Potential for Maladaptation During Active Management of Limber Pine
Active management is needed to sustain healthy limber pine (Pinus flexilis) forests in the southern Rocky Mountains as they are threatened by the interaction of the mountain pine beetle (Dendroctonus ponderosae) epidemic, climate change, and the spread of the non-native pathogen that causes white pine blister rust disease (Cronartium ribicola). Appropriate source material for restoration and proactive introduction of disease resistance needs to be developed taking into account background genetic differentiation that could hamper management success. In a common garden study in a greenhouse we evaluated the differential responses of limber pine populations from northern and southern portions of the Southern Rockies to different moisture regimes on early seedling growth. There were significant effects of source region, with seedlings from southern sources being larger than seedlings from the northern sources. Furthermore, there was a significant interaction between soil moisture regime and source region for water use efficiency, suggesting possible local adaptation. This research indicate that genetic differentiation exists among populations in the Southern Rockies, increasing the risk of maladaptation when moving seed far from its source for active management. Planting disease-resistant seedlings to increase the frequency of resistance to white pine blister rust in populations before pathogen invasion is recommended for the sustained health of ecosystems dominated by limber pine. However, early results reveal that genetic resistance to white pine blister rust is not distributed uniformly across the southern Rockies. This study suggests that supplementing southern populations with seedlings having heritable resistance to white pine blister rust from the north within this region should be done with caution due to the potential for maladaptation to stresses at the planting location. Key Findings are: Limber pine populations adapted to southern Colorado are difference from those from northern Colorado and southern Wyoming. Movement of seed within the Southern Rocky Mountains far from its source may result in poor tree performance and could be further impacted in a changing climate.Identifying seed sources with genetic resistance to white pine blister rust for proactive and restoration plantings are needed at a finer scale than the southern Rocky Mountains.
Forest Service Partners