COS 107-5 - Into the Third Dimension: Understanding the Vertical Microclimate Gradient in H.J. Andrews Experimental Forest

Abstract: There is a spatial mismatch between climate model data (kilometer-level) and the finer resolution (meter-level) at which birds interact with their environment. Thus, species are exposed to climate regimes at much finer resolutions than commonly available in climate models. This opens the possibility that they can behaviorally adapt to changing climate by moving within forests at fine spatial scales. However, little is known about vertical thermal gradients within the forest canopy. We vertically instrumented trees in second-growth and old-growth forests from the understory through the canopy trees to test whether forest understories are buffered from more severe temperature fluctuations higher in the canopy. We expect buffering effects to be particularly strong in old growth. The goal of this study is to determine the vertical scale at which certain forest types can serve as microclimatic refugia. We found patterns in vertical microclimate show temperature differences between the understory and canopy of up to 3 degrees Celsius indicating a thermal buffering capacity of forest understory. These data help us better understand vertical patterns in microclimate in Pacific Northwestern forests. As temperatures become more extreme, it is increasingly important to understand microclimatic variation within a landscape and whether certain habitats can serve as microclimate refugia for birds.