Soil macrofauna and nitrogen on a sub-Antarctic island

Abstract

The densities, diets and habitat preferences of the soil macrofaunal species on sub-Antarctic Marion Island (47°S, 38°E) are described. Their role in N cycling on the island is assessed, using a mire-grassland community as an example. Primary production on the island is high and this leads to a substantial annual requirement of nutrients by the vegetation. This requirement must almost wholly be met by mineralization of nutrient reserves in the organic matter. Rates of peat nitrogen mineralization mediated by microorganisms alone are much too low to account for rates of N uptake by the vegetation. Although soil macroinvertebrates, and bacteria represent a very small fraction of the total N pool, their interaction accounts for most of the peat N mineralization, as indicated by the amounts of inorganic N released into solution in microcosms. Extrapolation of the microcosm results shows that the soil macrofauna (mainly earthworms) stimulate the release of enough N from the mire-grassland peat to account for maximum N mineralization rates calculated from temporal changes in peat inorganic N levels and plant uptake during the most active part of the growing season. Considering that large numbers of mesoand microinvertebrates occur and must also contribute to nutrient mineralization, the soil faunal component is clearly of crucial importance to nutrient cycling on Marion Island. This is probably true of all sub-Antarctic islands.

Caterpillars benefit from thermal ecosystem engineering by wandering albatrosses on sub-Antarctic Marion Island

“…We address this assumption by examining the biomass of larvae of the flightless moth Pringleophaga marioni (Lepidoptera: Tineidae) with respect to the nutrient and physical environment of the nests. Larvae of P. marioni are key decomposers on Marion Island (Smith & Steenkamp 1992) and have been the subject of both ecological (e.g. Crafford 1990) and physiological (e.g.…”

Functional microarray analysis of nitrogen and carbon cycling genes across an Antarctic latitudinal transect

“…Indeed, due to a principal lack of insect and mammalian herbivores and detritivores at most locations (Smith and Steenkamp, 1992), food webs are primarily driven via bacterial and fungal detritus-based routes (Smith, 1994). Given their relative trophic simplicity, such ecosystems represent useful models for linking primary production and microbial nutrient cycling and disentangling the interrelated processes.…”

Deleterious effects of repeated cold exposure in a freeze-tolerant sub-Antarctic caterpillar

“…First, the responses of the larvae of P. marioni to freezing and to low temperatures are well understood (Klok and Chown, 1997;Sinclair and Chown, 2003;Sinclair et al, 2004). Second, caterpillars of P. marioni are ecologically important on sub-Antarctic Marion Island (46°54′S, 37°45′E) because of their wide distribution, large size (0.1-0.3·g) and role as keystone decomposers (Crafford et al, 1986;Smith and Steenkamp, 1992). Therefore, these freeze-tolerant larvae are a useful model for exploring the impact of the island's climate on the physiological responses of the fauna.…”