Understory management and fertilization affected soil greenhouse gas emissions and labile organic carbon pools in a Chinese chestnut plantation

Management practices markedly impact carbon (C) cycling in forest plantations. However, the interactive effects of understory management and fertilization on soil greenhouse gas (GHG) fluxes and labile organic C pools remain unclear in forest plantations. To investigate the effects of understory replacement, fertilization, and their interaction on soil GHG fluxes and labile organic C pools in a Chinese chestnut plantation, we conducted a 2 × 2 factorial experiment over a 12-month field study with four treatments: Control (understory removed without understory replacement or fertilization), understory replacement (understory removed and seeded with Medicago sativa L., MS), fertilization (F), and MS + F. The GHG fluxes were determined using a static chamber/GC technique. The seasonal pattern of GHG fluxes did not change in any of the treatments in this one-year study; however, soil GHG fluxes, total global warming potential (GWP) of GHG fluxes, and soil organic C (SOC), water soluble organic C (WSOC), microbial biomass C (MBC), and NO3−-N concentrations were significantly affected by MS, F, and their interaction. In addition, GHG fluxes, GWP, and SOC, WSOC, MBC and NO3−-N concentrations were markedly increased by fertilization, regardless of the understory replacement treatment (P < 0.05), but they were increased by understory replacement only in the fertilized plots. The GHG fluxes were correlated with soil temperature and WSOC in all plots (P < 0.05), but not with soil moisture and MBC. These findings suggest that understory replacement likely is the optimum management technique for reducing/minimizing GHG fluxes, while F can enhance the effects of MS on increasing soil organic C and nutrient availability. We conclude that a combination of a moderate rate of fertilization and understory replacement with legume species should be adopted to increase soil C sequestration, maintain soil fertility and sustainably develop chestnut plantations.