The Study Of Soil Organic Carbon And Soil Aggregate Stability Meadow Of Degraded Mountain In Wugong Mountain

Soil carbon pool is the largest carbon pool in terrestrial ecosystem.As one of the most widely distributed type of terrestrial ecosystems,the grassland ecosystem,which is an important part of the global carbon cycle,contains huge amount of carbon storage.The mountain meadow of the Wugong Mountain selected in this paper, is already in a serious degraded and fragmented situation because of the excessive tourism development and human disturbance,the increasing of carbon emissions in soil carbon pool, resulting in the regional imbalances in the carbon cycle, making the original carbon "sink" gradually turned into "carbon source".As the basis of soil structures, soil aggregates has an important significance to the sequestration of soil organic carbon,and the stability of soil aggregates has an important influence on the decomposition and transformation of soil organic carbon. Therefore, the study on the size distribution and stability of soil aggregates,the distribution and sequestration of soil organic carbon of the degraded mountain meadow on Wugong Mountain, helps to reveal the influence of mountain meadow under different degraded degrees to the distribution and sequestration of soil organic carbon, and provides theoretical bases for the study of carbon cycle in mountain meadow, and also provides scientific bases for the implementation of carbon sequestration measures and ecological restoration for the study area.The meadow communities selected as the research object in this paper,taking Miscanthus sinensis as the dominant species, are representative of the ridge line- from the peak of Wugong Mountain,Bai Hefeng(Jin Ding),to the direction of Diao Ma Zhuang Area(altitude 1750~1900m).They were randomly divided into 3 groups, each group contains four degradation types(non degraded, lightly degraded and moderate and severely degraded), a total of 12 plots, each plot area(10m * 10m). Selected the soil layers of undisturbed soil 0-20 cm and 20-40 cm for each plot,air drying 3/4 of each soil sample for wet sieve grading of aggregates.In addition, each quadrat sampling, promptly refrigerated fresh samples and the rest 1/4 air dried soil were used for the determination of active organic carbon fractions.The main results are as follows:1)With the increasing of degradation degree,the total organic carbon and active organic carbon fractions of Wugong Mountain mountain meadow soil decreased in general, significantly decreased in the soil layer of 0-20 cm, the MBC was the largest decline relatively(73.78%), significantly higher than that of the SOC,ROC,POC and DOC(respectively 44.48%, 59.79%, 71.45% and 68.51%),which indicating that the soil active organic carbon components affected by the change of the environment compared to total organic carbon were more sensitive and relative decline, microbial biomass carbon(73.78%), was significantly higher than that of soil total organic carbon, readily oxidizable organic carbon, particulate organic carbon and shows that the MBC is the most active and most easily changed;from the proportion of the SOC by each component.2) In the soil layer of 0-40 cm,the content of aggregates,those size of >2mm and <0.25 mm, was the highest among the degradation types,respectively between 29.81-54.82% and 16.02-47.72%, and with the degree of degradation increasing, showing a substantial rise and fall respectively;and the content of soil water stable aggregates of >0.25 mm decreased gradually, the fractal dimension of soil increased gradually,and the diameter of mean weight of soil decreased, indicated that the soil aggregate stability decreases, soil anti erosion ability declines.3) In the soil layer of 0-20 cm and 20-40 cm,the soil water stable aggregate organic carbon increased with the degradation degree decreased,the decline differed from the particle sizes,0-20 cm soil layer were higher than those of 20-40 cm soil layer;the organic carbon content of 1-0.5mm aggregates was the highest in the soil layer of 0-20 cm among different degradation types.The organic carbon storage showed that lightly degraded > non degraded> moderate degraded> severely degraded in the soil layer of 0-20 cm and 20-40 cm,indicated that with the deterioration increased, the protective effect of organic carbon in soil decreased,and decreased with the soil depth,different particle sizes showed as follows,[>2mm]>[<0.25mm]>[2-1mm]>[1-0.5mm]>[0.5-0.25mm].4) The content of SOC showed the positive correlation with the mean weight diameter(R2=0.6913),indicating that with the aggravation of grassland degradation,the content of SOC decreased gradually, so as the aggregate stability and the soil anti erosion ability.Except the size of <0.25 mm, there were significant or extremely significant correlation between the organic carbon and mean weight diameter among different particle sizes,the particle size of 2-1mm and the mean weight diameter were of the highest correlation, the correlation coefficient was 0.847, indicating the stability of aggregates decreased, the soil macro aggregates(>0.25mm) organic carbon content will decrease, especially the 2-1mm size.The results of the study show that: Wugong Mountain mountain meadow degradation led to the loss of soil organic carbon content significantly.The carbon storage decreased linearly,and even the soil carbon cycle imbalanced. Therefore, I suggest that we should take carbon sequestration measures to improve the soil structure, and improve the content of soil organic carbon as soon as possible.