The impact of seasonal variation and forest type on soil organic carbon mineralization in typical forest ecosystems on the Chinese Loess Plateau

Abstract

The mineralization of soil organic carbon (SOC) is essential in the global carbon cycle. The forest type, season, and soil properties affect the characteristics of SOC mineralization in forest ecosystems, but their relative contributions remain unknown. In this study, soil samples from three typical forest types, Pinus tabulaeformis forest (PTF), Quercus acutissima forest (QAF), and mixed P. tabulaeformis and Q. acutissima forest (MF), were collected from China’s Loess Plateau throughout four seasons. Soil physicochemical factors, enzyme activity, microbial community composition, and SOC mineralization characteristics were investigated. Forest type, season, and their interactions significantly affected cumulative carbon mineralization (C_m) and potentially mineralizable carbon (C₀). Only seasonal variations significantly affected the mineralization rate constant (K). C_m and C₀ were highest in spring, whereas the K values were highest in summer. Interestingly, the QAF forest had substantially lower C_m and C₀ values in summer than the PTF and MF forests. Structural equation modeling (SEM) was used to determine the effects of forest type and season on SOC mineralization characteristics. SEMs explained 88%, 84%, and 58% of the variation in C_m, C₀, and K, respectively. The standardized total effects of season and forest type were −0.735 and −0.047 for C_m, −0.485 and −0.004 for C₀, and −0.446 and −0.117 for K. These findings show that on the Loess Plateau, seasonal fluctuations have a greater impact on SOC mineralization than forest type. They indicate that compared to coniferous and mixed forest types, broad-leaved forests had a relatively lower capacity for carbon mineralization. Our knowledge of the role of various environmental factors in controlling SOC dynamics in forest ecosystems is expanded by these studies.