Graduation Date

Summer 2021

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Forestry, Watershed, & Wildland Sciences

Committee Chair Name

Lucy Kerhoulas

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Rosemary Sherriff

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Phil van Mantgem

Third Committee Member Affiliation

Community Member or Outside Professional

Subject Categories

Forestry

Abstract

California is experiencing increasingly severe and prolonged droughts, which are contributing to changes in tree stress and forest mortality. Many factors affect a tree’s drought response, including competition, climate, and site and tree characteristics. Northern California provides a suitable venue to explore the effects of these factors, as it spans a variety of site conditions and includes habitat for conifers with different adaptations and requirements. This study used annual 13C discrimination and growth metrics to assess differences in drought resistance and resilience in conifers adapted to coastal and montane ranges at both wet and dry sites, as well as differences in environmental factors that affect species-level drought responses. Coastal species (Sitka spruce and western hemlock) were more sensitive to drought than montane species (Shasta fir, Brewer spruce, sugar pine, and western white pine). Coastal trees were more sensitive to drought at dry sites than wet sites. Montane species exhibited smaller differences in drought resistance between wet and dry conditions, but varied in factors contributing to physiological response among species. This study suggests that in most situations, conifers in northern California weathered the 2012 – 2016 drought with reasonably high resistance and resilience. However, many of these trees may be at risk for increased stress and mortality in the event of longer and/or more frequent, severe drought. Management strategies for conifers in one region may not be suitable for the same species in another region, and the effects of competition and community composition on drought resistance and resilience must be carefully considered.

Citation Style

APA

Share

Thesis/Project Location

 
COinS