IDENTIFYING SPATIAL PATTERNS IN THE TROPICAL RAIN-FOREST STRUCTURE USING HEMISPHERICAL PHOTOGRAPHS

This work emphasises the usefulness of hemispherical photography for i dentifying spatial patterns in the tropical rain forest structure. Str uctural variability was investigated at a local (intra-site) scale, in relation to the forest mosaic, and at a regional (inter-sites) scale, for its implication in forest typology. Four primary forest sites, fr om 0.6 to 1 ha, were investigated in Central Sumatra, Indonesia. In a first instance, a qualitative analysis of the forest 3-D structure was found to be very helpful in the interpretation of quantitative result s related to forest dynamics. The quantitative analysis was undertaken through the assessment of three structural characteristics: (1) the c anopy openness (CO), or visible sky as seen from all directions of the hemisphere, (2) the spherical variance (SV), which quantifies the spa tial dispersion of gaps and, (3) the plant area index (L-p), defined a s half the surface area of canopy elements per unit ground area. At th e local scale, maps of the CO values gave an indication about disturba nce location and extent, providing an interesting document for studies on forest dynamics. At the regional scale, between-sites comparisons of CO, SV and L-p values added new information on forest structural di fferences when compared to dendrometric measurements. These results em phasised the fact that rain forest may exhibit high structural variabi lity, even within a same bioclimatic region and a narrow altitude rang e. Hemispherical photographs could be a quick means of further investi gating this spatial variability and it's relation to physical environm ent, thus providing information that is crucial for the refining of fo rest typology in the area.