Elevated temperature exacerbates the effects of drought on the carbon and hydraulic characteristics of Robinia pseudoacacia seedlings

Abstract The rising temperature and extreme drought induced by climate change will considerably affect plant growth and survival. However, the interactive effects of elevated temperature and drought on carbon (C) balance and hydraulic traits remain unclear. In this study, we investigated the C exchange, hydraulic characteristics and total nonstructural carbohydrate (TNC) availability of different organs in Robinia pseudoacacia seedlings during drought and re-watered periods under two temperature treatments. Our study showed that drought reduced C assimilation and increased loss of plant xylem conductivity (PLC). In addition, elevated temperature exacerbated the effect of drought on the C exchange rate and hydraulic characteristics. The TNC concentrations were lower in roots than in other tissues, and seedlings exposed to drought also showed decreased TNC concentrations in specific tissues (roots, stems and leaves) and in the whole seedlings. Seedlings showed lower TNC concentrations under elevated temperature than at ambient temperature, suggesting that elevated temperature accelerated the consumption of stored TNCs. After short-term re-watered, the C exchange rate and hydraulic characteristics of drought seedlings showed larger recovery under ambient temperature than under elevated temperature. Our findings suggest that elevated temperature exacerbate the risks of hydraulic failure and C starvation in R. pseudoacacia under drought, which may increase the drought-induced seedling mortality of R. pseudoacacia in drought-prone regions under future climate scenarios.