Fun with Science Club®


			Big trees die from clear-cutting, even when they're not cut. Carrie Straight 05.25.01 In rainforests, large trees create a huge canopy providing shade, fruit, flowers, and shelter for many animals. As humans move into the rainforests, the forests are increasingly more fragmented. We know that this fragmentation affects the animals, but how does the fragmentation affect the trees? Some researchers wanted to know more above how the fragmentation changed the trees. These researchers set up about 60 study sites in the rainforest of Brazil. Starting in the 1980’s they periodically visited each plot, systematically recording the size and types of trees on each plot. Before the area became fragmented, they found no difference in the number of trees per hectare or the number of large trees. After the area became fragmented, the researchers labeled the plots as either edge, which means that the center of the plot was within 300 m of an area that was cut, or interior, which means the plot center was not within 300 m of a cut area. The researchers then compared the species, size, and health of the trees between the edge plots to the interior plots. The edge plots had more dead trees and more of those dead trees were large. The researcher hypothesized these trees died, because weather may hit these large “edge” trees harder, the number of parasitic vines (they live off tree’s nutrients) increase near edges, and the edge might be too dry. Increasing numbers of dying large rainforest trees creates problems for the rainforest ecosystem reducing the habitat for other plants and animals.


			Laurance, William F., Patricia Delamônica, Susan G. Laurance, Heraldo L. Vasconcelos, and Thomas E. Lovejoy. 2000. Rainforest fragmentation kills big trees. Nature 404: 836.