Herrick Considerations when applying thresholds to

Considerations when applying thresholds to management : 

Considerations when applying thresholds to management

Outline: 

Outline Relationships between thresholds and ecosystem health Using S&T models to help make policy and management decisions [ranking the likelihood of autogenic (and non-autogenic) recovery]

Thresholds and Ecosystem Health: 

Thresholds and Ecosystem Health Thresholds are an indicator of ecosystem health (not vice versa)

Thresholds and Ecosystem Health: 

Thresholds and Ecosystem Health Thresholds are an indicator of ecosystem health (not vice versa) Some ecosystem health indicators may also serve as threshold indicators (both reflect changes in ecological processes)

Thresholds and Ecosystem Health: 

Thresholds and Ecosystem Health Thresholds are an indicator of ecosystem health (not vice versa) Some ecosystem health indicators may also serve as threshold indicators (both reflect changes in ecological processes) IIRH helps understand processes associated with threshold and non-threshold transitions

Thresholds and Ecosystem Health: 

Thresholds and Ecosystem Health Thresholds are an indicator of ecosystem health (not vice versa) Some ecosystem health indicators may also serve as threshold indicators (both reflect changes in ecological processes) IIRH helps understand processes associated with threshold and non-threshold transitions IIRH can be used to identify processes that have been modified To decide if management action is required To select appropriate management actions AND the appropriate scale and location in the landscape (rills and water flow patterns)

Slide7: 

1961 Mesquite Ecological threshold crossed?

Slide8: 

1961 2002 Fenced and ungrazed since ca. 1960 Mesquite Mesquite Ecological threshold crossed? Yes, probably

Slide9: 

Nov. 1971 BLM photo point Ecological threshold crossed?

Slide10: 

Nov. 1971 BLM photo point Nov. 1990 Ecological threshold crossed? No, probably not

Slide11: 

Nov. 1971 BLM photo point Rainfall (y=inches) Nov. 1990 Ecological threshold crossed? No, probably not

State transition: Non-eroding grassland  eroding shrubland: 

State transition: Non-eroding grassland  eroding shrubland

Pattern (of plants, soil carbon & nutrients): 

Pattern (of plants, soil carbon & nutrients) Soil nutrients become increasingly concentrated under shrubs (Valentine, 1941)

Pattern/Process: 

Pattern/Process Soil & water runoff and erosion increase during shrub invasion as interspace infiltration declines 0 20 40 60 80 100 120 interspace canopy interspace canopy Shrubland Grassland Single-ring infiltration (mm/h)

Pattern/Process threshold: 

Pattern/Process threshold Wind erosion thresholds are crossed as gap sizes increase due to grass mortality (often, but not always, associated with shrub invasion)

Applying S&T Models to Policy and Management: 

Applying S&T Models to Policy and Management

State transition: Non-eroding grassland  eroding shrubland: 

State transition: Non-eroding grassland  eroding shrubland

Slide19: 

Probability of autogenic recovery Status of key process (wind erosion) or property (gap size) Resilience begins to decline – increasing probability of transition (Briske et al. 2006 – NFB’s vs. PFB’s)

Slide20: 

Probability of autogenic recovery Status of key process (wind erosion) or property (gap size) ”THRESHOLD”

Slide21: 

Probability of autogenic recovery Status of key process (wind erosion) or property (gap size) ”THRESHOLD” Depends on: Things we know and can accurately measure or predict (soil erodibility = f(soil texture and aggregation))

Slide22: 

Probability of autogenic recovery Status of key process (wind erosion) or property (gap size) ”THRESHOLD” Depends on: Things we know and can accurately measure or predict (soil erodibility = f(soil texture and aggregation)) Things we know but can’t accurately measure or predict (gap size distribution temporal dynamics = f(precipitation, etc.))

Slide23: 

Probability of autogenic recovery Status of key process (wind erosion) or property (gap size) ”THRESHOLD” Depends on: Things we know and can accurately measure or predict (soil erodibility = f(soil texture and aggregation)) Things we know but can’t accurately measure or predict (gap size distribution temporal dynamics = f(precipitation, etc.)) Things we don’t know (???)

Slide24: 

Probability of autogenic recovery Status of key process (wind erosion) or property (gap size) ”THRESHOLD” Conclusion Our level of certainty about the probability that a threshold transition has occurred is highly variable

Slide25: 

Probability of autogenic recovery Status of key process (wind erosion) or property (gap size) But we DO have some control… over whether a threshold is crossed, and whether or not post-threshold recovery occurs

Slide26: 

Probability of autogenic recovery Status of key process (wind erosion) or property (gap size) Limit dry season grazing (limits large gaps during highest winds)

Slide27: 

Probability of autogenic recovery Status of key process (wind erosion) or property (gap size) Limit dry season grazing Herbicide program

Slide28: 

Probability of autogenic recovery Status of key process (wind erosion) or property (gap size) Limit dry season grazing Herbicide program ???

Decision Constraints: 

Decision Constraints Regulatory and political (incl. public perception – e.g. fire) Technical Financial Resources available Opportunity cost Cost of not taking action Benefit:cost relative to other projects to which resources could be allocated

Conclusions: 

Conclusions Need to indicate uncertainty associated with probabilities We know more, and less, than we think we know Recovery potential is stochastic – be ready to act

Conclusions: 

Conclusions Need to indicate uncertainty associated with probabilities We know more, and less, than we think we know Recovery potential is stochastic – be ready to act S&T applications will vary among land managers and those who provide incentives for management

Conclusions: 

Conclusions Need to indicate uncertainty associated with probabilities We know more, and less, than we think we know Recovery potential is stochastic – be ready to act S&T applications will vary among land managers and those who provide incentives for management Acknowledgements: - Jornada team - IIRH team

Extra Slides: 

Extra Slides

Transitions: 

Transitions Community: any not involving a threshold State: “threshold” Ecological site: Factors Long-term change in weather resulting in a climate that better matches another sub-MLRA Soil loss, deposition, inversion or mixing resulting a soil profile that better matches another ecological site Combination of soil and climate change resulting in a significantly different potential Where site transitions are identified, need to clearly reference original site in all interpretations

Slide35: 

Red Lake vs. Scrape site photos