|DOHERTY, KEVIN - Us Fish And Wildlife Service|
|KERBY, JAY - Nature Conservancy|
|SITZ, ANGELA - Us Fish And Wildlife Service|
|FOSTER, LEE - Oregon Department Of Fish & Wildlife|
|CAHILL, MATT - Nature Conservancy|
|JOHNSON, DUSTIN - Oregon State University|
|SPARKLIN, BILL - Us Fish And Wildlife Service|
Submitted to: The Wildlife Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2021
Publication Date: 8/3/2021
Citation: Doherty, K., Boyd, C.S., Kerby, J., Sitz, A., Foster, L., Cahill, M., Johnson, D., Sparlkin, B.D. 2021. Threat-Based state and transition models predict sage-grouse occurrence while promoting landscape conservation. The Wildlife Society. 45(3):473-487. https://doi.org/10.1002/wsb.1200.
Interpretive Summary: Sage-grouse habitat is being negatively impacted by a variety of ecosystem disturbances including invasion by exotic annual grasses and expansion of native conifer species with altered fire intervals; however, habitat management is often directed by site scale habitat preferences of the bird rather than by addressing underlying ecosystem dysfunction. We investigated the use of ecosystem threat-based state and transition models (TBSTM) to predict presence or absence of sage-grouse in a large sagebrush steppe landscape impacted by both exotic annual grasses and expanding conifer populations. Our results indicate a high correlation between level of ecosystem dysfunction (as defined by states within TBSTM models) and presence of sage-grouse. These results suggest that within our study area, managing ecosystem problems (annual grasses and conifer) can equate to managing for habitat needs of sage-grouse populations, which allows managers and management planners to simultaneously prioritize and address both ecosystem dysfunction and habitat needs of sage-grouse.
Technical Abstract: A recent collaboration between federal, state and private partners in southeast Oregon developed mental models to distill complex plant-based community ecology for management. The mental models were then turned into a simplified, habitat-classification system that addressed landscape-level threats to the sagebrush ecosystem. The simplified, habitat-classification system formed the foundation of Threat-based State and Transition Models (TBSTM). We quantitatively linked greater sage-grouse (Centrocercus urophasianus, hereafter sage-grouse) lek occurrence to a landscape-level habitat classification based upon the TBSTM framework. We investigated whether TBSTM classifications were able to spatially predict locations of sage-grouse breeding areas equivalently to landcover variables that have been studied for over a decade. We showed the TBSTM framework was able to predict the locations of sage-grouse accurately (R2 = 0.70, AUC = 0.91,Correctly Classified = 83%). Model fit statistics were similar to the model built with traditional land cover variables (R2 = 0.65, AUC = 0.89, Correctly Classified = 80%). The high degree of model fit for the TBSTM framework allows conservation practitioners a direct, quantifiable, and biological link to understand outcomes of transitioning habitats from various threat states to sagebrushdominated landscapes with a perennial understory across large landscapes. Sage-grouse are well known to respond to landscape-level amounts of habitat and exhibit low tolerance to threats. We documented similar responses between threats such as the percentage of conifers within 560-m and the conifer threat bin at the same spatial scale. Our work also quantified the importance of having a healthy perennial-grass understory and perennial-grass patches in conjunction with sagebrush cover across large landscapes. Our work suggests that understory grass communities at landscape scales may be limiting grouse occurrence in certain parts of Oregon.