Effects of Understory Vegetation Conversion on Soil Greenhouse Gas Emissions and Soil C and N Pools in Chinese Hickory Plantation Forests

Abstract

Forest management, especially understory vegetation conversion, significantly affects soil greenhouse gas (GHG) emissions and soil C and N pools. However, it remains unclear what effect renovating understory vegetation has on GHG emissions and soil C and N pools in plantations. This study investigates the impact of renovating understory vegetation on these factors in Chinese hickory (Carya cathayensis Sarg) plantation forests. Different understory renovation modes were used in a 12-month field experiment: a safflower camellia (SC) (Camellia chekiangoleosa Hu) planting density of 600 plants ha−1 and wild rape (WR) (Brassica napus L.) strip sowing (UM1); SC 600 plants ha−1 and WR scatter sowing (UM2); SC 1200 plants ha−1 and WR strip sowing (UM3); SC 1200 plants ha−1 and WR scatter sowing (UM4); and removal of the understory vegetation layer (CK). The results showed that understory vegetation modification significantly increased soil CO2 and emission fluxes and decreased soil CH4 uptake fluxes (p < 0.01). The understory vegetation transformation significantly improved soil labile carbon and labile nitrogen pools (p < 0.01). This study proposes that understory vegetation conversion can bolster soil carbon sinks, preserve soil fertility, and advance sustainable development of Chinese hickory plantation forests.