The Pando aspen clonal colony

The tree called the Pando aspen (green bands at hill’s base and midsection) has an estimated 47,000 trunks and weighs 59 million kilograms, but it is dwindling. Credit: Lance Oditt, Studio 47.60 North

Ecology

World’s biggest plant shrinks as hungry deer move in

Wily herbivores have breached a fence intended to protect the 43-hectare ‘Pando’ aspen.

A vast aspen grove that is renowned as one of the world’s biggest living organisms is shrinking as a result of human activity and browsing deer.

One aspen tree can sprout thousands of genetically identical trunks to form a single, sprawling clone known as a ‘forest of one tree’. The biggest known clone is the Pando, a quaking aspen (Populus tremuloides) in Utah that covers 43 hectares and is thought to have survived for thousands of years.

Paul Rogers and Darren McAvoy at Utah State University in Logan reviewed aerial photographs of the Pando dating back to 1939. They also examined the aspen’s condition in 65 plots across fenced and unfenced sections of the grove.

The researchers found that the forest has thinned and that roads and settlements are encroaching on the grove. Mule deer (Odocoileus hemionus) are devouring vulnerable shoots in unfenced sections and are also slipping through the longest fence, which has some sections that are decades old. Only one fence, enclosing just 7 hectares of the ancient tree, has been effective at protecting this valuable habitat, the authors say.