The site was clearcut logged in late May/early June 1991. Slash was broadcast burned on 11 September 1991 with a moderate- to high-intensity fire. The full experiment consists of a randomized complete-block design with a control and eight treatments (A through I; see below) in which one or more species is removed from the post-disturbance community (see details in Halpern et al. 1997). Treatments were assigned randomly to nine 2.5 x 2.5 m experimental units (treatment areas) in each of 25 blocks (~11 m on a side). Within a block, treatment areas are arranged in a 3 x 3 array with ~1-m spacing (see Related Materials: Plot Layout). Species’ removal treatments were initiated in June 1992, synchronous with the first post-disturbance measurement of vegetation. For the first 7 years, removals were conducted monthly (April to June). Seedlings were pulled by hand and vegetative shoots were clipped at the ground surface (see Entity 2 for counts of seedlings and shoots removed). Subsequently, removals have been conducted at the time of vegetation measurement, but the stems removed are no longer counted. Sampling of six treatments was discontinued between 1996 and 1998 when removal or target species became uncommon. The remaining three treatments (A = control; H = Rubus ursinus removed; and I = Berberis nervosa and Gaultheria shallon removed) were maintained through 2018. Following a controlled burn of the site in September 2018 -- to limit spread of the larger Terwilliger Fire -- species' removals were terminated in treatments H and I. However, cover measurements have continued in treatments A, H, and I (see details in Halpern and Antos 2022).
Treatment codes (A-I), removal species, and response variables for the nine treatments include:
Halpern, Charles B., Miller, Eric A., Geyer, Melora A. 1996, Equations for predicting above-ground biomass of plant species in early successional forests of the western Cascade Range, Oregon (Pub. No: 2262)
Halpern, Charles B., Antos, Joseph A., Geyer, Melora A., Olson, Annette M. 1997, Species replacement during early secondary succession: the abrupt decline of a winter annual (Pub. No: 1890)