Predicting Treatment Longevity after Successive Conifer Removals in Sierra Nevada Aspen Restoration
University of Wisconsin Press
Populus tremuloides (quaking aspen) stands throughout the Sierra Nevada Mountains are undergoing succession to conifers. Removal of conifers is being tested, however, little is known about treatment longevity—the time taken for stand density to return to pretreatment levels. To determine longevity of treatments removing conifers below different size limits, we developed tree growth equations from data collected in 1 ha plots around Lake Tahoe in P. tremuloides stands with varying amounts of conifer, and simulated stand development after treatment in two stands. At Ward Creek, cutting all conifer < 35 cm diameter at breast height (DBH) generated the most wood that could practically be piled and burned inside the stand, but only reduced stand density by 16%. After 13 years of predicted treatment longevity, a second treatment was simulated with options of light, medium, or heavy cutting (50, 60, or 75 cm DBH limits). This gave treatment longevity of 23, 29, and 40 years respectively but did not restore P. tremuloides dominance. At Cookhouse Meadow, cutting conifer < 35 cm DBH had 16-year treatment longevity, after which time two treatments were compared. Cutting conifers < 50 cm DBH enhanced P. tremuloides’ representation from 27% to 37% of stand basal area and had 23-year treatment longevity. Raising the DBH limit to 60 cm left P. tremuloides representing 45% of stand basal area, and extended treatment longevity to 36 years. Our findings indicate that a series of treatments will be needed to restore and maintain P. tremuloides communities, and will eventually require removal of large conifers (> 75 cm DBH).
Berrill, J.-P., C. M. Dagley, and S. A. Coppeto. 2016. Predicting Treatment Longevity after Successive Conifer Removals in Sierra Nevada Aspen Restoration. Ecological Restoration 34:236-244.