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Individual Highlight

How do old clearcuts affect old-growth?

Photo of Lingering ecological effects can be found along the edges of past harvests for decades. Lingering ecological effects can be found along the edges of past harvests for decades. Snapshot : The edge influence of past clearcutting on the structure of neighboring uncut old-growth forests is widespread and persistent. These indirect and diffuse legacies of historical timber harvests complicate forest management decision-making in old-growth forest landscapes by broadening the traditional view of stand boundaries.

Principal Investigators(s) :
Bell, David M. Spies, Thomas
Research Location : H.J. Andrews Experimental Forest; Oregon
Research Station : Pacific Northwest Research Station (PNW)
Year : 2017
Highlight ID : 1365

Summary

Clearcuts often create stark boundaries between forest habitats. These ecological "edges" can affect neighboring undisturbed ecosystems for some distance in from the edge. Although most clearcutting on national forest land in the Pacific Northwest ended in the 1990s, past clearcuts leave a legacy of edge influence that has not been closely examined. A new study led by research foresterDavid Bell took on the question of how historical timber harvests have affected the structure of neighboring old-growth forests in western Oregon. Bell and his team used a remote-sensing technique called LiDAR to map tree basal area (a measurement related to tree density and biomass) in lower and middle-elevation mature and old-growth forests in the H.J. Andrews Experimental Forest. They then assessed how harvest edges have affected tree basal area and how those effects varied with harvest size and age. They found that forests within 240 feet of harvest edges had 4 to 6 percent less live tree basal area than forests tucked in the interior away from edges. They were surprised to find that the length of time since harvest had little or no effect: whether the harvest happened 13 years ago or 60 made little difference on the structure of surrounding unharvested forest area. This implies that the edge influence persisted over many decades in spite of forest recovery processes. Roughly 60 percent of the forest they studied in the H.J. Andrews Experimental Forest remains uncut, but a substantial percentage of that forest appears to have suffered reduced growth or increased mortality because of the indirect effects of historical timber harvests. Bell's study is important in examining the subtle impact of human activity on forest landscapes in western Oregon and showing how widespread and long-lasting the edge influence of past clearcutting has been on neighboring old-growth forest.

Forest Service Partners

External Partners

 
  • Oregon State University