Soil autotrophic and heterotrophic respiration respond differently to land-use change and variations in environmental factors

Abstract

Converting natural forests to intensively managed plantations markedly alters soil carbon (C) dynamics. However, the impact of such land-use change on soil respiration (RS) components remains unclear. The objective of this study was to examine the effect on RS, autotrophic respiration (RA) and heterotrophic respiration (RH) of converting a natural evergreen broadleaf forest to an intensively managed Moso bamboo (Phyllostachys edulis) plantation. A two-year field study was carried out to assess the seasonal dynamics of RS, RA and RH in three broadleaf forest-bamboo plantation pairs, using a portable soil CO2 flux measurement system. Results showed that converting the evergreen broadleaf forest to the bamboo plantation increased the annual cumulative RS and RH by 18.8% and 20.9%, respectively, but did not change the annual cumulative RA. Soil temperature alone explained 48% and 79% of seasonal variations in RA and RH, respectively, in the evergreen broadleaf forest, and 68% and 79%, respectively, in the bamboo plantation. The land-use change increased the apparent temperature sensitivity (Q10) of RA, but did not affect that of RH. Regardless of the land-use type, both RA and RH were positively correlated with soil water soluble organic C, but not with soil moisture content. The RH was positively correlated to soil microbial biomass C (MBC) in the evergreen broadleaf forest, but not in the bamboo plantation. The RA was not correlated with soil MBC, regardless of the land-use type. Therefore, soil RA and RH responded differently to land-use change and variations in environmental factors, suggesting that partitioning of RS to different components is essential to elucidate mechanisms associated with changes in RS induced by land-use change and to predict RS under different climate change scenarios.