黄土丘陵区降雨、土壤水分和苗木成活率的关系

Relationship of Rainfall,Soil Moisture and Seedling Survival Rate in Loess Hilly Region

降雨量通过影响土壤水分而间接影响苗木成活率。为了研究降雨、土壤水分和苗木成活率之间的关系,对半干旱黄土丘陵区降雨、土壤水分和造林成活率相关性进行试验和分析,结果表明:(1)该区域降雨对土壤含水量的贡献可用回归方程进行模拟,模拟结果表明:低于6.3mm的降雨不会显著增加土壤含水量,属无效降雨;(2)建立了土壤含水量和苗木成活率的数学模型;(3)对山杏、山桃、沙棘、柠条4种树种而言,土壤含水量分别低于5.1%,6.0%,6.5%,4.6%时其造林成活率为0;满足85%的造林成活率的土壤含水量分别为11.9%,13.0%,13.8%,12.0%;(4)若以多年春季平均土壤含水量9.8%为本底值,对山杏、山桃、沙棘和柠条而言,只有在降雨量分别高于18.1,24.6,29.7,18.6mm时,造林成活率才能达到85%以上。

Rainfall indirectly impacts the seeding survial by affecting soil moisture. For the purposes of learning the relationship between rainfall, soil moisture and seedling survival, the field experiment of rainfall, soil moisture and seedling survival rate was conducted in loess hilly region. The results were analyzed and the conclusion was drawn as follows： （1） the effects of rainfall on soil moisture could be simulated by the regres- sion equations, the results showed that, the rainfall lower than 6.3 mm had no contribution to soil moisture; （2） the equations of soil moisture and seedling survival rate of four species were developed also; （3） the soil moisture, for Prunus armeniaca , Prunus davidiana , Hippophae rhamnoidea and Caragana korshinsleii , was lower than 5.1%, 6.0%, 6.5%, 4.6% ,respectively, the seedling survival rate was O; soil moisture greater than 11.9%, 12.9%, 13.8%, 12.0%, respectively, the seedling survival rates of four species were higher than 85% ; （4） based on annual mean spring soil moisture of 9.8%, the rainfalls demanded for 〉85% seedling survival rate of Prunus armeniaca , Prunus davidiana , Hippophae rharnnoidea and Caragana kor- shinskii were 18.1 mm, 24.6 mm, 29.7 mm and 18.6 mm, respectively.