Canopy gaps in Douglas-fir forests of the Cascade Mountains

Types and rates of mortality were measured and canopy gap formation rates were estimated from 5- to 15-year records of mortality in 34 permanent plots in mature (100- to 150-year-old) and old-growth (>200-year-old) Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco)/western hemlock (Tsugacanadensis (Raf.) Sarg.) forests in western Oregon and Washington. Gap surveys were conducted in a mature and an old-growth stand, and characteristics of 40 gaps and regeneration were measured. Most canopy trees died without disrupting the forest in both mature (87.6%) and old-growth stands (73.3%). The amount of forest area per year representing new gaps was 0.7% in mature stands and 0.2% in old-growth stands. The gap survey found a higher proportion of gaps in the mature stand than in the old-growth stand. Most regeneration (> 1 m tall) in gaps was western hemlock; Douglas-fir regeneration did not occur. The ratio of seedling density in gaps to density under canopies was about 3 for the mature stand and about 9 for the ol...

[1]  J. A. Huff.  First Year Ecological Effects of the Hoh Fire, Olympic Mountains, Washington , 1980 .

[2]  J. R. Runkle.  Comparison of methods for determining fraction of land area in treefall gaps , 1985 .

[3]  W. Platt,et al.  Gap Light Regimes Influence Canopy Tree Diversity , 1989 .

[4]  N. Brokaw.  Gap-phase regeneration in a tropical forest. , 1985 .

[5]  C. Uhl,et al.  Vegetation Dynamics in Amazonian Treefall Gaps , 1988 .

[6]  James R. Runkle,et al.  Treefalls Revisited: Gap Dynamics in the Southern Appalachians , 1987 .

[7]  Alan B. Berg,et al.  Snag Characteristics and Dynamics in Douglas-Fir Forests, Western Oregon , 1980 .

[8]  L. C. Kuiper,et al.  The structure of natural Douglas-fir forests in Western Washington and Western Oregon. , 1988 .

[9]  C. Lorimer.  Relative Effects of Small and Large Disturbances on Temperate Hardwood Forest Structure , 1989 .

[10]  C. T. Dyrness,et al.  Natural Vegetation of Oregon and Washington , 1988 .

[11]  T. Spies,et al.  Light regimes beneath closed canopies and tree-fall gaps in temperate and tropical forests , 1990 .

[12]  T. Nakashizuka.  REGENERATION PROCESS OF CLIMAX BEECH (FAGUS CRENATA BLUME) FORESTS : IV. GAP FORMATION , 1984 .

[13]  J. Franklin,et al.  Ecological characteristics of old-growth Douglas-fir forests. , 1981 .

[14]  C. T. Dyrness.  Early Stages of Plant Succession Following Logging and Burning in the Western Cascades of Oregon , 1973 .

[15]  C. C. Grier,et al.  Old‐Growth Pseudotsuga menziesii Communities of a Western Oregon Watershed: Biomass Distribution and Production Budgets , 1977 .

[16]  Lawerence S. Barden.  Repeatability in Forest Gap Research: Studies in the Great Smoky Mountains , 1989 .

[17]  Jerry F. Franklin,et al.  Coarse Woody Debris in Douglas-Fir Forests of Western Oregon and Washington , 1988 .

[18]  K. Lertzman.  Gap-phase community dynamics in a sub-alpine old growth forest , 1989 .

[19]  J. Franklin,et al.  Aspects of Succession in the Coniferous Forests of the Pacific Northwest , 1981 .

[20]  Jerry F. Franklin,et al.  Thirty-six years of tree population change in an old-growth Pseudotsuga–Tsuga forest , 1988 .

[21]  J. Franklin,et al.  Fire and Other Disturbances of the Forests in Mount Rainier National Park , 1982, Quaternary Research.

[22]  J. Connell,et al.  Mechanisms of Succession in Natural Communities and Their Role in Community Stability and Organization , 1977, The American Naturalist.

[23]  G. H. Stewart,et al.  Forest development in canopy openings in old-growth Pseudotsuga forests of the western Cascade Range, Oregon. , 1986 .

[24]  L. A. Isaac.  Reproductive habits of Douglas-Fir. , 1943 .

[25]  C. Halpern.  Twenty-one years of secondary succession in Pseudotsuga forests of the western Cascade Range, Oregon , 1987 .

[26]  Jerry F. Franklin,et al.  Tree Seedlings on Logs in Picea‐Tsuga Forests of Oregon and Washington , 1989 .