Study On Variation Of Carbon And Nitrogen Components Of Soil In Napahai Wetland Reserve

The response of Alpine wetland on the global/regional climate change and human activities was extremely sensitive, and its soil environment and components were more easily in response to changes of hydrological. Variation of soil carbon/nitrogen and its components in Alpine wetland, was an important way to identify regional environment and ecological response. Napahai, lying in the middle part of Hengduan Mountain, northwestern Yunnan is a unique and seasonal marsh wetland. At 50-90s of the last century, rapid degradation of Napahai watland was occurred.In this thesis, Concentrations of SOC, LOC, DOC, TN, RAN, DON, AN, NN and pH at 3 layers(lst 0-10cm,2nd 10-20cm,3rd 20-30cm)were analyzed for the 4 types of soils-Abandoned Farmland Mesophytic Meadow Soil (AFMMS), Mesophytic Meadow Soil (MMS), Wet Meadow Soil (WMS), and Marsh Soil (MS) in Napahai wetland reserve,correspondingly their degradation degrees from high to low.The major results are:(1)The characteristics of soil organic carbon components variation, in the horizontal direction, for the 4 soils (AFMMS, MMS, WMS, MS) in Napahai wetland reserve, Except LOC concentration at the middle and down layers of AFMMS were slightly higher than those at corresponding layers of MMS, the order of the concentrations of SOC, LOC and DOC at other layers of the 4 soils were AFMMS< MMS< WMS< MS, it revealed the effects of human disturbances within the wetland region. From up to down in the soil profiles, SOC, LOC and DOC concentrations of AFMMS, MMS and WMS, as well the DOC concentration of MS, declined from top to down layer, the decease between the top and middle layer was significantly larger than that between the middle and down layer. While the concentrations of SOC and LOC of MS increased from the top to middle layer and then declined to the down layer. The SOC in the top layer variation of 4 soils in Napahai wetland reserve, fanned brought the loss of SOC, after more than 10 years of natural recovery process, SOC of AFMMS failed to return to the appropriate level of MMS.(2) The characteristics of N components variation, in the horizontal direction, for the 4 soils, the concentrations of N components in the top layer showed significant variation as AFMMS<MMS<WMS<MS, but no obvious variation in the middle and down layers except the layers of MS; From up to down of the soil profiles, the concentrations of N components of AFMMS, MMS and WMS decreased gradually, but N components relatively concentrated in the top layer and the differences between the middle and down layer were low. The orders of the TN and RAN concentrations of MS were the middle layer> the top layer>the down layer, which indicated relative enrichment in the top and middle layers; but the concentrations of DON and IN of MS decreased downwards and relatively enriched in the top layer.(3) For the 4 soils, LOC/SOC varied from 8.6% to 16.8%; the order of LOC/SOC at each layer was AFMMS>MMS>WMS>MS, it revealed that if soil was dryer, the turnover rate of the biological activity of soil organic carbon pools was higher. Except DOC/LOC at MS top layer reached 8.74%, the ranges of DOC/SOC and DOC/LOC were 0.21%-0.80% and 3.64%-4.99%. LOC showed highly positively related to SOC (p<0.01 or 0.05) for MMS, WMS and MS, but lowly for AFMMS, LOC and SOC had a higher correlation under natural conditions and a low correlation under strong human disturbance.(4) Both DON and IN concentrations accounted for very low percentages of RAN of the 4 types of soils, which were respectively about 1.94%-4.73%,2.10%-4.04%. Therefore, among the research of soil available nitrogen, in addition to IN and DON, we should pay more attention to other available nitrogen fractions.(5) The corresponding relationship between the variation of N components in the top layers and the soil moisture condition among the 4 types of soils showed, under the lower soil moisture condition, the concentrations of N components and C/N ratios will be also lower, but the percentages of RAN and DON to TN will be higher. It concluded wetland becoming dry would accelerate the loss of N components of the wetland soil, especially in the top layer. Regulating measures should be taken to control further wetland drying in the future Napahai wetland conservation and management.