Habitat Heterogeneity Of Karst Ecological System And Plant Adaptability

This paper described①the habitat heterogeneity of karst ecological system,②the diurnal changes of main microclimatic factors with different habitat,③the effects of habitat heterogeneity on plant community diversity,④the net photosynthetic rate,⑤water use efficiency in Quercus glauca grown in karst land. The main result were as followings:(1)①Result of cody index of species replacement showed the changes of species replacement rate was:β1>β3>β2 by variation of elevation gradient. It had a high degree of heterogeneity and species replacement rate between the lower slope and near it, these two sites differ greatly in topography, species composition varied among different slope, On the contrary, the species replacement rate between of them was not clear in the same topography. Our investigations went to prove that the many same shrub species grown in different elevation gradient.②Result of PCA analyses indicated that the difference of air temperature and relative humidity in earth`s surface between slower slope and middle slope were significant. Different special slopes had the difference and heterogeneity of light intensity in a day, the difference of soil temperature got clear between any two study sites, and the variation between the slower slope and middle slope showed a great significance.③The temperature difference of earth`s surface and soil between any two sites, among forest edge and outer of forest, edge and interior of forest, and the tendency of difference both the air temperature and soil temperature showed that the difference between interior and outer of forest >outer of forest and the edge > interior and edge of forest . The difference of light intensity between interior and edge of forest became not significant in the earth`s surface. In a word, the variation of microclimatic factors between the edge and outer of forest was significant, it can be considered that they had a high degree heterogeneity.(2)The diurnal changes of primary microclimatic factors mainly related to the community structure, canopy and slope direction. Because of the influence of trees shade, the light intensity in the slower slope community got low and little variation, while it had high degree relative humidity, because the canopy of trees stopped moisture flowing under canopy. On the contrary, the light intensity of the upper slope was intense, but the humidity was less than others, because the horizontal moisture rapidly flowed, so it had high light intensity and low temperature. The difference of microclimatic factors between of the typical communities were related to communities structure and community development. Result indicated that the variation of temperature were: Cleitanthus saichikii community >Cephalomappa sinenswas community>Ardwasia depressa community, while the humidity variation was reverse. Result showed that the variation range of temperature and humidity with different disturbance were: uncultivated land>forest gap centre in a day. Our investigations went to prove that the variation of temperature in the same height showed that a great difference in different forest edge sites, the variation was: outer of forest>forest edge>inner of forest. The humidity decreased by special gradient all sites. The light intensity of outer of forest was the highest in a day. At noon, the difference of soil temperature between of them became greatly significant, but the difference decreased at pm.(3)The study on the influence of the heterogeneity habitat to species diversity of plant community in Nonggang. The results showed that species diversity varied by the difference of heterogeneity habitat,βdiversity decreased by altitudinal gradient and the variation of a value. The shrub layer diversity variation hadn't regular with the typical community height. The species diversity and species composition were obvious difference by the different disturbance type. Results of PCA analyses stated that altitudinal gradient and soil types were the important factors as the first component had effects on community diversity, the secondary principal component may reflect soil moisture correlated with community diversity , but the exposure couldn't be overlooked(4)According to the character of drought in different topographic location in karst land. The result of physiological characteristics of photosynthesis, transpiration and water use efficiency in Quercus glauca grown in different slope location karst land showed that the max photosynthesis rate in Quercus glauca was late in a day. It could be considered a adaptability to the drought land. It was the primary microclimatic factors that the effects of light intensity to the photosynthesis in Quercus glauca in the karst land at noon. The transpirations rate also was high in a day, so they had a strong transpiration pull, resulted in uptake more water from the soil, thus reduced the potential damage by sunburn. The changes of stomatal conductance in Quercus glauca decreased with leaf water potential decreased, in order to reduce transpiration and conserve water.