Understanding the Importance of Resilience and Resistance to the Restoration of Sagebrush Rangelands

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1 Understanding the Importance of Resilience and Resistance to the Restoration of Sagebrush Rangelands Jeanne Chambers, RMRS Rick Miller, OSU Jim Grace, USGS

2 Resilience, Resistance and Thresholds Resilience = the capacity of an ecosystem to maintain its fundamental structure, processes and functioning when subjected to stress, disturbance or invaders Resistance to invasives = the biotic and abiotic factors and ecological processes in an ecosystem that limit the population growth of an invading species

3 Resilience, Resistance and Thresholds n Thresholds define the limits of natural variability, and are crossed when an ecosystem does not return to the original state via natural processes after disturbance or invasion and transitions to a new, alternative state

4 Great Basin Vegetation Types Forest to Alpine Mtn Sagebrush & Woodland Wyoming Sagebrush Salt Desert Shrub Annual Precipitation

5 High Resilience Low Salt Desert Shrub Wyoming Sage Temperature Precipitation Mountain Sage Mountain Brush Resilience increases with elevation over gradients of available resources and net productivity Higher productivity & more favorable growing conditions More rapid recovery after disturbance Increased capacity to compete with invaders Elevation (Wisdom & Chambers 2009; Brooks and Chambers 2011)

6 High Resilience Low Resilience is influenced by local site conditions Salt Desert Shrub Wyoming Sage Mountain Sage Mountain Brush Aspect, & slope, Soil characteristics Temperature Precipitation Ø Effective precipitation Ø Solar radiation & degree days Ø Soil water & nutrient holding capacity Elevation

7 High Resistance to cheatgrass Low Salt Desert Shrub Wyoming Sage Mountain Sage Temperature Precipitation Elevation Mountain Brush Resistance reflects the fundamental niche of the invader + site conditions Resistance is higher in stressful environs Historically, Wyoming sagebrush types least resistant to cheatgrass

8 High Resistance to cheatgrass Low Salt Desert Shrub Wyoming Sage Mountain Sage Temperature Precipitation Elevation Mountain Brush Resistance is influenced by site conditions Resistance is lower on south-facing slopes Resistance may decrease after disturbance due higher temp & more water v A warming climate may result in a shift in the fundamental niche

9 Factors that Influence Resilience and Resistance Ecological memory or condition v Soil stability and erosion v Species composition and abundance of native plants and animals, seed banks, and seed sources v Type, presence, abundance of invasive species Severity and frequency of disturbance - v Inappropriate livestock grazing, conditions conducive to high severity fires, and fire return intervals less than the historical interval

10 Effect of Elevation and Fire Three years post-burn 70 Mean Biomass (g/m 2 ) Annual Forbs Annual Graminoids Perennial Forbs Perennial Graminoids Control Burn Control Burn Control Burn m 2103 m 2225 m 2225 m 2347 m 2347 m Productivity & site potential change with elevation Herbaceous biomass increases with elevation both pre- and post burn Ø Higher productivity can result in greater resilience Wyoming Sage Mountain Sage Mountain Brush Intermediate Tree Cover (~30 to 40%) (Dhaemers & Chambers in process)

11 Effect of Tree Cover and Fire Three years post-burn Mean Biomass (g/m 2 ) % 38% Annual Forbs Annual Graminoids Perennial Forbs Perennial Graminoids 74% Control Burn Control Burn Control Burn Ecological condition decreases with increasing tree cover Perennial herb biomass decreases with tree cover both pre- and post burn Annual herb biomass increases with tree cover Low Low Intermediate Intermediate High High Tree Cover Ø Resistance and resilience decrease as tree cover increases (Dhaemers & Chambers in process)

