Above‐ and belowground strategies of tropical montane tree species are coordinated and driven by small‐scale nitrogen availability

The question whether the strategies of above- and belowground plant organs are coordinated as predicted by the plant economics spectrum theory is still under debate. We aim to determine the leading dimensions of tree trait variation for above- and belowground functional traits, and test whether they represent spectra of adaptation along a soil fertility gradient in tropical Andean forests.We measured leaf, stem and fine root functional traits, and individual-level soil nutrient availability for 433 trees from 52 species at three elevations between 1000 and 3000 m a.s.l.We found close coordination between above– and belowground functional traits related to the trade-off between resource acquisition and conservation, whereas root diameter and specific root length formed an independent axis of covarying traits. The position of a tree species along the acquisition–conservation axis of the trait space was closely associated with local soil nitrogen, but not phosphorus, availability.Our results imply that above- and belowground plant functional traits determine at which edaphic microhabitats coexisting tree species can grow, which is potentially crucial for understanding community assembly in species-rich tropical montane forests.