lichen inventory of white rocks open space (city of

The Southern Rocky Mountains and adja-cent prairies of Colorado (EPA Level III Eco -regions; Chapman et al. 2006) are character-ized by a mosaic of environments typical ofmany montane portions of North America,particularly western North America (Will-Wolfet al. 2006). Boulder County alone ranges in

elevation from under 1524 m (5000 ft) to over4267 m (14,000 ft), traversing mixed grassprairies (with tallgrass relicts), submontaneforested foothills, and alpine environmentsabove treeline. Among these dominant vegeta-tion zones are patches of much rarer habitattypes, such as outcroppings of sandstone or

Western North American Naturalist 75(3), © 2015, pp. 301–310

LICHEN INVENTORY OF WHITE ROCKS OPEN SPACE (CITY OF BOULDER, COLORADO)

Erin A. Tripp1

ABSTRACT.—A lichen inventory of White Rocks Open Space (City of Boulder, CO), a unique outcropping of exposedunstable sandstones, is presented. White Rocks is an ecologically important, ~40.5-ha (100-acre) protected area whosebiological significance is in part attributable to geological and climatological history as well as degree of preservation,but also because it represents a biodiversity reservoir in a sea of agriculture and urban development. This inventoryresulted in documentation of 56 species, including 1 new record to the United States, 1 new record to Colorado,2 species new to science, and 2 additional species potentially new to science pending further study. Several species,though common at White Rocks, are locally rare within Boulder County and the Front Range Mountains of Coloradoowing to a paucity of exposed sandstone. Such species instead have affinities to habitats more typical of eastern and farwestern Colorado, such as the state’s high plains and sage-juniper scrub. A checklist of the 56 species is presented alongwith an assessment of taxon abundance and preliminary delimitation of 5 lichen communities. General discussion ofecology and management recommendations is provided. The present study is intended to begin the process of morefully documenting the lichen biota of Boulder City, Boulder County, and surrounding areas. Data herein also contributenew knowledge to the North American lichen biota as a whole via a comprehensive inventory of a sandstone formation,of which there exist relatively few. The inventory highlights the ecological significance of Open Space programs nation-wide, particularly those in densely populated areas such as the Denver–Boulder–Longmont urban triangle. The discov-eries reported here were made within a 10-min drive of the University of Colorado, demonstrating the potential forfurther discovery in Colorado lichenology.

RESUMEN.—Presentamos un inventario de líquenes de White Rocks Open Space (Ciudad de Boulder, Colorado), unafloramiento único de areniscas blandas expuestas. White Rocks es una área ecológica protegida importante de 40.5 ha(100 acres) de extensión, cuya importancia biológica es atribuible, en parte, a su historia geológica y climatológica, así comoa su nivel de preservación, y a que representa una reserva de biodiversidad en un océano de agricultura y desarrollourbano. Este inventario resultó en la documentación de 56 especies, incluyendo 1 nuevo registro en Estados Unidos,1 nuevo registro en Colorado, 2 nuevas especies para la ciencia y, a la espera de nuevos estudios, 2 especies adicionalespotencialmente nuevas para la ciencia. Varias especies, aunque habituales en White Rocks, raramente se localizan en elCondado de Boulder y en las Montañas Front Range de Colorado debido a la escasez de piedra arenisca expuesta. Dehecho, estas especies tienen afinidad con hábitats más típicos del este y el lejano oeste de Colorado, como las llanuras ylas arboladas de salvia y enebros del estado. Presentamos un listado de las 56 especies, junto con una evaluación de laabundancia del taxón y la delimitación preliminar de 5 comunidades de líquenes. Se proporciona una discusión generalsobre la ecología y proporcionamos recomendaciones para su manejo. El presente estudio tiene como objetivo iniciar elproceso de documentación de la biota de líquenes de Boulder City, el condado y sus alrededores de forma más com-pleta. Los datos que presentamos también contribuyen al nuevo conocimiento de la biota de líquenes de América delNorte a través del inventario completo de una formación de piedra arenisca, sobre las cuales existen relativamente pocosinventarios. El inventario que se describe aquí destaca la importancia ecológica de los programas de Open Space (Espa-cio Abierto) a lo largo del país, sobre todo aquellos llevados a cabo en zonas densamente pobladas, como el triángulourbano Denver–Boulder–Longmont. Los descubrimientos aquí documentados se realizaron a una distancia de 10 minu-tos en automóvil de la Universidad de Colorado, lo que demuestra el potencial de futuros descubrimientos sobreliquenología en Colorado.

