Factors driving change in average tolerance scores in eastern North America

Abstract

Forests are dynamic systems and species composition change is a natural part of forest dynamics; however, growing evidence shows accelerated species composition changes in eastern North America with links to climate change. Several studies have focused on the eastern United States, but none have used long-term range-wide data from the USA and Canada. Here, we combine Forest Inventory and Analysis (FIA) data from the USA with several Canadian provincial datasets to assess drivers of plot-level change in average tolerance. Results show that disturbances, both human and natural, are mainly driving short-term changes in tolerance. Initial stand conditions also influence rates of changes in average tolerance. Climate, and more specifically climate change, have minor impacts on tolerance except when coupled with severe disturbances. Understanding factors influencing changes in tolerance and identifying changes beyond those expected under natural development enables a better understanding of the scope of potential changes driven by climate change.