United States Forest Service

National Lichens & Air Quality Database and Clearinghouse

Air Pollution Sensitivity Ratings for Macrolichens in the Western US

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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 8 kg/ha/yr in the western US, relatively few sites received < 0.7 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 2000-2012 was about 3 kg/ha/yr in the western US, relatively few sites received < 0.2 kg/ha/yr.

Taxonomy follows the 19th North American Checklist.

* Brief Methods Summary

1. Western US ratings are based on 6699 surveys across the western US west of the Great Plains states, primarily following the US Forest Inventory & Analysis lichen communities indicator protocol. Includes southern AK, WA, OR, CA, ID, NV, AZ, NM, CO, UT, WY, MT.
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 western 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: Western US Sensitivity Ratings

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

Scientific Name	No. of Detections	Sensitivity to Nutrient Nitrogen Deposition	Sensitivity to Acid Deposition
Ahtiana pallidula	272	oligotroph	sensitive
Ahtiana sphaerosporella	195	oligotroph	sensitive
Alectoria imshaugii	978	oligotroph	sensitive
Alectoria lata	12	eutroph	sensitive
Alectoria sarmentosa	2445	oligotroph	sensitive
Alectoria vancouverensis	84	oligotroph	sensitive
Anomalobaria anomala	548	oligotroph	sensitive
Anomalobaria anthraspis	424	oligotroph	sensitive
Bryocaulon pseudosatoanum	49	oligotroph	sensitive
Bryoria bicolor	146	oligotroph	intermediate
Bryoria capillaris	1177	oligotroph
Bryoria carlottae	38	oligotroph	intermediate
Bryoria cervinula	41	oligotroph	sensitive
Bryoria fremontii	1095	oligotroph	sensitive
Bryoria friabilis	332	oligotroph	sensitive
Bryoria furcellata	30	oligotroph	sensitive
Bryoria fuscescens	1483	oligotroph	sensitive
Bryoria glabra	598	oligotroph
Bryoria implexa	12	oligotroph	intermediate
Bryoria lanestris	97	oligotroph
Bryoria nadvornikiana	36	oligotroph	sensitive
Bryoria pseudocapillaris	32	oligotroph	sensitive
Bryoria pseudofuscescens	862	oligotroph	sensitive
Bryoria simplicior	195	oligotroph	sensitive
Bryoria spiralifera	17	oligotroph	sensitive
Bryoria subcana	16	oligotroph	sensitive
Bryoria tenuis	103	oligotroph	sensitive
Bryoria trichodes	468	oligotroph	tolerant
Bunodophoron melanocarpum	25	oligotroph	sensitive
Candelaria concolor	868	eutroph	tolerant
Cavernularia hultenii	615	oligotroph	intermediate
Cavernularia lophyrea	265	oligotroph
Cetrelia cetrarioides	127	eutroph	tolerant
Cladonia albonigra	37	oligotroph	sensitive
Cladonia bellidiflora	215	oligotroph	sensitive
Cladonia cariosa	62	mesotroph	sensitive
Cladonia carneola	164	oligotroph
Cladonia cenotea	29	oligotroph	tolerant
Cladonia coccifera	18	oligotroph	sensitive
Cladonia cornuta	184	oligotroph	intermediate
Cladonia decorticata	23	oligotroph	sensitive
Cladonia deformis	35	oligotroph	sensitive
Cladonia fimbriata	470		tolerant
Cladonia grayi	10	oligotroph
Cladonia macilenta var. bacillaris	9	mesotroph	sensitive
Cladonia multiformis	22	mesotroph	sensitive
Cladonia norvegica	33	mesotroph	sensitive
Cladonia ochrochlora	756		tolerant
