Xylem hydraulic safety and construction costs determine tropical tree growth

• Published in: Plant, cell and environment Vol. 41; no. 3; pp. 548 - 562
• Main Authors: B. Eller, Cleiton, V. Barros, Fernanda, R.L. Bittencourt, Paulo, Rowland, Lucy, Mencuccini, Maurizio, S. Oliveira, Rafael
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01-03-2018
• Subjects: Cavitation; cloud forests; Computer simulation; Construction costs; drought; Economic models; Environmental conditions; Forests; Growth patterns; Growth rate; hydraulic safety margin; Hydraulics; Life history; Mathematical models; Mortality; Optimization; plant hydraulics; Rainforests; Safety; Safety margins; Stomata; Tradeoffs; trade‐off; tree mortality; Trees; Tropical forests; Wood; Xylem; trade-off; tree mortality; plant hydraulics; drought; hydraulic safety margin; cloud forests
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.13106

Faster growth in tropical trees is usually associated with higher mortality rates, but the mechanisms underlying this relationship are poorly understood. In this study, we investigate how tree growth patterns are linked with environmental conditions and hydraulic traits, by monitoring the cambial growth of 9 tropical cloud forest tree species coupled with numerical simulations using an optimization model. We find that fast‐growing trees have lower xylem safety margins than slow‐growing trees and this pattern is not necessarily linked to differences in stomatal behaviour or environmental conditions when growth occurs. Instead, fast‐growing trees have xylem vessels that are more vulnerable to cavitation and lower density wood. We propose the growth ‐ xylem vulnerability trade‐off represents a wood hydraulic economics spectrum similar to the classic leaf economic spectrum, and show through numerical simulations that this trade‐off can emerge from the coordination between growth rates, wood density, and xylem vulnerability to cavitation. Our results suggest that vulnerability to hydraulic failure might be related with the growth‐mortality trade‐off in tropical trees, determining important life history differences. These findings are important in furthering our understanding of xylem hydraulic functioning and its implications on plant carbon economy.
We investigate the relationships between tropical cloud forest trees hydraulic traits and their growth patterns. Our results indicate the existence of a growth‐hydraulic safety trade‐off that has several important ecological and physiological implications. This trade‐off can be explained using the fast–slow plant economic theory and represented with a profit optimization model. Our findings are an important contribution to the development of a wood economic spectrum theory for tropical trees