Forest Health Implications of Calcium Perturbations in TreesEPA Grant Number: U915728
Title: Forest Health Implications of Calcium Perturbations in Trees
Investigators: Borer, Catherine H.
Institution: University of Vermont
EPA Project Officer: Edwards, Jason
Project Period: August 1, 2000 through August 1, 2002
Project Amount: $89,448
RFA: STAR Graduate Fellowships (2000) RFA Text | Recipients Lists
Research Category: Fellowship - Forestry , Academic Fellowships , Biology/Life Sciences , Ecological Indicators/Assessment/Restoration
The objective of this study is to investigate the physiological roles of calcium (Ca) in trees, as well as the broader ecosystem consequences of anthropogenically-altered Ca availability in forest tree species. The overarching hypothesis for this work is that significant reductions in environmental Ca availability coupled with acidic leaching can result in an insufficient supply of a small, but physiologically important pool of Ca within tree foliage, the plasma membrane associated Ca (mCa). Inadequate mCa may act as a predisposing factor, leading to increased susceptibility to future declines as a result of environmental stresses, which may impact the future health and sustainability of forested ecosystems.
Three primary research questions are addressed: (1) Can low soil Ca availability impact mCa in addition to total foliar Ca? (2) Can reduced mCa predispose plants to sensitivity to an array of environmental stresses? and (3) Is mCa one of the primary sources of messenger Ca involved in signaling environmental cues?
A series of studies will be conducted at three scales: (1) At the cellular level, the investigator will examine Ca signal transduction processes and assess the ability of red spruce (Picea rubens Sarg.) cells to physiologically respond to environmental cues that are known to include alterations of cytoplasmic Ca in their signaling pathways. Fluorescent techniques will be adapted to assess cytoplasmic Ca concentration so that signal transduction and cellular responsiveness in cells with perturbed mCa status can be investigated. Cells will be subjected with various levels of mCa to short-term environmental cues, including low temperature signals, to separate the role of mCa in signal transduction from its role in membrane stability. (2) At the individual tree level, the study will investigate whether reduced mCa in red spruce seedlings impairs their ability to respond to environmental cues and stresses. Through soil-based nutrient manipulations, a population of seedlings has been created with a range of mCa. With these plants, the photosynthetic and stomatal responsiveness to short-term environmental changes in temperature, CO2 availability, and relative humidity will be investigated. Longer-term responsiveness to normal seasonal conditions also is being monitored by assessing autumn/winter membrane stability and cold tolerance development. (3) At the stand scale, the nature of the relationship between Ca nutrition (measured as mCa and total foliar Ca) and environmental responsiveness (measured as winter cold hardiness) of mature red spruce trees growing in a site with naturally low soil calcium availability will be evaluated. This will allow the determination of whether Ca deficiency can be defined by a threshold in mCa, below which physiological impairment occurs.
By studying the physiological roles of calcium (Ca), inadequate levels of mCa will be shown to be a predisposing factor to environmental stresses, leading to future declines of forest tree species.