Aberturas del dosel y espectro de la luz en el sotobosque de una selva nublada andina de Venezuela


Article on canopy gaps and understory light spectrum in a Venezuelan Andean cloud forest.

Creation Date: Spring 2001
UNT College of Engineering
UNT Scholarly Works
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Past 30 days: 2
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Creator (Author):
Acevedo, Miguel F.

University of North Texas; Universidad de Los Andes

Creator (Author):
Monteleone, Susan

Lindsey Wilson College

Creator (Author):
Ataroff, Michele

Instituto de Ciencias Ambientales y Ecológicas

Creator (Author):
Estrada, Carlos A.

Instituto de Ciencias Ambientales y Ecológicas

Publisher Info:
Publisher Name: Universidad del Zulia
Place of Publication: [Maracaibo, Venezuela]
  • Creation: Spring 2001

Article on canopy gaps and understory light spectrum in a Venezuelan Andean cloud forest.

Department: Geography

Abstract: The effect of canopy gaps on the spectral characteristics of light received by the understory of a cloud forest was studied at La Mucuy, Sierra Nevada National Park, in the Venezuelan Andes. Measurements were taken at 22 points along two 40m transects oriented in the east-west (EW) and north-south (NS) directions and that intersected at the middle. For each point, a digital image of 60% of the area of a hemispherical photograph was analyzed calculating the percent of gap area (PAA) and reflecting foliage (AFR), as well as six canopy gaps fragmentation metrics. These metrics were: number of gaps (NA), gap density (DA), mean area of gaps (AMA), largest gap index (IAM), mean shape index (MIF) and mean fractal dimension (MDF). These variables, in addition to leaf area index (IAF) measured in the field, were selected as variables to represent canopy structure. Low values of PAA revealed shaded conditions; its correlation with AFR indicated that light reflected by the foliage towards the understory decreased with a reduction in gap area. The IAF resulted independent of the other structural variables. The area in gaps was found to be highly fragmented in many small and irregularly shaped gaps. Canopy transmittance (ratio of understory over incident light) spectra indicated shaded conditions with strong attenuation in the photosynthetic range and a steep slope near 700 nm. The spectra taken along the NS transect showed a larger magnitude and lower variability than in the EW transect. Two prominent peaks were observed and found to be correlated, one in the far red and another in the green. These two peaks and their corresponding slopes were selected to represent spectral characteristics. A canonical correlation analysis indicated a relationship between the structural and spectral variables. In the NS transect the strongest relation was for the peak in the far red with PAA, but in the EW transect, the strongest relation was for the peak in the green with IAM and NA. Since IAM is very large in the EW transect, with low PAA and NA, the size of the largest gap may affect the understory spectral characteristics. No relationship was found between IAF and the spectral variables, suggesting that the understory light spectrum in this forest site is controlled by the area in gaps, its size distribution and shape, rather than by light transmitted through the foliage.

Physical Description:

19 p. : ill.

Keyword(s): Andes | canopies | cloud forests | gaps | light | solar radiation | spectra | Venezuela
Source: Ciencia, 2001, Maracaibo: Universidad del Zulia, pp. 165-183
Alternate Title: Canopy gaps and understory light spectrum in a Venezuelan Andean cloud forest
UNT College of Engineering
UNT Scholarly Works
  • ARK: ark:/67531/metadc330574
Resource Type: Article
Format: Text
Access: Public
Publication Title: Ciencia
Volume: 9
Issue: 2
Page Start: 165
Page End: 183
Peer Reviewed: Yes