Response of soil nematode fauna to naturally elevated CO2 levels influenced by soil pattern

As experimental elevation of CO2 in short-term experiments may produce orga nic matter with decomposition characteristics different from those produced under long-term equilibrated conditions, we sampled the soil nematode faun a near a natural CO2 vent in Northland, New Zealand. Various indices of the nematode fauna showed significant effects, with all being significantly co rrelated with soil pH, microbial carbon and atmospheric CO2 across the 33 s ampling points. There was a general decrease in nematode abundance and dive rsity, but an increase in dominance and proportion of bacterial-feeding nem atodes with increasing atmospheric CO2 concentration. However, when the nem atode data from gley and organic soils present at the site were differentia ted most of the significant correlations were with soil microbial carbon; t hey were positive in the organic soil but negative in the gley soil. That t hese responses can be related to soil carbon and to microbial carbon demons trates that any general response to long-term CO2 enrichment represents an integration of specific responses by the soil biota in the various soils pr esent.