Effects of Tree Functional Traits on Soil Respiration in Tropical Forest Plantations

Abstract

Fast-growing tree species, including Eucalyptus sp. and Acacia sp., are widely used to rehabilitate degraded tropical forestland quickly, while mitigating climate change. However, the extent of carbon losses through soil respiration (RS) often remains unknown. Moreover, the promotion of these non-native species has raised concerns over their impact on other ecosystem services, including N2-fixation-induced soil acidification and nutrient cycling. This study compared two non-native and native species, with one of each being N2-fixing, growing in 11-year-old monospecific plantations in NE Thailand. Hourly RS was measured monthly over one year and combined with stand characteristics, as well as soil microclimatic and chemical properties. Mixed-effects models were used to capture this hierarchical, diurnal, and seasonal dataset. RS rates were influenced by soil temperature and moisture following a parabolic relation, and negatively affected by acidity. Overall, RS varied significantly according to species-specific microclimates and productivity. Despite the high input of organic matter, non-native species failed to ameliorate extreme soil moisture or temperature; limiting microbial decomposition and reducing RS. Hopea odorata produced moderate levels of carbon sequestration, but maintained soil fertility. The choice of tree species can significantly affect carbon sequestration and storage, as well as nutrient cycling, and careful species selection could optimize these ecosystem services.