The Role of Lichens in Air Quality Monitoring

The Role of Lichens in Air Quality Monitoring on Federal Lands What information can lichen monitoring provide to air resource managers? Linda Geiser, US Dept. of Agriculture-Forest Service, Pacific Northwest Region Air Resource Management, PO Box 1148, Corvallis OR 97330

What are lichens? British soldiers Button lichen Lichens are symbiotic organisms consisting of a fungus and an alga and/or a cyanobacterium. Lung lichen

What physiological properties make lichens useful indicators of air quality? Ø Range of air pollution sensitivities across species. Lichens exhibit a range of sensitivities to S- & N compounds in acid rain, sulfur dioxide, ammonia, and fluoride. Changes in distribution or populations of the most sensitive lichens provide an early warning that air pollution is beginning to adversely affect the ecosystem. The mix of species and abundances at any one site can be used to position the site along an air quality gradient. Ø High surface area and no roots. Lichens on trees and shrubs obtain nutrients from the air, precipitation, and substrate run-off. Tissue levels of many pollutants are correlated with ambient atmospheric levels. Ø Readily absorb water and lack specialized barriers to prevent vapor loss. Daily cycles of wetting and drying produce a dynamic equilibrium between concentration and leaching of pollutants. As pollution concentrations change, so do concentrations in lichens. Mobile elements: S, N, K, Ca, Mg, Na. – can change significantly over a few months. Less mobile elements: Pb, Cd, Ni—change more slowly.

What kinds of data are collected? ØLichen communities and floristics ØTissue analyses ØTransplants ØLaboratory

#1. Documenting deposition of pollutants in a Class 1 Area and tracing their source. Mt. Zirkel Wilderness, Routt NF, Colorado Yellow lines circle lichen monitoring plots (black triangles) REFERENCE: Jackson, LL, L Geiser, T Blett, C Gries, D Haddow. 1996: Biogeochemistry of lichens and mosses in and near Mt. Zirkel wilderness, Routt National Forest, Colorado: influences of coal-fired power plant emissions. Open-File Report, 96 -295, U. S. Department of the Interior, U. S. Geological Survey. 162 pp.

Mt. Zirkel Wilderness, Routt NF, Colorado Stable S isotope ratios in lichens were significantly heavier in the MZW and Routt NF than at regional sites. This was consistent with a local sulfur source with a heavy isotopic signature resulting from the combustion of marine-influenced coals from the Yampa Valley.

#2. Check a site within an area with established background ranges. Lichen monitoring sites indicated by yellow triangles Klondike Gold Rush National Historic Park, Skagway, Alaska REFERENCE: Furbish, C. E. , L. H. Geiser and C. Rector. 2000. Lichen-air quality pilot study for Klondike Gold Rush National Historical Park and the City of Skqaway, Alaska. Klondike Gold Rush National Historical Park Natural Resources Management Program. Report released December 2000.

Klondike Gold Rush National Historic Park, Skagway, Alaska Mean concentrations of Al, Cd, Cr, Cu, Fe, Pb, Ni, P, K, S, Zn in the lichen, Hypogymnia enteromorpha, were higher in Klondike Gold Rush NHP samples than Tongass National Forest samples.

Lichen tissue was collected along a transect from the APC mill, through the town of Sitka to the Ferry Terminal (red dots). #3. Mapping deposition patterns from a point source. Tongass National Forest, Sitka, Alaska REFERENCE: Geiser, LH/ Derr, CC/ Dillman, KL 1994: Air Quality Monitoring on the Tongass National Forest. Methods and Baselines Using Lichens. - USDA-Forest Service, Alaska Region Technical Bulletin 46. 85 pp.

Tongass National Forest, Sitka, Alaska Typical cover of lichens on alder in the Sitka area Lichens were absent from alder <0. 25 mi from the pulp mill, an SO 2 source.

Tongass National Forest, Sitka, Alaska 3 -D view of lichen tissue concentrations in # of sd from Tongass clean sites mean (vertical axis) vs sampling site location (horizontal axes). Far right is < 1 km from the pulp mill, center is Sitka city center, far left is the ferry terminal, 14 mi distant.

#4. Estimating deposition from calibrated lichen data. Pacific Northwest National Forests Lichen tissue collections were made within 1 km of 8 NADP monitors in Oregon and Washington (black dots on national map above).

Pacific Northwest National Forests Lichen sulfur concentrations, weighted by precipitation, accurately predicted wet deposition of sulfur to within about 0. 3 kg/ha/yr.

Pacific Northwest National Forests A map of wet deposition of sulfur in Pacific NW national forests constructed using calibrated lichen data. Values ranged from < 0. 7 (dark blue) to > 4. 0 (red) kg/ha/year. A map of wet deposition of nitrogen was similar.

