Lindh, Briana Christine. 1994. The response of understory plants to canopy closure in a second-growth forest in the Oregon Cascades. Portland, Oregon: Reed College. 58 p. B.A. thesis.
Management of Pacific Northwest forest lands for timber has increasedthe frequency of disturbance in the landscape and thereby increased thepercent of young forest in the landscape. Young forests typically have lessunderstory plant cover than any other forest successional stage. High coverand diversity of understory plants, however, are desirable for a variety ofmanagement objectives. This thesis examines the changes in understoryplant cover around canopy closure in a second-growth forest. The dataexamined in this thesis are part of a long term study of succession afterclearcut logging in the Oregon Cascades. This study is the first attempt tomonitor long-term successional changes after logging on a single site.Invading and residual herb cover declined by 30 and 60% respectively in theperiod leading up to and just after canopy closure. Invading shrub coverdeclined by almost 80% during the period examined. The only group ofspecies that increased in cover after tree canopy closure were the shade-tolerant woody species that had been present in the watershed before logging.Trends in species abundance are examined in terms of their shade-tolerance.Failure of understory plant regeneration is examined as an alternativehypothesis for plant declines. Hypotheses about the composition of the floraof a managed landscape are examined in light of the results of the presentstudy.