DOI: 10.5061/dryad.3f2j7
title: Data from: Biotically driven vegetation mosaics in grazing ecosystems: the battle between bioturbation and biocompaction

description: Grazing ecosystems ranging from the arctic tundra to tropical savannas are
 often characterized by small-scale mosaics of herbivore-preferred and
 herbivore-avoided patches, promoting plant biodiversity and resilience.
 The three leading explanations for bistable patchiness in grazed
 ecosystems are: i) herbivore-driven nutrient cycling, ii) plant
 growth-water infiltration feedback under aridity, and iii) irreversible
 local herbivore-induced abiotic stress (topsoil erosion, salinity).
 However, these insufficiently explain the high temporal patch dynamics and
 wide-ranging distribution of grazing mosaics across productive habitats.
 Here we propose a fourth possibility where alternating patches are
 governed by the interplay of two important biotic processes: bioturbation
 by soil fauna that locally ameliorates soil conditions, promoting tall
 plant communities, alternating with biocompaction by large herbivores that
 locally impairs soil conditions, and promotes lawn communities. We review
 mechanisms that explain rapid conversions between bioturbation- and
 biocompaction-dominated patches, and provide a global map where this
 mechanism is possible. With a simple model we illustrate that this fourth
 mechanism expands the range of conditions under which grazing mosaics can
 persist. We conclude that the response of grazing systems to global
 change, as degradation or catastrophic droughts, will be contingent on the
 correct identification of the dominant process that drives their
 vegetation structural heterogeneity.
description: Howison et al 2017
 Bioturbation BiocompactionTITLE: Biotically driven
 vegetation mosaics in grazing ecosystems: the battle between bioturbation
 and biocompaction AUTHORS: Ruth A. Howison, Han Olff, Johan van de Koppel,
 and Christian Smit Corresponding author: Ruth A. Howison
 (ruthhowison@gmail.com) BifurcationModel.zip Bifurcation model resulting
 in figures 2 and 3, designed and written by Johan van de Koppel and Ruth
 Howison, using R. R Core Team (2015). R: A language and environment for
 statistical computing. R Foundation for Statistical Computing, Vienna,
 Austria. URL https://www.R-project.org/. Phase planes depicting the
 bifurcation analysis of simple plant-herbivore models, showing the more
 classical A) Herbivore-plant quality feedback, and B) Water-infiltration
 feedback. Phase planes depicting the bifurcation analysis of
 plant-herbivore models with bioturbation, showing that the interplay
 between bioturbation and biocompaction strongly expands the conditions
 under which heterogeneity can persist in grazing ecosystems, with A) only
 bioturbation feedback and B) the consequence of combining bioturbation and
 biocompaction feedbacks." GIS_Rainfall_Texture_Analysis.zip Analysis
 by Ruth Howison and Han Olff, using ESRI ArcMap 10.3 for Desktop Global
 prediction of the regions where patchiness generated by bioturbation and
 biocompaction is possible, eliminating for unsuitable conditions,
 specifically certain soil characteristics and rainfall. Incompatible soils
 include; permafrost, sand (&gt; 70% sand fraction and &lt; 15% clay
 fraction), organic soil (histosols or &gt; 20% organic material dry mass),
 and rainfall &lt; 400 and &gt; 1200 mm/yr and representing limits to
 forage quantity and quality required to maintain large herbivores. Data
 sources used: harmonized world soil database (HWSD) version 1.21, 2)
 Rainfall parameters were delineated using the global precipitation surface
 available from BioClim.org (Hijmans et al. 2005)