Tanner B. Harris

Serpentine Geoecology of Eastern North America: A Review

Abstract Serpentine outcrops are model habitats for geoecological studies. While much attention has been paid to serpentine outcrops worldwide, the literature on eastern North American serpentine and associated biota is scant. This review examines the available literature, published and unpublished, on geoecological studies conducted on serpentine in eastern North America, from Newfoundland through Québec and New England south to Alabama. Most serpentine outcrops in the region have been mapped, but there have been few intensive mineralogical and pedological investigations. The limited soil analyses available suggest elevated levels of heavy metals such as Ni, near-neutral pH values, and Ca∶Mg ratios < 1, characteristic of serpentine soils worldwide. Botanical studies to date have largely focused on floristic surveys and the influence of fire exclusion and grazing on indigenous vegetation. To date, 751 taxa of vascular plants belonging to 92 families have been reported from serpentine outcrops in the region. Two taxa, Agalinis acuta and Schwalbea americana, are federally endangered in the United States while many others are listed as rare, endangered, or imperiled in one or more states or provinces. Globally, six species, Adiantum viridimontanum, Minuartia marcescens, Pycnanthemum torrei, S. americana, Scirpus longii, and Symphyotrichum depauperatum are listed as imperiled (G2) while one species, Agalinis acuta, is listed as critically imperiled (G1). Cerastium velutinum var. villosissimum is the only recognized serpentine endemic plant for eastern North America while Adiantum viridimontanum, Aspidotis densa, M. marcescens, and S. depauperatum are largely restricted to the substrate. Based on current distributions, we propose that A. viridimontanum and M. marcescens be considered endemic to serpentine substrates in eastern North America. Studies on cryptogams list 165 species of lichens and 146 species of bryophytes for the region. None of the species found appear to be restricted to the substrate. Compared to other regions of the world, ecophysiological and evolutionary investigations are scant. Biosystematic investigations are restricted to the taxa Adiantum aleuticum, C. velutinum var. villosissimum, and S. depauperatum. Plant-soil relations, especially the capacity to hyperaccumulate metals such as Ni and the ecological consequences of metal accumulation, are also under explored. One report from eastern Canada lists Arenaria humifusa, M. marcescens, Packera paupercula, and Solidago hispida as hyperaccumulating Ni although the findings have yet to be confirmed by subsequent investigations. Overall, serpentine geoecology in eastern North America remains largely unexplored.

LICHENS OF PINE HILL, A PERIDOTITE OUTCROP IN EASTERN NORTH AMERICA

Abstract Despite a large body of work on the serpentine-substrate effect on vascular plants, little work has been undertaken to describe lichen communities growing on serpentine soils derived from peridotite and other ultramafic rocks. Most such work has been conducted in Europe and western North America. Only one study to date has examined the lichen flora of an ultramafic outcrop in eastern North America. The current paper examines the lichen flora of a peridotite outcrop from Deer Isle, Hancock County, Maine, U.S.A. The lichen flora is presented along with relevant ecological and geochemical data. Sixty-three species were found, comprising 35 genera. Two species, Buellia ocellata and Cladonia symphycarpia, are new reports for New England. Fuscopannaria praetermissa, Psorula rufonigra, and Spilonema revertens are new reports for Maine. Twenty species including one genus, Lobaria, are new reports for ultramafic soils worldwide. Buellia ocellata, P. rufonigra, and S. revertens are reported from several localities on the outcrop. Soil analyses were conducted for pH, electrical conductivity, cation exchange capacity, heavy metals, and cations. Soil pH and cation and heavy metal concentrations are similar to those reported from west coast ultramafic soils suggesting that a similarly strong substrate effect may exist for species present on ultramafic soils in eastern North America.

LICHENS OF THE CALLAHAN MINE, A COPPER- AND ZINC-ENRICHED SUPERFUND SITE IN BROOKSVILLE, MAINE, U.S.A.

Abstract Metal-enriched habitats often harbor physiologically distinct biotas able to tolerate and accumulate toxic metals. Plants and lichens that accumulate metals have served as effective indicators of ecosystem pollution. Whereas the diversity of metal-tolerant lichens has been well documented globally, the literature of metal-tolerant lichen communities for eastern North America is limited. We examined the lichen flora of the Callahan Mine, a Cu-, Pb-, and Zn-enriched superfund site in Brooksville, Hancock County, Maine, U.S.A. Through collections along transects across metal-contaminated areas of the mine, we documented 76 species of lichens and related fungi. Fifty species were saxicolous, 26 were terricolous. Forty-three species were macrolichens, 31 were microlichens. Although no globally rare or declining species were encountered at the mine, two regionally rare or declining species, Stereocaulon tomentosum and Leptogium imbricatum, were found. The species found at the Callahan Mine were mostly ecological generalists frequenting disturbed habitats. Two extensively studied Cu-tolerant lichens, Acarospora smaragdula and Lecanora polytropa, and other known Cd-, Cu-, Pb-, and Zn-tolerant taxa, were found at the site.

