黄土高原半湿润区苜蓿草地土壤干层形成及水分恢复

研究了黄土高原地区不同生长年限苜蓿草地0～1000 cm土层土壤水分消耗规律.结果表明,荒地与苜蓿草地土壤干层出现的区域及发生的程度不同:荒地在80～100 cm土层深度,出现轻度干层;生长年限低于8a(含8a)的苜蓿草地,在250～350 cm土层出现轻度干层,生长年限超过8a,出现中度干层,干层范围延至500 cm土层以下.苜蓿生长超过18a,0～200 cm上层土壤水分开始恢复,年均恢复1.49%;但在200～1000 cm土壤深层,18、26年生苜蓿草地土壤含水量仅为10.20%,深层土壤通体干化,水分难以恢复.

Dry soil layer forming and soil moisture restoration of alfalfa grassland in the semi-humid region of the Loess Plateau

Soil water variations at the 0-1000 cm layers in alfalfa grassland with different years of growth (3a, 4a, 6a, 8a, 12a,14a,18a, 26a), dry soil layer formation and soil moisture restoration were investigated in the semi-humid region of the Loess Plateau. The study resealed that dry soil occurred in different soil layers of wild and alfalfa lands in a varying degree. Thus, slightly dry soil layer occurred in 80-100 cm soil of wild land; slightly dry soil layer appeared in 250-350 cm soil of the grassland with alfalfas growing for 8 years and less, and moderately dry soil layer appeared in the grassland with alfalfas growing for more than eight years and expanded beyond 500 cm deep below ground, indicating that as the alfalfa growth period prolonged, dry soil layer extended its lower boundary downward and got intensified. The grasslands with alfalfa growing for more than eighteen years began to recover their soil water contents in 0-200 cm upper soil at an average annual rate of 1.49%. The grasslands with alfalfa growing for eighteen and twenty-six years had soil water content of only 10.20% in 200-1000 cm deep soil showing the occurrence of soil drying through the soil layer.