1University of Colorado, Department of Ecology & Evolutionary Biology and Museum of Natural History, UCB 350, Boulder, CO 80309. E-mail:[email protected]

301

shale, eastern woodland relict forests, andfens. Given this biological mosaic and thegeneral ecological significance of Colorado’snative habitats, the lichen biota of the state isexpected to be particularly rich and represen-tative of numerous other ecosystems of west-ern North America. Yet, a comprehensiveaccount of lichens in Colorado is lacking.Instead, most literature on the biota exists astaxon-specific reports of occurrences. Shushanand Anderson (1969) provided the only at -tempt at a full checklist of the state’s lichens(448 species treated), but this work was basedentirely on literature reports rather than veri-fication of specimens held in herbaria. Beyondthis, there have been a limited number ofregional inventory efforts (Anderson 1962,Dakota Sandstone; Egan 1970, Mt. Audubonalpine; Hale 1982, Flat Tops Wilderness Area;McCune et al. 1998, macrolichens associatedwith the USFS’s Forest Health MonitoringProram; Shrestha and St. Clair 2009, SanJuan–Rio Grand National Forest; see additional

references listed in Shushan and Anderson1969, as well as a review of lichenologicalinventory work in Colorado presented inShrestha and St. Clair 2009). The present con-tribution adds to the list of local or regionalinventories in the state and serves as initialsteps toward a revision of the lichen biota ofBoulder County and surrounding areas.

White Rocks Open Space

White Rocks Open Space (Fig. 1) representsan ~40.5-ha (100-acre) ecologically importantprotected area, situated within and proximalto the eastern limits of the City of Boulder,Colorado. Its biological significance is in partattributable to its geological history, climato-logical history, and degree of preservation(MacPhail et al. 1970), but also because it rep-resents an important biodiversity reservoirin a sea of agriculture and urban development(i.e., the Boulder–Denver–Longmont urbantriangle). White Rocks is a rare and fragileoutcropping of sandstone that rises directly

302 WESTERN NORTH AMERICAN NATURALIST [Volume 75

Fig. 1. Western end of sandstone outcropping at White Rocks Open Space, showing depressions and rises typical oflarge, upper rock shelf. The iconic “Flatiron” mountains of the City of Boulder toward the west are seen in background.

above the northern margin of Boulder Creek.The outcropping itself consists of a large 1- to2-tiered sandstone shelf, with both horizontaland vertical exposed surfaces, and is ~1000 min length oriented east–west. This prominentoutcropping is flanked by a slightly moreminor adjacent sandstone exposure directly tothe east, which is some ~800 m in length. Theoutcrops belong to the Fox Hills Sandstone ofthe Laramie Formation, dating to ~67 millionyears (MacPhail et al. 1970, Weimer 1973,Hirschfeld 2013a, 2013b). The sandstone atWhite Rocks is, as the name implies, verywhite in color and composed primarily ofquartz with minor amounts of montmorilliniteclay. The White Rocks outcropping is knownin particular for its peculiar jointed polygonsor “turtlebacks” that characterize horizontalsurfaces of the exposed rock (Fig. 2). Thesepolygons are thought to be derived from fluc-tuating levels of moisture content in the mon-tomorillinite clay, which combine with otherenvironmental factors to induce stresses andcracks, culminating in polygons (Netoff 1971).The sandstone itself is extremely fragile andsusceptible to weathering by foot travel ornatural phenomena such as strong rains or highwinds, but its erosion is slowed substantiallyby characteristic “case hardening” of thesuperficial-most surfaces of the turtlebacks,which derives from hardened clay strength-ened by a biotic crust—primarily lichens.

