黄土丘陵区湾塌地乔灌林土壤水分动态监测

Dynamic Observation of Soil Moisture on Arbor and Shrubbery in Sinking Lands in Loess Hilly Region

湾塌地乔灌幼林生长季土壤水分变化规律，一般丰水年水分活跃层和次活跃层的含水量高低随降雨多少而变化，６～７月为最低值，９～１０月达最大值，土壤水分恢复补偿。旱年亏缺。幼林郁闭前密度对土壤水分影响不明显，而５年生刺槐林和４年生沙棘林土壤水分发生分异。乔灌郁闭成林生长季始末土壤水分变化规律同幼林。且４月份土壤水分受前一年降雨的影响，而汛期降雨则影响生长季末土壤水分的恢复或亏缺。一般全剖面可恢复补偿８０％左右，旱年严重亏缺。沙棘林的相对稳定层水分偏高３％～７％．

The change rule of soil moisture of the young growth of arbor and shrub in sinking lands during growing season is that the moisture content of soil-moisture active and sub-active layers in rich Precipitation year will vary with precipitation amount, getting to minimum from June to July,and maximum from September to October when soil moisture could be restored. But in drought year the soil moisture deficit will appear. The planting density have not obvious influence on soil moisture before young growth closing,while soil moisture in 5-year-old Robinia pseudoaeacia forest or 4-year-old Hippophae rhamnoides shrubbery will differ from onetanother. In changing rule of soil moistuer during from one another. In changing rule of soil moisture during growing season, arbor and shrubbery on closing is alike with its young growth. Moreover the soil moisture in April is affected by the rainfall in former year,and the rainfall of flooding season influences recovery or deficit of soil moisture at the end of growing season. Generally in the whole vertical section the soil moisture may be restored to 80% or so. The soil moisture is deficient seriously in drought year. The soil moisture of the relatively stable layer in Hippophae rhamnoiles shrubbery is 3%-7% slightly higher than others.