Field Soil Respiration Rate on a Sub-Antarctic Island: Its Relation to Site Characteristics and Response to

Botanical, soil chemistry and soil microbiology variables were tested as predictors of in situ soil respiration rate in the various terrestrial habitats on sub-Antarctic Marion Island (47˚S, 38˚E). Inorganic P and total N concentration were the best predictors amongst the chemistry variables and bacteria plate count the best of the microbiology variables. How-ever, while these chemistry and microbiology variables could accurately predict soil respiration rate for particular habi-tats, they proved inadequate predictors across the whole range of habitats. The best suite of predictors comprised only botanical variables (relative covers of five plant guilds) and accounted for 94 % of the total across-habitat variation in soil respiration rate. Mean field soil respiration rates (2.1- 15.5 mmol CO2 m–2·h–1) for habitats not influenced by sea-birds or seals are similar to rates in comparable Northern Hemisphere tundra habitats. Seabird and seal manuring en-hances soil respiration rates to values (up to 27.6 mmol CO2 m–2·h–1) higher than found at any tundra site. Glucose, N, P or N plus P were added to three habitats with contrasting soil types; a fellfield with mineral, nutrient-poor soil, a mire with organic, nutrient-poor soil and a shore-zone herbfield heavily manured by penguins and with organic, nutrient-rich soil. Glucose addition stimulated soil respiration in the fellfield and mire (especially the former) but not in the coastal herbfield soil. N and P, alone or together, did not stimulate respiration at any of the habitats, but adding glucose to fell-field soils that had previously been fortified with P or NP caused a similar increase in respiration rate, which wa