Despite the small geographic size of WhiteRocks, the preserve is known to harbor severalrare vascular plants as well as invertebrates,likely because of microhabitat diversity thereinrepresented (Byars 1936, Weber 1949, 1970,Clark et al. 2001). Microhabitat differentiationat White Rocks is attributable to small-scalevariation in relative humidity and water availa -bility, exposure to wind and sun, mineralcontent, aspect and steepness of slopes (Mac -Phail et al. 1970), and the biotic environmentitself. Examples of microhabitats representedat White Rocks include (1) large sandstonesurfaces exposed to high radiation and windsintermixed with (2) shaded, deep to shallowcrevices, (3) steep walls and ledges with over-hangs that border riparian forests below, (4)large bowl-shaped depressions and smallerdepressions (including turtlebacks) that be -come short-term catchments for water, (5)regions of sandstone with naturally higherclay content (and thus higher water-holding

capacity), (6) regions of sandstone with greatercase hardening attributable to evaporativeprocesses, clay content, and biotic crusts thatleave behind a substrate that is more resistantto weathering, (7) bands of separation betweenFox Hill Sandstone formations interrupted byexposed Pierre shales, and finally (8) mineralinclusions (chert or calcareous material) thatform concretions and are intermixed amongsandstones. Based on this diversity of micro-habitats, the existing knowledge of the biota ofWhite Rocks, and research elsewhere that hasdocumented rich and unique lichen biotas oncomparable sandstone formations (Fink 1904,Gilbert 1980, Showman 1987, Clark et al. 2001),White Rocks is hypothesized to host a uniquecommunity of lichens that is unrepresented orunderrepresented in Boulder County, as wellas across the state. Indeed, other sandstoneoutcrops in North America host rare or un -usual species of lichens such as Dibaeis absolutaand Ramalina petrina (Skorepa 1973, Showman1987).

Despite a history of research and generalinterest in the White Rocks Open Space, noinventory or assessment of lichens of thisunique outcropping has been conducted. Themost relevant prior works regarding the lichenbiota of the immediate area (Colorado’s “FrontRange”) are those of Anderson (1962) andWeber (in Hogan 1993). Anderson (1962) sur-veyed lichens of the Dakota sandstone ofnorth central Colorado but excluded manycrustose species from that work. Weber (inHogan 1993) provided a synoptic list of thelichens of Boulder’s Mountain Parks, but thislist lacks numerous species (especially crus-tose taxa) and taxonomy therein is outdated.Thus, the objective of the present investiga-tion was to conduct an inventory of lichensof White Rocks Open Space. This inventorybuilds baseline information about the biodi-versity of this important preserve, enableslong-term conservation planning and resourcemanagement in a data-driven manner, facili-tates future lichen taxonomic and ecologicalresearch in the area, and improves our capacityto educate the broader public about the im -portance of lichens in urban environments.

METHODS

Between June and September 2014, a licheninventory of White Rocks Open Space (City of

2015] LICHENS OF WHITE ROCKS, BOULDER, CO 303


Fig. 2. Turtlebacks (polygons) characteristic of horizontal surfaces at White Rocks, derived from fluctuating levels ofmoisture content in the montomorillinite clay, which combine with other environmental factors to induce stresses and cracks.

Fig. 3. Approximate boundaries of the White Rocks lichen inventory (red outline), which closely mirrors the areadelimited by Boulder as the White Rocks Conservation Target.

Boulder, CO) was conducted over the courseof 6 site visits. The area covered by this surveywas ~40.5 ha (100 acres) (Fig. 3). The inven-tory was conducted primarily via new fieldcollections rather than existing museum speci-mens, given the lack of adequate representa-tion of this site among lichen herbaria (www.lichenportal.com), including the University ofColorado Herbarium (COLO). Occasionalhistorical specimens from White Rocks housedat COLO were additionally studied as part ofthis work but yielded no additional speciesbeyond those discovered during fieldwork(see Results).

