Disturbance type influences plant community resilience and resistance to Bromus tectorum invasion in the sagebrush steppe

Tim Seipel,Bruce D Maxwell,Erik A Lehnhoff,Kimberley T Taylor,Lisa J Rew,Borja Jiménez‐Alfaro

doi:10.1111/avsc.12370

Abstract

AbstractQuestionHow does type of disturbance alter plant community composition when an invasive species with high intrinsic population growth rate is present? The sagebrush steppe is a cold semi‐arid steppe dominated by the native shrub Artemisia tridentata Nutt., native bunchgrasses, and has been invaded by the non‐native winter annual Bromus tectorum L.LocationSagebrush steppe, Montana, USA.MethodsWe assessed the effect of fire and soil disturbance, due to bulldozing to create a firebreak, on the resilience of plant communities and their resistance to invasion by B. tectorum. Plant species richness and species composition were monitored for 3 years at two sites post‐fire and firebreak construction.ResultsBurned plant communities were resilient and had similar native grass cover and native species richness compared with the unburned sites after 3 years. Soil disturbance from firebreak construction resulted in species composition that was distinct and had lower native grass cover. Type of disturbance also affected the community's resistance to B. tectorum. Bromus tectorum cover was similar in burned and unburned areas, but increased up to three times and remained high where soil disturbance occurred, suggesting a shift to an alternative state.ConclusionIn this northern portion of the sagebrush steppe, communities with native plant cover were resilient to fire but not soil disturbance, which facilitated B. tectorum increase and a transition to an alternative state. In areas of high native plant cover, management tactics should avoid soil disturbance.

Highlights

Many plant communities are resilient to the particular disturbance regimes under which they evolved (e.g. Keeley et al 2011; Chambers et al 2014)
Soil disturbance from firebreak construction resulted in species composition that was distinct and had lower native grass cover
To manage for ecosystems that are resilient to disturbance and resistant to plant invasions within the sagebrush biome, we need to understand the interaction of plant community resilience with resistance to B. tectorum invasion and how the interaction is affected by different types of disturbance which could lead to different plant community states or varying recovery times (Germino et al 2016)

Summary

Introduction

Many plant communities are resilient to the particular disturbance regimes under which they evolved (e.g. Keeley et al 2011; Chambers et al 2014). Major changes in the magnitude and frequency of disturbances can push a plant community across resilience and resistance thresholds, potentially transforming it to an altered or novel stable state The alteration of disturbance regimes either through type of disturbance or frequency of disturbance can reduce resilience, resulting in longer recovery time and decreased resistance to invasion that leads to greater dominance by non-native plants, and a more rapid shift to an alternative state. Understanding how plant communities respond to disturbance, especially when the plant community has been altered by the presence of an invasive species, is important for managing ecosystems to mitigate against undesirable changes (Hobbs and Huenneke 1992; Keeley 2006, Standish et al 2014)

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