Climate change and edaphic conditions: predicting future growth of a critical boreal tree species - Jack Pine (Pinus banksiana)

Abstract

Global climate predictions anticipate increased temperature, variable total precipitation, as well as a greater number and intensity of severe precipitation events. Deepening our understanding of the complex relationships between climatic factors, tree growth, and edaphic conditions is key for predicting future suitable habitat for environmentally and economically salient tree species. Jack Pine (Pinus banksiana) provide crucial structural habitat and are an important species for timber production in the Upper Midwest. Jack Pine habitat ranges across extremes of an edaphic gradient. However, little is known about how these differing conditions influence growth performance as a function of oscillating climate. In this study, I assessed the effect of climatic variability on the growth of trees under different edaphic conditions (two sites with dry soils and one site with wet soils). Using tree core increments from three forest sites in Michigan’s northern lower peninsula, tree growth was analyzed as a function of climate, age, and prior growth using a hierarchical Bayesian framework. As expected, trees in the wet soils had the highest growth rates. Individuals in all sites responded positively to increased spring temperature, whereas those in the wet site showed the highest response to increased summer precipitation. However, under predicted drier conditions the growth response in the wet site was expected to decline by 33%, while those in the two drier sites were expected to decline by 2 and 19%, equalizing growth rates across all three sites. Further, the decline in growth associated with drier summers will exceed any benefits conferred by warmer spring temperatures in the wet site. Sites near bogs and intermittent wetlands are currently associated with high growth performance. However, under the forecasted climate for the region, trees growing in these sites will likely lose their advantage.