The influence of provenance on radial growth and drought resilience of lodgepole pine in Fraser Experimental Forest, Colorado, U.S.A.
Date
2024
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Abstract
Climate change poses unprecedented challenges to forested ecosystems, particularly in drought-affected areas in the western United States, where increased temperatures and shifting precipitation regimes are negatively impacting locally adapted tree species. In response, researchers and land managers are exploring innovative forest adaptation strategies to maintain forest resilience, such as assisted migration. This study examines the potential of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) to be utilized in forest assisted migration efforts in western North America, drawing from the understanding that this widespread species displays intraspecies variation in growth-climate associations due to local adaptations across its extensive geographic range. We make use of a provenance study established in the early 1980s in Fraser Experimental Forest, Colorado, U.S.A. to examine the effect of seed source, or provenance, on growth-climate responses and drought resilience of lodgepole pine in its southernmost range. We investigate two primary research questions. First, does provenance climate influence the radial growth response of lodgepole pine trees? Second, do lodgepole pine trees from climatically drier provenances exhibit greater resilience to drought, as measured by annual radial growth before and after drought events? To address our first question, we employed dendrochronological methods and a generalized linear mixed-effects modeling approach utilizing climate data to analyze the variation in overall radial growth of trees explained by the difference in provenance and study site climates during our study period, 1992-2021. In addressing our second question, we utilized the Standardized Precipitation Evapotranspiration Index (SPEI) and metrics of quantifying drought resilience to determine the impact of provenance site aridity on tolerance to drought during our selected drought period, 2001-2002. Our analyses revealed significant differences in radial growth between trees from different provenances. Specifically, we found that trees originating from provenance sites with greater growing season average vapor pressure deficit, yet higher precipitation, exhibited increased radial growth. In analyzing drought resilience, we found that trees from provenances with higher average temperatures and greater evapotranspiration showed greater resilience to drought, aligning with previous research linking seed source climate aridity to drought tolerance. Interestingly, we also found that trees from sites with greater climate moisture index compared to their growing site exhibited greater radial growth resilience to drought, suggesting that certain populations may be less sensitive to moisture deficits. Our research sheds light on the relationship between provenance climate with radial growth response and drought resilience in an assisted migration context. Our findings suggest that provenance climate aridity may confer resilience to trees during resource-limited events. More broadly, our study underscores the potential of utilizing local adaptations and intraspecies variability of tree species in climate adaptation efforts aimed at mitigating the impact of climate change in forested ecosystems.
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Subject
climate adaptation
forest ecology
provenance experiment
climate change
assisted migration
lodgepole pine