C. Mayrsohn P. S. Doescher Elizabeth St. Pierre J. C. Tappeiner J. D. Bailey 1998 <p>We studied understory composition in thinned and unthinned Douglas-fir (<i>Pseudotsuga menziesii</i> (Mirb.) Franco)/western hemlock (<i>Tsuga heterophylla</i> (Raf.) Sarg.) stands on 28 sites in western Oregon. These stands had regenerated naturally after timber harvest, 40–70 years before thinning. Commercial thinning had occurred 10–24 years previously, with 8–60% of the volume removed from below with the intent to homogenize spacing among trees. Undisturbed old-growth Douglas-fir stands were present for comparison on 18 of these sites. Total herbaceous cover was greater in thinned (25% cover) stands than in unthinned (13% cover) or old-growth (15% cover) stands. Species richness was also greater in thinned (137) than in unthinned (114) and old-growth (91) stands (<i>P</i>=0.05). Part of the increased richness was caused by the presence of exotic species in thinned stands, but there were also more native grass and nitrogen-fixing species in thinned stands than in unthinned or old-growth stands. Groups of species differed among stand-types. For example, the frequency of tall cordate-leaved species was greater in old-growth stands (<i>P</i>=0.009), but their relative cover was different only between old-growth and unthinned stands (<i>P</i>=0.08). Both the cover and frequency of grasses and sedges in thinned stands were greater than in unthinned or old-growth stands (<i>P</i>≤0.002). Ordination of shrub cover showed differences among old-growth and unthinned stands compared to thinned stands, mainly because of the amount of <i>Gaultheria shallon</i> Pursh and <i>Polystichum munitum</i> (Kaulf.) Presl in heavily thinned stands. Ordination of herbaceous community data showed that there were much stronger differences among sites than among stand-types. The lack of difference among stand-types demonstrates the resiliency of herbaceous communities to disturbance associated with past and current forest management.</p> application/pdf 10.1016/S0378-1127(98)00408-3 en Elsevier Understory vegetation in old and young Douglas-fir forests of western Oregon article