Thesis
Thinning effects under an upper diameter restriction on size class diversity and future demography of dry-pine and mixed-conifer forests in the Silver Lake Ranger District, Fremont-Winema NF
Washington State University
Master of Science (MS), Washington State University
05/2020
DOI:
https://doi.org/10.7273/000004043
Handle:
https://hdl.handle.net/2376/124958
Abstract
Silvicultural prescriptions to mechanically treat fire-prone forests and restore historical conditions have been a central management focus throughout the dry forest types of western North America. To guide forest restoration, federal policies have placed restrictions on harvesting trees of a given diameter, called upper-diameter caps, to preserve remaining large trees. Strict regulations constrict decisions that managers can make when implementing treatments and may have unintended implications towards restoring historic diameter distributions and age proportions. Diameter data from a number of treated and untreated stands in the Silver Lake Ranger district of the Fremont National Forest across both the more xeric dry pine type and a more mesic mixed conifer type were compared to each other and to reference old-growth stands. It was found that thinning with a diameter cap in place reduced values from several measures of diameter distribution diversity. This effect was persistent after fifty years of modeled stand development. The dry pine type experienced great simplification of diameter distributions through restoration than did the mixed conifer type. Tree core data revealed that 25% of ponderosa pine trees in the dry pine forest type met age criteria of old-growth yet not protected by the upper diameter cap. Thinning with a diameter cap may reduce risk of stand-replacing fire and help restore large tree populations but may not recreate diameter distributions and tree age proportions reflective of historic old-growth forests.
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Details
- Title
- Thinning effects under an upper diameter restriction on size class diversity and future demography of dry-pine and mixed-conifer forests in the Silver Lake Ranger District, Fremont-Winema NF
- Creators
- SEAN M ALEXANDER - Washington State University, UNKNOWN
- Contributors
- Mark Swanson (Advisor) - Washington State University, School of the Environment (CAHNRS)
- Awarding Institution
- Washington State University
- Academic Unit
- School of the Environment (CAS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900890793601842
- Language
- English
- Resource Type
- Thesis