Air Pollution Sensitivity Ratings for Macrolichens in the Eastern US

Nitrogen- (fertilizing) and sulfur- (acidifying) containing air pollutants are two pollutants of widespread ecological concern in the United States. When pollutants in the air are deposited to vegetation and soils, whether dissolved in precipitation or dry deposited in particulate form, this is called .atmospheric deposition.. Some lichens are highly sensitive to small changes in nutrient nitrogen availability or to the small changes in acidity (pH), and some prefer a higher nutrient nitrogen environment or can tolerate more acidity than others. As total deposition increases, depending if the pollutants are nitrogen or sulfur containing, or both, it shifts the composition of species present to favor more nutrient nitrogen-loving and/or more acidity-tolerant species. After a certain point, the overall number of species starts to decline and in very high deposition areas, it becomes increasingly difficult to find any lichens at all. Also as deposition increases, the dominant, ecologically important species tend to be displaced by weedy species that do not replace those roles. For example, the beard or forage lichens are preferred as food and nesting materials for wildlife, and cyanolichens are associated with high diversity and abundance of invertebrates. These groups of species tend to be the most sensitive to both nitrogen and sulfur containing air pollutants. Variation in lichen sensitivities to these pollutants is then used to monitor deposition through lichen community surveys.

The ratings below are based on national scale surveys by the US Forest Service. See * below for methods.

Key to Lichen Sensitivity Ratings

Nitrogen Requirement: O = oligotroph, M = mesotroph, E = eutroph

Oligotrophs are most abundant under fertilizing nitrogen deposition regimes averaging 0.5 to 4.2 kg N/ha/yr and are increasingly difficult to find as deposition increases above 4.2. Mesotrophs prefer a moderate nutrient regime, 4.2 to 8.0 kg N/ha/yr, and are harder to find above 8.0 and below 4.2. Eutrophs tolerate and are often enhanced by N deposition loads above 8.0 kg N/ha/yr. Highest mean annual nitrogen deposition at lichen survey sites from 2000-2012 was about 17 kg/ha/yr in the eastern US, relatively few sites received < 3.5 kg ha/yr.

Tolerance to acidity: S = sensitive, I = intermediate, T = tolerant

Sensitive (S) lichens are most abundant under acid deposition regimes averaging 0.5 to 4.2 kg N/ha/yr and are increasingly difficult to find as deposition increases above 4.2. Intermediate (I) lichens are most frequently found where S deposition ranges between 4.2 to 8.0 kg S/ha/yr, and are harder to find above 8.0 kg. Tolerant (T) lichens can be unaffected by S deposition at or above 8.0 kg S/ha/yr. Highest mean annual sulfur deposition at lichen survey sites from 1993-2012 was about 32 kg/ha/yr in the eastern US, relatively few sites received < 3 kg/ha/yr.

Taxonomy follows the 19th North American Checklist.

* Brief Methods Summary

  1. Eastern US ratings are based on 2156 systematic surveys across public and private forests east of the Mississippi River following the US Forest Service Forest Inventory & Analysis lichen communities indicator protocol. States not surveyed: MS, TN, KY, FL. Does include northern MN.
  2. Deposition measure: Community Multi-Scale Air Quality (CMAQ) 5.0.1 modelled estimates for total N and S deposition for the continental US from 2000-2012 at a 12 km grid scale with bi-directional NH3 air-surface exchange using the Massad formulation. Alaska deposition estimates were based on on-site deposition measurements and calibrated lichen element concentrations (Root et al. 2013 Forest Ecol. & Mngmt, 306:1-8).
  3. 3-year rolling mean deposition was calculated for each survey site, including survey year and previous 2 years.
  4. Survey sites were assigned to deposition increments of 0.5 kg/ha/yr, requiring a minimum of 35 sites per increment. To incorporate the high end of the deposition gradients, with fewer plots, the increment length was increased up to 1.5 kg.
  5. Number of detections per deposition increment was plotted for each species occurring in the eastern US.
  6. Splines were fit for each species using the function .smooth.spline. with a flexibility setting (.spar.) equal to 0.5 in the software R (v. 3.1.1 R Development Core Team 2014).
  7. The deposition associated with peak detection frequency along the spline was recorded.
  8. Sensitivity ratings were assigned as above based on deposition at peak detection frequency after filtering out rare species and species with ambiguous response curves.

