Response Of The Succession And Distribution Of Vegetation In Hulun Lake To Climate Change

Wetland ecosystem is a kind of high biodiversity ecosystem with the character of both water and land ecosystem, it is not only a transition ecosystem but with its own distinguish feathers. Wetland ecosystem had important value of ecosystem service thus played an important role in population, ecosystem and biosphere. Wetland ecosystem also has great research values. Recently like all the other countries in the world, China is suffering the expense of both economic and environment caused by wetland shrink.33% of the wetland disappeared from 1978 to 2008 and the reason is believed to be climate change and human activities. The loss of wetland actually is the change of landscape and vegetation distribution, both landscape change and vegetation redistribution is of great importance for the protection of ecosystem. Based on the field study and modern data analysis techno, we gained a clear idea of the structure of the Hulun lake ecosystem, and explained the succession pattern and distribution feather of the dominant species in Hulun lake retreat area. The result is expected to be the valuable for the protection of wetland ecosystem and the biodiversity.1) Quantitative classification, ordination and biodiversity analysis of vegetation Communities in Hulun lake retreat areaHulun lake, the largest inland lake in Inner Mongolia, had suffered a 15-year lake retreat from 1998 to 2012. The lake retreat had formed a 5km × 3km rectangle shape wetland. The vegetation of the rectangle shape wetland was investigated in mid-August,2012. With the help of Spatial sequence instead of time successional sequence method, the succession sequence of the sample spot was revealed. After used Two-way Indicator Species Analysis (TWINSPAN),70 sample plots had been divided in 6 groups in Division 5 level. Detrended Correspondence Analysis(DCA) was also adopted and the successional sequence was revealed:Chenopodiaceae pioneer community (first stage)→ Phragmitesaustralis community (second stage)→ Leymus chinensis community (final stage). After comparing each succession stage’s biodiversity index (Patrick, Simpson, Shannon-wiener and Pielou indice) and growth style, we found that:(1) The final stage of the succession had the highest biodiversity, evenness and richness (2) The evenness of the vegetation dropped down a little from the first stage to the second stage, and recovered in the final stage (3) The proportion of the perennial plant steadily increased from stage one to final stage.2) The response of the spatial distribution of vegetation to the soil factors in Hulun lake retreat areaBased on the data collected in 2012, we performed another vegetation and soil survey in 2013. After analysis the data with the method of ward cluster and CCA, we found the distribution of the community is like bands parallel with the lake shore. The external area is named G5 and G1 and the dominant species are Stipa krylovii Roshev and Leymus chinensis.The middle area is named G2 and G3, the dominant species are Phragmites australis and Carex duriuscula. The interior area is named G4 and the dominant species are Chenopodiaceae species. The interpretation of the vegetation distribution by CCA using Soil moisture, Soil Organic matter, Soil total N, Soil electric conductance and Soil pH is 65.37%. The band form distribution of species is caused by the band form distribution of soil Environment factors. G1 and G5 grows in the external area is because the dominant species are of high competition in low soil moisture area, and the soil salinity separated the 2 groups. G2 and G3 lies in the middle area because of the moderate soil moisture, the soil salinity and SOC separated the 2 groups. G4 grows next to the lake because of the high tolerance of soil moisture and soil salinity. The high soil salinity caused by high evaporation prevents other species from invading the area. Above all, the Environment factors especially the soil moisture and soil salinity determines the distribution of the vegetation.3) The response of the distribution of the vegetation to the explanation of Hulun lakeWe performed the vegetation and soil factors survey in 2014 in the back ground of 2 consecutive years of 30% increase preciption. We aim to analysis the climate change and the redistribution under the disturbance. After using CCA and ward cluster we found that the lake expandation significantly affected the Environment factors beside the lake. The G3 area besides the lake soil moisture signfifcantly increased but had little effect on G5 which is far away from the lake. Also the soil salinity beside the lake increased.The lake expandation changed the vegetation distribution. G4 disappeared because of the flood. G3 area dominent species changed from Carex duriuscula to Phragmites australis and Scirpus planiculmis because the latter 2 species can tolerate the flood threaten. In G2 area the soil salinity is increasing and in the future the dominent species might change from Phragmites australis to Carex duriuscula according our model.4) Soil respiration feather of 4 different type of grassland in growing season in the condition of lake area explanationThe experiment was performed in Hulun lake, Inner Mongolia in June and August,2014.4 kinds of typical grassland (dominant species are Stipa capillata, Leymus chinensis, Phragmites australis and Carex duriuscula) soil respiration had been measured by using li-6400 gas exchange system and Li-6400-09. The results are shown below. First, the diurnal variety of soil respiration of Stipa capillata, Leymus chinensis and Carex duriuscula was a one peak curve both in June and August because of the temperature, the peak appeared in different time because of the different photosynthesis rate in June and August. Phragmites australis shows a steady line because the temperature did not affect so much as other 3 kind of plants. Soil respiration in August is higher than that in June. Comparing with the mean value in June, Stipa capillata increased 62.81%, Leymus chinensis increased 79.26%, and Phragmites australis increased 233.69%. Phragmites australis increased faster than others because of the high biomass. Carex duriuscula remained the same in June and August because of the high water content in soil caused by lake water rise.