Variations in soil aggregate stability and aggregate-associated C-N-P stoichiometry by stand type in Chinese fir

Abstract

Research on the variations in soil aggregate stability and ecological stoichiometry at aggregate scales by stand type is of great significance to investigating the distribution, limitation, balance, and cycling of chemical elements. We measured the variations in soil aggregate stability, organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) contents and stocks, in addition to their stoichiometric ratios by stand type (mixed stands of Chinese fir and Mytilaria laosensis and Chinese fir and Michelia macclurei and pure stand of Chinese fir), and aggregate size (<0.25, 0.25-1, 1-2, and >2 mm) in soil profile (0-20 and 20-40 cm) in Guangxi, China. Soil OC and TN contents and C/N, C/P and N/P ratios were more distributed in aggregates of <0.25 mm in the three stands; in contrast, soil OC, TN, and TP stocks were more obvious in aggregates of >2 mm. In comparison to the pure stand, the mixed stands showed significantly higher levels of soil aggregate stability, aggregate-associated OC and TN contents with stocks, TP content, C/N and C/P ratios. The C/N ratio, TN and TP contents, and TP stocks were the key factors in the stand types affecting the stability of soil aggregate changes. Hence, constructing mixed stands and applying appropriate amounts of N and P fertilization can improve soil fertility and promote degraded soil restoration.