Table: Eastern US Sensitivity Ratings

Download this table (.csv format, opens in Excel)

Scientific NameNo. of DetectionsSensitivity to Nutrient
Nitrogen Deposition
Sensitivity to Acid
Ahtiana aurescens60oligotroph 
Anaptychia palmulata82 tolerant
Bryoria capillaris16oligotrophsensitive
Bryoria furcellata178oligotrophintermediate
Bryoria fuscescens35oligotrophsensitive
Bryoria nadvornikiana38oligotrophsensitive
Bryoria trichodes49oligotrophsensitive
Bulbothrix scortella60eutrophtolerant
Candelaria concolor454mesotrophsensitive
Candelaria fibrosa26mesotrophsensitive
Canoparmelia caroliniana234eutrophtolerant
Canoparmelia cryptochlorophaea16eutrophintermediate
Canoparmelia texana29eutroph 
Cetrelia chicitae36oligotrophsensitive
Cetrelia olivetorum88oligotrophsensitive
Cladonia caespiticia101eutrophtolerant
Cladonia cenotea13oligotrophsensitive
Cladonia chlorophaea200oligotrophsensitive
Cladonia cristatella79oligotrophsensitive
Cladonia cylindrica68eutrophtolerant
Cladonia didyma17eutrophtolerant
Cladonia floerkeana9eutroph 
Cladonia grayi30oligotroph 
Cladonia macilenta var. bacillaris166eutrophtolerant
Cladonia ochrochlora572 tolerant
Cladonia pyxidata32mesotrophsensitive
Cladonia rei21oligotroph 
Cladonia squamosa63oligotrophsensitive
Coccocarpia palmicola13eutroph 
Collema nigrescens12oligotrophintermediate
Collema subflaccidum45oligotrophsensitive
Crespoa crozalsiana77eutrophtolerant
Evernia mesomorpha576oligotrophsensitive
Flavoparmelia baltimorensis22eutrophtolerant
Flavoparmelia caperata1398eutrophtolerant
Flavopunctelia flaventior96mesotrophsensitive
Flavopunctelia soredica71mesotrophsensitive
Heterodermia albicans80eutrophtolerant
Heterodermia casarettiana26eutrophtolerant
Heterodermia granulifera15eutrophtolerant
Heterodermia hypoleuca12eutrophtolerant
Heterodermia obscurata255eutrophtolerant
Heterodermia speciosa144mesotrophsensitive
Heterodermia squamulosa28eutrophtolerant
Hyperphyscia syncolla9 sensitive
Hypogymnia krogiae72oligotrophintermediate
Hypogymnia physodes742oligotrophintermediate
Hypogymnia tubulosa52oligotrophintermediate
Hypotrachyna croceopustulata9eutrophtolerant
Hypotrachyna horrescens124eutrophtolerant
Hypotrachyna livida227eutrophtolerant
Hypotrachyna minarum231eutrophtolerant
Hypotrachyna osseoalba20eutrophintermediate
Hypotrachyna pustulifera23eutroph 
Hypotrachyna revoluta13oligotroph 
Hypotrachyna showmanii46eutrophtolerant
Imshaugia aleurites176oligotrophsensitive
Imshaugia placorodia15eutroph 
Leptogium austroamericanum13eutrophtolerant
Leptogium cyanescens133oligotrophsensitive
Leptogium saturninum18oligotrophsensitive
Lobaria pulmonaria193oligotrophsensitive
Lobaria quercizans128oligotrophsensitive
Melanelixia fuliginosa44eutrophtolerant
Melanelixia subargentifera12mesotrophsensitive
Melanelixia subaurifera636oligotrophintermediate
Melanohalea exasperatula11mesotroph 
Melanohalea halei44oligotrophtolerant
Melanohalea olivacea50oligotrophintermediate
Melanohalea septentrionalis148oligotrophsensitive
Menegazzia subsimilis34oligotrophsensitive
Myelochroa aurulenta620eutrophtolerant
Myelochroa galbina346oligotrophsensitive
Nephroma helveticum16oligotrophsensitive
Nephroma parile10mesotrophsensitive
Pannaria conoplea14oligotrophsensitive
Parmelia saxatilis34mesotroph 
Parmelia squarrosa492oligotrophsensitive
Parmelia sulcata1169oligotroph 
