COS 222-3 - Ecophysiology of jack pine (Pinus banksiana) under climate change: how will a warmer and drier climate affect productivity and mortality of jack pine in the Great Lakes Region?

Abstract: The ecological and physiological principles underlying age related declines in tree and stand productivity have been of long-term interest to foresters and ecologists. The hydraulic limitation hypothesis now acts as our best working model of this age-related decline, describing how taller trees experience more physical resistance in conducting water and nutrients up into their canopies. Additionally, this model, in conjunction with current climate change projections, predicts that large and mature trees will become increasingly more vulnerable to drought stress associated with climatic warming.

My study looks at the age-related growth decline and mortality of jack pine (Pinus banksiana) throughout northern Michigan, examining site and stand specific characteristics, as well as broader climatological trends and their influences on jack pine. Further, my study looks to create management recommendations crucial for ensuring the sustainable habitat management of the conservation-reliant Kirtland’s warbler (Setophaga kirtlandii). My approach combines dendroecological methods examining interannual trends in xylem accumulation, as well as whole tree and plot-level measurements to characterize the growth of jack pine across space and time. Sampling locations were selected along a climatological gradient of temperature, precipitation, and vapor pressure deficit to provide insight into how impending climate change is likely to impact the growth and survivorship of jack pine.

The results of this study show that stands growing in more xeric areas experience an average of 30% higher rates of mature tree mortality as compared to stands growing under more mild conditions. Furthermore, trees growing in more mild conditions are on average 4.5 meters taller by age 50 than what is achieved by trees of the same age growing in more xeric climates. Preliminary stem analysis indicates that individual tree productivity is influenced not only by climate alone, but also the complex interaction between mortality risk, inter-tree competition, and water resource allocation. With stands on more xeric sites having trees which maintain a more consistent rate of growth over time as compared to the asymptotic growth observed in trees growing under more mild conditions.