Effects Of Vegetation Degradation On The Soil Resistance And Carbon Composition Characteristics Of Gahai Wetland

As an important part of the alpine wetland in Q inghai-Tibet Plateau,the Gahai wetland soil carbon pool is an important indicator of wetland change of Q inghai-Tibet Plateau.In recent years,the vegetation of wetland has been degenerated to some extent due to climate change and human-induced effects,causing significant changes in the composition of the original carbon stocks in wetlands.In view of this,we selected Gahai wetland which locate at the southeast of Q inghai-tibet plateau,meanwhile,we analyzed the differences and the temporal dynamics of light and heavy organic carbon in different vegetation degradation stages wetland to reveal the characteristics and transformation of soil carbon pool which in different degradation of vegetation wetland.The relationship provides the basic data for accurately understand the carbon cycle of wetland ecosystems,and evaluating the potential of soil carbon sequestration and accurately estimating the carbon budget of wetland ecosystems.The main results are as follows:?1?With the aggravation of vegetation degradation,the biomass of the swamp meadow was significantly decreased?P<0.05?.The results showed that the aboveground biomass of the UD stage was significantly higher than LD and MD stages about130.14%and 183.78%respectively.The distribution characteristics of underground biomass were similar to aboveground biomass.Under 0-40 cm soil profile,the underground biomass decreased significantly with the degradation of vegetation?P<0.05?,Respectively higher than LD,MD stage about 51.98%,634.04%.With the aggravation of vegetation degradation,the soil anti-scourability of swamp meadow was significantly decreased?P<0.05?.The UD stage was 1.80,2.77 and 8.66 times of that in LD,MD and HD stages.?3?Degradation of vegetation has a significant effect on light organic carbon in Gahai wetland soils.The average content of light soil organic carbon in 0-100 cm soil layers were:UD?1.31 g/kg?>LD?1.16 g/kg?>HD?1.09 g/kg?>MD?0.83 g/kg?.In general,with the degradation of vegetation intensified,the light organic carbon content gradually decreased,but the severe degradation slightly increased.Light organic carbon shows obvious surface aggregation;it is enriched in 0-10 cm soil layer.The light group organic carbon in the swamp meadow showed obvious seasonal changes in each stage of degradation.In the 0-10 cm and 10-20 cm soil layers,the soil light fraction organic carbon in the UD stage showed a trend of"down-up-down",with the highest in May,the lowest in July and September,and the slight increase in August.Other degenerative stages fell and stabilized in June.The range of light organic carbon variation in 20-40 cm and 40-60 cm soil layers decreased changed between from0.16 to 2.97 g/kg,the UD,LD and MD stages was highest in May and and tend to be stable in July,bimodal curve in HD stage.The seasonal variation characteristics of light carbon in 60-80cm and 80-100cm soil layers were basically the same,both fluctuated with time and changed between from 1.26 and 1.54 g/kg.?4?There was significant difference of heavy fraction organic carbon contents in marsh meadow under different stages of degradation.the average content were listing in the following order:HD?12.96 g/kg?>UD(12.36 g·kg^-1)>LD?12.07g/kg?,with the aggravation of vegetation degradation significantly increased?P<0.05?.From the entire soil layer,the content of soil organic carbon fluctuated between 6.51¹8.60 g·kg^-1,and the vertical distribution was similar to light fraction organic carbon.The variation of soil heavy organic carbon was same in all degraded stages.In 0-10,10-20,20-40 and 40-60cm soil layers,giving linear decrease with time,the significant difference occured between different months?P<0.05?.In 60-80 and 80-100 cm soil layers.Each degradation stage showed a single peak curve,slightly increasing in June and decreasing linearly from July to September.?7?Soil light organic carbon had a positive correlation with aboveground biomass,underground biomass,soil water content,soil anti-scourability,and negatively correlated with heavy organic carbon.Heavy organic carbon was negatively correlated with each index.The light and heavy organic carbon were significantly correlated with the underground biomass,soil water content and soil anti-scourability.