Assessment of natural resource and watershed condition: Oregon Caves National Monument and Preserve

Halofsky, Jessica; Peterson, David; Morgan, Harriet; Krosby, Meade; Roth, John

This report describes a natural resource condition assessment for Oregon Caves National Monument and Preserve (OCNMP). The overall objective of this assessment is to evaluate and articulate the present ecosystem conditions in OCNMP based on a review of available information. Information and data gaps were also identified to help guide future research, monitoring, and management actions. Resources covered in the assessment include vegetation, aquatic ecosystems, terrestrial wildlife, ecological processes, and chemical and physical characteristics. Specific indicators were used to evaluate condition for each resource or category of condition. For each indicator, condition status, trend in condition, and confidence in the assessment were evaluated. To assess indicator condition status and trend, all available information (e.g., data, publications, and reports) generated by park staff, and by other research and monitoring efforts in OCNMP were reviewed. When available, greater weight was given to published and peer-reviewed information. Information from outside of OCNMP was considered if it was deemed relevant. Assessment of natural resource condition in OCNMP suggests that many indicators are within the historical range of variability (HRV) or defined criteria (e.g., subalpine vegetation, streamflow, aquatic macroinvertebrate communities, water quality, air quality, and soil resources) (Table ES-1) where HRV cannot be quantified. Other indicators were determined to be outside of HRV or defined criteria (e.g., lower and mid-montane forest structure, stream morphology and sediment input, riparian vegetation structure and composition, and infrequent mega-storms or landscape-scale debris flows). The condition of some resources could not be evaluated because of a lack of data (e.g., amphibians). Resources determined to be in degraded condition were primarily affected by historical land-use activities in the Preserve portion of OCNMP, specifically timber harvest, roads, and recreation (in the Bigelow Lakes area). However, extensive timber harvest has not occurred on the now-established Preserve since the 1990s, and recent inventory suggests that succession is proceeding in the previously harvested forests. Fire exclusion has also likely affected forest structure and composition across OCNMP, and there is evidence that a warming climate may have affected forest understory species composition. Thinning and fuel treatments in previously harvested forests of the Preserve may have multiple benefits, including increasing species and structural diversity, and lowering forest density and fuel levels, and thus susceptibility to fire and drought. Continued monitoring of conditions at OCNMP will be important to evaluate effects of changing conditions from climate change and other stressors on natural resources. The Preserve, in particular, is lacking in data useful for evaluating biophysical conditions, particularly for animal populations. Both restoration treatments and monitoring will need to be carefully planned to optimize allocation of available funding, perhaps in collaboration with adjacent landowners and other stakeholders.

Assessment of natural resource and watershed condition: Oregon Caves National Monument and Preserve

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