Lichens were sampled using standard fieldcollection techniques employed in previousstudies (e.g., Lendemer and Tripp 2008,Lendemer et al. 2013). All accessible habitatsand substrates contained within the ~40.5-ha(100-acre) preserve were targeted (i.e., theupper and lower flat rock outcrops, the imme-diately adjacent accessible portions of verticalrock faces, the lower floodplain zone that isdensely vegetated and has few exposed rocks,and the adjacent prairie habitats includingsoil and plant substrates). To capture totaldiversity as best as possible, terricolous (soil),saxicolous (rock), corticolous (bark), and ligni-colous (decaying wood) substrates were sam-pled. However, given the fragile nature of rocksurfaces and the relatively small size of thepreserve, care was taken to (1) remove smallamounts of material for vouchers and to do soaway from a pathway that is used by staffmembers for tours and monitoring, and (2)make only the minimal number of voucherspecimens needed to produce a completeinventory (i.e., a given species was sampledonly once unless additional collections wereneeded to confirm identifications, as in thecase for several crustose species). Care wasalso taken to avoid the general area of a long-term Bald Eagle nest atop a large snag on thenorthern margin of Boulder Creek. Locality,habitat, substrate, and ecological data wererecorded for all vouchers. Additionally, I esti-mated taxon abundance on a quantitative toqualitative scale with 5 rankings: rare, infre-quent, occasional, common, and abundant. Aspecies that was seen only once was consid-ered rare, whereas a species that was seen 2–4times was considered infrequent. Rankings ofoccasional, common, and abundant were as -sessed qualitatively rather than based on the

precise number of thalli seen. All collectionswere photographed in the field using a NikonD7100 digital SLR with a 105-mm 1:1 macro -lens and ring flash, in preparation for a fieldguide (Tripp in press). One to 2 vouchers percollection were made, and the primary set ofspecimens is deposited at the University ofColorado Herbarium, Museum of NaturalHistory. Taxonomy and nomenclature followEsslinger (2014) for the most part.

Chemistry was studied using standard spottest reagents as outlined in Brodo et al. (2001).Thin Layer Chromatography was conductedusing Solvent C as outlined by Culberson andKristinsson (1970). Measurements and micro-graphs of macroscopic and microscope struc-tures were made as needed for identificationsusing an Olympus SZX10 stereomicroscopeand an Olympus BX51 compound epifluores-cence microscope equipped with a Retiga2000R imaging system. Thin sections of thalliand ascomata were made by hand using arazor blade then mounted in water or iodine.

RESULTS

A total of 82 collections were made andphotographed in the field, and the collectionsyielded 56 species of lichens (Table 1). Thetotal number of species on a given substratewas as follows: 50 saxicolous, 4 corticolous,and 2 terricolous. Of the 56 species, 40 werecrustose, 11 were foliose, 4 were squamulose,and 1 was fruticose. On an abundance scalewith 5 rankings, the number of species perranking was as follows: 9 abundant, 9 com-mon, 19 occasional, 12 infrequent, and 7 rare(Table 1). These 82 collections also yielded 2species new to science (Tripp and Lendemer2015), 2 additional species putatively new toscience (currently under further investiga-tion), 1 new report to the United States, and 1new report to Colorado (Table 1).

DISCUSSION

The present study serves as the first docu-mentation of the lichen biota of a rare sand-stone formation in Boulder County, Colorado.Somewhat remarkably, there have been veryfew lichen inventories of sandstone formationsin North America. By far the most relevant tothe present study was that of Anderson (1962),who inventoried the Dakota sandstone forma-tion of northern Colorado. He documented


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(i.e.

, red

apo

thec

ia, i

ncon

spic

uous

thal

li) w

ithin

Nor

th A

mer

ican

her

bari

a is

iden

tifie

d as

Cal

opla

ca a

rena

ria

(Per

s.) M

üll.

Arg

. The

col

lect

ion

from

Whi

te R

ocks

has

a d

efin

itive

, alb

eit t

hin,

gra

y th

allu

s th

atre

acts

K+

pur

ple

in w

ater

mou

nt a

nd d

oes

not a

ppea

r to

be

obvi

ousl

y pa

rasi

tic o

n ot

her

liche

ns. A

s su

ch, t

he n

ame

Cal

opla

ca a

trof

lava

is h

ere

appl

ied

to th

is c

olle

ctio

n, in

stea

d of

C. a

rena

ria

or C

. epi

thal

lina.

3. T

he m

anus

crip

t rep

ortin

g th

ese

2 ne

w s

peci

es in

clud

es m

olec

ular

exp

lora

tion

of e

volu

tiona

ry r

elat

ions

hips

to c

lose

rel

ativ

es (T

ripp

and

Len

dem

er 2

015)

.

