Eavesdropping: PhD-project captures the chatter of the riparian zone

Having a buffer zone of forest in the riparian zone nearest streams helps shade the water surface and promotes biodiversity both in and around the water. But what kind of buffer zone is most effective after a clearcut the surrounding forest? A narrower but untouched strip of trees, or a slightly wider one where selective tree harvesting is allowed?

These are the questions asked by Ernie Haglund, PhD-student at the Swedish University of Agricultural Sciences (SLU) in Umeå. His project surveys insects, vascular plants, mosses and more along streams with different types of buffer zones. The diversity is monitored both before and after clear cutting in order to track changes over time.

– A clear-cut area next to the buffer zone affects both temperature and humidity, as wind enters from the open site. How wide should the buffer be to fulfill the functions we want? Can we compensate for or even improve the buffer through selective tree harvesting? says Ernie Haglund.

Machine learning helps listening in on birds and bats

The project is part of the WIFORCE research program, funded by the Knut and Alice Wallenberg Foundation. But thanks to a 50,000 SEK scholarship from Gösta Edström’s Honorary Fund, through the forestry company Södra Skog, Ernie Haglund has been able to expand his study even further. The additional funds allow 24 sound boxes equipped with microphones to record birds and bats in the differently managed buffer zones. With the help of technology the different species can then be identified.

– Birds sing to prove themselves to both partners and competitors, while bats emit sounds for navigation. Both groups can be identified from sound recordings, but it takes time. Instead, I use machine learning, where the sounds are compared against what we’ve defined as a specific species, such as a particular bat, explains Ernie Haglund.

He hopes that this broad approach—where several different species groups are studied simultaneously and over time—will capture the many complex relationships between species, habitats, and forest management methods.

– We’re looking at communities of species such as plankton, insects, plants, and fish. But the terrestrial vegetation also consists of species—mosses and vascular plants—that are often threatened by habitat loss. Nature is complex; species interact and depend on one another. This scholarship allows me to add not just two more species groups, but two very important ones. It helps me understand the bigger picture, says Ernie Haglund.

– Nature is complex; species interact and depend on one another. The communities of species in the streams, plants and insects for example, are surrounded by completely different communities on land. These interact in ways that make it difficult to tell where the forest ends and the stream begins. This scholarship allows me to add not just two more species groups, but two very important ones. I hope to contribute in understanding the bigger picture, says Ernie Haglund.