title: Lichen-based critical loads for atmospheric nitrogen deposition in Western Oregon and Washington Forests, USA.
abstract: Critical loads (CLs) define maximum atmospheric deposition levels apparently preventative of ecosystem harm. We present first nitrogen CLs for northwestern North America's maritime forests. Using multiple linear regression, we related epiphytic-macrolichen community composition to: 1) wet deposition from the National Atmospheric Deposition Program, 2) wet, dry, and total N deposition from the Communities Multi-Scale Air Quality model, and 3) ambient particulate N from Interagency Monitoring of Protected Visual Environments (IMPROVE). Sensitive species declines of 20-40% were associated with CLs of 1-4 and 3-9 kg N ha(-1)y(-1) in wet and total deposition. CLs increased with precipitation across the landscape, presumably from dilution or leaching of depositional N. Tight linear correlation between lichen and IMPROVE data suggests a simple screening tool for CL exceedance in US Class I areas. The total N model replicated several US and European lichen CLs and may therefore be helpful in estimating other temperate-forest lichen CLs.
authors.affiliation: US Forest Service Pacific Northwest Region Air Resource Management Program, Siuslaw National Forest, PO Box 1148, Corvallis, OR 97339, USA. lgeiser@fs.fed.us
authors.forename: Linda H
authors.initials: LH
authors.lastname: Geiser
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Jovan
authors.forename: Doug A
authors.initials: DA
authors.lastname: Glavich
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Porter
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000378:metabolism*; D004784:Environmental Monitoring; D005843:Geography; D008011:Lichens / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D009922:Oregon; D014481:United States; D014861:Washington
chemical_list: D000393:Air Pollutants; D009584:Nitrogen