Studies On Ecological Adaptability Of Caragana Davazamcii In Erdos Plateau, Inner Mongolia

Caragana davazamcii,which is one of the dominant species of shrub ecosystem in Erdos plateau of Inner Mongolia,distributes widely in the ecotone between typical steppe and typical desert. C.davazamcii can tolerate drought, chilling and low-nutrient soil, and has strong reproductive , Thus it was paid attention broadly. In this study, Five habitats were selected according to the gradient of precipitation and some individuals of C. davazameii transplanted to Huhhot Arboretum as a contrast to Erdos populations. Multivariate membership function in fuzzy control theory , hierarchical cluster analysis method and population genetics analysis method were used to discuss ecological adaptability and adapted strategy of C. davazamcii population under different moisture conditions through variances of morphological characters, physiological characters, genetic diversity. The results were as follows:1. C.davazamcii is xerophilous shrub, and its morphological characters showed character of xerophilous plants. There was difference among morphological characters of C.davazamcii populations in different habitats due to long-term environmental effect. The common characteristics were as follows: with the decrease of average rainfall , trichnmes density, stomata density and stomata index of leaves all increased; the sunken stomata was more significant;, cuticle became thicker , the differentiation of mechanism tissue of vein increased gradually, rate of palisade tissue and spongy tissue of leaves increased. Multivariate membership function analysis indicated that drought resistance of C.davazamcii in different habitats was V >III> II >IV> I >T . There was not significant negative correlation between average rainfall and drought resistance of C. davazamcii, but the general changes of morphological structure was influenced by drought. Hierarchical cluster analysis showed that morphological adaptabilities were similar in different habitats with similar climate conditions, otherwise difference was obvious.2. There was close correlation between physiological active changes in plant and environmental changes , and physiological active changes were sensitive and quick .Thus the habitats from east to west were selected as series of moisture changes, and we compared dynamic changes between equal water year-2003 and high water year-2004, the results showed that the reactions of physiological adjustive ways to water were different with the changes of moisture condition. Physiological activities in 2003 were all higher than those in 2004 It was found that instant water changes had significant effect on physiological metabolism of C. davazamcii. Multivariate membership function analysis indicated that drought resistance of C.davazamcii in different habitats was III>IV>II> I >V>T. and drought tolerance of C.davazamcii populations in the middle transited habitats were better. Besides they were more sensitive to the change of environmental conditions .Hierarchical cluster analysis indicated that physiological adaptability of C.davazamcii with the habitats from east to west showed geographical relationship. I and II were in the same type; III and IV were in the same type; V and T were in the two types respectively. It showed that physiological adaptabilities were similar in different habitats with similar environmental conditions, otherwise difference was obvious.3. Inter-simple sequence repeat (ISSR) was used to analyze the genetic diversity and genetic structure of C.davazamcii populations in different habitats. ISSR produced 151 amplified fragments of which 149 were polymorphic fragments, the percentage of polymorphic loci was 98.68. C.davazamcii had abundant genetic diversity, which was the genetics base of abroad distributing and planting large areas. With changes of the habitats from east to west, the Nei's gene index and Shannon's information index increased, so genetic diversity increased. Total genetic diversity of the six habitats (H-r)was 0.2929, genetic diversity within population (Hs) was 0.2275,genetic diversity among population(DsT)was 0.0654, genetic differentiation coefficient(GsT)was 0.2234,and gene flow was 1.7386.The results indicated that most variation in C.davazamcii existed within populations, gene flow existed among populations, so it belongs to hybridization, which was the genetics base of strong adaptability. Genetic distance among six populations was little, but it increased slowly with changes of the habitats from east to west, while genetic identity decreased. All these indicated that moisture changes, especially long-term moisture conditions formed had an effect on genetic diversity of C.davazamcii. Clustering analysis showed six populations of C.davazamcii got together gradually with changes of the habitats from east to west. The clustering analysis results were as the same with physiological adjustable adaptability. I and II were in the same type; III and IV were in the same type; Vand T were in the two types respectively. It showed that molecular adaptabilities were similar in different habitats with similar environmental conditions, while genetic differentiation was significant in the habitats with different environmental conditions.4. Ecological adaptive strategy of C.davazamcii population was that morphological structure tended to be more xerophytes and physiological adaptability tended to deal with water stress and to gain more water, genetic structure tended to be more complicated and diversificated.In a word, C.davazamcii has strong adaptability and is able to take active adaptive living ways in arid environment.