The growth response of forests and woodlands to increasing temperatures and altered precipitation regimes will play a key role in mitigating or accelerating the pace of climate change. Growth responses to climate will not only vary across ecosystems due to stark differences in resource availability and species physiology, but also within ecosystems due to local physiographic factors such as elevation, aspect, and soil type, which alter local water and energy balance. We investigated how recent climate warming has impacted tree growth among three tree species in two Rocky Mountain ecosystems: pinyon pine, a widely distributed species of semi-arid woodlands, and Engelmann spruce and subalpine fir, two widely distributed species of subalpine forests. We investigated the growth trend of individual trees through time, determined the climate variables most important for driving growth, and quantified the interactions between climate and landscape physiography that are influencing the long-term growth trends and potential for ecological change across the study region.
Results/Conclusions
Growth declines were observed in subalpine fir and pinyon pine over the past century while Engelmann spruce growth increased during this time period. Growth of pinyon pine and subalpine fir was negatively affected by summer temperatures and associated increases in water deficits and positively affected by seasonal precipitation. The magnitude of growth responses to these climate variables varied across the landscape due to topographic effects on water and energy balance and soil available water capacity. In contrast, Engelmann spruce was uniformly unresponsive to climate. In addition to highlighting the importance of species-level differences in growth response to climate, our results also identify interactions between climate and local physiography as controls on long-term growth trends, and suggest that the local landscape physiography can mediate climate related stress in forest and woodland ecosystems.