Influence of trampling-induced microtopography on growth of the soil crust bryophyteCeratodon purpureusin Jasper National Park

Abstract

The growth of the moss Ceratodon purpureus (Hedw.) Brid. is enhanced by microtopography created by ungulates on silt-rich dune soils. Ungulates such as elk (Cervus elaphus) are important structural modifiers of the soil on the shore of Jasper Lake, Jasper National Park, Canada. Ungulates increase microtopography at the soil surface by creating hoof prints and small raised mounds from kicked-up soil. Experiments with artificial microtopography revealed that C. purpureus grew faster (1) inside artificial hoof prints, (2) in the shade of soil mounds and plastic barriers, and (3) on north-sloping soil, probably owing to provision of shelter from desiccation. A laboratory study of soil drying rates in the presence and absence of shelters supported this trend. Furthermore, patterns of moss height in naturally occurring hoof prints indicated that the response of moss to this microrelief is scale-dependent, with the strongest response occurring at the finest scale investigated. Finally, at larger spatial scales, moss cover did not decline with increasing hoof print density until 25% of the ground was covered by hoof prints. The incidental creation of microhabitat by ungulates seems to buffer C. purpureus from the negative crushing effects of trampling.Key words: Ceratodon purpureus, ecosystem engineering, facilitation, microtopography, soil crust, trampling.