Variation in canopy openness and light transmission following selection cutting in northern hardwood stands: an assessment based on hemispherical photographs

Abstract

The objective of this study was to determine how canopy openness (CO) and light transmission are affected by selection cutting, and how they vary over time following harvesting in northern hardwood stands. We sampled five sugar maple-yellow birch-beech (Acer saccharum-Betula alleghaniensis-Fagus grandifolia) stands in Québec (Canada). The stands had been logged, using the selection system, at different times (2-14 years) before the study, and were used as a chronosequence. We also sampled portions of each stand which had been kept as uncut controls. Ten 1 ha plots were sampled (five cuts and five paired controls). We took 20 hemispherical photographs per plot, at 5 m above-ground, which was above most understory vegetation. The CO, light transmission (gap light index (GLI) sensu Canham (1988)), sunflecks characteristics, and angular distribution of openings from the zenith were calculated for each photograph. Selection cutting increased CO, especially within 60 • of the zenith. The greater CO in the cuts allowed a greater light transmission (GLI), longer sunflecks, and a longer cumulative daily sunflecks duration (CDSD). The differences observed between the cuts and the control plots in terms of CO, GLI, and CDSD were greatest in the more recent cuts, and decreased as a function of time since logging. The relationships were best described by negative logarithmic (CO) and negative exponential (GLI, CDSD) models. In the youngest cut (2 years old), the CO, GLI, and CDSD were on average 2.3-2.5 times higher than in the control, while in the oldest cut (14 years old), the same variables were 1.6-1.7 times higher than in the control. The results of this study emphasize the importance of taking into account the temporal variation in canopy openness and light transmission after canopy disturbances such as selection cutting because that variation will likely have an important influence on regeneration dynamics.

Analysis of deciduous tree species dynamics after a severe ice storm using SORTIE model simulations

“…Dense shurb and tree understory can be found in other similar hardwood forests of eastern North America (Beaudet and Messier, 2002;Majcen and Richard, 1992). Dense understory vegetation has been shown to rapidly occupy the understory following any dramatic increase in light availability (Beaudet and Messier, 2002). Many shade intolerant species such as Quercus, Betula and Fraxinus did initially increase their seedling and sapling densities following the ice storm, but the lack of any subsequent major disturbance presumably impeded further development of this functional group in our simulations.…”

“…Lack of long-term responses can also be explained by the absence of a dense understory shrub and tree vegetation in the model. Dense shurb and tree understory can be found in other similar hardwood forests of eastern North America (Beaudet and Messier, 2002;Majcen and Richard, 1992). Dense understory vegetation has been shown to rapidly occupy the understory following any dramatic increase in light availability (Beaudet and Messier, 2002).…”

Light Intensity and Soil Compaction as Influenced by Ecotourism Activities in Pahang National Park, Malaysia

“…Then, values obtained from this study are discussed and ecologically compared with the other studies elsewhere. Tree requires light to grow, and thus light may influence the regeneration dynamics [25,26]. The bigger size of canopy openness will then allow some amounts of light penetration directly into the forest floor and trigger the tree seed germination [27].…”

Do partial cuts create forest complexity? A new approach to measuring the complexity of forest patterns using photographs and the mean information gain

“…In the lower layers (mid-forest and understory) the openness of the canopy allows more light to penetrate through the layers of the community (Beaudet and Messier 2002) and therefore allows the juxtaposition of very bright areas with darker spots, but also in the same pictures, more subtle gradients of lights in the more densely vegetated areas (see the mid-forest layer in the partial cuts in Fig. 3e).…”