Coupled hydraulic and whole-plant economic strategies in twenty warm-temperate woody species.

The iso- to anisohydric continuum describes how plant regulate water potential and has been used to classify species hydraulic strategies. The slow to fast continuum is a whole-plant strategy for resource acquisition and utilization. The relationship between hydraulic and whole-plant economic strategy could provide a comprehensive method for assessing plants performance. We quantified the degree of isohydricity of 20 woody species in a warm temperate forest. We also measured other functional traits associated with hydraulic and economic strategies (leaf gas exchange, pressure-volume traits, predawn and midday water potential, native and maximum stem hydraulic conductivity, Huber value, and wood density), then explored the underlying trade-offs. Pearson correlations and PCA were performed to assess relationships between isohydricity and other functional traits. We found a coordinated series of iso- anisohydric and slow-fast spectra, where species percentage loss of hydraulic conductivity (PLC) and wood density (WD) were the two most powerful proxies. Along the coordinated continuum, the anisohydric species had higher leaf gas exchange, PLC, and water potential at the turgor loss point, and lower WD than the isohydrics. We found that isohydric species have high drought tolerance, giving them a greater chance of survival than the anisohydric species as drought events are anticipated to be more frequent and severe under global climate change. Identification of associated spectra among plant ecological strategies may increase understanding of how woody plants in temperate forests will respond to climate changes.