LB 24-232 - Intraspecific variation in leaf pressure-volume traits: biophysical constraints, and implications for in-situ and remote sensing of leaf water potential

Background/Question/Methods

Functional traits are critical for understanding and predicting ecological processes across scales from organ to ecosystem function across climate gradients. The role of intra-specific trait variation (ITV) can be defined at a wide range of scales, with implications for many community and ecosystem-wide processes, though remains unquantified for many key ecophysiological traits, such as pressure volume (PV) curve parameters. We defined a “reference ITV”, the variation among sun leaves of replicate individuals of given species grown in similar conditions, which enables quantification of ITV for the conditions under which species-level ecophysiological traits are frequently measured. Further, ITVref has important implications for new approaches for estimating leaf water status from spectroscopic measurements with the input of mean species-level traits such as PV parameters. We hypothesized that, given their functional importance in defining drought response thresholds, PV parameters would show conservative trait variation (i.e., low ITVref) relative to other leaf morphological traits, and thus mean PV traits can be used for estimation of leaf water potential based on remote or in situ measurements of leaf water content. We also tested whether intraspecific relationships among PV traits were similar to those previously established based on biophysical rationales across species.

Results/Conclusions

We compiled a database of pressure volume curves for leaves of 51 species and additional leaf structural traits for 39 of those species. We found low ITVref among PV parameters compared to morphological traits, strong correlation among traits and their variation for relationships established across species and illustrated dependence of leaf water potential predictions on leaf spectra over ITV. These results highlight a strong importance for intraspecific variation in the prediction of leaf water status remotely.