Abstract
We sought to answer the question: How do we restore characteristics of old-growth evergreen mixed-conifer forests in young even-aged stands on upland terrain at Headwaters Forest Reserve (HFR)? We described the old-growth reference condition for three stands at HFR. In each old-growth stand, trees within a 1-ha plot were inventoried. We found coast Douglas-fir (Pseudotsuga menziesii var. menziesii) and tanoak (Notholithocarpus densiflorus) well represented while coast redwood (Sequoia sempervirens) dominated in terms of size. Numbers of understory and overstory trees ha−1 and average tree sizes were similar among sites, suggesting these were useful goals for restoration. Adjacent to each old-growth stand, we measured recent growth rates of second-growth trees and remnant old trees across a range of tree sizes, stand structures, and densities. The resultant growth models of redwood and Douglas-fir enabled us to project the development of precommercially thinned young stands at HFR forward in time under two silvicultural prescriptions: (i) no further management; and (ii) partial harvesting simulated before trees attained 30 cm dbh. The partial-harvesting prescription reduced stand density and set the young stand on a more rapid trajectory towards the reference condition found at HFR.
Highlights
Restoration ecologists frequently use the concept of reference conditions to describe a desired ecosystem state when establishing restoration goals or evaluating restored sites [1]
We described old-growth reference conditions and measured tree growth at Headwaters Forest Reserve (HFR) (40°38′12.59′′N, 124°04′39.37′′W), a 3025-ha property located 9.7 km southeast of Eureka, California (Figure 1)
Our dbh increment data and model simulations indicated that Douglas-fir was more sensitive to competition than redwood
Summary
Restoration ecologists frequently use the concept of reference conditions to describe a desired ecosystem state when establishing restoration goals or evaluating restored sites [1]. When few contemporary examples of the reference condition exist, these remnants may be rare or unusual forests with composition and structure that is not typical of the forest type across its entire geographic range. Such is the case for coast redwood forests, where researchers have focused on the iconic pure coast redwood stands growing on alluvial flats [4,5]. Most coast redwood forests in northern California are located on sloping, upland terrain, where an evergreen mixed-conifer composition prevails [6] Most of these “upland redwood” forests have been harvested, leaving the remaining old-growth in patches dispersed throughout the landscape [7]
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