Experimental Forest

Experimental Forests are Forest Service properties dedicated to scientific research. Cascade Head Experimental Forest (CHEF) was established in 1934 as a study site for Sitka spruce-western hemlock forests, commonly found along the coasts of Oregon, Washington, and Southeast Alaska. The forests here are typical of the coastal temperate rain forest bioregion: they receive abundant rainfall, experience moderate annual temperatures, and have very fertile soils resulting in highly productive forests.

In 1934 CHEF was primarily covered with a forest that came in after the huge Nestucca Fire of the late 1840s. Stands of spruce and hemlock that survived the fire are found closer to the coast. The Nechesney Indians burned some of the forest close to the ocean in the early 1900s. Some of the more gentle country to the east, homesteaded by European settlers and abandoned in the early 1920s, now supports even-aged, single canopy forests with dense shrub understories. Some of the highest growth rates and greatest volumes per hectare reported for any temperate forest in the world are reported for this area. Experimental clearcutting, shelterwood cutting, thinning, and salvage from large windstorms have impacted about 25% of the forested area.

Early foresters recognized the importance of setting up plots in “natural” stands to learn how forests change and grow over time. The Douglas-fir plot, a Reflections site, is one of 12 one-acre plots established in Cascade Head Experimental Forest (CHEF) during the early 1930s. One of the beauties of a plot in an experimental forest is that it provides a permanently protected site for forest ecologists to do research.

Whereas today all data gathering and analysis are computerized, data were originally gathered in notebooks and then copied at night in indelible ink onto data sheets; all data statistics were, of course, hand calculated. Generally the plots were re-measured every five years, providing a now continuous stream of data that is over 75 years in length, longer than the professional life of almost any forest scientist.

The weather station, hidden in the depths of the Douglas-fir plot, records temperature, relative humidity, rainfall, and available light on the forest floor. Using ropes dangling from trees, researchers climb to the forest canopy, gathering data on nitrogen content of needles, needle elongation, time of bud formation, and seasonal growth rates. Placing weather sensors in the canopy and on the forest floor, scientists have discovered that the forest canopy is a much drier and colder place to live than the forest floor.

In a much broader context, the Douglas-fir plots at CHEF are a subset of a group of similar plots spread throughout the Pacific Northwest. Viewed as a group, these plots give a more regional picture of how Douglas-fir forests develop, as well as how and why trees die and the consequent role of dead wood in nutrient cycling and building of soils.

Wind is a constant agent of change and destruction all along the Oregon coast. Hurricane force winds can be an annual occurrence. The shallow-rooted Sitka spruce are easily blown over by these gale force winds, especially when soils are water saturated. In the past, the Forest Service almost always salvaged all wind-blown trees. Research since the late 1980s has demonstrated the important role that down wood plays on the forest floor: providing cover and habitat for small animals, creating protection for young seedlings, and adding to soil fertility. Salvage logging is consequently not nearly as prevalent as it once was.

The Experimental Forest Reflections sites include the Douglas-Fir Plot and the Sitka Spruce Stand.