Research on the
Ecosystem Effects of Cryptobiotic Crusts
What Are Cryptobiotic Crusts ?
Thin biological crusts which cover the ground surface are a common
feature of pristine areas in alpine tundra, cold desert shrub-steppe, and high
latitude polar ecosystems. These
cryptobiotic crusts (also known as "cryptogamic" or
"microbiotic" crusts) vary in thickness from just a few millimeters to
more than a few centimeters. They
are composed of varying proportions of lichens, mosses, cyanobacteria, and
fungi, depending upon the environment and degree of crust development.
Cryptobiotic crusts reach their greatest development in cold and often
seasonally-dry locations where the cover of vascular plants is sparse to
moderate. Complex plant communities
of patchy low shrubs, forbs and grasses reside in the cryptobiotic matrix.
The crusts are highly susceptible to damage and destruction from physical
disturbance. For instance, the
impact of human tread can compress and dislodge sections of crust, with recovery
proceeding very slowly, if it occurs at all.
Despite its fragility and common occurrence in these ecosystems, little
is known about the functional importance of these crusts.
We do know a great deal about the composition of crusts in some ecosystems and
some of their functional attributes in laboratory settings. Only
recently have a number of functional questions been addressed in the field. How
do they affect the development and maintenance of the dominant vascular plants
in these areas? Do they have
significant roles in major ecosystem properties such as mineral nutrient and
carbon cycling? What might be the
ecosystem significance of substantial disturbance to these crusts?
Publications on Crusts
WG, Glew KA, and LG Dickson (2001) Functional Influences of Cryptobiotic Surface
Crusts in an Alpine Tundra Basin of the Olympic Mountains, Washington, U.S.A. Northwest Science
LC, Gold WG (1999) Seed production, seedling survival and establishment in a
High Arctic polar desert. Canadian
Journal of Botany
WG (1998) The influence of cryptogamic crusts on the thermal environment and
temperature relations of plants in a high arctic polar desert, Devon Island,
N.W.T., Canada. Arctic &
Alpine Research 30(2): 108-120.
WG, Bliss LC (1995) Water limitations and plant community development in a polar
desert. Ecology 76:1558-1568.
WG, Bliss LC (1995) The nature of water limitations for plants in a high arctic
polar desert. In: T Callaghan (ed) Global Change and Arctic Terrestrial
Ecosystems. Ecosystems Research Report 10. Directorate-General Science, Research
and Development; European Commission. pp. 149-155.
LC, Gold WG (1994) The patterning of plant communities and edaphic factors along
a high arctic coastline: implications for succession. Canadian
Journal of Botany 72:1095-1107.
Devon Island, N.W.T., Canada
Buckhorn Cirque, Olympic Mountains, Washington