12 Effect of Elevation, Fire and Herbaceous Species Number of plants Number of plants Year Year 2 Burn Ppt 19.9 cm Ppt 21.7 cm Control Burn Ppt 20.3 cm Ppt 27.0 cm Control Ppt = Oct 1 - June 30 Burn Ppt 27.2 cm Ppt 28.9 cm Control Resistance increases with elevation Higher elevations and colder soil temperatures result in ecophysiological constraints Site characteristics and growing season conditions have greater effects on establishment than fire or herbaceous species removal 6400' 7180' 7800' (Chambers et al. 2007)

13 Effect of Elevation, Fire and Herbaceous Species Effects of burning and removal on growth and reproduction are additive & similar over elevations v Removal 2 to 3 fold v Burning 2 to 6 fold v Removal + Burning 10 to 30 fold Ø Disturbances that increases resources decrease resistance Ø Mechanism is growth and reproduction not establishment Ø Perennial herbaceous species increase resistance via competition for resources

14 Environmental Conditions Ecological Condition Species Composition Disturbance Characteristics Restoration Objectives Abiotic Environment -Effective ppt -Solar radiation & degree days -Soil water & nutrient holding capacity Pinyon & Juniper -Cover -Age Sagebrush -Type, cover Perennial herbaceous -Cover,diversity Treatment characteristics -Type, size, shape, Intensity Maintain desirable proportion of sagebrush Increase perennial herbaceous vegetation Topograhy -Elevation -Slope -Aspect Livestock grazing -Duration -Intensity Invasives -Cover,diversity Decrease risk of invasion Post-treatment precipitation

15 Management Approach n A basic approach for managing and restoring these ecosystems using the concepts of resistance and resilience includes: v First develop an understanding of factors influencing ecological resistance and resilience for vegetation types/ ecological site types at risk (SageSTEP). Second assess environmental characteristics and ecological conditions of the vegetation types/ecological site types at landscape scales. Third prioritize management activities & determine appropriate treatments based on relative resilience and resistance. v v

16 Case Study North Monitors Tree Expansion Mountain Sagebrush Mountain Brush Mountain Sagebrush Black Sagebrush Wyoming Sagebrush Resilience Resistance 18

17 Black Sagebrush Wyoming Sagebrush Cut and Leave Masticate Resilience & Resistance Elevation relatively low Precipitation &productivity - moderately low Abundance of invasives cheatgrass present; locally abundant Grazing allotment vacant Ecological condition good Management Implications Slower recovery due to low productivity Higher risk of cheatgrass spread, especially after fire Ø Use mechanical treatments Ø Minimize surface disturbance Lack of fine and contiguous fuels

18 Mountain Sagebrush Cut and Leave No Treatment Resilience & Resilience Elevation intermediate Precipitation &productivity -moderate Ecological condition fair/low Abundance of invasives cheatgrass present on south slopes Grazing allotment active Management Implications Low recovery due to high tree cover & depleted understory Moderate risk of cheatgrass spread, especially on south slopes Higher risk of severe fire Ø Create fuel breaks Ø Treat areas with low tree abundance use mechanical methods Ø Revegetate following wildfire Ø Manage grazing

19 Mountain Sagebrush Mountain Brush Resilience & Resilience Elevation high Precipitation &productivity -moderately high Ecological condition good Abundance of invasives cheatgrass largely absent Grazing allotment active Management Implications Higher recovery rates Lower risk of severe fire Ø Treat with prescribed fire Ø Manage grazing Lower risk of cheatgrass spread v Monitor results adapt management

20 Down the Road Collaborative SageSTEP and GB Science Delivery Project Publications Resilience to disturbance and resistance to invasive alien grasses in arid and semi-arid ecosystems Guidelines for using resilience and resistance concepts in the context of ecological site types

21 Acknowledgements Bob Blank Dave Board Matt Brooks Lea Condon Carla D Antonio Jessica Dhaemers Susan Meyer Mike Pellant Bruce Roundy Robin Tausch Peter Weisberg Alison Whitaker Mike Wisdom Exotic Bromus Grasses in the Western US: Current and future invasions, impacts, and management - USDA AFRI REENet Integrating ecological forecasting methods to improve prioritization of invasive species management USGS Powell Center