Lichen-Based Critical Loads in the US Pacific Northwest

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Critical Loads Meeting North Cascades National
Park September 5-7, 2006

Lichen-Based Critical Loads in the US Pacific
Northwest
Linda Geiser, Doug Glavich, Sarah Jovan,
USDA-Forest Service, Pacific Northwest
Region Peter Neitlich, USDI-National Park
Service, Western Arctic National Parklands
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Background

• Many lichens are highly sensitive to N
  S-containing air pollutants
• NOx, SO2
• In solution produce nitrite, nitrate, sulfite
  bisulfite nutrients at low concentrations ,
  toxic at high concentrations, interfering with
  biochemical processes, especially photosynthesis
• In solution produce nitric and sulfuric acids
  which lower pH of substrates affecting lichen
  community composition
• NH3
• Absorbs readily to lichen surfaces in solution
  forms NH4. Some experiments show this ion is
  removed from solution by lichens preferentially
  compared to nitrate. Low concentrations have
  fertilizing effect but high levels raise
  substrate pH and favor weedy, nitrophytic
  species.

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Background
Because individual species have differing
sensitivities to air pollutants, pollution
affects lichen community composition.
Group Sub-Group Indicator Species
Clean Air Regional distribution Bryoria capillaris, Lobaria oregana, Sphaerophorus globosus, Usnea filipendula, U. scabrata
Sub-regional distribution Ahtiana pallidula, Alectoria sarmentosa, Bryoria fuscescens, Cavernularia hultenii, Cavernularia lophyrea, Hypogymnia apinnata, H. enteromorpha, H. metaphysodes, Menegazzia terebrata, Nephroma bellum, Nodobryoria oregana, Platismatia herreii, P. lacunosa, P. norvegica, Pseudocyphellaria anomola, P. crocata, Usnea cornuta
Polluted Air Regional nitrophytes Candelaria concolor, Physcia adscendens, Xanthoria polycarpa
Sub-regional nitrophytic or tolerant species Evernia prunastri, Hypogymnia physodes, H. tubulosa, Leptogium saturninum, Melanelia exasperatula, M. fuliginosa, M. subaurifera, M. subelegantula, Parmelia sulcata, Physcia aipolia, P. tenella, Physconia americana, P. enteroxantha, P. isidiigera, P. perisidiosa, Platismatia glauca, Ramalina farinacea, R. subleptocarpha, Tuckermannopsis chlorophylla, Xanthoria candelaria, X. fallax
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Background

• We can map air quality using lichen community
  composition. Polluted sites are dominated by
  weedy, nitrophilous lichens. Clean areas have
  few or no nitrophilous lichens and are dominated
  by native, large, leafy and pendulous
  macrolichens that play valuable ecological roles.

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Background

• Lichen thalli accumulate nitrogen and sulfur in
  proportion to community-based air scores.

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Background

• The Forest Service maintains an extensive
  database for lichen communities and elemental
  content in WA, OR, ID, MT, CA

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Background

• Estimating lichen thallus N ( dw) thresholds.
• Clean and polluted populations are mixed together
  in data.
• Because most sites are in clean areas, lower half
  of distribution curve should be all clean sites.
  
• In clean area, distribution of N in Letharia
  vulpina is normal.
• Because normal distribution curve is symetrical,
  can reflect smooth curve horizontally at peak
  density (Nlevu 0.57) and predict 97.5
  quantile of clean sites to use as a threshold
• Clean Site Threshold for N dw in Letharia
  vulpina
• (0.57-0.3152) 0.57 0.82 N

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Background

• Map of N levels in lichen thalli. Thresholds are
  the predicted 97.5 quantiles for Platismatia
  glauca and Letharia vulpina at clean sites.

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Developing Lichen-Based Critical Loads

• If lichen data can be related to atmospheric data
  then there is a basis for estimating critical
  loads.

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Developing Lichen-Based Critical Loads

• Potential Approaches
• 1. Lichen communities vs. NH4 concentrations in
  bulk wet deposition.