Parmeliella triptophylla11oligotrophsensitive
Parmeliopsis ambigua47oligotrophintermediate
Parmeliopsis capitata44oligotrophintermediate
Parmeliopsis hyperopta26oligotrophsensitive
Parmotrema austrosinense11eutroph 
Parmotrema cetratum55eutrophtolerant
Parmotrema crinitum53mesotrophtolerant
Parmotrema dilatatum37eutrophtolerant
Parmotrema eurysacum47eutroph 
Parmotrema gardneri26eutrophtolerant
Parmotrema hypoleucinum11eutrophtolerant
Parmotrema hypotropum371eutrophtolerant
Parmotrema louisianae9eutrophtolerant
Parmotrema margaritatum89eutrophtolerant
Parmotrema mellissii10 intermediate
Parmotrema perforatum154eutrophtolerant
Parmotrema perlatum61eutrophtolerant
Parmotrema praesorediosum57eutrophintermediate
Parmotrema rampoddense37eutrophtolerant
Parmotrema reticulatum287eutrophtolerant
Parmotrema stuppeum35eutrophtolerant
Parmotrema subisidiosum68eutrophtolerant
Parmotrema submarginale120eutrophtolerant
Parmotrema subrigidum52eutrophintermediate
Parmotrema subtinctorium24eutroph 
Parmotrema tinctorum62eutrophintermediate
Parmotrema ultralucens24eutrophtolerant
Parmotrema xanthinum20eutrophintermediate
Phaeophyscia adiastola47eutrophtolerant
Phaeophyscia ciliata82mesotrophsensitive
Phaeophyscia hirsuta12mesotroph 
Phaeophyscia hirtella32mesotrophsensitive
Phaeophyscia hispidula14mesotrophsensitive
Phaeophyscia pusilloides567mesotroph 
Phaeophyscia rubropulchra1209eutrophtolerant
Physcia adscendens104mesotrophsensitive
Physcia aipolia268mesotrophsensitive
Physcia americana226eutrophtolerant
Physcia crispa12eutrophtolerant
Physcia millegrana996eutrophtolerant
Physcia neogaea47eutrophtolerant
Physcia stellaris547mesotrophsensitive
Physciella chloantha65 sensitive
Physciella melanchra10mesotrophsensitive
Physconia perisidiosa285mesotrophsensitive
Platismatia glauca103oligotrophintermediate
Platismatia tuckermanii212oligotrophsensitive
Polycauliona polycarpa136mesotrophsensitive
Pseudevernia cladonia12eutrophtolerant
Pseudevernia consocians60eutroph 
Pseudocyphellaria crocata15oligotrophintermediate
Punctelia appalachensis15eutroph 
Punctelia bolliana38mesotrophsensitive
Punctelia graminicola40eutroph 
Punctelia missouriensis73eutrophtolerant
Punctelia perreticulata499eutrophtolerant
Punctelia reddenda16eutrophtolerant
Punctelia rudecta1305eutrophtolerant
Pyxine sorediata329oligotroph 
Pyxine subcinerea160eutroph 
Ramalina americana336oligotrophsensitive
Ramalina dilacerata78oligotrophsensitive
Ramalina intermedia24mesotrophsensitive
Ramalina sinensis18mesotrophsensitive
Tuckermanella fendleri42eutrophtolerant
Tuckermannopsis americana152oligotrophsensitive
Tuckermannopsis ciliaris92oligotrophtolerant
Tuckermannopsis orbata197oligotrophintermediate
Tuckermannopsis sepincola11mesotrophintermediate
Usnea cavernosa19mesotrophsensitive
Usnea cornuta12eutroph 
Usnea filipendula68oligotrophsensitive
Usnea glabrescens23mesotrophsensitive
Usnea hirta246oligotrophintermediate
Usnea longissima18oligotrophsensitive
Usnea mirabilis31eutrophtolerant
Usnea mutabilis71eutrophtolerant
Usnea rubicunda70eutrophtolerant
Usnea strigosa323eutrophtolerant
Usnea subfloridana259oligotrophsensitive
Usnea subfusca12eutroph 
Usnea subscabrosa22eutrophtolerant
Usnea trichodea18oligotrophintermediate
Usnocetraria oakesiana460oligotroph 
Vulpicida pinastri131oligotrophsensitive
Xanthomendoza fallax97mesotrophsensitive