Manipulation of density of Pseudotsuga menziesii canopies: preliminary effects on understory vegetation

  • Published source details Thysell D.R. & Carey A.B. (2001) Manipulation of density of Pseudotsuga menziesii canopies: preliminary effects on understory vegetation. Canadian Journal of Forest Research, 31, 1513-1525.


This study is summarised as evidence for the following.

Action Category

Thin trees within forests: effects on understory plants

Action Link
Forest Conservation
  1. Thin trees within forests: effects on understory plants

    A replicated, randomized, controlled study in 1993-1996 in temperate coniferous forest in Washington State, USA (Thysell & Carey 2001) found that variable density thinning increased plant species richness and diversity and the proportion of exotic plant species. Total species richness (thinned: 24-27; unthinned: 16-17 species/100 m2 plot), native species richness (thinned: 21-22; unthinned: 15-17), Shannon's index of diversity (thinned: 2.5-2.7; unthinned: 1.9-2.0) and the percent of exotic species (thinned: 12%-17%; unthinned: 2%) were higher in thinned plots. Two thinned (variable density thinning to a 2:1 ratio of >4.75 and <4.75 residual trees/ha respectively) and two unthinned treatment units (13 ha) were established in 1993 in each of four sites. Data were collected in 1994 and 1996 in 15 plots (25 m2) in each treatment unit.


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