Home » People » Alex Foster

Alex Foster

Headshot photo of Alex Foster.

Pacific Northwest Research Station
Olympia Forestry Sciences Lab

Contact via email
Phone: (360)753-7680
Fax: (360)753-7737

Statement of Research:

As a forester turned ecologist, I have always been fascinated with the unique biodiversity found at the interface between aquatic and upland areas, and the role that disturbance plays with the interaction of physical and biological processes there.

Projects & Activities:

A small stream cascades over a large log in a step-pool configuration common to headwater streams.

Photo by Alex Foster

Small, Forested Wetlands
Starting in 2004, we examined wetland features along
headwater streams as part of a larger study focused on
the effects of forest management in headwater riparian
areas. We were interested in the frequency, surface area
and other attributes associated with the many small cryptic,
wetlands observed along the headwater streams of the
forestry study. Read more

Cispus River Elk Study

Study Location:
Gifford Pinchot National Forest, Cowlitz Valley Ranger District, Lewis County, Washington.

Project Lead Investigators:
Thomas D. Stokely, Extension Forester, Central Oregon, Oregon State University; Alex D. Foster, Ecologist, US Forest Service, PNW Research Station

Collaborators: Gifford Pinchot National Forest; Washington Department of Fish and Wildlife; Mary Rowland, USFS PNW Research Station; with added financial support from the Rocky Mountain Elk Foundation

Since adoption of the Northwest Forest Plan, forest management on US federal lands in western Oregon and Washington generally forgo regeneration harvest in favor of variable-density thinning (VDT) as a way of increasing forest diversity, moving forest stands toward old-growth characteristics while simultaneously providing timber outputs. VDT sometimes involves the creation of canopy gaps of various sizes as a way of increasing forest diversity. It is likely that gap size and landscape configuration of harvest units may affect the foraging behavior of Roosevelt elk (Cervus canadensis roosevelti), an iconic species in the Pacific Northwest. Unfortunately, the relative effects of elk foraging behavior, or ungulate herbivory in general, are not well understood in a VDT context.

Three-pane photo panel of elk habitat restoration

Elk habitat restoration on the Gifford Pinchot National Forest, southwest Washington state. A. variable-density (variable-retention) thinning treatment; B. 0% retention (gap); C. 100% retention, unthinned stand. Photos: Thomas Stokely.

Bull elk photographed by camera trap

Bull elk captured by a camera trap at the unharvested plot in a thinning unit. Photo: USFS.

A study was initiated in 2018 on the Gifford Pinchot National Forest in Washington state that addresses several questions about elk herbivory in commercial VDT thinning areas. Using a combination of camera traps, forage vegetation surveys, and small fenced exclosures, we will attempt to determine how elk utilize gaps of various sizes (2–10 acres) compared to thinned and unharvested areas in relation to forage availability. We will also assess how gap size, configuration, and forage planting factor into forage utilization and how local forage utilization by elk relates to nutrition and habitat use at larger spatial scales (e.g., Rowland et al. 2018). This study will inform public and private land managers about VDT in relation to elk foraging behavior.

Landslides and Debris Flows

Study Location:
Capitol State Forest, Washington Department of Natural Resources, western Washington

Project Lead Investigators:
Alex D. Foster, Shannon M. Claeson, and Peter A. Bisson (emeritus), US Forest Service, PNW Research Station; John Heimburg, Washington Department of Fish and Wildlife, Olympia, Washington

Landslides and debris flows are common disturbance mechanisms in steep, headwater streams in the Pacific Northwest. A debris flow starts as a landslide along a stream, forming a fast-flowing slurry of water, sediment, and boulders, combined with uprooted trees from the riparian area and down wood that has accumulated in the stream channel over time. Debris flows often take out bridges, culverts, and other infrastructure along their path. The scouring action of the debris flow and the debris deposits it leaves behind reconfigure the stream channel and, in the process, usually decimates biota within the stream and adjacent riparian area. Two side-by-side debris flows occurred in an area where we had pre-disturbance biological data, providing us with a rare opportunity to study ecosystem recovery. Over 5 years of monitoring, a story of rapid transformation unfolded. While the streams adjusted to their new channels, salmonids were quick to recolonize, as were their food sources such as aquatic insects, yet some animals including crayfish and tailed frogs were slower to recolonize. One of our key findings was that if source populations are present, stream food webs can recover quite rapidly after severe disturbances like this.