VASCULAR PLANTS OF ADJACENT SERPENTINE AND GRANITE OUTCROPS ON THE DEER ISLES, MAINE, U.S.A.

Abstract We performed a comparative study of the vascular flora of a serpentine outcrop, Pine Hill, and that of a granite outcrop, Settlement Quarry, from Little Deer Isle and Deer Isle, respectively, Hancock County, Maine. We established four transects along a gradient from exposed to forested areas within each outcrop. Plants were recorded for presence and percent cover from circular plots along each transect. Soil and tissue samples were collected to examine soil-tissue elemental relations. One hundred thirty-two taxa were recorded from serpentine and 89 from granite. Fifty-seven taxa were shared by both sites. Species richness (α diversity) and diversity indices (Shannon-Weaver and Simpson) suggested significant differences between sites and within sites. Principle Component Analysis suggested substrates differed significantly between sites and between exposures within sites. Tissue analyses suggested intraspecific variation with respect to tissue elemental concentrations, especially in Achillea millefolium, Oenothera biennis, Prunus virginiana, Selaginella rupestris, Spiraea alba var. latifolia, and Vaccinium angustifolium. Serpentine populations of many taxa showed low tissue Ca∶Mg ratios (< 1) and high Ni concentrations. Two-way ANOVA showed significant substrate × species effects for several elements, including those that typically characterize serpentine substrates (Ca, Mg, Cr, Ni), suggesting significant genetic variation within species with respect to substrate. Finally, we compared our species list for Pine Hill with a plant survey done at Pine Hill and five additional serpentine sites of Maine in 1977 and provide a list of 285 vascular plant taxa from 62 families for serpentine in Maine.

ORNITHOCOPROPHILOUS PLANTS OF MOUNT DESERT ROCK, A REMOTE BIRD-NESTING ISLAND IN THE GULF OF MAINE, U.S.A.

Abstract Plants growing on seabird-nesting islands are uniquely adapted to deal with guano-derived soils high in N and P. Such ornithocoprophilous plants found in isolated, oceanic settings provide useful models for ecological and evolutionary investigations. The current study explored the plants found on Mount Desert Rock (MDR), a small seabird-nesting, oceanic island 44 km south of Mount Desert Island (MDI), Hancock County, Maine, U.S.A. Twenty-seven species of vascular plants from ten families were recorded. Analyses of guano-derived soils from the rhizosphere of the three most abundant species from bird-nesting sites of MDR showed significantly higher (P < 0.05) NO3−, available P, extractable Cd, Cu, Pb, and Zn, and significantly lower Mn compared to soils from the rhizosphere of conspecifics on non-bird nesting coastal bluffs from nearby MDI. Bio-available Pb was several-fold higher in guano soils than for background levels for Maine. Leaf tissue elemental analyses from conspecifics on and off guano soils showed significant differences with respect to N, Ca, K, Mg, Fe, Mn, Zn, and Pb, although trends were not always consistent. Two-way ANOVA indicated a significant interaction between species and substrate for Ca, Mg, Zn, and Pb tissue accumulation, showing that for these four elements there is substantial differentiation among species found on and off of guano soil. A compilation of species lists from other important seabird-nesting islands in the region suggested an ornithocoprophilous flora for northeastern North America consisting of 168 species from 39 families, with Asteraceae (29 taxa; 17.3%), Poaceae (25 taxa; 14.9%), Polygonaceae (10 taxa; 5.95%), Caryophyllaceae (9 taxa; 5.4%), and Rosaceae (9 taxa; 5.4%) as the most species-rich families. The taxa were predominantly hermaphroditic (69%) and perennial (66%) species, native (60%) to eastern North America.

Bryophytes of Adjacent Serpentine and Granite Outcrops on the Deer Isles, Maine, U.S.A

Abstract The serpentine-substrate effect is well documented for vascular plants, but the literature for bryophytes is limited. The majority of literature on bryophytes in extreme geoedaphic habitats focuses on the use of species as bioindicators of industrial pollution. Few attempts have been made to characterize bryophyte floras on serpentine soils derived from peridotite and other ultramafic rocks. This paper compares the bryophyte floras of both a peridotite and a granite outcrop from the Deer Isles, Hancock County, Maine, and examines tissue elemental concentrations for select species from both sites. Fifty-five species were found, 43 on serpentine, 26 on granite. Fourteen species were shared in common. Twelve species are reported for the first time from serpentine soils. Tissue analyses indicated significantly higher Mg, Ni, and Cr concentrations and significantly lower Ca∶Mg ratios for serpentine mosses compared to those from granite. Soil analyses demonstrated significant differences between the two substrates.

