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International Journal of Forestry Research
Volume 2009, Article ID 581412, 8 pages
Research Article

Influence of Gap Size and Position within Gaps on Light Levels

Département des Sciences Biologiques, Centre D'étude de la Forêt, Université du Québec à Montréal, Succursale Centre-Ville, Case Postale 8888, Montréal, QC, Canada H3C 3P8

Received 25 May 2009; Accepted 28 July 2009

Academic Editor: Andrew Gray

Copyright © 2009 Benoit Gendreau-Berthiaume and Daniel Kneeshaw. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The previous studies have reported maximum light levels at different positions within gaps but many of these studies are based on gaps of different size. The objective of this study is to evaluate the influence of gap size and position within gap on light distribution in gaps and under the canopy north of gaps in a mixedwood temperate forest. For three gap sizes, with gap widths ranging between 0.5 and 1.5 times the height of the surrounding stand, light was measured at different positions along the north-south axis in each gap using two different techniques (hemispherical photographs and instantaneous measurements). In small gaps, the position with the most light was close to the northern edge although not under the canopy north of the gap. For both methods, the position with the highest light level shifted from the north towards the center of gaps as gap size increased which clarifies some of the variability in light measurements previously observed in gap studies. Higher light levels in the northern part of small and medium gaps compared to the southern portion could allow management of a mixture of species with intolerant species in the northern portions of gaps and tolerant species to the south.