Debris flows are common disturbances in montane streams of the Pacific Northwest. They both scour channels and move and deposit large volumes of sediments, boulders, and wood that eventually create new habitats for aquatic species. Photo: Shannon Claeson, USFS.

Selected Publications:

Note: Most PDF files linked in the publications section of this page were not created by the USDA Forest Service, and may not be accessible to screen-reader software. Many publications are open access, and links to the html versions on the journal websites are also provided, where applicable.

Foster, A.D., A.A. Basile. 2022 (in press). Ecoregion 6.2.14 Southern Rockies: Fraser Experimental Forest, Colorado. In: Ryan, D.F., ed. Biological Responses to Stream Nutrients: A Synthesis of Science from Experimental Forests and Ranges. Gen. Tech. Rep. PNW-GTR-981 Portland, OR. U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station.

Devine, W.D., E.A. Steel, A.D. Foster, T.V. Minkova, K.D. Martens. 2021. Watershed characteristics influence winter stream temperature in a forested landscape. https://www.fs.fed.us/pnw/pubs/journals/pnw_2021_devine001.pdf

Foster, A.D., S.M. Claeson, P.A. Bisson, J. Heimburg. 2020. Aquatic and riparian ecosystem recovery from debris flows in two western Washington streams. Ecology and Evolution 10: 2749-2777. DOI: 10.1002/ece3.5919.

Rowland, M.M., M.J. Wisdom, R.M. Nielson, J.G. Cook, R.C. Cook, B.K. Johnson, P.K. Coe, J.M. Hafer, B.J. Naylor, D.J. Vales, R.G. Anthony, E.K. Cole, C.D. Danilson, R.W. Davis, F. Geyer, S. Harris, L.L. Irwin, R. McCoy, M.D. Pope, K. Sager-Fradkin, M. Vavra. 2018. Modeling elk nutrition and habitat use in Western Oregon and Washington. Wildlife Monographs. 199(1): 1-102.

Foster, A.D., D.H. Olson, L.L.C. Jones. 2014. A review of the biology and conservation of the Cope's Giant Salamander, Dicamptodon copei Nussbaum, 1970 (Amphibia: Caudata: Dicamptodontidae) in the Pacific Northwestern region of the USA. Life: the Excitement of Biology 2(4): 210-246. DOI: 10.9784/LEB2(4)Foster.01

Bisson, P.A., S.M. Claeson, S.M. Wondzell, A.D. Foster, A. Steel. 2013. Evaluating headwater stream buffers: lessons learned from watershed-scale experiments in southwest Washington. In Anderson, P. D. and K. L. Ronnenberg (eds). Density management for the 21st Century: west side story. Gen. Tech. Rep. PNW-GTR-880. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station: 169-188 Link to the full GTR at http://www.fs.fed.us/pnw/pubs/pnw_gtr880.pdf or at http://www.treesearch.fs.fed.us/pubs/44785

Foster, A.D., J. Ziegltrum. 2013. Riparian-associated gastropods in western Washington: community composition and the effects of forest management. Northwest Science 87(3): 243-256.

Foster, A.D., S.M. Claeson. 2011. Habitats and seasonality of riparian-associated millipedes in southwest Washington, USA. Terrestrial Arthropod Reviews 4: 203-220.

Janisch, J.E., A.D. Foster, W.J. Ehinger. 2011. Characteristics of small headwater wetlands in second-growth forests of Washington, USA. Forest Ecology and Management 261(7) 1265-1274.