| The soil moisture of locust forest at different period and slope aspect from different geographic locations in the Loess Plateau is analyzed with the help of the model of the moisture niche-fitness.The results show that the value of the soil moisture niche-fitness of locust forest declines gradually from the South(Chunhua County,97.5%) to the North(Mizhi County, 53.2%) of the Loess Plateau.The growth of the locust forest is affected more by the soil moisture factor.The highest value of the moisture niche-fitness is in the north-slope,while the lowest is in the south-slope.During the growth period in a year,the drought in spring can reduce the soil moisture capacity,and it can even cause the lowest soil moisture niche-fitness at the beginning of July.Along with the increase of the age and thickness of stand,the soil moisture niche-fitness is in a downward trend.So the suitable density of stand can promote the growth of the forest. |