Prediction of the vertical scaling of soil organic carbon in temperate forest soils using percolation theory

Abstract

Abstract. Forest soil stores a large portion of soil organic carbon (SOC), making it one of the essential components of global carbon cycling. There is apparent spatial variability of SOC in forest soils, but the mechanism that regulates the vertical pattern of SOC is still not clear. Understanding the vertical distribution as well as the transport process of SOC can be of importance in developing comprehensive SOC models in forest soils, as well as in better estimating terrestrial carbon cycling. We propose a theoretical scaling derived from percolation theory to predict the vertical scaling of SOC with soil depth in temperate forest soils, with the hypothesis that the content of SOC along soil profile is limited by the transport of solute. The powers of the vertical scaling of 5 published datasets across different regions of the world are −0.920, −1.097, −1.196, −1.062, and −1.038, comparing with the theoretical value of −1.149. Field data from Changbai Mountain region, Jilin, China, with spatial variation of SOC correlating strongly to temperature, precipitation, and sampling slope is constrained well by theoretical boundaries predicted from percolation theory, indicating that the vertical transport so as the content of SOC along soil profile is limited by solute transport, which can be described by percolation theory in both small and large scales. Prediction of SOC content in Changbai Mountain region based on an estimated SOC content at 0.15 m from available data demonstrates a good agreement with field observation, suggesting the potential of collaborating the presented model with other surface soil models to predict SOC storage and carbon cycling in temperate forest soils.