Quantifying the traits that control drought responses and recovery processes is a primary goal of tree hydraulic research. The most common of these traits include the water potential at 50% loss of hydraulic conductivity (P50), the P50 safety margin, and a species’ degree of isohydry or anisohydry. While many theories and lines of inquiry have investigated the predictive utility of these traits, few studies have sought a holistic understanding of how these traits are coordinated within individual species, and how they interact to influence tree physiology during and post-drought. We sought to test the interrelationships between common hydraulic traits and link those traits to variation in drought and recovery responses. To do so, we applied an experimental soil moisture reduction to seven species of tree sapling for six weeks, and resumed watering for another six week period to quantify each species’ recovery. Throughout, we measured hydraulic traits and monitored drought-induced changes in gas exchange, leaf water potential (ΨL), and hydraulic conductivity.
Results/Conclusions
Overall, our species’ hydraulic traits were not correlated, as some anisohydric species had surprisingly low resistance to embolism (P50) and small safety margins. This hydraulic sensitivity, combined with drastic reductions in photosynthesis and ΨL during water stress, caused large amounts of hydraulic damage that hindered recovery for weeks. We saw no evidence for a trade-off between hydraulic risk and the maintenance of photosynthesis in anisohydric trees during drought, and therefore no benefit of being anisohydric either during or post-drought. Our results indicate the need to examine the traits that underlie anisohydric behavior and to consider the environmental, biological, and edaphic processes that may allow this strategy to flourish in forests.