Contrasting drought sensitivity and post-drought resilience among three co-occurring tree species in subtropical China

The impact of drought stress on dominant tree species of subtropical China, and the capacity of these species to recover from drought, is relatively unknown. Three ecologically important tree species (Syzygium rehderianum, Castanopsis chinensis and Schima superba), with contrasting drought sensitivities, were grown in pots under well watered conditions in the glasshouse before being subjected to two drought treatments (i.e. higher intensity and shorter-duration fast drought(FD);lower intensity and longer-duration slow drought(SD)) towards mortality, and then re-watered to assess the rate of physiological recovery. Dry mass production and physiological traits related to water and carbon relations were measured over the experimental period. FD led to faster declines in hydraulic and photosynthetic function than SD in all species, while hydraulic failure occurred towards mortality in all species under both drought treatments. Although NSC responses varied among drought treatments and species, carbon starvation was not observed. S. rehderianum exhibited more rapid declines in leaf water potential and gas exchange traits, and shorter time-to-mortality, followed by C. chinensis and S. superba. Following re-watering, all three species showed rapid recovery of leaf water potential, while rapid recovery in stem hydraulic conductivity was not evident in any species. Furthermore, C. chinensis exhibited full rapid recovery of photosynthesis, but photosynthetic recovery in S. rehderianum and S. superba was slower than recovery of water potential, reflecting differential stomatal and biochemical limitations. The response of the three species to drought was strongly correlated with xylem embolism resistance, but recovery following drought was complex and partially associated with stomatal and biochemical traits. Under future longer and severe droughts, these species may diverge in drought responses and recovery, perhaps driving shifts in forest community structure in subtropical China.