It’s been known for years that forests with a lot of different tree species grow better and faster than forests with just one kind of tree. Now, for the first time, scientists say they know why. It’s shapes.

It turns out trees of different species find a way to get along with their neighbors by spreading branches out to fill in gaps where sunlight is available — they play off each other’s shape. And that maximizes their combined ability to soak up the sun falling on a particular plot of land.

The new information could not just help foresters provide more fiber for the region’s wood products industry, it could also help reduce climate-changing effects of greenhouse gases.

A study published this week in the scientific journal Nature Ecology & Evolution by scientists from the University of Minnesota and Université du Québec à Montréal looked at 37 plots of trees that had been planted in Montreal four years previously, ranging from a monoculture (only one tree species across the entire plot) to a plot with 12 different tree species commonly found in northern forests.

They used basic tools such as measuring tapes and height poles to differentiate the vertical growth of branches and leaves as well as the amount of trunk biomass that trees produced under the various combinations of species. They found that in plots with multiple species, the different natural growth forms and light requirements of the various species, combined with their ability to modify their growth to their neighbors, made it possible for the trees to send branches into places where they could better use the available light, growing better together than in single-species plots.

From the Faribault Daily News: