Use of hemispherical photographs in forest ecology: measurement of gap size and radiation totals in a Bornean tropical rain forest

Study of forest dynamics commonly requires measurement of canopy gap size. Hemispherical photographs can be analysed to provide various measures whereby gaps can be ranked in order of size. For ten artificial gaps in a Bornean tropical rain forest these measures were better correlated with gap micro...

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Bibliographic Details
Published in:Journal of tropical ecology 1993-05, Vol.9 (2), p.131-151
Main Authors: Whitmore, T. C., Brown, N. D., Swaine, M. D., Kennedy, D., Goodwin-Bailey, C. I., Gong, W.-K.
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
Borneo
Canopy gaps
Ecophysiology
Forest canopy
forest canopy gaps
Forest ecology
forest light climate
Forest regeneration
Fundamental and applied biological sciences. Psychology
hemispherical photographs
Metric photography
Photosynthetically active radiation
Plants
Synecology
Terrestrial ecosystems
Tropical forests
Tropical rain forests
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Summary:Study of forest dynamics commonly requires measurement of canopy gap size. Hemispherical photographs can be analysed to provide various measures whereby gaps can be ranked in order of size. For ten artificial gaps in a Bornean tropical rain forest these measures were better correlated with gap microclimate than gap area measured physically on the ground. All these measures are however relative. For detailed (e.g. ecophysiological) studies the greater detail provided by absolute measures of photosynthetically active radiation (PAR) are required. Long term PAR values can be computed from hemiphots so long as measurements in the open nearby are available. Correction for cloudy weather is essential. Computed and measured PAR are compared for the test gaps. Both have inherent limits which means that below c. 15% canopy openness, differences in PAR between gaps cannot be assessed accurately.
ISSN:0266-4674
1469-7831
DOI:10.1017/S0266467400007112