Study On Diversity Of Water-using Mechanics Of Dominant Plants Of Artifical Robinaia Pseudoacacia Forest

The paper regards 30-year-old artificial Robinia pseudoacacia forests on shady slope in Yan'an Gonglu mountain as the research object, through determining water parameters(water potential,the water saturation deficiency ,the main PV water relation parameters)of 12 species under and out of Robinia pseudoacacia forests in different periods(initial growing period, vigorously growing period and the end-growing period),analysis on the characteristics of water utilization and balance mechanism, as well as divides into different functional groups by water utilization strategies of the dominant species, in order to clarify the relation between community stability and water-using diversity of various species.The main conclusions of this paper are:1.The water balance of dominant species in Robinia pseudoacacia forests show polymorphism. The water potential daily course of 12 dominant species under and out of forest are almost same in different stages, from 4:00 to21:00, water potential are "high - low - high " trendency, which have a negative correlation with the light intensity and temperature. The water potential values are different between plants in the same habitats, as well as water potential are altered with habitats changing, difference of water potential a day of same plant out of forest is greater than that under forest.2.Retention and resistance to dehydration of dominant species in Robinia pseudoacacia forests show polymorphism. In different stages, the average of natural water saturation deficit (N.W.S.D), critical water saturation deficit (C.W.S.D) and natural water requirement of 12 dominant species out of forest are higher than under forests. In the water saturation deficit values,there are remarkable difference among 12 species , and the change of water saturation deficit value of 12 species between different habitats is diversity.3. Water balance approaches of the different species in arid environment are varied. In different periods, in order to adapt to arid environment, the species reduce theψssatψstlp and RWCtlp, but increaseεmax for achieving the water balance. In the same habitat, the water parameters of 12 dominant species showed polymorphism. In different stages, the extent of water relation parameters value of same specie between different habitats was not the same.4. There are significant differences about water parameters of same species in different seasons, which show a big variety. Water parameters of 12 dominant species with seasonal variation show regularity. Water potential values from May to September is"high - low– high"trend. The value of N.W.S.D, C.W.S.D and natural water requirement are July> May> September, the order ofψssat value andψstlp value is May<July<September.5.In different seasons, the strategies of dominant species are divided into 3-5 types by cluster analysis in accordance with the change of Water parameters. In same group, the changes of water parameters between different habitats are similar. In different seasons,the species in one group are not all same ,which shows water adaptive strategies of same specie is also altered flowing season and environment changing, both the diversity of diurnal , seasonal changes of water parameters and the changes of water utilization strategies avoid the competition for water among different species ,which means a great deal to community development.