Consequences of Stand Age and Species’ Functional Trait Changes on Ecosystem Water Use of Forests

Abstract

Determining how trees move water from the soil to the atmosphere has been central to the study of forest productivity and hydrology for over a century. Improved predictive understanding of stand age and water yield will become even more important as humans modify forest stand age structure through forest management and/or climate change. Successional changes in plant species and/or plant functional traits increase uncertainty in estimates of stand transpiration as forest stands age because of the lack of theory on how tree species influence transpiration. This chapter investigates how changes in stand age can impact stand transpiration. We focus on reanalyzing published datasets from two of our own chronosequences of stand-scale transpiration. Our goal is to determine the minimal model complexity needed to maximally capture this variation in stand transpiration across chronosequences. We seek to answer the following question: “If we chose a reference stomatal conductance from one stand age of the entire chronosequence to put into a model, would modeled transpiration for the other ages be biased?” We then explore the relative roles of stomatal conductance, leaf and sapwood area in explaining these patterns in our study and in other published studies of forest chronosequences.