Water balance of three plantations in hilly areas of South China

To inform tree species selection for vegetation restoration, we assessed the water balance of three plantations — exotic broadleaf Acacia mangium, native broadleaf Schima wallichii, and native conifer Cunninghamia lanceolata — based on 2017–2018 field measurements in hilly areas of South China. Hydrological components were quantified using rain gauges (canopy interception), litter devices (litter interception), sapflow sensors (stand-scale transpiration), soil moisture sensors (soil water storage), and weirs (surface runoff). No clear evidence was found that any tree species exhibited excessive deep water source extraction throughout the two whole study years, but drainage decreased in most months of 2018 despite 114.5 mm more rainfall than in 2017. A. mangium consistently showed evapotranspiration-to-precipitation ratios above one and dry-season drainage deficits in both years, whereas the two native species exceeded this threshold only in 2018 and did not show drainage deficits in either dry season. This suggests the exotic A. mangium was more water-limited and may pose greater risks to catchment water balance in the dry season. Among the three species, native S. wallichii demonstrated the greatest canopy interception during extreme rainfall in 2018, the lowest wet-season surface runoff, and the highest drainage in 2018 as well as in the wet season of 2017 (excluding April), indicating its relative hydrological advantage for afforestation especially under increasingly extreme rainfall. All species had low stand-scale transpiration-to-precipitation ratios, with C. lanceolata showing significantly lower transpiration, significantly higher soil evaporation, and the highest surface runoff—suggesting that, after 30 years of growth, this native conifer may pose risks to water balance sustainability due to inefficient water use and increased flood risks. Longer-term and larger-scale research is needed to confirm these patterns.