4. T

his

is a

n us

nic-

acid

con

tain

ing

spec

ies

that

is n

ot r

eadi

ly a

scri

babl

e to

any

thin

g in

Śliw

a’s

mon

ogra

ph (2

007)

of t

he L

ecan

ora

disp

ersa

com

plex

. S

5. S

imila

r to

Lec

idea

hog

anii,

thi

s co

llect

ion

has

a hy

men

ium

var

iabl

y st

aine

d w

ith a

pin

k pi

gmen

t; it

how

ever

diff

ers

from

L. h

ogan

ii by

its

turq

uois

e ep

ihym

eniu

m, I

- m

edul

la, a

nd m

uch

thin

ner

thal

lus.

Mor

e co

llect

ions

of

the

Lec

idea

and

Lec

idel

la c

omm

unity

are

nee

ded

to g

auge

the

com

mon

ness

of t

his

taxo

n. I

t is

incl

uded

in th

e ab

ove

chec

klis

t bec

ause

it r

epre

sent

s a

diffe

rent

ent

ity fr

om c

onge

ners

pre

sent

at W

hite

Roc

ks.

6. T

he n

ame

Lec

idea

tes

sella

ta is

uns

atis

fact

ory

for

this

tax

on; f

or e

xam

ple,

col

lect

ions

from

Whi

te R

ocks

hav

e an

I-

med

ulla

, a d

ark

gray

tha

llus,

and

lack

a b

lack

pro

thal

lus.

How

ever

, unt

il th

e ge

nus

or t

his

spec

ies

is fu

lly r

evis

ed in

wes

tern

Nor

th A

mer

ica

and

the

man

y en

titie

s co

ntai

ned

with

in L

. tes

sella

ta a

re s

epar

ated

out

, thi

s is

the

mos

t sui

tabl

e na

me

for

Whi

te R

ocks

mat

eria

l.

7. R

inod

ina

veno

stan

a w

as r

ecen

tly r

epor

ted

as n

ew to

Nor

th A

mer

ica,

from

a s

ands

tone

form

atio

n in

Sas

katc

hew

an (F

reeb

ury

2014

). T

his

colle

ctio

n re

port

ed h

ere

serv

es a

s th

e fir

st d

ocum

enta

tion

of R

. ven

osta

na in

the

Uni

ted

Stat

es, a

lthou

ghth

ere

is s

ome

poss

ibili

ty th

at e

vent

ually

, it m

ight

be

sepa

rate

d ou

t as

a ta

xon

new

to s

cien

ce (J

. She

ard,

per

sona

l com

mun

icat

ion)

.

8. T

his

reco

rd r

epre

sent

s th

e fir

st c

onfir

med

rep

ort o

f thi

s sp

ecie

s fo

r C

olor

ado.

130 species over a stretch of ~105 km (65 mi),ranging from Boulder northwards along theFront Range of the Rocky Mountains (seeadditional reports of psammophilous speciesadded by Anderson and Carmer 1974). BeyondAnderson’s study, Hale (1982) studied thelichens of Flat Tops Wilderness Area in Routtand White River National Forests, Colorado,but only a portion of the survey area containsexposed sandstone. Fink (1904) studied thelichen composition of sandstone riprap habitatin Iowa, an artificial habitat some 30 years oldat the time of Fink’s work. Showman (1987)studied the macrolichens of Crane Hollow inOhio, but that site was mostly forested andcontained only very small outcroppings ofsandstone. Finally, Rushforth et al. (1982)studied the lichens of Zion National Park andfound that species diversity was highest onsandstone boulders, but that study was eco-logical rather than taxonomic and no checklistwas presented. Thus, the present contributionfills a niche among modern lichen checklistswithin North America.

Lichen Communities of White Rocks

A preliminary circumscription of lichencommunities present at White Rocks is pre-sented below. These communities are notbased on quantitative composition data (e.g.,see Will-Wolf et al. 2006), nor are they inter-preted in light of environmental variables andvariation present at White Rocks. Rather, it isintended that the discussion below serves as afirst pass at understanding general communitytypes, which can then be used by ecologistsduring furture attempts to more quantitativelydefine lichen communities at the site. Thesepreliminary community circumscriptions canalso be used by Open Space management staffin conservation or other ecological studies ofthe White Rocks lichen biota.

