2013-01-14

Pine Beetle Outbreak Buffers Watersheds from Nitrate Pollution

A research team involving several scientists from the University of Colorado Boulder has found an unexpected silver lining in the devastating pine beetle outbreaks ravaging the West: Such events do not harm water quality in adjacent streams as scientists had previously believed.

According to CU-Boulder team member Professor William Lewis, the new study shows that smaller trees and other vegetation that survive pine beetle invasions along waterways increase their uptake of nitrate, a common disturbance-related pollutant. While logging or damaging storms can drive stream nitrate concentrations up by 400 percent for multiple years, the team found no significant increase in the nitrate concentrations following extensive pine beetle tree mortality in a number of Colorado study areas.

"We found that the beetles do not disturb watersheds in the same way as logging and severe storms," said Lewis, interim director of CU's Cooperative Institute for Research in Environmental Sciences. "They leave behind smaller trees and other understory vegetation, which compensate for the loss of larger pine trees by taking up additional nitrate from the system. Beetle-kill conditions are a good benchmark for the protection of sub-canopy vegetation to preserve water quality during forest management activities."