Cladonia pleurota	42	oligotroph	sensitive
Cladonia pyxidata	127	mesotroph	sensitive
Cladonia scabriuscula	29	oligotroph	intermediate
Cladonia squamosa	567		sensitive
Cladonia straminea	13	oligotroph	sensitive
Cladonia sulphurina	97	oligotroph	sensitive
Cladonia transcendens	568	eutroph	intermediate
Cladonia umbricola	160	oligotroph	tolerant
Cladonia verruculosa	53	mesotroph	sensitive
Collema furfuraceum	148	eutroph	sensitive
Collema nigrescens	72	eutroph	intermediate
Collema subflaccidum	9	mesotroph	sensitive
Dendriscocaulon intricatulum	20	oligotroph	intermediate
Dendriscosticta wrightii	12	oligotroph	sensitive
Enchylium conglomeratum	13	oligotroph	sensitive
Erioderma sorediatum	34	oligotroph	sensitive
Esslingeriana idahoensis	580	oligotroph	sensitive
Evernia divaricata	35	mesotroph	sensitive
Evernia mesomorpha	10	oligotroph	sensitive
Evernia prunastri	1217	eutroph	tolerant
Flavoparmelia caperata	31	eutroph	intermediate
Flavopunctelia darrowi	27	mesotroph	sensitive
Flavopunctelia flaventior	146	eutroph	intermediate
Flavopunctelia praesignis	46	mesotroph	sensitive
Flavopunctelia soredica	431	mesotroph	sensitive
Fuscopannaria ahlneri	22	oligotroph	intermediate
Fuscopannaria laceratula	52	oligotroph	sensitive
Fuscopannaria leucostictoides	81	oligotroph	intermediate
Fuscopannaria mediterranea	32	mesotroph	intermediate
Fuscopannaria pacifica	101	oligotroph	intermediate
Fuscopannaria praetermissa	26	oligotroph	sensitive
Heterodermia leucomela	36	eutroph	intermediate
Heterodermia rugulosa	34	mesotroph	sensitive
Hyperphyscia adglutinata	39	mesotroph	sensitive
Hypogymnia apinnata	1151	oligotroph	intermediate
Hypogymnia austerodes	129	oligotroph
Hypogymnia bitteri	47	oligotroph	sensitive
Hypogymnia duplicata	251	oligotroph	sensitive
Hypogymnia enteromorpha	1734	mesotroph	sensitive
Hypogymnia farinacea	11	mesotroph	sensitive
Hypogymnia heterophylla	72	oligotroph	sensitive
Hypogymnia imshaugii	2546	oligotroph	sensitive
Hypogymnia inactiva	1456	mesotroph	sensitive
Hypogymnia occidentalis	986	oligotroph	sensitive
Hypogymnia oceanica	250	oligotroph	intermediate
Hypogymnia physodes	2055	eutroph	tolerant
Hypogymnia rugosa	180	oligotroph
Hypogymnia tubulosa	1634	mesotroph
Hypogymnia vittata	119	oligotroph
Hypogymnia wilfiana	1067	oligotroph	sensitive
Hypotrachyna pulvinata	11	mesotroph	sensitive
Hypotrachyna revoluta	9	eutroph
Hypotrachyna sinuosa	454	eutroph	sensitive
Imshaugia aleurites	30		tolerant
Imshaugia placorodia	70	mesotroph	sensitive
Kaernefeltia californica	44	oligotroph	intermediate
Kaernefeltia merrillii	1116	oligotroph	sensitive
Lathagrium fuscovirens	34	mesotroph	sensitive
Leioderma sorediatum	10	oligotroph	sensitive
Leptochidium albociliatum	22	mesotroph	intermediate
Leptogidium contortum	105	oligotroph	sensitive
Leptogium arsenei	13	mesotroph	sensitive
Leptogium brebissonii	59	oligotroph	sensitive
Leptogium burnetiae	25	oligotroph	intermediate
Leptogium cyanescens/td>	23	mesotroph	sensitive
Leptogium denticulatum	17	mesotroph	sensitive
Leptogium milligranum	11	mesotroph	sensitive
Leptogium pseudofurfuraceum	121	mesotroph	sensitive
Leptogium saturninum	101	mesotroph	sensitive
Leptogium teretiusculum	9	eutroph	sensitive
Letharia columbiana	1171	oligotroph	sensitive
Letharia vulpina	2387	oligotroph	sensitive
Lobaria amplissima	13	oligotroph	sensitive
Lobaria hallii	84	oligotroph	intermediate
Lobaria linita	217	oligotroph
Lobaria oregana	630	oligotroph	sensitive
Lobaria pulmonaria	770	oligotroph	sensitive
Lobaria retigera	14	oligotroph	sensitive
Lobaria scrobiculata	275	oligotroph
Loxosporopsis corallifera	86		tolerant
Melanelixia fuliginosa	205	eutroph	tolerant
Melanelixia glabra	140	eutroph	tolerant
Melanelixia subargentifera	79	eutroph
Melanelixia subaurifera	302	eutroph	sensitive
Melanohalea elegantula	1048	oligotroph	sensitive
Melanohalea exasperata	64	mesotroph	intermediate
Melanohalea exasperatula	1472	mesotroph	sensitive
Melanohalea olivacea	10	oligotroph	sensitive
Melanohalea subolivacea	1759		sensitive
Menegazzia subsimilis	299	eutroph	sensitive
Montanelia disjuncta	19	eutroph	intermediate
Montanelia panniformis	17		sensitive
Montanelia sorediata	18	oligotroph	sensitive
Montanelia tominii	29	mesotroph	intermediate
Nephroma arcticum	24	oligotroph
Nephroma bellum	301	oligotroph	tolerant
Nephroma helveticum	443	oligotroph	sensitive
Nephroma isidiosum	37	oligotroph	intermediate
Nephroma laevigatum	148	oligotroph	sensitive
Nephroma occultum	29	oligotroph	intermediate
Nephroma parile	195	oligotroph	tolerant
Nephroma resupinatum	324	mesotroph	sensitive
Niebla cephalota	30	eutroph	intermediate
Nodobryoria abbreviata	1289	oligotroph	sensitive
Nodobryoria oregana	1267	oligotroph	sensitive
Parmelia pseudosulcata	252	oligotroph	tolerant
Parmelia saxatilis	318		sensitive
Parmelia squarrosa	129	oligotroph
Parmelia sulcata	2446	eutroph	tolerant
Parmeliella parvula	11	oligotroph	sensitive
Parmeliella triptophylla	29	oligotroph	intermediate
Parmelina coleae	89	eutroph	sensitive
Parmeliopsis ambigua	1371	oligotroph	sensitive
Parmeliopsis hyperopta	1908	oligotroph	sensitive
Parmotrema arnoldii	145	eutroph	sensitive
Parmotrema crinitum	35	oligotroph	sensitive
Parmotrema perlatum	131	eutroph	sensitive
Peltigera collina	629	eutroph	intermediate
Phaeophyscia ciliata	92		intermediate
Phaeophyscia decolor	20	mesotroph	sensitive
Phaeophyscia endococcina	26	mesotroph	sensitive
Phaeophyscia hirsuta	362	mesotroph	sensitive
Phaeophyscia hirtella	9	oligotroph	sensitive
Phaeophyscia hispidula	43	mesotroph	sensitive
Phaeophyscia kairamoi	15	oligotroph	sensitive
Phaeophyscia nigricans	79	mesotroph	sensitive
Phaeophyscia orbicularis	212	eutroph	intermediate
Phaeophyscia sciastra	43	mesotroph	sensitive
Physcia adscendens	1309	eutroph	tolerant
Physcia aipolia	583	eutroph	sensitive
Physcia biziana	631	eutroph	sensitive
Physcia caesia	163	mesotroph	sensitive
Physcia dimidiata	544	eutroph	intermediate
Physcia dubia	196	mesotroph	sensitive
Physcia stellaris	333		sensitive
Physcia tenella	330	eutroph	tolerant
Physcia tribacia	18	mesotroph	sensitive
Physciella chloantha	159	mesotroph	sensitive
Physciella melanchra	25	eutroph	sensitive
Physciella nepalensis	17	oligotroph	sensitive
Physconia americana	213	eutroph	intermediate
Physconia elegantula	33	mesotroph	sensitive
Physconia enteroxantha	282	eutroph	intermediate
Physconia fallax	26	eutroph	tolerant
Physconia grisea	11	mesotroph	sensitive
Physconia muscigena	46	mesotroph	sensitive
Physconia perisidiosa	510	eutroph	intermediate
Placidium arboreum	9	mesotroph	sensitive
Platismatia glauca	2943	mesotroph	tolerant
Platismatia herrei	1446	mesotroph	sensitive
Platismatia lacunosa	210	oligotroph	sensitive
Platismatia norvegica	598	oligotroph
Platismatia stenophylla	1063	mesotroph	sensitive
Polycauliona candelaria	276		tolerant
Polycauliona polycarpa	1735	eutroph	tolerant
Polycauliona tenax	21	eutroph	intermediate
Polychidium muscicola	29	oligotroph	sensitive
Protopannaria pezizoides	63	oligotroph	sensitive
Pseudevernia intensa	80	mesotroph	sensitive
Pseudocyphellaria crocata	287	oligotroph	intermediate
Pseudocyphellaria mallota	13	oligotroph	sensitive
Pseudocyphellaria rainierensis	50	oligotroph	sensitive
Punctelia graminicola	10	mesotroph	sensitive
Punctelia hypoleucites	37	mesotroph	sensitive
Punctelia perreticulata	92	eutroph	sensitive
Ramalina dilacerata	269	mesotroph	sensitive
Ramalina farinacea	1028	eutroph	tolerant
Ramalina leptocarpha	24	eutroph	intermediate
Ramalina menziesii	98	mesotroph	intermediate
Ramalina obtusata	9		intermediate
Ramalina pollinaria	37	mesotroph	intermediate
Ramalina roesleri	154	oligotroph	intermediate
Ramalina sinensis	57	mesotroph	sensitive
Ramalina subleptocarpha	94	eutroph	tolerant
Ramalina thrausta	72	oligotroph	sensitive
Rusavskia sorediata	34	mesotroph	sensitive
Scytinium cellulosum	13	mesotroph	sensitive
Scytinium gelatinosum	19	eutroph	sensitive
Scytinium lichenoides	108	mesotroph	intermediate
Scytinium palmatum	63	eutroph	sensitive
Scytinium polycarpum	94	eutroph	tolerant
Sphaerophorus globosus	1457		sensitive
Sticta beauvoisii	90	oligotroph	sensitive
Sticta fuliginosa	339	mesotroph	sensitive
Sticta limbata	235	eutroph	sensitive
Teloschistes chrysophthalmus	10	eutroph	intermediate
Tuckermanella coralligera	33	mesotroph	sensitive
Tuckermanella fendleri	118	mesotroph	sensitive
Tuckermanella weberi	11	mesotroph	sensitive
Tuckermannopsis chlorophylla	2219	oligotroph
Tuckermannopsis orbata	1525	mesotroph	sensitive
Tuckermannopsis platyphylla	1511	oligotroph	sensitive
Tuckermannopsis sepincola	13	oligotroph	sensitive
Tuckermannopsis subalpina	86	mesotroph	sensitive
Usnea cavernosa	68	mesotroph	sensitive
Usnea cornuta	251	eutroph
Usnea filipendula	947	mesotroph	sensitive
Usnea flavocardia	428	eutroph	sensitive
Usnea fragilescens	91	oligotroph	sensitive
Usnea glabrata	286	eutroph	intermediate
Usnea glabrescens	79	mesotroph	intermediate
Usnea hirta	544	mesotroph	sensitive
Usnea intermedia	31	mesotroph	sensitive
Usnea lapponica	836	oligotroph	sensitive
Usnea longissima	200	oligotroph	sensitive
Usnea pacificana	129	mesotroph	sensitive
Usnea parvula	13	oligotroph	sensitive
Usnea rubicunda	31	oligotroph	sensitive
Usnea scabrata	642	oligotroph	sensitive
Usnea silesiaca	64	oligotroph	tolerant
Usnea subfloridana	312	mesotroph	sensitive
Usnea subgracilis	33	oligotroph	sensitive
Usnea substerilis	130	eutroph	sensitive
Usnea wasmuthii	18	eutroph
Vahliella leucophaea	17	mesotroph	sensitive
Vahliella saubinetii	32	mesotroph
Vulpicida canadensis	755	oligotroph	sensitive
Vulpicida pinastri	137	mesotroph	sensitive
Xanthomendoza fallax	1441	eutroph
Xanthoria parietina	38	eutroph	sensitive

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