Title: Do remnant old-growth trees accelerate rates of succession in mature Douglas-fir forests?
Author: Keeton, William S.; Franklin, Jerry F.;
Source: Ecological Monographs. 75(1): 103-118
Publication Series: Miscellaneous Publication
Description: Biological legacies left by natural disturbances provide ecological functions throughout forest stand development, but their influences on processes of ecological succession are not completely understood. We investigated the successional role of one type of biological legacy: remnant old-growth trees persisting in mature Pseudotsuga menziesii (Douglas-fir) forests in the U.S. Pacific Northwest. We tested the hypothesis that remnant old-growth Tsuga heterophylla (western hemlock) and Thuja plicata (western red cedar) trees enhance the reestablishment of shade-tolerant conifers by increasing the availability of seed. Reestablishment of shade-tolerant conifers is a key process in late-successional forest development because it leads to vertical differentiation of the canopy and eventual codominance of shade-tolerant species. Two study areas were selected in the southern Washington Cascade Range, USA. Both had an unfragmented, mature forest cover that was regenerated naturally following wildfire. Twelve study sites were selected, including sites with and without remnant T. plicata and T. heterophylla. Overstory structure and composition, microsite variables, and conifer regeneration were systematically sampled using nested belt transects and quadrats. Sites with remnant T. heterophylla and T. plicata had significantly higher densities of conspecific seedlings. Multivariate analyses showed remnant T. heterophylla and T. plicata presence and density to be the strongest predictors of seedling densities, although the basal area of mature conspecific trees, relative density, aspect, stand age, and microsite characteristics were important secondary predictors. Microsite variations explained regeneration patchiness. Seedling densities were strongly correlated with proximity to remnant trees, exhibiting a negative exponential decline with distance. Shade-tolerant conifers are likely to reestablish faster at sites with remnant seed trees, but canopy disturbances are probably necessary for subsequent height growth. Remnant shade-tolerant conifers are an important biological legacy and seed source influencing rates of ecological succession in mature P. menziesii stands. Successional and stand development models should explicitly incorporate this dynamic.
Keywords: biological legacies, ecological succession, old-growth, forest trees, Pacific Northwest forests (USA), Pseudotsuga menziesii, regeneration, remanant trees, residual trees, seed source, stand development, Thuja plicata, Tsuga heterophylla
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
- You may send email to firstname.lastname@example.org to request a hard copy of this publication. (Please specify exactly
which publication you are requesting and your mailing address.)
XML: View XML
Keeton, William S.; Franklin, Jerry F. 2005. Do remnant old-growth trees accelerate rates of succession in mature Douglas-fir forests?. Ecological Monographs. 75(1): 103-118
Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility