脆弱区,人工灌草植被土壤干燥化发生频繁。土壤干化层的形成影响生物小循环并削弱水文大循环,严重制约植被建设成效和区域生态稳定。为阐明人工灌草植被土壤干燥化过程,并确定适宜的种植年限,选择该区典型人工灌草植被—柠条和苜蓿为研究对象,分析两种植被土壤水分和地上生物量随生长年限的变化特征。结果表明:2—8年生柠条和1—7年生苜蓿对剖面土壤水分消耗强烈,并随生长年限呈快速下降趋势,9—12年生柠条和8—11年生苜蓿1.0—4.0 m剖面含水量分别降低至8.2%—9.0%和8.5%—10.5%之间,并处于相对稳定状态。4—5年生柠条地1—1.4 m开始产生干层,6年生柠条地干层深度达2.4 m,干层厚度为1.4 m;9—12年生柠条地干层深度超过4.0 m。2—4年生苜蓿地无干燥化;5年生苜蓿生长季末土壤干层深度达3.6 m,干层厚度为2.6 m,且7年生以后土壤干层的深度超过4.0 m。因此,为调控土壤干层,减少深层土壤干化的发生,建议柠条和苜蓿的生长年限分别不要超过6年和5年,其对应的地上最大干生物量分别为5050 kg/hm²和19...

The process of soil desiccation under artificial shrub and grass in northern Loess Plateau

The water-wind erosion crisscross region, located in northern Loess Plateau, is a typical ecologically fragile area. Soil desiccation occurs frequently under artificial shrubs and grass. The formation of dried soil layer (DSL) affects eco-hydrological cycle and threatens vegetation construction and ecological stability. To understand the soil desiccation process under artificial shrub and grass and to determine their suitable planting years, dynamics of soil water content and aboveground biomass with growth year for caragana and alfalfa were analyzed in the Liudaogou catchment. The results showed that soil water was consumed strongly and decreased rapidly under 2-8-year old caragana and 1-7-year old alfalfa. After then, soil water was relatively stable, changing slightly between 8.2%-9.0% under caragana and 8.5%-10.5% under alfalfa, respectively. The DSL was develop at depth of 1-1.4 m under 4-5 year-old caragana. The DSL reached 2.4 m depth, and the thickness of the DSL was 1.4 m under 6 year-old caragana. The depth of DSL exceeded 4.0 m under 9-12 year-old caragana. There was no desiccation under 2-4 year-old alfalfa, however, the DSL reached at 3.6 m depth and the thickness was 2.6 m at the end of growing season for 5 year-old alfalfa. The depth of DSL exceeded 4.0 m after 7 year-old alfalfa. Therefore, in order to decrease the risk of DSL formation, it is suggested that the growth years of caragana and alfalfa should not exceed 6 and 5 years, respectively. Their corresponding maximum dry biomass is about 5050 kg/hm² for caragana and 1980 kg/hm² for alfalfa, respectively. The results can provide scientific basis for management of artificial vegetation and regulation of DSL in northern Loess Plateau.