Using historical reconstructions of moist mixed conifer forests to inform forest management on the Malheur National Forest.

Abstract

National Forest works collaboratively with diverse stakeholders to accelerate the pace and scale of forest restoration. Both informal joint fact-finding, empirical research, and multi-party monitoring are used to inform planning and adjust implementation of restoration treatments in an adaptive management framework. Knowledge of historical dynamics is often used to guide restoration on the Malheur because scientists, managers, and stakeholders believe restoring forest structure and composition to the historical range of variability will make forests more resilient to future climate and disturbance regimes. There is a strong shared understanding of the role of frequent, low-intensity fire in fostering resilience of dry, ponderosa pine dominated forests. However, there has been little empirical research describing historical disturbance dynamics in moister landscape settings. USDA Forest Service silviculturists and researchers from Oregon State University investigated historical fire patterns, forest structure, and composition in moist mixed conifer stands on the Malheur National Forest. The findings of this partnership demonstrate that moist mixed conifer forests historically experienced similar fire return intervals, had similar basal area, and in most cases are more departed from historical conditions than dry ponderosa pine forests. Tools were also developed to aid in selection of large-diameter, fire-intolerant species for removal. This research and ongoing fact-finding and dialogue with stakeholders have been used to adapt silvicultural prescriptions over time. A multi-party monitoring program is being implemented to answer stakeholder questions about the effects of restoration treatments, while generating baseline data to answer questions about intermediate and long-term environmental effects.

Exceptional variability in historical fire regimes across a western Cascades landscape, Oregon, USA

“…And there is no evidence from our field observations or other research in these forest types to suggest that old‐growth structure is at heightened risk from uncharacteristic disturbance as a result of fire exclusion policies (Franklin & Johnson, 2012). There is little reason to believe that silvicultural interventions that have been successful in relinking critical pattern‐process feedbacks in dry forests (see Lindsay & Johnston, 2020; Prichard et al, 2021; Tepley et al, 2020; Vernon et al, 2023) would achieve forest resilience objectives in older western hemlock or silver fir series forests on the west slope of the Cascades (Halofsky et al, 2018). Although we do not recommend thinning or other types of restoration forestry in western hemlock or silver fir series forests, additional research is warranted to investigate the degree to which changes to fire management policies are appropriate to facilitate future fire in these forest types.…”

Diameter limits impede restoration of historical conditions in dry mixed‐conifer forests of eastern Oregon, USA

“…Although restoration targets are informed by historical reconstructions (Lindsay and Johnston 2020), post‐treatment stand basal area targets within the study are also designed to reduce mortality related to intra‐tree competition for resources, which often involves thinning stands to lower basal areas than our basal area targets for simulated thinning (e.g., USDA 2018). The relatively broad range of post‐treatment basal area targets adopted for this study (11 m 2 /ha to 16 m 2 /ha) are designed to account for the full range of historical conditions we reconstructed and to ensure that we do not overstate the degree to which strict diameter caps on thinning limit the ability of managers to meet restoration objectives.…”

“…Research was conducted within mixed‐conifer forests stands across the Ochoco and Malheur National Forests of eastern Oregon, the ancestral homeland of the Northern Paiute, Cayuse, and Umatilla people. We limited our historical reconstructions and simulation analysis to mixed‐conifer stands because of the strong interest on the part of USFS managers and collaborative partners in developing silvicultural strategies for this forest type (Lindsay and Johnston 2020). Mixed‐conifer forests in this study area contain both shade‐intolerant western larch ( Larix occidentalis ) and ponderosa pine ( Pinus ponderosa ) and relatively shade‐tolerant Douglas‐fir ( Pseudotsuga menziesii ) and grand fir ( Abies grandis ; Simpson 2007).…”