A Forest with No Canopy

Researchers investigate the productivity of kelp forests, sans the iconic kelp
Sunlight filters down through a canopy of giant kelp

Sunlight filters down through a canopy of giant kelp to the understory algae below. Photo Credit: Douglas Klug

A lush canopy is a defining feature of most of the planet’s forests. But canopy-forming species can be particularly vulnerable to disturbances and environmental change. So the question is: What is a forest without its trees?

A new paper out of UC Santa Barbara’s Marine Science Institute (MSI) and the University of Virginia seeks to address part of this question by looking at how the productivity of kelp forests changes when its biggest species is gone. After a 10-year removal experiment, the researchers discovered that, while smaller understory algae did take advantage of the brighter conditions, they weren’t able to compensate for the lost productivity of the missing giant kelp, the largest alga in the world. The study, published in Ecology Letters, covers only one aspect of forest ecology; however, it reveals the fundamental importance of canopy-forming species.

A forest canopy performs many functions. It forms habitat, creates microclimates, provides food and much more. The understory can’t fill all these different roles, but there is one place where it could compensate for the loss of the canopy: primary production, which is how much organic carbon plants and algae produce from sunlight during a given amount of time in a given area.

When giant kelp is removed, suddenly there’s plenty of light and space for understory algae to grow. The increased light should foster a flourishing forest floor that might compensate for the lost canopy. However, the data indicates that giant kelp is simply so incredibly productive that the understory algae can’t possibly make up the difference, even under ideal conditions.

MSI Principal Investigators