Science: Ecology

Department: Environmental Sciences

Supervising Faculty Member: Howard Epstein

Specialization: Ecology

Research Focus: This research is part of a broader project to evaluate the potential for broad-scale conversion from conifer forest to shrub-dominated ecosystems in the context of a warming climate and increasing fire activity in the Klamath Mountains of southwestern Oregon and northern California. When conifer forests are burned severely, the vegetation that develops after fire is dense and dominated by shrubs and resprouting broadleaved tree species. Over time, conifer seedlings eventually establish and grow taller than this vegetation to form a new forest canopy. Until then, however, the vegetation is prone to repeated fire that could reset the development sequence. If climatic warming leads to an increase in fire frequency or a decrease in the rate of post-fire conifer forest recovery, there is growing concern that many of the shrub-dominated systems could be perpetuated almost indefinitely through a cycle of repeated burning. Our broader project involves field and modeling studies to evaluate the potential for these changes and explores options for forest managers under alternative future scenarios.

In the 2015 field season, we sampled 57 plots in recently burned forests to characterize vegetation composition, structure, and post-fire successional trajectories. One component of our sampling was to harvest conifer seedlings so we could reconstruct their height-growth using a method called stem analysis. In this method, we cut the tree and collect cross-sections at regular intervals along the stem, and then we count the tree rings in each section to determine how long it took the tree to reach each height interval. For example, if we count 15 rings at ground level and 10 rings at 50 cm, we know that the tree was 5 years old when it reached 50 cm tall. We are evaluating how long it takes conifers to grow taller than the dense, shrubby vegetation, and then determining if they experience a subsequent growth release.

Position Description: The main task of the USOAR student would be to assist with measuring the growth rings in the stem analysis samples, where the measurements would allow us to quantify the growth in tree volume per year and the volume increment at different heights along the stem. These measurements will help us to evaluate tradeoffs in allocation to diameter growth vs. height growth. A large portion of the work will be conducted using a stereo microscope connected to a computer that records measurements of the width of each tree ring. The student will learn much about tree growth and wood anatomy. The student will also gain experience with dendro-ecological techniques that are useful in addressing a variety of research questions in forest ecology, from stand development patterns to disturbance history and climate reconstruction. There may also be opportunity for the student to contribute to GIS and remote sensing analyses that evaluate post-fire regeneration patterns in the Klamath Mountains.

Required Skills/Knowledge: The primary skill needed for this position is close attention to detail. The student will be trained to provide the skills needed to conduct the work, and then the student will be able to work independently after the initial training.

Computer software: The student should have basic knowledge and experience with data entry in Excel or other spreadsheets. Additional software experience is not necessary, but it would be useful for the student to have experience in developing graphs in software such as R. W

Training: No formal training or certification is required.

What You Will Learn: The primary learning outcomes from this project are (1) background in forest ecology and post-fire successional dynamics, (2) methods and applications for tree-ring based approaches to forest ecology research, and (3) data organization and processing methods that will be needed when the student eventually leads his or her own research.

Web site link to research: https://www.sites.google.com/a/pdx.edu/klamath-climate-and-fire/