Plant Community Structure over an Elevation Gradient in Manongarivo Special Reserve, Madagascar

Publication Year:
2014
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Repository URL:
https://digitalcollections.sit.edu/isp_collection/1762
Author(s):
Sugden, Scott; Washington and Lee University
Tags:
Earth Sciences; Forest Biology; Forest Sciences
paper description
This study examines how plant community structure changes across an elevation gradient in Manongarivo Special Reserve, Madagascar. Three vegetation surveys were conducted at each of six different elevations (300m, 500m, 700m, 850m, 1000m, 1150m) on the southern slope of Bekolosy Mountain, near the southwestern border of the reserve. Each of these surveys focused on the diameter, height, and crown position of trees in a 156.25m2 plot, as well as the presence or absence of mosses and vines. At each of the six survey elevations, point-quadrat vertical structure data was also collected for the underbrush, up to a maximum height of 2.50m. Average diameter declines noticeably with altitude, from 10.36cm at 300m to 6.66cm at 1150m, with average total height exhibiting a similar but less defined pattern, from 10.74m at 300m to 6.09m at 1150m. Underbrush density increases with altitude, presumably due to an observed decrease in forest canopy closure allowing more sunlight and rainfall to reach the forest floor. Net wooded area also declines with altitude, though population density remains consistent or increases, indicating that smaller trees are more numerous at elevation. Correspondingly, the species diversity of large trees decreases with elevation. Moss coverage also increases as a function of elevation due to an assumed increase in humidity, though vine coverage remains mostly constant. Future research is necessary to measure changes in the abiotic qualities across this gradient, such as changes in average temperature or soil nutrient richness, to identify specific causes for the observed changes in the plant community.