Data from: Rainfall-dependent impacts of threatened ecosystem engineers on organic matter cycling

1) Species loss is often associated with a decline in ecosystem functions.
Globally, digging mammals (or ecosystem engineers) are functionally
important, altering soil processes at local scales. However, their effects
on the process of decomposition are poorly understood, particularly at
larger scales, where the environment may moderate the magnitude of
effects. 2) We tested the landscape-scale effects of reintroducing
ecologically extinct digging mammals on two aspects of nutrient cycling
over a large environmental gradient in Australia, where many digging
mammals became extinct or ecologically extinct following the arrival of
Europeans. 3) We measured the impacts of digging mammals on soil organic
matter content and plant litter decomposition over a 3000 km transect,
where annual average rainfall varied between 166 and 877 mm. We set up
paired study plots (n = 8-10) inside and outside five reintroduction
reserves. We took soil samples to assess soil organic matter content and
set up litter bags to measure plant litter decomposition over 4 and 12
months. We used macro-invertebrate exclusion and control treatments to
determine the relative importance of macroinvertebrates in decomposition
with and without digging mammals. 4) Soil organic matter was greater in
re-introduction areas, but the magnitude of the effect was driven by
productivity (average annual rainfall as a proxy), with little effect of
digging activity at the wettest sites. Short-term plant matter
decomposition was greater in the presence of digging mammals, and their
effect was dependent on the amount of rain that fell during the study
period. Long-term litter decomposition increased with annual rainfall,
independent of digging mammals. Unexpectedly, macroinvertebrate exclusion
increased decomposition rates over 12 months. 5) Reintroduction of digging
mammals substantially alters soil processes and organic matter
decomposition, but impacts are rainfall-dependent. Restoring native
digging mammals to their historical distribution is likely to reverse
degradation of ecosystem processes, but the magnitude of this effect
depends on the environment.