Event Title

Quantifying Fuels Along Successional and Invasion Gradients in Sagebrush Ecological Sites of the Great Basin

Presenter Information

Robert Arkle

Location

Eccles Conference Center

Event Website

http://www.restoringthewest.org/

Abstract

In many sagebrush landscapes of the Great Basin, fire and invasion by nonnative plants can alter successional trajectories and create dynamic fuel conditions. Poorly quantified or constantly changing plant communities and fuel conditions hinder attempts by land managers to predict and control fire behavior, restore native plant communities, and maintain ecosystem services. We assessed how fuel loads change along successional and invasion gradients and across years in sagebrush ecological sites throughout the Great Basin. Preliminary results suggest that successional stage (i.e., prevalence of shrub cover) had a large effect on herbaceous biomass. On average, areas with ≥10% shrub cover had 57% less herbaceous biomass than areas with <10% shrub cover. When shrubs were absent, increasing bunchgrass cover did no have a strong effect on herbaceous biomass, likely because nonnative annuals accounted for more biomass when bunchgrasses were sparse. An invasion gradient (i.e., prevalence of nonnative plants) had a stronger effect on herbaceous biomass than did successional stage. In some invasion-prone areas (e.g., Snake River Plain), cover of nonnative forbs (Sisymbrium altissimum, Salsola tragus) contributed substantially more herbaceous biomass that did cheatgrass (Bromus tectorum). Down woody debris as infrequently encountered and did not contribute appreciably to fuel loads regardless of the successional stage. Inter-annual variability is herbaceous biomass was substantial (e.g., 45% change between years) and correlated with annual precipitation. Below average precipitation led to not only reductions in annuals, but also reductions of perennial grass cover (e.g., Poa secunda). However, herbaceous biomass varied less between wet and dry years in sites with relatively high shrub cover (>20%) that in sites with little or no shrub cover (<5%). Preliminary findings such as these could help land management agencies predict dynamic fuel conditions, fire risk, and fire behavior across the large landscapes they manage.

Comments

Robert Arkle, U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Snake River Field Station, Boise, Idaho, phone: (208) 426-5205, email: rarkle@usgs.gov.

Co-authors: Douglas J. Shinneman, David S. Pilliod, Susan K. McIlroy, and Nancy F. Glenn

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Oct 28th, 9:00 AM Oct 28th, 9:30 AM

Quantifying Fuels Along Successional and Invasion Gradients in Sagebrush Ecological Sites of the Great Basin

Eccles Conference Center

In many sagebrush landscapes of the Great Basin, fire and invasion by nonnative plants can alter successional trajectories and create dynamic fuel conditions. Poorly quantified or constantly changing plant communities and fuel conditions hinder attempts by land managers to predict and control fire behavior, restore native plant communities, and maintain ecosystem services. We assessed how fuel loads change along successional and invasion gradients and across years in sagebrush ecological sites throughout the Great Basin. Preliminary results suggest that successional stage (i.e., prevalence of shrub cover) had a large effect on herbaceous biomass. On average, areas with ≥10% shrub cover had 57% less herbaceous biomass than areas with <10% shrub cover. When shrubs were absent, increasing bunchgrass cover did no have a strong effect on herbaceous biomass, likely because nonnative annuals accounted for more biomass when bunchgrasses were sparse. An invasion gradient (i.e., prevalence of nonnative plants) had a stronger effect on herbaceous biomass than did successional stage. In some invasion-prone areas (e.g., Snake River Plain), cover of nonnative forbs (Sisymbrium altissimum, Salsola tragus) contributed substantially more herbaceous biomass that did cheatgrass (Bromus tectorum). Down woody debris as infrequently encountered and did not contribute appreciably to fuel loads regardless of the successional stage. Inter-annual variability is herbaceous biomass was substantial (e.g., 45% change between years) and correlated with annual precipitation. Below average precipitation led to not only reductions in annuals, but also reductions of perennial grass cover (e.g., Poa secunda). However, herbaceous biomass varied less between wet and dry years in sites with relatively high shrub cover (>20%) that in sites with little or no shrub cover (<5%). Preliminary findings such as these could help land management agencies predict dynamic fuel conditions, fire risk, and fire behavior across the large landscapes they manage.

https://digitalcommons.usu.edu/rtw/2015/Posters/20