Species Diversity Of Plantation Communities And Quantitative Methodologies For Ecotone Determination On The Upper Reaches Of The Minjiang River

The arid valley of the Minjiang River was a fragility ecological environment, which caused by the climate of Qinghai-Tibet plateau and the local geography environment. Biodiversity resources were the foundation of ecosystem and sustainable development on this area. However, under the anthropogenic influences and severe natural environments, the ecological environment was depravation, disaster appeared frequency, which serious obstruct the social development and threaten to the whole drainage basin of Minjiang River. Therefore, it is necessary to take research on the biodiversity, which make a foundation theoretical basis for vegetation restoration and ecosystem reconstructing. This paper based on the vegetation of the elevation(1790-2510 m, the same below) on the arid valley of the Minjiang River, the characteristic on vegetation, species diversity and their altitudinal patterns was carried out. Meanwhile, the correlation between species richness or diversity and environment factors was also researched. Based on the Moving split-window techniques, the vegetation ecotone was quantitative detected. The results as follows:1. In this investigation region, there are 252 species of vascular bundle plant, which belong to 57 families and 146 genera respectively. There are 2 tree species, which belong to 2 families and 2 genera respectively, and 133 shrub species, which belong to 34 families and 58 genera respectively, and 117 herb species, which belong to 35 families and 91 genera respectively. The plant of families and genera was obviously. Compositae, Rosaceae and Graminea were the dominant genera in families. Rosaceae, Compositae and Caprifoliaceae were the dominant species in families. Salix, Cotoneaster and Spiraea were the dominant species in genera. Shrub was the primary life form of plant, which account for 48.02%. With the rising of elevation, the average height and coverage of the shrub and herb was obviously increased, and the species composition, behaviors change from the arid plant to semi-humid and to subalpine. It indicated that the characteristic of community's structure was obviously on the elevation gradient. 2. Plant communities of species richness have large difference on the elevation. With the rising of the elevation, species richness increased first and then decreased and finally increased. The species richness was minimal on the lower altitude (1790m), and better on the middle altitude (2100 m), and maximal on the high altitude (2510 m).3. Plant communities of species a diversity have large difference on the elevation. The Shannon-Wiener index of shrub species diversity increased first and then decreased and finally increased with the elevation. But the Simpson and Pielou index was not obvious on the elevation. The Shannon-Wiener index of plant communities for herb species diversity also have large difference on the elevation, which increased first and then decreased and finally increased with the elevation, but the value on fluctuant was lower than the shrub. The Simpson and Pielou index was not obvious on the elevation.4. Theβdiversity of communities on the adjacent sites was difference on the elevation. With the rising of elevation, the Jaccard, Sorenson and Bray-Curtis index of communities on the adjacent sites was decreased first and then increased and finally decreased, but the Cody similarity index was increased first and then decreased and finally rapidly increased. Similarity index of shrub, herb and communities was maximal on the 1790 m altitude, and the Cody index was minimal, which species' replace of rate was lower. At the 2510 m altitude, community similarity index was minimal and dissimilarity was maximal. The rate of species' replace was higher. Otherwise, species' replace of rate was high on the middle altitude.5. The result of correlation analysis between species richness or a diversity and environment factors indicated that species richness of shrub and herb was positive correlations with elevation, soil bulk densities, PH value, moisture and organic matter, and the elevation, moisture,PH value was positive correlations with the species Shannon-Wiener index. The correlations between species Simpson or Pielou index with environment factors was indistinctively. The results of regress analysis showed that PH value and elevation was principal component to the species richness and diversity. Diagram of DCCA on communities and environment factors indicated that soil nutrient, soil moisture and elevation was higher correlation. Characteristic of the plant communities on the altitudinal pattern was affected synthetically by soil nutrient, soil moisture and elevation.6. Based on the shrub important values and communities present-absent date, with the Squared Euclidean Distance (SED) methods used for the moving split-window, the results showed that the peak was obvious on the plant communities. The ecotone was interlaced by Rosa, Corylus mandshurica, Spiraea shrub and Elaeagnus umbellate, Quercus liaotungensis, Quercus, Which altitude area was 2060-2240 m,located in 2120-2160 m, panned 120-160 m, belong to gradual type. The ecotone was the dry valleys shrubs community and Mountain forest.