Topic: Adaptation Planning, Forests and Wildfire | Region: United States | Year: 2018

Mapping Potential Future Range Shifts in Southwestern White Pine

  • Samual Cushman, US Forest Service
  • Kristen Waring, Northern Arizona University
  • Christian Wehenkel, Universidad Juárez del Estado de Durango
  • Alejandro Lael-Sáenz, Universidad Juárez del Estado de Durango
  • Chris Toney, US Forest Service
  • Carlos Lopez-Sanchez, Universidad Juárez del Estado de Durango
  • Completed
  • US Forest Service
  • Northern Arizona University
  • Universidad Juárez del Estado de Durango
  • National Science Foundation

We modeled the current and potential future distribution of Southwestern white pine (Pinus strobiformis), a high elevation conifer species found in the mountains of the southwestern United States and Mexico. These models are being used by the US Forest Service and other forest managers to help conserve this climate-sensitive species under threat from increasing drought stress and an expanding outbreak of white pine blister rust.

Journal Article

Project Background

Southwestern white pine (SWWP) is considered a keystone species of the high elevation forests of the southwestern United States and Mexico because of its nutritious seeds which support wildlife and the tree cover it provides in harsh alpine environments where trees are scarce. This species is sensitive to extreme drought and white pine blister rust (WPBR), both of which are on the rise as the regional climate warms and summer precipitation decreases.

An understanding of the climatic constraints on SWWP distributions and how climate interacts with soils and topography to determine the range of this species is important for projecting the future impacts of climate change and for devising effective management strategies to help conserve SWWP. Project partners will use the insights and projections from this study to guide transplanting locally adapted drought-tolerant and WPBR-resistant variants of SWWP to areas where the current population is not well adapted to future conditions. In addition, partners are using the model predictions to help guide field surveys that are designed to detect WPBR outbreaks and also map local genetic adaptations to climate and resistance to WPBR.

Approach

The US Forest Service and the mexican Comisión Nacional Forestal survey and inventory tree species at thousands of plots on federal forest lands throughout the southwestern United States and Mexico, respectively. We identified and gathered data related to the climatic, soil, and topographic conditions potentially related to the occurrence of SWWP. From these data, we trained models to predict the probability of SWWP presence throughout the region.

From these models, we mapped the current and potential future distributions of SWWP under different emissions scenarios, and identified areas of potential range contraction, range expansion, and refugia where this species may persist in the future. We also assessed the potential climate impacts on SWWP in terms of overall suitable area and fragmentation of SWWP populations.

Results and findings

• A warmer and drier future climate may pose extreme risk of drought stress.
• Winter warming may cause failure to meet the chilling requirement for budburst.
• As a result, the southwestern white pine distribution will shift dramatically by 2080.
• The range shift of this keystone species may have profound ecological consequences.
• Our results inform management and conservation efforts to mitigate these threats.