High hydraulic safety linked to low relative phosphorus availability across a range of tropical and subtropical species

Abstract

Nitrogen (N) or phosphorus (P) bioavailability constrain the magnitude of terrestrial carbon uptake and plant growth in tropical and subtropical regions, while carbon metabolism is coupled with plant hydraulic systems; therefore, nutrient availability changes are likely to exacerbate or alleviate drought-induced plant mortality. Most studies have neglected the hydraulic failure risk degree and are limited to single species fertilization experiments. We aimed to fill this gap by examining how variation in the relative P availability to N, as reflected by foliar N:P ratios, influences plant hydraulic failure risk degree across a broad range of species by collecting published data and conducting field experiments. The results demonstrated that increasing relative P availability to N would decrease the hydraulic safety margin (increase hydraulic failure risk) by regulating the leaf area: stem area ratio and changing vessel wall reinforcement. This study suggests that forests would potentially face increasing drought-induced mortality if relative P availability is increased through human activities including fertilization, while the mortality risk would decrease with a decrease in relative P availability due to heavy N deposition in tropical and subtropical regions. Relative P availability should be considered when assessing the forests vulnerability to global change.