Landscape Dynamics And Suitability Assessment Of Endangered Plant Tetraena Mongolica's Habitats

Tetraena mongolica Maxim.,which is only found to be very xerophytic and gregarious on sandish grassland in Western Ordos Plateau of Inner Mongolia,belongs to a endangered relic plant species of Zygophyllaceae.Because of origin antiquity,strong resistance and an ideal object to study the origin of biology diversification and evolution of environment,T. mongolica has important academic research value and to be attentioned widely.But in recent years,the entironment and landscape pattern in the distribution region of T. mongolica has taken place remarkable changes.The primary plants landscape pattern has been fragmented and the habitat was islanding.So the population area of T. mongolica has been declining and the plant species has fallen into severe endangered.The paper took T. mongolica as an research object,took the distribution region of T. mongolica as research area,took the different population patches of T. mongolica as habitat units,and 4 sensing images of T. mongolica's distribution region in different period(s1977,1990,2000,2005)and the technology of remote sensing,geographical information system and global positioning system was used to analyze the temporal and spatial changes characteristic of landscape pattern and the effect factors and their function shares based on the dynamic changes analysis of T. mongolica population areas. Through a comparative study of quantitative and structure characteristics of T. mongolica populations in different habitats,the paper analyzed the spatial difference of T. mongolica's adaptability to different habitats and the effects of habitats or landscape pattern changes on population's dynamic.Based on the analysis of T. mongolica's habitat needs,the paper set up the main ecological factors which affect T. mongolica's survival and selected their substitutive indexes. The habitat suitability of T. mongolica was assessed based on the habitat evaluation procedure. The results showed:1.T. mongolica is mainly distributed in the narrow region between Yellow River and Zhuozi Mountain,and the distribution area is 2824.31km2,it is composed of 8 populations. The population area of T. mongolica has been decreasing in the research period,It had decreased 19.36% and 13.40km2/a during 28 years. But the decreasing speed of T. mongolica population area is varied in different temporal and spatial scale,the annual decrease rate is most during 1990-2000,and it is least during 1977-1990.And the annual rate of decreasing is in an increasing trend year after year. On the spatial scale,the decreasing area is most in Taositu population and least in Dishan population,the annual decrease rate is most in Qianlishan population and least in Wujiamiao population.2.T. mongolica is the basic landscape type in the research region,but the landscape pattern of its habitat has been changed largely from 1977. On landscape scale,Patch number,Patch density,Landscape shape index,Shannon's diversity index and Shannon's evenness index increased,while Mean patch size and Dominance index decreased year after year. It indicated that the landscape pattern tend to be complicated,fragmented and poly_basic in the distribution region of T. mongolica. In the different habitats of T. mongolica,the landscape patterns in Shizuishan,Taositu,Qianlishan and Wuda populations were fragmented. The landscape structure tend to be diversification and complicated.While the landscape patterns in Wujiamiao,Qipanjing and Hainan populations were integritied relatively and there were preponderant patches which connected each other in the landscape. In the all of landscape types,T. mongolica was the maximal landscape component in the research region,but its dominant status reduced in period of 28 years and its distribution tend to be dispersed and fragmented. While the farming land,town and industry land,desertification land and else vegetations increased largely and tend to be connectd. Their effects on landscape were increasing gradually.3.The substitutive indexes of climate fluctuation and human activities changes in the research region were analyzed. It indicated that the trend of drought and the lack of rain has been severed from 1977 in the distribution region of T. mongolica. And with the population increasing and development of industry and fast urbanization,the survival entironment of T. mongolica is more severe. The cumulative impact of driving force of T. mongolica's habitat was analyzed and the results show that the accumulative impact of natural factors came to the maximum in the fourth year,while the accumulative impact of human activities was the most significant in the sixth year. The impacts of human activities on T. mongolica's habitat was in a longer time period and more significant than the natural factors. From the contribution of the information of principal components,the ratio of the contribution of human activities was 55.66%,the contribution of natural factors was 44.34%. Therefore,human activities was the main reasons for T.mongolic's habitat deteriorating.4.The quantitative and structure characteristics of T. mongolica population in different habitats were difference. It indicated that T. mongolica's adaptability to different habitats were different. The density and abundance were higher in populations of Hainan and Dishan,but they were lower in populations of Qipanjing and Wuda.The coverage,height and crown breadth were higher in populations of Dishan and Wujiamiao,but they were lower in populations of Wuda and Qianlishan. The conspicuousness and summed domimamce ratio were higher in populations of Dishan,Wujiamiao and Qipanjing,but they were lower in populations of Wuda and Qianlishan. The diameter-class,age-class,width-class and height-class structure of T. mongolica populations were different in different habitats,it indicates that T. mongolica's adaptability to habitats were higher in the populations of Dishan,Wujiamiao and Qipanjing,and they were lower in population of Wuda and Qianlishan.5.Habitat suitability of T. mongolica was assessed. It indicated that climate and terrain in the research region were not restrictive factors to survival and endanger of T. mongolica. While human activities made the less suitable habitat and unsuitable habitat increased by 1.42%,and the area which the survival habitat degenerate to less suitable habitat was 33.71km2. It showed human activities may be the key factor result in part endanger of T. mongolica. In the different habitats,the habitats quality were higher in populations of Wujiamiao,Dishan and Qipanjing,and they were lower in the populations of Wuda and Qianlishan.