Spatial and temporal variation in plant hydraulic traits and their relevance for climate change impacts on vegetation and tree mortality

Background/Question/Methods

Plant hydraulics form the backbone of terrestrial woody plant productivity, influencing global water and biogeochemical cycles and vulnerability to drought and climate change. Recently, plant hydraulics have been highlighted as a major way through which trees could succumb to drought and climate stresses and that many forests globally appear to operate near their hydraulic safety margin. While interspecies differences in hydraulic traits are widely documented, intra-specific variability in hydraulics over space and time is much less well understood. Here, I present a conceptual framework for this intra-specific variability, reviewing the mechanisms that could drive this variability and the consequences for vegetation response to climate change. I perform a meta-analysis on the published studies of intra-specific variation in a prominent hydraulic trait – the water potential at which 50% conductivity is lost (P50) – and set this variation in context with inter-specific variability and variability of plant functional types used by a dynamic global vegetation model.

Results/Conclusions

I find that intra-specific variability is of ecologically relevant magnitudes, equivalent to around 50% of the inter-specific variability within a genus, and is larger in angiosperms than gymnosperms. Furthermore, plant functional types appear to be poorly situated to capture key differences in hydraulic traits across species. I conclude with a discussion of the implications of intra-specific variability on climate change impacts and modeling of vegetation response to anthropogenic climate change, highlighting the need for multi-trait and multi-species studies that quantify variation over a species’ entire geographic range.