With its wide canopy and thick understory, an old-growth forest could potentially act as a buffer against increasing temperatures, as well as keep animals and plants cool under its shade, a new study in Oregon revealed.

Led by postdoctoral scholar Sarah Frey, a team of scientists from Oregon State University compared temperature regimes under the canopy in primeval and plantation forests in the Oregon cascades.

Frey said little is actually known about the more subtle differences in temperature between mature forest types, although experts know that closed-canopy forests are likely to be cooler than open areas.

To find out the subtle differences, Frey and her colleagues collected temperature data from 2012 and 2013 at 183 locations, about more than one third of which were in plantations. They also assessed forest structure data which were collected through LiDAR (Light Detection And Ranging), an aerial mapping technique with lasers that can detect extremely small-scale differences in forest structures.

What the team discovered is this: when matched with the characteristics of younger second-growth forests, the characteristics of old-growth forests lessen maximum summer and spring air temperatures as much as 4.5 degrees Fahrenheit (2.5 degrees Celsius).

Frey said subtle yet vital gradient in structure from old-growth forests to plantations have a marked effect on these forests' temperatures.

Researchers said temperature is greatly affected by elevation and even tiny changes in topography, but the way forests were managed was a crucial factor in determining temperature differences.

Study co-author and university professor Matt Betts said that to the untrained eye, old-growth forests and plantations might only look similar when it comes to factors that affect temperature such as canopy cover.

"So, the magnitude of the cooling effect of old-growth structure is somewhat surprising," said Betts.

Implications Of The Study

To their knowledge, Frey and her team's study is the first broad-scale test of whether subtle changes in forest structures due to different management practices can actually influence forest temperature regimes.

Researchers said landowners who include biodiversity as a management goal could boost their aims by fostering standards with high biomass, closed canopies, and complex understory vegetation.

Management practices that could create "microclimates" -- for amphibians, birds, insects, and even mammals -- promote conservation for species that are temperature-sensitive should temperatures increase as a result of global warming.

The study, which is featured in the journal Science Advances, was funded by the National Science Foundation.

Photo: Oregon State University | Flickr

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