Initial litter quality drives the consistent negative effects of fauna exclusion on litter decomposition in diverse ecosystems: A global meta-analysis

<p class="MsoNormal"><strong><span>Aim:</span></strong> <span>Despite the extensive research done on the consequences of faunal impacts on litter decomposition in different experimental contexts, a thorough assessment of their impacts and causes in various habitats around the world is still missing. Here, we aimed to explore general patterns and key drivers (e.g.,</span> <span>climate, environment, litter quality) of faunal effects on litter decomposition in terrestrial and aquatic ecosystems.</span></p> <p class="MsoNormal"><strong><span>Location: </span></strong><span>Global.</span></p> <p class="MsoNormal"><strong><span>Time period: </span></strong><span>1980-2022.</span></p> <p class="MsoNormal"><strong><span>Major taxa studied: </span></strong><span>Plant litter and fauna.</span></p> <p class="MsoNormal"><strong><span>Methods: </span></strong><span>We investigate the effects of fauna exclusion on litter decomposition in terrestrial and aquatic ecosystems through a meta-analysis of 819 pairs of observations from 110 studies on terrestrial litter decomposition and 402 pairs of observations from 60 studies on aquatic litter decomposition.</span></p> <p class="MsoNormal"><strong><span>Results: </span></strong><span>Fauna exclusion reduced litter decomposition rates in terrestrial and aquatic ecosystems by 34% and 46% on average, respectively. In terrestrial ecosystems, the faunal effects differed among climate zone, precipitation level, and decomposition duration. Faunal effects were larger in warmer and moister climates, and decreased with the extension of decomposition time. However, in aquatic ecosystems, these moderating variables did not affect the negative effects of fauna exclusion. We also found that the faunal effects on litter decomposition were mainly associated with the initial litter quality and climate in terrestrial ecosystems, and with the initial litter quality in aquatic ecosystems.</span></p> <p class="MsoNormal"><strong><span>Main conclusions: </span></strong><span>Fauna exclusion had consistent negative effects on litter decay in both terrestrial and aquatic ecosystems, and </span><span>initial litter </span><span>quality was the main factor that determined the extent of faunal effects on litter decomposition. Our findings highlight the significance of fauna diversity</span><span> </span><span><span>conservation worldwide, and underscore the need to incorporate fauna effects into dynamic models of litter decomposition in order to examine the effects and processes of land-water-atmosphere carbon fluxes.</span></span></p>