Abstract: A Study of the depletion and restoration of soil water in closed and non-closed natural grassland of the semi-arid loess hilly region shows that with normal rainfall, the yearly fresh yield on the closed grassland amounts to 5860.7 kg/hm² while that of the non-closed grassland is only 785.4 kg/hm². During the plant growing period,compensatory water for the closed grassland totalled 39.4 mm, and for the non-closed one,29.2 mm.In an abundant precipitation year,the grassland’s dry substance yield averaged 2.65 kg/(hm²·mm);in a mormal precipitation year,1.94 kg/(hm²·mm), and merely 0.64 kg/(hm²·mm) in a scanty precipitation year. In the non-closed grassland,construction of water-storing ditches and wells had increased the water conent of soil of 0～500 cm depth 11.5%～13.5% in 13 years(1987～1999),3%～5.2% higher than the grassland without constructing any water-storing projects, and had increased the fresh yield by 5～8 times. The soil water regulation plans promote the growth of plant and raise the grassland yield.

Key words: Grassland science, Loess hilly region, Natural crassland, Characteristic and regulation of soil water

摘要： 以黄土丘陵半干旱区天然草地土壤水分为重点,研究封育和未封草地土壤水分的消耗与恢复过程。结果表明:平水年封育草地鲜草产量达5860.7kg/hm²,未封草地鲜草产量仅785.4kg/hm²,植物生长期降水补充量封育草地39.4mm,未封草地29.2mm;在丰水年干物质生产2.65kg/(hm²·mm);平水年1.94kg/(hm²·mm);枯水年仅0.64kg/(hm²·mm)。在未封草地上采用工程整地措施修筑蓄水带和蓄水沟,13年0～500cm土壤含水量为11.3%～13.5%,比对照提高3.0～5.2个百分点,鲜草产量提高5～8倍。采用调控措施集蓄土壤水分是促进植物生长和提高草地生产力的关键。

关键词: 草原学, 黄土丘陵区, 天然草地, 土壤水分特征, 土壤水分调控