Ecological Water Requirement Of Robinia Pseudoacacia Forest In Yanan

The lacking water problem is the main factor that limit vegetation restoration in the Loess Hilly Region.In order to attain real right tree or grass on right sight,being on converting slope farmland into forest(grassland),we must prior considerate that the ecological water requirement whether could be satisfy.Therefore the study of vegetation ecological water requirement has important significance to eco-environment restoration of the Loess Hilly Region.With forest ecosystem water balance as the starting point,this thesis takes Robinia pseudoacacia of Yangou watershed in Loess Hilly Region as the research object,with the long-term meteorological data,considering soil and vegetation factors,we calculate the Robinia pseudoacacia ecological water requirement in growing season.The main results are as follows:The ecological water requirement of Robinia pseudoacacia in growing season means the evapotranspiration of Robinia pseudoacacia in growing season.The value is related to climate,soil and vegetation species.And it can be estimated by introducing the soil factor(K_s)and tree species factors(K_t)to potential evapotranspiration.With the characteristic values of soil water availability (temporary-wilt,growth-retard),and further proposes the minimum ecological water requirement and suitable water requirement of Robinia pseudoacacia in growing season.The results revealed that the minimum and suitable ecological water requirement of young Robinia pseudoacacia in Yangou watershed are approximately 231mm,457mm;the minimum and suitable ecological water requirement of adult Robinia pseudoacacia are approximately 330mm,653mm.The peak value is on Augest.The calculated result is in accord with the measured results.By the water balance of the Robinia pseudoacacia forest ecosystem in their growing season,removal of the recharge by rainfall,if we take the minimum ecological water requirement as the quota,whether in wet year,average year or dry year,the rainfall can satisfy the basic living of young or adult Robinia pseudoacacia forests.If we take the suitable ecological water requirement as the quota,the rainfall can satisfy the normal growth of young Robinia pseudoacacia forest in wet year and average year,but can not satisfy it in dry year,and the ecological water shortage is 42.6mm;Whether in wet year,average year or dry year,the rainfall can not satisfy the normal growth of adult Robinia pseudoacacia forests,the ecological water shortage are 90mm,173.1mm,and 238.6mm.To vegetation Restoration in the Loess Hilly Region,we should accord to purpose to deside where to plant trees.