Document: LIS-3-58-18

Climate change effects on enchytraeid worms (Oligochaeta) and C release in tundra soils.

COLE, L.* ^1,2, R.D.BARDGETT ² and P.INESON ^1,3

Institute of Terrestrial Ecology, Merlewood Research Station, Grange-over-Sands, Cumbria, LA11 6JU United Kingdom ¹
Lancaster University, Lancaster, Lancashire LA1 4YQ United Kingdom ²
University of York, Heslington, York YO10 YDD United Kingdom ³

Abstract:
It is becoming increasingly apparent that ecosystem responses to climate change may be regulated by below-ground feedback processes, which are mediated by responses of soil biota to atmospheric CO₂ enrichment and warming. This study examined the response of soil fauna and their interactions with microbes to climate change (soil warming), and the consequences of this for decomposition and nutrient cycling processes in organic tundra soils. Enchytraeid worms (Oligochaeta) were the dominant soil fauna of these tundra soils, with a single species Cognettia sphagnetorum (Vedj.) comprising 75% of the below-ground biomass. Field studies revealed that enchytraeid densities were correlated to soil temperature, and their vertical distribution was related to soil moisture status. A series of microcosm studies were carried out showing that when at field densities, enchytraeids significantly increased microbial respiration (by 35%) and the leaching of dissolved organic carbon (DOC) (by 94%) from the surface litter of tundra soils. Enchytraeids had no effect on the growth and nutrition of the upland grass species F. ovina (L.) since grazing of the microbes by enchytraeids may have enhanced their ability to sequester N and P, despite a reduction in microbial biomass (by 23%, as total PLFA). These results suggest that enchytraeids indirectly drive the processes of decomposition and nutrient mineralization, and hence plant nutrient availability, through their interactions with the soil microbial community. A second experiment examined the effects of soil warming (to 5 C above current mean summer temperatures) and revealed a reduced functional role of enchytraeids in regards to their influence on C mineralization, suggesting future warming may reduce their biological contribution to C mineralization. However, soil warming enhanced nutrient uptake by F. ovina, despite the loss of the beneficial role of enchytraeids for plant nutrient availability and acquisition, suggesting that increased primary production in these ecosystems in response to future warming, may maintain the role of these soils as terrestrial C stores.

Keywords: enchytraeids, soil warming, C cycling

This abstract is being presented at: 9:00 AM in session:
Oral Session #23: Soil Ecology.