Exploring Environmental Drivers of Growth for Tree Species Associated with a Rare Limestone Bluff Cedar–Pine Forest in Vermont

Abstract - The limestone bluff cedar–pine forest is a rare upland natural community that is threatened by development and invasion by exotic species. Furthermore, the sensitivity of this forest-type to changes in climate and pollution exposure is unknown. We collected xylem increment cores from 4 conifer species (Thuja occidentalis [Northern White Cedar], Juniperus virginiana [Eastern Red Cedar], Pinus strobus [Eastern White Pine], and Tsuga canadensis [Eastern Hemlock]) and 4 hardwood species (Quercus rubrum [Northern Red Oak], Quercus alba [White Oak], Fagus grandifolia [American Beech], and Fraxinus americana [White Ash]) within and close to a cedar–pine forest along the eastern shore of Lake Champlain in Vermont and correlated radial tree growth to precipitation, snow, temperature, and pollution data to assess which factors influenced growth during the time period 1937–2016. We examined growth and possible environmental drivers of it for a variety of species to evaluate how unique these may be for the cedar and pine trees emblematic of the limestone-bluff community. For both conifers and hardwoods, precipitation exhibited the strongest positive correlations with growth and occurred with greater frequency compared to other climate and pollution parameters. Snow was positively associated and temperature was negatively associated with growth for all species. Despite growing over calcium-rich bedrock, and especially for the conifers, pollution seemed to limit growth in years prior to pollution reductions enacted following the 1990 Amendments to the Clean Air Act.