The Scale-Correlation Analysis Between Soil Organic Carbon Density And Its Influence Factors Based On Wavelet

The soil organic carbon(SOC) pool is a key component of carbon pool in terrestrial ecosystems, it's helpful not only to the regional carbon cycle research, reasonable sampling distance and to provide evidence for regional ecological environmental conservation and sustainable utilization of resources, but also to provide basic data for the research of soil carbon storage and carbon balance in our country. Based on GIS, wavelet transform, correlation analysis and other research methods, this thesis estimates the SOC density in mountain area of Guangdong Province, analyzes spatial distribution characteristics of different soil types and vegetation types, studies the influence of NDVI and topographic factors (altitude, slope and aspect) on SOC density distribution, and use one-dimensional discrete wavelet transform with DB6 wavelet generating function to make multi-scale decomposition of each factors, the goal is to quantitatively reveal multi-scale spatial distribution pattern of SOC density, as well as the multi-scale correlation with its influencing factors. The major research contents and conclusions are as follows:(1) Analyzing the influence of different NDVI, altitude, slope and aspect levels on the SOC density distribution in mountain area of Guangdong Province by means of zonal statistics model. Overall, the SOC density of 0-20cm and 0-100cm depth both increase with increasing NDVI, gradually increase with higher altitude, but a various range at different altitude levels, increase at first, then decrease with the increase of slope, the SOC density of sunny slope is above that of shady slope.(2) Taking the SOC density and its influence factors including NDVI, altitude, slope and aspect in mountain area of Guangdong Province as research objects, one-dimensional discrete wavelet transform is applied to quantitatively reveal multi-scale spatial distribution pattern of SOC density, as well as the multi-scale correlation with its influence factors.The spatial variability of SOC density is controlled by the influence degree of dominant factors at different scales, the spatial heterogeneity is more intensive at the 1km or bigger scale; the characteristic scale of each transect differs because of various soil and vegetation types, terrain features, as well as planting system, tillage practices and other human activities.The correlation between SOC density and influence factors is scale-dependent with varying degree, the positively controlling of NDVI and elevation on SOC density increased with the sale getting bigger, at the scale of 2km, 8km and 16km, NDVI has the most intensive controlling, at the scale of 8km and 16km, elevation shows its greatest influence; the control action of slope is rather weak, with a less significant correlation depending on scale, the negative effect of aspect after the 2km scale shows stronger control when the scale increases; There is a different scale-correlation on the same transect with various depth; The SOC density of different transects is affected by various factors, of which NDVI and elevation are the main factors, slope and aspect only react with individual transects at the larger scales, the more the influence factors the greater the scale, the reason for this difference is mainly related to various terrain and climate characteristics of each transect.