#5. Combining lichen community and tissue data to indicate patterns of anthropogenic influence and its effects on vegetation. Alaska and Pacific Northwest Regions Red dots indicate monitoring locations where lichen community surveys and tissue analysis have been completed by the USFS Air program. In PNW forests, monitoring is co-located with the CVS (= USFS national Forest Inventory Assessment) 3. 4 mi grid.

Sensitive, ecologically important lichens, many endemic, are sparse to absent in areas where acid rain is high.

Growth of pollution-loving, weedy species is enhanced where nitrogen pollution is high.

Lichen communities indicate a pollution gradient Lichen communities Ordination of sites by lichen communities. Plots (represented by triangles) with smiliar communities are close together in space. Environmental variables are overlaid on the ordination Axis 1 is correlated with increasing sulfur and nitrogen pollution. Axis 2 is correlated with decreasing distance from the coast and warmer winter temperatures. In this analysis, urban parks and the Columbia River Gorge National Scenic plots receive the highest pollution scores.

#7. Determining whether instrumented monitoring is warranted Hell’s Canyon National Recreation Area Could ancient rock art be threatened by air pollution?

Hell’s Canyon National Recreation Area Nitrogen concentrations in lichen tissue and abundance of the nitrogen-loving lichen, Xanthoria, were highest at sites closest to the Snake River.

Hell’s Canyon National Recreation Area Average tissue concentrations of nitrogen at all sites in Hell’s Canyon were elevated relative to background sites in the western US Conclusion: Instrumented monitoring is warranted.

Summary: Advantages of lichen monitoring Ø Good indicators of deposition containing sulfur, nitrogen, metals, other elements, radionuclides and some hydrocarbons/organochlorines. Ø Demonstrates presence of contaminants in the ecosystem. Ø Lichen communities are good summarizers of air quality—respond to the synergistic mix of pollutants in the air. Ø Lichen communities (species richness, composition and abundance) can be used to indicate whether anthropogenic activities are affecting the ecosystem Ø Relatively fast and inexpensive—many measuring points can be made in a short time that summarizing air quality over past months or years. Ø Useful in areas of rugged topography where modeling is inadequate. Ø Useful in remote areas—does not require electric power. Ø Can be used to map relative differences in air quality over a geographical area of interest and to track changes over time. If air pollution tolerant species are used, can map polluted areas. Ø Source apportionment is possible using multi-element analysis and isotope ratios.

Summary: Advantages of lichen monitoring Ø Compliments instrument measurements and other monitoring information. Element analyses, community analyses used in combination with direct measurements or other bioindicatorscan corroborate each other, making a more convincing argument for decision-makers. Ø Plentiful existing data for the PNW and Alaska and Canada for metals, and in arctic for POPs, some data for radionuclides from Canada. Preliminary thresholds for metals. Ø Can link to existing programs: FHM (lichen communities) and USFSPNW (communities and tissue analysis). Ø Not mobile, concentrations reflect local conditions. Ø Easy to collect, lichens are widespread and easy to recognize. Ø Deposition can be estimated from lichen tissue levels if instrumented sites are available for calibration. Ø Multi-element analysis can evaluate multiple stressors simultaneously, good idea to measure effects of sulfur and nitrogen deposition together with other pollutants.

Summary: Limitations of lichen monitoring Ø Lichens are relatively insensitive to many air toxics (metals, radionuclides, organics)– lichen communities affected more by acid rain, SO 2, N deposition and fluorine. I. e. may be able to show presence of enhanced tissue levels but not adverse effects to ecosystem. Ø Cannot separate wet from dry deposition or different forms of sulfur or nitrogen containing pollutants using lichens—measure total N, total S and total deposition. Ø Some metals are not easily leached from lichen thalli and may remain concentrated for 10+ years. Can use transplants, select species with annual growth (Hylacomium splendens) or collect from substrate of known age (last five terminal bud scars). Or, because epiphytic lichens grow rather quickly, can monitor changes over time of the population mean. Ø Interference from local dust: use enrichment factor from local soils (Al). Ø Tissue analysis cannot differentiate wet from dry deposition. May not be able to distinguish different forms of a single element.

Summary: Limitations of lichen monitoring Ø Multivariate analysis is often required to separate the pollution signal from other environmental variables (elevation, precip, forest continuity, relative humidity, available substrates) OR restrict the range of these variables within the study area. Ø To obtain accurate and repeatable readings of metals, tissue concentrations of metals should be in the 0. 1 ppm range or higher. Check detection limits of laboratory before analysis. Ø Lichen analysis for POPs is analytically challenging because concentrations are usually low and natural lichen substance interfere with analyses. But much base work has been completed for the arctic. Ø Must have sufficient material– lichens may be difficult to find where acid rain, SO 2 or N deposition is a problem. Can use transplants. Must compare different sites using the same species. Ø Regulatory personnel are often unfamiliar with lichen monitoring methods. Can establish LACs, develop an MOU, or calibrate data to units used by regulatory agencies.