Soil respiration and its determinants on a sub-Antarctic island

The effect of temperature on soil respiration at field moisture holding capacity was assessed for 100 sites representing 21 habitats on sub-Antarctic Marion Island (47°S, 38 °E). Respiration rates were compared across habitats and related to soil chemistry, soil microrganism counts and botanical characteristics. Median Q10 across the 100 sites was 2.0, in the lower part of the range reported for soils elsewhere. Q10 did not differ with temperature between 5 and 20 °C, indicating a mixed community of soil microorganisms having different responses to temperature. Respiration rates are about an order of magnitude higher than those reported at the same temperature for surface soils from Northern Hemisphere tundra. Edaphic richness (high concentrations of available P, inorganic N and total N), associated with large soil microbial populations and substantial relative covers of nitrophilous or coprophilous plants and caused by manuring by seals and seabirds, is the main determinant of soil respiration rate. The islandʹs habitats were originally defined on the basis of canonical correspondence analysis of structural (vegetation and soil chemistry) variables. Since habitat-mean soil respiration rate correlated highly positively with the mean positions of the habitats on a canonical axis interpreted as representing a gradient in the intensity of animal influence, it is concluded that the habitat classification reflects differences in at least one ecosystem functional attribute, soil respiration.