Variations of soil organic C components under different degradation conditions in Napahai wetland reserve
纳帕海湿地不同退化状态下土壤有机碳素的分异特征

There are four major types of soils in Napahai wetland reserve,northwest Yunnan,i.e.,Abandoned Farmland Mesophytic Meadow Soil(AFMMS),Mesophytic Meadow Soil(MMS),Wet Meadow Soil(WMS),and Marsh Soil(MS),correspondingly their degradation degrees from high to low.Soil organic carbon(SOC),labile organic carbon(LOC) and dissolved organic carbon(DOC) contents and their correlation at three layers(1st layer 0~10 cm,2nd layer 10~20 cm,and 3rd layer 20~30 cm) for the 4 types were investigated.Results showed that except that LOC contents at the 2nd and 3rd layers of AFMMS were slightly higher than those at corresponding layers of MMS,the orders of the contents of SOC,LOC and DOC at the other layers of the 4 soils were AFMMS < MMS < WMS < MS,which clearly reflected the degradation conditions of the 4 soils within the wetland region.From up to down in the soil profiles,soil SOC,LOC and DOC contents of AFMMS,MMS and WMS,as well as the DOC contents of MS,declined from top to down layer;the decrease between the 1st and 2nd layers was significantly larger than that between the 2nd and 3rd layers;while the contents of SOC and LOC of MS increased from the 1st to 2nd layer and then declined to the 3rd layer.LOC/SOC(%) of the 4 soils varied from 8.6 % to 16.8 % and LOC/SOC at 3 layers of the 4 soils was AFMMS > MMS > WMS > MS,which indicated dryer soil had a higher turnover rate of the biological activity of SOC.Except extremely human-disturbed AFMMS,LOC contents are significantly positive to SOC contents for the other 3 types of soils;furthermore,the variations of LOC contents and LOC/SOC(%) have correlations with soil types.Compared with SOC and DOC,LOC is more suitable to detect the changes of wetland SOC pool.The study indicated the variation of wetland hydrology and vegetation controlled by topography has significant influence on the variation of wetland SOC and its labile components;high disturbance(e.g.wetland reclamation and drainage) usually causes obvious loss of wetland SOC and its labile components.For the degraded sub-alpine wetlands like Napahai where significant hydrological changes were observed,hydro-ecological regulation measures should be taken to prevent their further degradation.