From: Liz Kimbrough, MONGABAY.COM, More from this Affiliate
Published January 10, 2014 09:06 AM

Tree Island restoration

Worldwide, large swaths of land lay barren in the wake of agricultural expansion, and as global forest cover continues to decline, carbon and water cycles, biodiversity, and human health are impacted. But efforts to restore abandoned pastures and agricultural plots back into functioning forest ecosystems are often hindered by high costs and time requirements. Fortunately, scientists have developed a new method for a more cost effective solution to forest restoration, the establishment of "tree islands."



Typically, forest restoration involves planting rows of trees, plantation style, which cover the entire restoration site. However, a team of researchers led by Rakan A. Zahawi of Las Cruces Biological Station in Costa Rica and Karen Holl of UC Santa Cruz recently tested an innovative method known as applied nucleation or the "tree island method" to facilitate forest recovery. In the tree island method, clusters of trees are spread out across the site instead of covering the whole deforested area. For this study, the researchers tested three different treatments on abandoned pasture plots in Costa Rica: planting tree islands, plantation style planting, and no planting or what is known as "passive restoration."

"We were surprised," Karen Holl told, "that the applied nucleation strategy was as effective in facilitating the natural establishment of forest tree seedlings as planting the entire area with trees, even though we only planted 27% of the trees in the applied nucleation treatment."

The establishment of tree islands, around the size of 100m2, serves as "activation energy" of sorts. As the trees grow, they shade out competitive pasture grasses and also attract frugivorous (i.e fruit-eating) birds that spread the tree seeds around. Once the bird-dispersed trees reach maturity, they provide habitat for more seed dispersing birds and animals, which will bring more seeds. Once this ecological process is jump-started successfully, it should proceed without further intervention.

"There are large areas of degraded lands in the tropics that are in need of restoration and there simply aren't enough resources to do so," says Holl. "The overarching goal for the tree island method is that we will be able to restore forest in former agricultural lands in a more economical manner so larger areas can be restored with the added benefit that this restoration approach will create habitat conditions that are more similar to the forest than planting trees in straight lines."

Read more at ENN affiliate Mongabay.

Restoring farmlands image via Shutterstock.

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