Legacies of afforestation on soil nematode community composition, structure, and diversity in a northern Canadian prairie

Abstract

We examined how legacies of afforestation affect soil food webs using the composition, structure, and diversity of soil nematode communities along a prairie restoration chronosequence. Vegetation and soil nematode surveys were conducted across a restoration chronosequence of tree removal (2, 5, and 20 years) in a former plantation in Riding Mountain National Park, Canada, established on a Great Plains rough fescue prairie. Nematodes were extracted using sugar-gradient centrifugation, counted and assigned to feeding groups. Remaining plantation and recently restored prairies were characterized by bacterial feeding nematodes whereas the oldest restored prairie and control prairie were dominated by plant-root feeders. Nematode diversity did not reach the level observed in the prairie even 20 years following the removal of trees. Nematode community diversity and structure was strongly correlated with the composition of restored plant communities. Invasion of restored prairies by exotic grasses corresponded with a strong decline in the diversity of plant-root feeders. Legacies of afforestation can impact prairie soils years after trees have been removed and can lead to shifts in feeding structure and a loss of diversity in the soil food web. As grasslands continue to decline globally, considering soil faunal communities may help evaluate the outcomes of ecosystem restoration and maintain their key functions.