March 4, 2014
Amazon Canopy Study Can Predict Responses To Climate Change And Human Activity
redOrbit Staff & Wire Reports - Your Universe Online
By studying thousands of canopy tree species in the western Amazon, researchers from the Carnegie Institution for Science’s Department of Global Ecology have uncovered geographically nested patterns of chemical traits they say will help determine how the ecosystem will respond to changes in land use and climate.
Writing in the March 3 edition of the Proceedings of the National Academy of Sciences (PNAS), the study authors set out to determine how much variation there is in the chemicals generated by plants when they convert sunlight into carbon-based energy and take nutrients from the soil to synthesize various products.
To find out, they climbed into the Amazonian canopy and discovered a large-scale nested pattern of chemical assembly involving thousands of trees. This pattern varied greatly based on elevation and soil content, the researchers explained in a statement Monday.
“The western Amazon harbors thousands of plant species that grow at different elevations and in different soils on different geologies,” the Institute said. “Amazonian canopy trees are of particular interest because they create the habitat occupied by a tremendous diversity of other plants and animals. They are also at great risk due to climate change and other human interference such as mining, cattle ranching, and agriculture.”
The investigators scaled the treetops to collect and analyze the foliage of over 3,500 canopies across 19 forests throughout Peru, and found that the canopy chemical traits were organized in a mosaic. Furthermore, that mosaic was controlled by changes in the underlying soils and by elevation.
The chemical variation in co-existing species was also found to far exceed the variation within each individual type of plant. These discoveries help demonstrate the fact that different species of Amazonian plants comprise a “diverse matrix of growth and survival strategies” that shed new light on how the forests came together and evolved over the years, lead author Greg Asner and his colleagues noted.
“We discovered that this incredible region is a patchwork mosaic of trees with chemical signatures organized into communities to maximize their growth potential given their local soils and elevation – two geological factors they must negotiate as living organisms,” Asner said. “Within these communities, the trees have evolved chemical portfolios that are different from one another, maybe to help each species take a place in its community – what we call a niche.”
Since forest canopies are hard to access, they are quite difficult to study. The researchers needed to collect thousands of samples in order to make sure they had equal exposure to sunlight, making them comparable in terms of solar-driven chemical synthesis. Doing so required them to climb hundreds of feet, going to the outer edge of each canopy and obtaining the majority of canopy tree species in the region.
The PNAS study is the first in the Institute’s field and laboratory-based Spectramonics program, which probes the association between function and biodiversity in tropical forest plant species. The researchers said their findings will help them better understand the immense diversity of the Amazon rain forest, while also demonstrating how global warming and human activity could impact the function of the area later on this century.
“I view the results as a wake-up call that we are shaking up a special tropical region full of chemically unique forest communities that have undergone millions of years of evolution and biogeographic construction,” said Asner. “Land use and climate change are two very obvious pressures on the western Amazon. They are already threatening whole patches in a kaleidoscopic quilt of chemical diversity that underpins these ecosystems.”