Northward range expansion of rooting ungulates decreases detritivore and predatory mite abundances in boreal forests

The last decades wild boar populations have expanded northwards,
colonizing boreal forests. The soil disturbances caused by wild boar
rooting may have an impact on soil organisms that play a key role in
organic matter turnover. However, the impact of wild boar colonisation on
boreal forest ecosystems and soil organisms remains largely unknown. We
investigated the effect of natural and simulated rooting on decomposer and
predatory soil mites (total, adult and juvenile abundances; and proportion
of adult-juvenile). Our simulated rooting experiment aimed to disentangle
the effects of a) bioturbation due to soil mixing and b) removing organic
material (wild boar food resources) on soil mites. Our results showed a
decline in the abundance of adult soil mites in response to both natural
and artificial rooting, while juvenile abundance and the relative
proportion of adult-juvenile were not affected. The expansion of wild boar
northwards and into new habitats has negative effects on soil decomposer
abundances in boreal forests which may cascade through the soil food web
ultimately affecting ecosystem processes. Our study also suggests that a
combined use of natural and controlled experimental approaches is the way
forward to reveal any subtle interaction between aboveground-belowground
organisms and the ecosystem functions they drive.