Assessment of Forest Sensitivity to Nitrogen and Sulfur Deposition in Maine (Conference of New England Governors and Eastern Canadian Premiers Forest Mapping Group)

Miller, Eric

This is a general report for all of Maine that shows no ANP specific information, but ANP is part of the mapping and assessment of sensitivity. Executive Summary 'Acidic Deposition in Northeastern North America Although sulfur emissions have decreased as a result of SO2 control programs, projected emissions of acidifying sulfur and nitrogen compounds are expected to have continuing negative impacts on forests. These emissions present some of the most serious long-term threats to forest health and productivity in northeastern North America. Excess sulfur and nitrogen deposition may reduce the supply of nutrients available for plant growth. Nutrient depletion leads to increases in the susceptibility of forests to climate, pest and pathogen stress which results in reduced forest health, reduced timber yield, and eventual changes in forest species composition. Forest Sensitivity Mapping Project Conceived by the Conference of the New England Governors and Eastern Canadian Premiers (NEG/ECP), under the direction of its Committee on the Environment, their 1998 Acid Rain Action Plan called for the formation of a Forest Mapping Working Group to conduct a regional assessment of the sensitivity of northeastern North American forests to current and projected sulfur and nitrogen emissions levels. This group is charged with identifying specific forested areas most sensitive to continued sulfur and nitrogen deposition and estimating deposition rates required to maintain forest health and productivity. This report provides new information on the potential risks posed by sulfur and nitrogen air pollution to MaineÆs forest resources. How Was This Assessment Done? Evaluating forest sensitivity to acidic deposition requires information on: pollution loading to forest landscapes; the interaction of pollutants with forest canopies; plant nutrient requirements; and the ability of soils to buffer acid inputs and replenish nutrients lost due to acidification. Recent scientific advances in estimating each of these factors have made it feasible to produce maps of forest sensitivity to acid inputs from atmospheric nitrogen and sulfur. An integral part of this project was an open dialog with scientists, air resource specialists, foresters, and members of provincial, state and federal governments about data, methodology, and interpretation of results. Appropriate methods, models and mapping techniques and data requirements were developed during a pilot study of Vermont and Newfoundland which was completed in 2003 (NEG/ECP-FMG 2003). This report describes how these methods were applied to the analysis of forest sensitivity to acid deposition in Maine. Summaries of forest sensitivity in Vermont, New Hampshire, Massachusetts, Connecticut, and Rhode Island are also included in this report to provide spatial context for the Maine results. Forest Sensitivity Assessment Metrics Critical load of sulfur + nitrogen is the level of deposition below which no harmful ecological effects occur for a forest ecosystem. Deposition index is the difference between the critical load and current deposition and is used to identify sensitive forest ecosystems. 3 Assessment of Forest Sensitivity to Nitrogen and Sulfur Deposition in Maine 15 December 2006 The approach we have used to determine acceptable levels of deposition is an ecological assessment based on a steady-state1, ecosystem mass balance (see Appendix) for nutrient cations (calcium, magnesium, and potassium). Two metrics critical load and deposition index express the result of this assessment. The critical load of sulfur + nitrogen is the level of deposition below which no harmful ecological effects occur for a forest ecosystem. (See external holding link for full report.) /STUDY LOCATIONS:/ /ACADIA NATIONAL PARK/