Pine beetles have been ravaging forests in the American West for years now, and there is very little that can be done to stop them. However, not all is lost for the ecosystems of the Rocky Mountains. A new study from the University of Colorado (CU), Boulder shows that the beetles go for the older mature pine trees, leaving the younger pines and lower vegetation to grow. When this occurs near a stream or water body, the smaller pines more successfully extract nitrates from the water and sediments. They buffer watersheds from nitrate pollution, a common pollutant typically caused by logging or damaging storms.
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Major logging operations and damaging storms can fell an incredible amount of trees, trees which extract nitrates for their growth. Without this extraction, the nitrates find their way into streams and water bodies. Earlier studies have shown that stream nitrate concentrations can jump up by 400 percent for multiple years following such incidents.
“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.”
“The U.S. Forest Service and other agencies have established harvesting practices that greatly mitigate damage to forests caused by logging, and they deserve credit for that,” said Lewis. “But this study shows just how important the survival of smaller trees and understory vegetation can be to stream water quality.”
The pine beetles actually give the smaller trees a real advantage. By eliminating the larger pines, there is less competition for light, water, and nutrients. The CU researchers found that nitrate concentrations in the needles of the younger pines were higher than healthy pines found outside beetle-kill areas.
This study can be encouraging to environmentalists because it shows how nature will always find equilibrium in response to a disturbance, such as the outbreak of pine beetles. From death comes new life. In this case, that new life can also absorb more nitrate pollutants.
This study has been published in the Proceedings of the National Academy of Sciences
Pine Forest Affected by Pine Beetle image via Shutterstock