Adiantum viridimontanum, Aspidotis densa, Minuartia marcescens, and Symphyotrichum rhiannon: Additional Serpentine Endemics from Eastern North America

Abstract - Serpentine outcrops around the world are known to harbor disproportionately high rates of plant endemism. Remarkable cases of serpentine endemism occur in New Caledonia and Cuba, with 3178 and 920 endemic taxa, respectively, found solely on serpentine. Despite the patchy occurrence of serpentine in eastern North America from Québec and Newfoundland south to Alabama, only one taxon, Cerastium velutinum var. villosissimum, has been broadly recognized as a serpentine endemic for the region. Based on reports in the literature, we suggest that Adiantum viridimontanum, Minuartia marcescens, and Symphyotrichum rhiannon be considered endemic to serpentine soils from the east coast of North America. Aspidotis densa, with several disjunct populations on and off serpentine in western North America, is known solely from serpentine soils where it occurs in eastern North America and should be considered endemic to the substrate there. The geobotany of eastern North America in general is poorly understood, and additional taxonomic studies on the regions unique geologic substrates will likely yield further edaphic endemics.

Stressors and threats to the flora of Acadia National Park, Maine: Current knowledge, information gaps, and future directions1

Abstract Harris, T. B. (WRA, Inc., 2169-G East Francisco Boulevard, San Rafael, CA 94901), N. Rajakaruna (College of the Atlantic, 105 Eden Street, Bar Harbor, ME 04069), S. J. Nelson (Senator George J. Mitchell Center for Environmental and Watershed Research and Department of Plant, Soil and Environmental Sciences, University of Maine, 5710 Norman Smith Hall, Orono, ME 04469), and P. D. Vaux (Senator George J. Mitchell Center for Environmental and Watershed Research, University of Maine, 5710 Norman Smith Hall, Orono, ME 04469). Stressors and threats to the flora of Acadia National Park, Maine: Current knowledge, information gaps, and future directions. J. Torrey Bot. Soc. 139: 323–344. 2012.— Acadia National Park is a center of plant diversity in northeastern North America. The Parks varied habitats and flora are sensitive to a number of natural and anthropogenic perturbations. Stressors such as invasive plants, pest and pathogens, ozone, acidic fog and sulfur deposition, nitrogen deposition, heavy metals, fire and fire suppression, over-browsing, visitor use, hurricanes, and climate change have all had effects on the Parks habitats and plant species at some point and it is unclear how many of these stressors are currently affecting the flora of Acadia National Park. We discuss the botanical diversity of Acadia, assess the natural and anthropogenic stressors and threats affecting the Parks flora, and summarize critical information gaps to better assess the known stressors and threats to the flora. Understanding these stressors and threats is critical to making informed management decisions to preserve the botanical diversity of Acadia and other regional parks.

Metals and secondary metabolites in saxicolous lichen communities on ultramafic and non-ultramafic rocks of the Western Italian Alps

There is a long history of studies on lichens found in ultramafic habitats, but comparisons between lichen communities on different ultramafic lithologies are scant, and potential metabolic adaptations to the multiple edaphic stresses of ultramafic substrates have been widely neglected. The present work is the first to characterise differences in the abundance and structure of saxicolous lichen communities on different ultramafic lithologies (dunite, lherzolite, and serpentinite), analysed in two areas of the Western Alps (NW Italy). Differences between communities on various ultramafic lithologies were observed, including differences between a mafic control (Mg-Al metagabbro); however, factors other than the substrate were observed to drive more remarkable differences between lichen communities on ultramafics of alpine and pre-alpine areas. XRF analyses demonstrated that the mineral composition of different lithologies is reflected by metal contents in crustose lichens, with weathering processes accounting for relative shifts in elemental abundances between rocks and thalli. A thin layer cromatography screening of lichen secondary metabolites (LSMs), which are thought to regulate metal and pH homeostasis in thalli, revealed lithological vicariance among dominant lichen species with different LSM patterns and intraspecific variability in LSM production associated with differences in lithology and location. In particular, the presence or absence of norstictic acid in species or lineages/individuals on the different lithologies, in relationship to concentrations of Fe, Mg, and Ni in lichen thalli, was recognised as a metabolic adaptation to metal stress. Pull-up tests revealed that physical factors such as a differential surface disaggregation may contribute more towards differences observed in lichen abundance on the different lithologies investigated.

Lichens of Six Vernal Pools in Acadia National Park, Maine, USA

Abstract. Whereas lichen-habitat relations have been well-documented globally, literature on lichens of vernal pools is scant. We surveyed six vernal pools at Acadia National Park on Mount Desert Island, Maine, USA for their lichen diversity. Sixty-seven species were identified, including seven species that are new reports for Acadia National Park: Fuscidea arboricola, Hypogymnia incurvoides, Lepraria finkii, Phaeographis inusta, Ropalospora viridis, Usnea flammea, and Violella fucata. Five species are considered uncommon or only locally common in New England: Everniastrum catawbiense, Hypogymnia krogiae, Pseudevernia cladonia, Usnea flammea, and Usnea merrillii. This work represents the first survey of lichens from vernal pools in Acadia National Park and strongly suggests that previous efforts at documenting species at the Park have underestimated its species diversity. More work should be conducted to determine whether a unique assemblage of lichens occurs in association with this unique habitat type.