Abstract
Tree species largely differ in the amount of annual stem growth explained by current-year conditions. Historic conditions have been shown to additionally explain a significant fraction of the unexplained variance. So far there is no mechanism described explaining why species differ in such legacy effects, obscuring our understanding of species differences in annual stem growth responses to climate. We present a generic conceptual view on key processes determining stem growth. We link current and historic conditions and their impacts on growth by considering the lifetime of functional organs (leaves and sapwood) and reserves (carbon pool) as a way to quantify legacy effects. We propose how tree species with long organ lifetimes are determined by longer periods of historic conditions than species with short organ lifetimes, and why these species differ in their responses to current conditions. We investigated the hypothesis that including lifetime as variable in a process-based tree model allows for explaining different growth responses to current-year conditions. We show that species with short organ and reserve lifetimes are more sensitive to—and better track—current environmental conditions and therefore respond more strongly to current conditions than species with long lifetimes. Instead, the species with longer organ lifetimes respond more strongly to historic conditions and thus buffer their growth responses to current conditions. We propose the impact of historic environmental conditions being controlled by organ and reserve lifetimes and partially explaining the strength of legacy effects and the explanatory power of current-year environmental conditions on stem growth of different species.
Highlights
Reviewed by: Cate Macinnis-Ng, School of Biological Sciences, University of Auckland, New Zealand Victor Resco De Dios, Universitat de Lleida, Spain
We propose how tree species with long organ lifetimes are determined by longer periods of historic conditions than species with short organ lifetimes, and why these species differ in their responses to current conditions
We investigated the hypothesis that including lifetime as variable in a process-based tree model allows for explaining different growth responses to current-year conditions
Summary
Reviewed by: Cate Macinnis-Ng, School of Biological Sciences, University of Auckland, New Zealand Victor Resco De Dios, Universitat de Lleida, Spain. We propose the impact of historic environmental conditions being controlled by organ and reserve lifetimes and partially explaining the strength of legacy effects and the explanatory power of current-year environmental conditions on stem growth of different species. We can think of different qualities and quantities of the carbon pool serving the current physiological performance of a tree dependent on the years involved in building it up, analog to the organs discussed above In line with this argumentation, we assume that different environmental conditions of the past affect the amount and availability of the stored carbon and as such the actual stem growth in trees (Martinez-Vilalta et al, 2016; Galiano et al, 2017). A similar argumentation can be followed for the other organs and reserves carrying over information from multiple years to the present
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