Excluding arbuscular mycorrhiza lowers variability in soil respiration but slows down recovery from perturbations

Abstract

The role of mutualisms in mediating temporal stability in an ecosystem has been debated extensively. Here, we focus on how a ubiquitous mutualism, arbuscular mycorrhiza, influences temporal stability of a key ecosystem process, ecosystem respiration. We discriminated between two forms of temporal stability, temporal variability and resilience, and hypothesized that excluding arbuscular mycorrhiza would be detrimental for both of them. We analyzed a set of 10 parallel manipulation experiments to assess how excluding arbuscular mycorrhiza modulates temporal stability compared to other common experimental factors. We quantified the temporal variability of ecosystem respiration and the resilience to experimental perturbations (i.e., pulses, stresses, and a disturbance) following manipulations of mycorrhizal state. We observed lower temporal variability in the absence of arbuscular mycorrhiza in discord to our main hypothesis. Manipulating arbuscular mycorrhiza had a stronger impact on temporal variability than the pulse (application of urea), the stress (addition of salt), and a disturbance (experimental defoliation) but weaker than excluding primary producers or comparing across different plant species. Resilience to experimental perturbations declined in non-mycorrhizal microcosms. We present an empirical study on how mutualisms impact temporal stability. Arbuscular mycorrhiza differentially alters temporal variability and resilience, highlighting that generalizing across different forms of temporal stability could be misleading.