Effect of altered rainfall regimes on soil nematode communities in dryland ecosystems

Abstract

Current climate change predictions suggest ecosystems are to be subjected to fluctuations in precipitation, where some areas may become wetter and other areas drier. Both above and belowground systems will be impacted by such rainfall changes, yet research has predominantly focused on aboveground systems. I assessed the long-term effects of altered rainfall, specifically increased and reduced precipitation, on total nematode and trophic level abundances at six sites in Australia's drylands. I also set up an experiment to assess the effects of altered rainfall regimes on decomposition rates, a key soil process to which nematodes contribute, to understand how projected rainfall changes will impact ecosystem processes. Finally, I synthesized nematode responses to rainfall changes using a meta-analytical approach based on 74 independent observations from 46 studies which tested whether effects differed among ecosystem types and studies of different timescales. I also collected data on ecosystem functions where possible to assess links between changes in nematode abundances and functioning. In Australia's drylands, it was found that nematodes were consistently negatively impacted under decreased rainfall treatments, whereas increased rainfall had less consistent effects among trophic groups and sites; however, plant parasites and bacterivores showed the strongest responses to both treatments. Decomposition was seen to be strongly linked with changes in rainfall, and functioning was seen to be correlated with soil biota (nematodes) and soil chemistry (pH). The meta-analysis showed that all trophic groups, except fungal feeders, were negatively impacted by drought independent of treatment duration while effects of increased rainfall were observed only in longer term studies (>1 year) where total abundances and plant parasites increased. There is a need to assess this further in future studies as rainfall reductions are likely to have negative effects on nematode abundances and ecosystem functioning, while increased precipitation may favour plant parasites likely through increased plant productivity.

Date of Award	2021
Original language	English