Integrating dendroecology with other disciplines improves understanding of upper and latitudinal treelines

Abstract

Despite a consistent global relationship between the position of alpine and arctic treeline and temperature, fine-scale variability in treeline response to climate is widespread. In this chapter, we describe two advances in the application of dendroecology to treeline environments. First, we show that obtaining detailed, spatially explicit measurements of the environment can provide a more complete picture of how tree growth responds to climate. Substantial topoclimatic and environmental heterogeneity can occur at a very fine scale, a few tens of meters, at treeline. Unlike traditional approaches that aggregate tree growth across relatively broad areas, applying the approaches of landscape ecology and quantifying this heterogeneity can allow dendroecologists to better understand fine-scale, within-population variation in climate response. Second, the integration of dendroecological approaches with physiological ecology and soil biogeochemical studies can provide a more holistic understanding of tree growth, one that approaches trees as not merely being the sum of their rings, but as complex organisms whose growth integrates the impact of multiple limiting factors filtered through distinct physiological processes. In regions with cold soils, for example, we show that nutrient limitation can strongly mediate the response of tree growth to climate warming. Together, these approaches allow us to understand the causes of fine-scale variation in treeline response to warming, reconcile that variation with global-scale correlations between treeline and temperature, and better predict future responses of treeline ecosystems to warming.