Effects of global warming on nematode diversity in a Swedish tundra soil -: a soil transplantation experiment

The implications of global warming on nematode populations were studied in a soil transplantation experiment. Blocks of peat from an ombrotrophic mire at Abisko, northern Sweden, were transplanted to nine warmer sites in Sweden in June 1996. The changes in nematode abundance and species composition were followed by monthly samplings from July to December 1996 with a final sampling in June 1997. In all sites except the most northern the total nematode numbers increased during the study period. However, especially at the three northern-most sites the composition of the nematode fauna changed very little. Most species from the mire survived in all transplants and the number of immigrating species was low. The most clearcut effects on faunal composition were seen in blocks transferred to open sites in central and southern Sweden. This was also indicated by the Maturity index (sensu Bongers) and Renkonen numbers (comparing similarity in fauna structure between source sire and transplantation sites). These parameters had the lowest values in blocks placed in the exposed sites where the greatest fluctations in temperature and moisture occurred. One conclusion of the study is that a climatic change has no rapid influence on the composition of the nematode fauna: soil structure and vegetation have a stronger influence. If the soil structure and vegetation start to change this will certainly also influence the nematode fauna. Upon warming above certain temperature thresholds, expected changes would result in an increased rate of mineralization followed by higher abundance of fungal and bacterial feeders belonging to the Secernentea.