Burning Invasive Juniper Trees

Burning western junipers after they have been cut down instead of just leaving the trees on the ground helps native grasses get reestablished, according to new ARS studies.
Photo courtesy of Dave Powell, U.S. Forest Service

In the past century, junipers have begun to dominate some sagebrush grasslands in the western United States. Rangeland managers sometimes just cut down the invasive trees and leave them where they fall, which can help protect the soil from erosion. But the dead trees are an increased fire risk and may also create conditions that help cheatgrass--an invasive annual that fuels fierce wildfires--crowd out native perennials.

Bates and Svejcar, who work at the Eastern Oregon Agricultural Research Center in Burns, Ore., cut down a group of junipers and then burned them during the winter one and two years after they were felled. A control group of felled trees at the site was left unburned.

Ten years after the trees were burned, total herbaceous and perennial grass cover was 1.5 to 2 times greater in the areas where trees had been burned than in the areas where they were not burned. Perennial grass density was 60 percent greater in the burned sites than in the unburned sites, and cheatgrass cover was twice as dense in the control area than in the two burn areas.

The researchers concluded that burning the cut trees in winter helped protect existing perennials at the site because the soils were wet and frozen. This protection gave the perennials a head start in their growth the following spring, when they needed an edge against invasive annuals.

More information: Results from this work, which support the USDA priority of responding to climate change, were published in Western North American Naturalist.

Provided by United States Department of Agriculture