Management Implications

Our analyses revealed that watersheds vary in spatial patterns of habitat abundance and risk, resulting in different implications for conservation and restoration of habitats. These differences in spatial patterns suggest that regional strategies could be developed for watersheds in each condition class to identify appropriate conservation and restoration prescriptions needed to meet management goals for each group of species. Targeting areas for management attention through this process complements other strategies to identify threats, such as the conservation by design approach used by The Nature Conservancy (Nachlinger and others 2001).

Results of our regional assessment serve as a working example for analysis of species of concern, but also provide a sound basis for comprehensive land use planning in the ecoregion. Cheatgrass invasion and woodland encroachment are two of the highest priority issues for both research and management of native shrublands in the Great Basin. Because of the potential mismatch of administrative scales at which management occurs and the ecological scales at which these threats operate, regional assessment can provide key context for local management solutions. Integrated management of both threats is needed to conserve sagebrush habitats affected by both cheatgrass and pinyon-juniper expansion. For example, prescribed burning of some sagebrush habitats may curtail woodland encroachment but also may enhance expansion of cheatgrass on susceptible sites. Alternatively, combinations of mechanical treatments to reduce pinyon-juniper density, followed by chemical treatments to reduce cheatgrass abundance, may effectively reduce the combined risks posed by cheatgrass and woodlands.

With any regional assessment encompassing a diverse set of species and habitats, uncertainty exists at several levels about the assumptions inherent in the analyses. For the Great Basin assessment, example areas of uncertainty include:

• The cover types associated with each species as habitat are assumed to contribute to population persistence, but additional factors beyond habitat abundance and configuration may influence populations. We have limited knowledge of how species respond to landscape-scale changes in native habitats, as brought about by displacement from cheatgrass and pinyon-juniper woodlands. Further studies of this topic are a high priority for research and management.
• Our predictions of risk of displacement of native shrublands, while based on a prior knowledge of environmental conditions affecting distribution of cheatgrass and pinyon-juniper, require extensive field evaluation before results are widely applied in management. Such validation is currently underway (Rowland and others 2006) and will reduce the uncertainty associated with model predictions.
• The combined effects of multiple threats, especially the potential synergy among threats, are not well understood. New research is needed to improve knowledge about cumulative effects on shrubland habitats and species.

Restoration in sagebrush and other arid shrubland communities will require substantial inputs of resources due to the lack of resiliency in these systems and the recent undesirable trends in vegetation dynamics and fire regimes affecting these communities (Hemstrom and others 2002). Concomitant with restoration, prevention and mitigation of threats that go beyond cheatgrass and woodland expansion, such as infrastructure associated with anthropogenic activities, (e.g., powerlines, roads, energy development), are critical for maintaining functioning habitats for shrubland-associated species of concern in the Great Basin and surrounding areas.