Vegetation and vertebrate abundance as drivers of bioturbation patterns along a climate gradient

Discussion Our study showed that while hole density decreased from arid to humid environments, no clear pattern could be discerned for the excavated soil volume along the investigated environ- mental gradient. However, the contribution of vertebrates to excavated soil volume was larger than that of invertebrates. For the latter, the relationship to the vegetation cover along the cli- mate gradient was consistently negative while for vertebrates it was partly positive. Before discussing the general results, a few comments should be made on the allometric relationships of the burrow characteristics. Based on the RMA analysis regressions, these rela- tionships were not isometric, as the relative depth of a burrow increased with the increasing diameter of the entrance. This finding suggests that, for bioturbators, larger animals dig deeper into the soil [51]. This relationship presumably reflects the anti-predator behavior of larger animals: with increasing body size animals want to keep their entrance as small as possible to exclude predators [52], but on the same time minimize burrowing cost [53] on one hand, but Fig 4. Fitted relation between excavated soil volume (log10-transformed) and fixed effects for invertebrates (yellow) and vertebrates (blue) at each site (Pan de Azu´car, Santa Gracia, La Campana, Nahuelbuta). (A) Vegetation cover [%], (B) hole density (log10-transformed). Data from both field campaigns were used. https://doi.org/10.1371/journal.pone.0264408.g004 PLOS ONE Vegetation and vertebrate abundance as drivers of bioturbation patterns along a climate gradient

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