Rangeland Ecology & Management

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SPATIAL RESILIENCE IN A SEMI-ARID SHRUBLAND: IMPLICATIONS FOR OPERATIONALIZING RESILIENCE IN ECOLOGICAL RESTORATION
Author
Wonkka, Carissa L.
Twidwell, Dirac
West, Jason B.
Rogers, William E.
Publisher
Society for Range Management
Publication Year
2015
Body

Restoration success in systems with alternative stable states is dependent on the ability to use interventions to shift resilience mechanisms from those that maintain a degraded state to those that support a desirable state. However, the utility of the resilience concept has been limited in practice by the difficulty of quantifying thresholds associated with management actions and ecosystem transformability. An alternative to quantifying ecological thresholds is to ascertain the relative resilience of an ecological state across identifiable ecosystem properties. We designed an experiment to determine the relative resilience of the shrub-dominated state in a brush encroached semi-arid rangeland across soils with different textures, ranging from fine clay to coarse sand. We randomly assigned plots on each soil type to one of three treatments: untreated control, hand-cutting followed by herbicide application, and roller-chopping. Despite widespread application in the study region, the two brush reduction methods assessed were not ubiquitously effective at overcoming the resilience of the shrubland state. Total woody cover differed among soils in treated plots three years following treatment, suggesting that the resilience of the woody-dominated state differs across soils. On both sandy and sandy-loam soils, chemical and mechanical brush removal temporarily restored grass dominance in the system, but woody plants quickly regained pretreatment levels of dominance. However, on clay soils, grass remained dominant for the duration of the study, suggesting that for these soils, both cut herbicide and mechanical treatments overcame shrubland resilience. Studies such as this one which explore relative resilience across a range of environmental conditions can be used to map areas of high and low resilience to intervention, allowing managers to target areas with underlying conditions that are more conducive to restoration. This is essential in systems such as the encroached rangeland in this study where broad-scale restoration efforts are cost prohibitive. 

Language
English
Resource Type
Text
Document Type
Conference Proceedings
Conference Name
SRM Sacramento, CA