Development and growth of root suckers of Populus euphratica in different forest gaps in Ejina Oasis
额济纳绿洲不同林隙胡杨根蘖的发生特征

Populus euphratica forests are the dominant ecosystems in Ejina Oasis, which play an important role in keeping the fragile ecological balance in the vast northwest areas of China. However, P. euphratica forests are undergoing severe degradation in recent years as a result of water shortage and pollution and human disturbance. Due to the failure of seed-originated seedlings, the regeneration of the forest mainly depends on the clonal growth of root suckers. In this study, we examined the relationship between the development and growth of root suckers and the environment factors in different forest gaps to gain a better understanding of the regeneration dynamics of this forest. The results of principal component analysis (PCA) indicate that environmental factors in the forest gaps can be classified into five components: the density of Sophara alopecuroides, soil moisture and compactness, size of forest gaps, human disturbance, and amount of P. euphratica adult individuals (DBH>15cm) at the edge of the forest gaps. However, the result of Spearman Correlation Analysis shows that these environmental factors have no significant influence on the density of P. euphratica root suckers. Therefore it seems that the root suckers of P. euphratica sprout randomly. Meanwhile, results of another Spearman Correlation Analysis suggest that the density of Sophara alopecuroides and human disturbance and the amount of adult individuals of P. euphratica have significant influence on height and basal diameter of root suckers. Based on our observation, we put forward a hypothesis of randomicity and resource heterogeneity to explain the mechanism in developing of P. euphratica root suckers. At the same time, we think that enormous tending to root suckers is indispensable to improve regeneration of P. euphratica forests.