Effects of Different Disturbance Degree on the Plant Characteristic Values and Community Species Diversity in Closure Area Response mechanisms of a county territory agro-pastoral system to climate fluctuations in an agro-pastoral transitional zone Psammophyte Resource Investigation of Qingshan Village,Yanchi County Study on the Effect of Different Water-retention Materials on Survival Rate and Growth of Plantation Afforested on Sandy Land of Yanchi County Research on the Adaptability of Several Newly Introdued Plants Grown on Sandy Land of Yanchi County of Ningxia A Discuss on Relationship between Soil Water Contents and Vegetation Recovery on Yanchi Sandy Land Study on Forest Type/Tree Species Structure Optimization of Yanchi Sandy Area Eco-economical Shelterbelt System in Ningxia Vegetation dynamics over 2000-2012 and its driving factors in Yanchi County, Ningxia Province