Serpentine geoecology of eastern North America:
|
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This review examines the available literature, published and unpublished, on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 Que´bec 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. Access |