USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Stocking guidelines for aspen restoration

Principal Investigators:
John-Pascal Berrill, Humboldt State University
Christa Dagley, Humboldt State University

Proposal [pdf]

Final Report [pdf]

Stocking Model [xlsm]

Additional Reports:
Berrill and Dagley 2012 [pdf]
Berrill and Dagley 2014 [pdf]

Please contact Dr. John-Pascal Berrill with questions regarding the reports and stocking model.

Project Summary

Quaking aspen (Populus tremuloides) forest communities in the Lake Tahoe Basin are undergoing succession to conifers that impact aspen vigor and stifle natural regeneration. Removal of conifers from aspen stands is undertaken around the Lake Tahoe Basin. However, little is known about stocking and treatment persistence: specifically, how much growing space must be provided to aspen trees and their root sucker regeneration for vigorous growth to be sustained until the next restorative thinning.

The report introduces the Aspen Stocking Assessment Model and provides examples of its use in simulating aspen‐conifer stand development before and after restorative thinning. Tree data collected in 2 ½ acre (one hectare) plots around the Lake Tahoe Basin were used to initiate the model. Different diameter‐limit thinning prescriptions (i.e., cut all conifer below a defined size) were simulated by removing records for smaller (cut) trees from the plot data and then recalculating density and average tree size for input into the Aspen Stocking Assessment Model.

This approach ensured that model simulations were based on realistic pre‐ and post‐thinning values. Treatment persistence – defined here as the time taken for stands to return to their pre‐treatment crowding levels – varied according to pre‐treatment stand density, species composition, and thinning intensity.