The Effects Of Factors On Seed Germination And Seedling Growth Of Populus Euphratica In Ejina Oasis

Populus euphratica Olive. is the unique tree species which can form large-are forest in extreme arid regions of China NW. However, because of the lasting degeneration, P. euphratica in Ejina Oasis has been facing a serve threat from 1990s. On the premise of sufficient ecological water supply, the successful regeneration of P. euphratica is the key point for its forest revegetation and protection at present. Therefore, according to the previous researches, in 2008,2009 and 2010, we chose some factors, including the age and growth situation of P. euphratica mother tree, soil substratum, water content, illumination and so on, to assay their influence on the P. euphratica seed germination and seedling growth by experiments. And the results were as follows:Seed germination rate was significant correlated by the seed harvesting time and the age of mother tree, which meant that they were the main factors affecting P. euphratica seed vitality. That is, the latter the collection time was, the more significantly the seed vitality declined. Moreover, there were remarkable variances between various age-classes and between various growth situations of mother trees. Totally speaking, the proportions of sterile seeds from the middle-aged trees or the trees with high dead branch rate were much higher than the other.The results of experiments on different environmental factors showed that both the soil substratum and water were significantly correlated with all the growth indexes of P. euphratica seedlings, which meant that their little changes would lead to the variances of energy distribution in the seedling growth. The environmental conditions under the P. euphratica forest were not suitable for the implantation and germination of its seed and seedling growth, but the flood plains provided the favorable soil situations for them after flooding. Besides, the critical condition of seedling survival under the water stress was 10% in 10 days. In the tolerance range, P. euphratica seedlings could adjust their energy distribution to adapt the environment under the water stress, that is, more energy would be assigned to their root growth. Meanwhile, P. euphratica seedling had a high adaptability to illumination:the cumulative over-ground biomass went greater with the illumination time, but the respond of root growth to illumination was not obvious, which was closely related with its habitat.