Responses of dune mosses to experimental burial by sand under natural and greenhouse conditions

Abstract

Sand movement is a predominant feature of mobile coastal and lake-shoreline sand dunes. Plants growing in these environments are able to withstand and survive periods of burial by sand. Although mosses are important dune stabilizers in temperate dunes, there are few studies focused on their response to burial by sand. In this study we examined the effects of burial by sand on 11 moss species that grow naturally on Lake Huron sand dunes and occur in a gradient of habitats from the foredunes along the shore to forested areas. Artificial burial treatments (sand depth of 0, 1, 3, 5 and 7 cm) were imposed under greenhouse and field conditions. We measured final plant cover and calculated the speed of emergence and an interpretive index (tolerance index) to compare burial responses among species by calculating a burial ratio which standardized the initial size of each species. In the greenhouse, Ceratodon purpureus and Ditrichum flexicaule recorded the highest mean speeds of emergence and Dicranum scoparium, Plagiothecium laetum, Dicranum flagellare and Brachythecium sp. 1 the lowest. In the field the trends were similar although the speed of emergence was much slower. Three types of response to burial were evident in plant cover: neutral, inhibition and stimulation. Although all eleven studied species were able to emerge from the different depths of burial, we observed that species colonizing areas with high sand mobility and deposition (C. purpureus and D. flexicaule) were the most tolerant and emerged from depths of up to 35 times their height. Species growing inland, at the base of trees (Dicranum scoparium, Brachythecium sp. 2, Plagiomnium cuspidatum and Dicranum flagellare) showed the least tolerance of burial.