title: Water availability predicts forest canopy height at the global scale.
abstract: The tendency of trees to grow taller with increasing water availability is common knowledge. Yet a robust, universal relationship between the spatial distribution of water availability and forest canopy height (H) is lacking. Here, we created a global water availability map by calculating an annual budget as the difference between precipitation (P) and potential evapotranspiration (PET) at a 1-km spatial resolution, and in turn correlated it with a global H map of the same resolution. Across forested areas over the globe, Hmean increased with P-PET, roughly: Hmean (m) = 19.3 + 0.077*(P-PET). Maximum forest canopy height also increased gradually from ~ 5 to ~ 50 m, saturating at ~ 45 m for P-PET > 500 mm. Forests were far from their maximum height potential in cold, boreal regions and in disturbed areas. The strong association between forest height and P-PET provides a useful tool when studying future forest dynamics under climate change, and in quantifying anthropogenic forest disturbance.
authors.affiliation: Institute of Botany, University of Basel, Schönbeinstrasse 6, Basel, 4056, Switzerland.
authors.forename: Tamir
authors.initials: T
authors.lastname: Klein
authors.affiliation: Institute of Botany, University of Basel, Schönbeinstrasse 6, Basel, 4056, Switzerland.|Department of Ecology & Evolution, University of Lausanne, Basel, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Randin
authors.affiliation: Institute of Botany, University of Basel, Schönbeinstrasse 6, Basel, 4056, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Körner
mesh_terms: D065928:Forests; D008954:Models, Biological; D013696:Temperature; D014197:Trees / Q000254:growth & development*; D058438:Water Cycle
keywords: Evapotranspiration; forest suppression; hydraulic constraints; range limits; tree height