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Research Interests

Current Projects

We use tools from ecophysiology, anatomy, and biomechanics to better understand plant’s function, especially when faced with biotic, abiotic, or multiple stresses.  Current projects include the following:

Role of Provenance and Effects of Xylem Morphology and Shoot Architecture on Drought Resistance and Vitality in Douglas-fir

The PNW Research Station’s Seed Source Movement Trial (Connie Harrington and Brad St. Clair) presents interesting material. This project makes use of their mesic coastal seed source (‘Oregon Coast Range’) and their more xeric Medford-area seed source (‘Oregon Siskiyou’) plants that are then grown essentially in reciprocal transplant gardens.  Using the last two years of a five-year old branch, we’ve been exploring whether the ‘Oregon Coast Range’ sources have more plasticity in their hydraulic strategy, as well as higher rates of water transport and more embolism-vulnerable branch xylem than the ‘Oregon Siskiyou’ sources.  We are using the same material to study morphological legacy--the extent to which one year’s morphology appears associated with the subsequent year’s vitality, and the specific roles of different parts of the growth ring for water transport during drought.  

Needle Insertion and Water Transport Patterns in Douglas-fir

This project is documenting the variability of which growth ring(s) a Douglas-fir needle draws water from depending on its age and other factors.  For example, a 3 year-old needle was originally plumbed to 3 year-old wood, but may now be attached to the original xylem, last year’s, or the current year’s xylem, or a combination.  Related work with dye ascents in Christmas trees over winter showed that peak water transport was not always in the outer growth rings. We are exploring these relationships.

Effect of Early, Late, and Double Drought on Seedling Performance of Different Provenances of Douglas-fir and Loblolly Pine

Do the provenances from dry zones have more adaptive strategies to drought than the more mesic-zone provenances?  In this greenhouse experiment, we are following physiological and anatomical measures as well as height, diameter, and biomass changes and thermal characteristics of plants from three seed sources of each species.  We expect that the provenances from the drier area will either have a more conservative growth strategy in the first place, or will be more reactive to the first drought such that the second drought is less deleterious to growth.

Effects of Fusarium on Drought Performance of Seedlings from Different Provenances of Douglas-fir and Loblolly Pine

When young seedlings are infected with the root pathogen Fusarium commune, their likelihood of dying from drought increases greatly.  This project explores the changes in morphology and physiology of infected vs. control seedlings with and without drought, with the hypothesis that lacking drought, seedling performance will not be affected by Fusarium, but after a drought, infected seedlings will show greater reductions in performance.  Further, the project is exploring the means by which the infection increases drought-susceptibility, and is asking whether the more drought-adapted provenances are less susceptible to performance reduction from Fusarium

Other Projects

Other projects explore how scientists can deduce the function of a structure, the effect of radial growth rate on wood quality in Douglas-fir, how release by thinning affects hydraulic architecture in extremely suppressed hardwoods, and whether the foliage area/xylem cross-sectional area relationship in very young seedlings suggests a change from hydraulic to mechanical limitation.