Air Score -0.56 15.88 NH4 mg l-1 r2 0.55,
prob gt F lt 0.0001
NADP at Marblemount, NOCA
The threshold air score, 0.21, corresponds to
about 0.06 mg/l NH4 in bulk precipitation
(NADP). Only poor correlation to kg/ha.
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Developing Lichen-Based Critical Loads

• Potential Approaches
• 2a. Lichen N vs. on-site measurements of total
  deposition.
• Lichen thalli accumulate N in proportion to
  deposition, especially throughfall deposition. If
  the lichen N concentration threshold is 1.0 N,
  then throughfall (dry plus wet) deposition would
  be about 2.4 kg NO3/ha. Wet deposition alone
  would account for about 0.4 kg of the total.

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Developing Lichen-Based Critical Loads

• Potential Approaches
• 2b. Lichen S vs. on-site measurements of total
  deposition.
• Lichen thalli accumulate sulfur in proportion to
  deposition, especially throughfall deposition. In
  this case more measurements are needed at clean
  sites to produce a more accurate response curve.
  Currently SO4 at the Lichen S threshold (0.8)
  would be lt 0 kg/ha.

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Developing Lichen-Based Critical Loads

• Potential Approaches
• 3a. Lichen N vs. CMAQ modeled estimates of
  depositional compounds
• 3b. Lichen community-based airscores vs. CMAQ
  modeled estimates of depositional compounds

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Developing Lichen-Based Critical Loads

• CMAQ Maps of dry and wet plus dry deposition are
  similar with highest N deposition estimates in
  the Puget Trough-Seattle metro region, Willamette
  Valley-Portland metro region, and Columbia Basin.
• Highest regional total deposition is 12
  kg/ha/yr, background levels are lt3 kg/ha/yr.
• Highest dry deposition is 8 kg/ha/yr,
  background levels are lt 2 kg/ha/yr. Dry dep
  accounts for 2/3 of total dep.

Dry Deposition
Dry Wet Deposition
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Relationship between lichen N, air score, and
CMAQ modeled DRY depositional pollutants
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Initial Estimates of Critical Loads

• Critical loads for total dry deposition of NO,
  NO2,, NH3,and HONO based on both lichen N
  lichen air scores is about 2 kg/ha/yr, a value
  similar to the throughfall deposition dry
  component critical load from the Gorge deposition
  study.

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Relationship between lichen N, air score, and
CMAQ modeled WET depositional pollutants
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Initial Estimates of Critical Loads

• Ions of NO3- and NH4 make up gt99 of wet
  deposition of N and about 1/3 of total
  deposition. Total annual wet deposition (kg/ha)
  does not correlate well with lichen based air
  scores, but if precipitation is accounted for,
  then a better correlation is observed. This
  means that critical loads for lichens for wet
  deposition would vary from site to site.

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Initial Estimates of Critical Loads

• This corresponds to 9.5 and 10.9 kg/ha of total N
  deposition per year (range 5.6-15.2) based on
  lichen N or lichen community air scores,
  respectively.

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Initial Estimates of Critical Loads

• Questions
• Why does dry deposition correlate with lichen
  response but not wet deposition?
• Why are some N species (PAN) negatively
  correlated with lichen N and air scores?
• Why are correlations better between CMAQ and west
  side lichen scores compared to east side lichen
  scores (pollution is more localized?, CMAQ
  estimates not as accurate?)
• Next steps?
• Try a subset of lichen data with best CMAQ data
  on finest grid scale, in geographical area where
  the lichen and CMAQ models best agree.
• Fund a field study to measure, lichen N, survey
  lichen communities and collect throughfall
  deposition at as many sites as possible to
  formulate critical loads for deposition of S and
  N.

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Initial Estimates of Critical Loads

• Where do we go from here?

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Acknowledgements

• Matt Porter, WSU, Laboratory for Atmospheric
  Research, for CMAQ data maps. THANKS MATT!
• Ray Drapek USDA-FS, PNW Research Station, Global
  Climate Change Laboratory, N for transposing the
  CMAQ data.
• Joe Vaughn, Brian Lamb, Susan ONeil for putting
  us in touch with Matt!
• Jim Russell, USDA-FS PNW Air Program and Tamara
  Blett, USDI-NPS Air Program for funding,
  feedback, and discussion.
• Elizabeth Waddell, USDI-NPS, and Mark Fenn,
  USDA-FS, PSW Research Station for inspiration and
  deadlines
• Greg Brenner, Pacific Analytics, for statistical
  advice