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Cloud forests and how trees get water


Most trees obtain water through their massive root systems, but did you know that some trees can absorb water through their leaves as well? This ability is called foliar uptake. Scientists recently discovered that trees in cloud forests use foliar uptake to obtain water. A cloud forest is a forest that has persistent or seasonally persistent fog or low-level cloud cover. Cloud forests are usually in the tropics or subtropics, have evergreen trees (trees that don’t lose their leaves) and tend to have a lot of mosses and vegetation in the understory of the trees.

Cloud Forest located in Mount Kinabalu, Borneo Photo Credit: Nep Grower
Cloud Forest located in Mount Kinabalu, Borneo Photo Credit: Nep Grower

Scientists became interested in how cloud forests work after they started studying some of the amphibians and migratory birds that live in cloud forests. For a long time, a lot was known about the animals, but not about the vegetation that provided homes for all these animals. This inspired a group of researchers from the University of California at Berkeley to research the cloud forests of Monteverde, Costa Rica. The cloud forests in Monteverde receive precipitation about 9 months out of the year. During the other three months, Monteverde receives very little precipitation, but it does get fog. Some parts of the forests will have fog for an average of 13 hours per day. This fog forms when moist air from the Caribbean Sea condenses under the forest’s canopy.

A quetzal - a bird that lives in cloud forest trees Photo Credit: Drew Fulton (Canopy in the Clouds)
A quetzal - a bird that lives in cloud forest trees
Photo Credit: Drew Fulton (Canopy in the Clouds)

In order to study where the water in the trees comes from, scientists heated a spot on their branches and then tracked how the warmed water under the spot moved.  If the water moved towards the leaves, it came from the roots.  If the water moved towards the trunk, it came from the leaves.  After studying trees both in and out of cloud forests, the scientists found that the trees in the cloud forests could store 20% more water for growth via foliar uptake than the trees outside of the cloud forests.   Scientists had long suspected that the ecology of cloud forests was tied to the fog and low-level clouds, but not until this research was conducted were they able to say that cloud forests do obtain water via the clouds.

For more information, here is a research group in Costa Rica that studies cloud forests.

Some of our GLOBE schools are near cloud forests.  We would love if you could share your pictures and experiences via email to science@globe.gov or by leaving a comment.  Also, for all our GLOBE schools – we want to wish you a Happy New Year and remind you to always keep investigating!  You might find something amazing.

-Julie Malmberg

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