Five lichen communities present at WhiteRocks are described below; the first 3 are rela-tively common, whereas the last 2 are minor.Conspicuously absent from White Rocks werecommon species of the lower montane foothillsof Boulder County with affinity to moisterenvironments (e.g., north-facing slopes) such asNephroma parile, Parmelia saxatilis, Peltigeracanina, Physconia enteroxantha, Physconiamuscigena, and Protoparmelia badia.

HORIZONTAL, LOOSE SANDSTONE (HLS).—This was by far the most commonly available

surface and also represents the most diverselichen community at White Rocks. The fragilenature of this community suggests that severalof the constituent lichens could be thought ofas biotic soil crusts with important ecologicalroles in slowing erosion. The following speciesare common constituents of HLS: Aspiciliacinerea, Acarospora strigata, Caloplaca atro -flava, Caloplaca pratensis, Candelariella rosu-lans, Lecanora argopholis, Lecanora garovaglii,Lecanora muralis, Lecidea patavina, Xantho -parmelia coloradoënsis, Xanthoparmelia lavi-cola. This community is dominated by Cande-lariella rosulans and Lecidea patavina.

TILTED, HARD SANDSTONE (THS).—Bouldersof varying sizes and consisting of sandstonethat is conspicuously harder in texture thanHLS dominate portions of the upper shelf atWhite Rocks. Lichens within this communityoccur on tilted to vertical surfaces, or on thetops of these boulders. The following speciesare common constituents of THS: Acarosporaobpallens, Acarospora socialis, Caloplaca saxi-cola, Caloplaca trachyphylla, Dermatocarponamericanum (usually in rock crevices), Diplo -schistes scruposus, Diplotomma venustum,Lecanora flowersiana, Lichinella stipatula,Montanelia tominii, Polysporina simplex, Psoratuckermanii (always in rock crevices), Rhizo-carpon disporum, Rhizoplaca chrysoleuca,Rinodina straussii, Staurothele areolata, andXanthomendoza trachyphylla. This communityis dominated by the small but pervasivecrustose species Staurothele areolata.

SHADED ROCK OVERHANG (SRO).—Thishabitat is limited in both size and lichendiversity at White Rocks. The only species thatis dominant in large, shaded rock overhangsis Lepraria finkii.

SOIL CRUST (SC).—At White Rocks, there isa conspicuous community of lichens that onlyinhabit the junction where sandstone and vege -tation meet. These species also extend ontoterricolous substrates of vegetated soils. Thiscommunity represents biotic soil crusts in thestrict sense of the phrase, but note that numer-ous species of the HLS community also fallunder the scope of biotic soil crust communi-ties given the extremely loose and fragilenature of those horizontal sandstone surfaces.The SC community consists primarily of Endo -carpon pallidulum and Placidium squamulosum.

CORTICOLOUS SURFACE (CS).—The corti-colous biota at White Rocks was, together


with SROs, the most species-poor of all 5communities (corticolous substrates were simi -larly poor in McCune et al. 1998). Celtisreticulata, Oligosporus filifolius, and Rhustrilobata were the most important vascularplant substrates. The following 4 species domi -nate the CS community: Physciella melanchra,Rinodina pyrina, Xanthomendoza fallax, andXanthomendoza galericulata.

Rare and Unusual Lichens at White Rocks

Although many species found at WhiteRocks are relatively common in similar habi-tats of western North America, sandstone out-croppings are unusual in the Front RangeMountains of Colorado. Given this, speciessuch as Acarospora obpallens, Endocarponpallidulum, Lecidella carpathica, Lecidellastigmatea, Lichenella nigritella, Lichenella sti-patula, Phaeophyscia nigricans, and Verrucariafurfuracea are relatively uncommon elementsof the local lichen biota and can be foundmore commonly in more arid portions of thestate, such as prairies and sagebrush orjuniper scrub.

