Tree spatial distribution in 1-hectare of Amazonian white-sand forest ("wet varillal"), Loreto, Peru
With the enthusiastic support of several undergrads from the Universidad Nacional de la Amazonia Peruana (UNAP), we established a 1-hectare (200 x 50 m) tree plot in a "wet varillal" forest of the Allpahuayo-Mishana National Reserve, Loreto, Perú. The goal was to study the spatial distribution of trees in relation to the sunlight reaching the forest floor, terrain slope, and drainage conditions.
All trees larger than 10 cm in diameter were mapped to scale within the plot, tagged with aluminum labels, and plotted within a XY coordinate grid. We also measured the slope terrain within the plot. The third most dominant species (by stem density, basal area and frequency) was the tree Dimorphandra macrostachia subsp. macrostachia (Fabaceae) shown in this photo (left). This canopy tree is restricted to the white-sand forests ("wet varillales") of Iquitos. Using the spatial distribution of trees recorded within the plot we demonstrated that in general this species has a random spatial distribution (O-ring statistics), although some individual trees prefers the most humid areas of the "varillal". Circles in the figure below represent the spatial distribution of this species within the plot. The gradient color represent a density map of this species.
Studies of tree spatial distribution can be used to improve management plans of trees in the Amazon, in such a way that the ecological edaphic preferences of species are taken into account both for reforestation or extraction with reduced impact. There are other ecological studies that can be carry out within the 1-ha forest plot now that have all the trees have been mapped, measured and tagged (for instance, plant-animal relationships, natural regeneration, forest biomass, mycorrhizal associations, nutrient cycling). Recently, an undergrad thesis studied the distribution of "varillal" birds and their foraging types within this plot. This permanent plot is being re-measured and monitored every two years and the data made available to the scientific community as part of the RAINFOR plot network (http://www.rainfor.org/). We hope that these results will encourage similar research projects in Loreto and other regions of the Amazon.
