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Resilience and alternative stable states after desert wildfires

Citation

Abella, Scott; Gentilcore, Dominic; Chiquoine, Lindsay (2020), Resilience and alternative stable states after desert wildfires, Dryad, Dataset, https://doi.org/10.5061/dryad.kwh70rz1x

Abstract

Improving models of community change is a fundamental goal in ecology and has renewed importance during global change and increasing human disturbance of the biosphere.  Using the Mojave Desert (southwestern USA) as a model system, invaded by non-native plants and subject to wildfire disturbances, we examined models of resilience, alternative stable states, and convergent-divergent trajectories for 36 years of plant community change after 31 wildfires in communities dominated by the native shrubs Larrea tridentata or Coleogyne ramosissima.  Perennial species richness on average was fully resilient within 23 years after disturbance in both community types.  Perennial cover was fully resilient within 25 years in the Larrea community, but recovery was projected to require 52 years in the Coleogyne community.  Species composition shifts were persistent, and in the Coleogyne community, the projected compositional recovery time of 550 years and increasing resembled a deflected trajectory toward potential alternative states.  Disturbed sites contained a perennial species composition of predominately short-statured forbs, subshrubs, and grasses, contrasting with the larger-statured shrub and tree structure of undisturbed sites.  Auxiliary datasets characterizing species recruitment, annual plants including non-native grasses, biocrust communities, and soils showed persistent differences between disturbed and undisturbed sites consistent with positive feedbacks potentially contributing to alternative stable states.  Resprouting produced limited resilience for the large shrubs Larrea tridentata and Yucca spp. important to population persistence, but did not forestall long-term reduced abundance of the species.  The non-native annual grass Bromus rubens increased on disturbed sites over time, suggesting persistently abundant non-native plant fuels and reburn potential.  Biocrust cover on disturbed sites was half and species richness a third of amounts on undisturbed sites.  Soil nitrogen was 30% greater on disturbed sites and no significant trend was evident for it to decline on even the oldest burns.  Disturbed desert plant communities simultaneously supported all three models of resilience, alternative stable states, and convergent-divergent trajectories among community measures (e.g., species richness, composition), timeframes since disturbance, and spatial resolutions.  Accommodating expression within ecosystems of multiple models, including those opposing each other, may help broaden theoretical models of ecosystem change.

Methods

Methods are documented in the associated paper.