Elevated CO2 alters functional attributes of nematode communities in forest soils

Abstract

Summary We tested the effects of elevated concentrations of atmospheric CO2 on herbivorous nematodes in soil supporting plantations of Loblolly Pine (Pinus taeda) or Sweet Gum (Liquidambar styraciflua) trees in FACE experiments in the Eastern USA. We expected any net increase in carbon allocation to the rhizosphere to increase the abundance, biomass or respiration of the nematode community. Data were analysed with effect of CO2 concentration nested within month and year to isolate the maximum potential effect of CO2 treatment on soil nematode communities. Elevated CO2 decreased total abundance of nematodes in both forests, but impacts were greater in Sweet Gum than Loblolly Pine forests. Soil nematode community respiration and biomass increased with elevated CO2 in Loblolly Pine, but decreased with fumigation in Sweet Gum forests. Fungivores were the only trophic group showing a consistent response at both sites, with reduced abundance, biomass and respiration at elevated CO2. Estimated total respiration of soil nematode communities ranged from 2·9–11·2 g C m−2 year−1 in Pine soils and 0·6–4·7 g C m−2 year−1 in Sweet Gum soils, representing ≤1% of net primary production in these forests. Our results indicate that effects of elevated CO2 on soil nematode communities will not necessarily have a simple functional relationship with rhizosphere carbon allocation.