Long-term effects of copper and ph on the nematode community in an agroecosystem

Abstract Four copper (0, 250, 500, and 750 kg Cu · haa−1) and pH (4.0, 4.7, 5.4, and 6.1 in 1 M KCl) treatments were applied to an arable agroecosystem. Effects on the nematode community were assessed after 10 years of exposure under field conditions. Both copper and pH had major influences on nematodes. The effect of copper was generally enhanced with decreasing soil pH. The lowest copper application rate which had a significant negative effect on the total number of nematodes was 250 kg. ha−1 at pH 4.0, which is equivalent to a copper concentration of 0.32 mg.L−1 in 0.01 M calcium chloride (Cu-CaCl2). Species composition and the abundance of trophic groups were more sensitive than the total number of nematodes. Combinations of high copper and low pH significantly reduced the number of bacterial-feeding nematodes, whereas the number of hyphal-feeding nematodes increased. Omnivorous and predacious nematodes showed the most sensitive response, becoming extinct when Cu-CaCl2 was 0.8 to 1.4 mg.L−1. Plant-feeding nematodes showed the largest differences in abundance and appeared to reflect the effects of copper and pH on primary production. The results suggest that the nematode community was also affected indirectly by copper and pH via other components of the soil food web. It is concluded that nematodes offer excellent perspectives to assess effects of pollutants at the community level.