Solar radiation transmission in and around canopy gaps in an uneven-aged <Emphasis Type="Italic">Nothofagus betuloides</Emphasis> forest |
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Authors: | Alvaro Promis Dirk Schindler Albert Reif Gustavo Cruz |
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Institution: | 1.Institute of Silviculture,University of Freiburg,Freiburg,Germany;2.Meteorological Institute,University of Freiburg,Freiburg,Germany;3.Department of Silviculture,University of Chile,Casilla,Chile |
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Abstract: | The transmission of direct, diffuse and global solar radiation in and around canopy gaps occurring in an uneven-aged, evergreen
Nothofagus betuloides forest during the growing season (October 2006–March 2007) was estimated by means of hemispherical photographs. The transmission
of solar radiation into the forest was affected not only by a high level of horizontal and vertical heterogeneity of the forest
canopy, but also by low angles of the sun’s path. The below-canopy direct solar radiation appeared to be variable in space
and time. On average, the highest amount of transmitted direct solar radiation was estimated below the undisturbed canopy
at the southeast of the gap centre. The transmitted diffuse and global solar radiation above the forest floor exhibited lower
variability and, on average, both were higher at the centre of the canopy gaps. Canopy structure and stand parameters were
also measured to explain the variation in the below-canopy solar radiation in the forest. The model that best fit the transmitted
below-canopy direct solar radiation was a growth model, using plant area index with an ellipsoidal angle distribution as the
independent variable (R
2 = 0.263). Both diffuse and global solar radiation were very sensitive to canopy openness, and for both cases a quadratic
model provided the best fit for these data (R
2 = 0.963 and 0.833, respectively). As much as 75% and 73% of the variation in the diffuse and global solar radiation, respectively,
were explained by a combination of stand parameters, namely basal area, crown projection, crown volume, stem volume, and average
equivalent crown radius. |
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Keywords: | Nothofagus betuloides Uneven-aged forest Hemispherical photographs Below-canopy solar radiation transmission Tierra del Fuego |
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