Four species at White Rocks represent taxaunknown to science or putatively unknown toscience. Two of these, Candelariella clarkiiand Lecidea hoganii, were treated in detailin Tripp and Lendemer (2015). Two others(Acarospora sp. and Lecanora sp.) are underfurther investigation and will be treated in afuture manuscript. Both the new Candelariellaand the new Lecidea are extremely rare atWhite Rocks: the former was found only onceand the latter only twice. Extensive searchesthrough suitable named and unnamed ma -terial in the COLO Herbarium failed to pro-duce further specimens that can be attributedto these species. As such, it is likely that bothspecies are rare locally and globally, and wehave recommended that both be consideredCritically Endangered under current IUCNconservation assessment guidelines (Tripp andLendemer 2015). Recent work at other ex -posed sandstone sites of the Fox Hills Forma-tion has similarly yielded new, rare species(Westberg et al. 2011). Finally, Rinodina venos-tana represents the first report of this taxonfrom the United States, and Verrucaria bel-traminiana represents the first confirmedreport of this species for Colorado (see Table 1).

This inventory demonstrates that sand-stone habitats in the Southern Rockies are

underexplored lichenologically yet host di -verse and unique communities. Moreover,these discoveries were made within a 10-mindrive of the University of Colorado, whoseherbarium hosts one of the largest and mostactive collections of lichens in western NorthAmerica. This demonstrates the potential fordiscovery that remains in Colorado, evenwithin or near dense urban areas.

CONCLUSIONS

The present study represents one of themost comprehensive, modern lichen invento-ries of a site within or around the SouthernRocky Mountain ecoregion. The primary pur-pose of this research was to provide a check-list of the lichens of this unusual habitat thatcan be used by the City of Boulder’s OpenSpace and Mountain Parks research andadministrative staff in managing, protecting,and continuing to learn from our local biologi-cal resources. It is anticipated that this studywill open additional avenues of lichen re -search and conservation at White Rocks. Witha baseline now in place, these data will forexample enable a study of lichen succession inan area with already higher-than-average ratesof erosion. Additionally, as comprehensiveinventories of additional sites are made andbecome available, these data will contributeto future calculations of biodiversity statisticsacross the state (e.g., levels of alpha and betadiversity and impacts of ecological and clima-tological gradients on lichen biodiversity).

White Rocks hosts a rich and, withinBoulder County, unique lichen community.Sandstone formations are particularly sensi-tive landscapes. Excessive foot traffic, thinsoils, and high rates of erosion create a rela-tively unstable environment and one withpotentially slower rates of regeneration. Givenrecent development and continued habitatdestruction throughout North America, thelichen inventory described herein is particu-larly timely and highlights the ecological sig-nificance of Open Space programs nation-wide, particularly those in densely populatedareas such as the Denver–Boulder–Longmonturban triangle.

ACKNOWLEDGMENTS

I thank first and foremost the City of Boul-der’s Open Space and Mountain Parks Program


for their years of dedication and funding towardsthe preservation of native habitats in Boulder,Colorado. In particular, Lynn Riedel was instru-mental in facilitating this inventory. MeganBowes provided further support for buildingknowledge of the local lichen biota. Dina Clark,Vanessa Díaz, and James Lendemer are thankedfor their field contributions. Sue Hirschfeldprovided helpful geological information. I amindebted to James Lendemer, Kerry Knudsen,Ted Esslinger, John Sheard, and Othmar Breussfor contributing some of the identifications.Finally, I thank Caleb Morse and RichardHarris for discussion on several species. Thisresearch was funded by a grant from Boulder’sOpen Space and Mountain Parks Program.

LITERATURE CITED

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CLARK, D.A., C. CRAWFORD, AND W.F. JENNINGS. 2001.Draft baseline plant survey of White Rocks and sur-rounding area in eastern Boulder County. Unpub-lished report prepared for the City of Boulder OpenSpace and Mountain Parks Department.

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EGAN, R.S. 1970. Alpine lichens from Mt. Audubon, BoulderCounty, Colorado. Bryologist 73:385–389.

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HALE, M.E. 1982. Lichens as bioindicators and monitorsof air pollution in the Flat Tops Wilderness Area,Colorado. Final Report, U.S. Forest Service ContractNo. OM RFP R2-81-SP35. 22 November 1982.

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G.T. NEBEKER. 1982. Lichen community structure inZion National Park. Bryologist 85:185–192.

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Received 5 March 2015Accepted 23 May 2015


lichen inventory of white rocks open space (city of

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