Gap Fraction Estimates over Selectively Logged Forests in Western Amazon

Ekena Rangel Pinagé,Eraldo A T Matricardi,Alessandra Rodrigues Gomes,Liliana Sayuri Osako

doi:10.4236/nr.2014.516083

Abstract

Gap fraction is a biophysical variable related to energy balance, forest fauna, micro-climate and regeneration, and is an important indicator of forest management quality. The objective of this study was to compare gap fraction estimates from undisturbed forests and different environments or strata of selectively logged areas. Moreover, gap fraction measurements were collected with two distinct instruments (optical canopy analyzer LAI-2000 and hemispherical photographs). Field data were collected from two sustainable forest management sites at Jamari National Forest, Rondonia State, Brazilian Amazon. Our results indicated significant differences between data acquired using these two instruments. For instance, the LAI-2000 data showed greater variation for each environment compared to hemispherical photographics data, and the data were also more sensitive to the increase in gap fraction. Small variations were found in the gap fraction means for the two study areas, and only data for the undisturbed area were significantly different. A gradient of increasing gap fraction that ranged from primary forests to log decks was observed. Furthermore, a multiple linear regression analysis determined the contribution of the selectively logged environments to decreased forest cover, confirming the observed gradient.

Highlights

Severe damage to the remaining forest is caused by conventional logging and by not applying forest manage-How to cite this paper: Pinagé, E.R., Matricardi, E.A.T., Osako, L.S. and Gomes, A.R. (2014) Gap Fraction Estimates over Selectively Logged Forests in Western Amazon
As the gap fraction of the strata increases, the difference between the two methods becomes larger. These results suggest that Leaf Area Index (LAI)-2000 data are more prone to overestimations of gap fraction in those situations
Garrigues et al [17] found that the sensitivity of the hemispherical photography method to illumination conditions is low (14% compared to 28% of LAI-2000), and reported that LAI-2000 gap fraction measurements for crop canopies are more variable than those obtained with the photos

Summary

Introduction

Severe damage to the remaining forest is caused by conventional logging and by not applying forest manage-How to cite this paper: Pinagé, E.R., Matricardi, E.A.T., Osako, L.S. and Gomes, A.R. (2014) Gap Fraction Estimates over Selectively Logged Forests in Western Amazon. Severe damage to the remaining forest is caused by conventional logging and by not applying forest manage-. (2014) Gap Fraction Estimates over Selectively Logged Forests in Western Amazon. Additional damage is caused when trees are felled. According to Johns et al [1], for each tree harvested 27 other with diameter at breast height (dbh) greater than 10 cm are damaged during conventional logging in the uplands. These combined damages cause forest canopy openness that is approximately 50% greater than that caused by sustainable forest management [2]

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Results

Conclusion