14-Year Response of Ponderosa Pine Stands to Pre-Commercial Thinning

Background & Objectives

Ponderosa pine is an important commercial species in the Inland Northwest.  Following harvest, natural regeneration of this species can reach very high levels, necessitating spacing or thinning treatments to achieve adequate yield.  Yet relatively little is known about the growth response of ponderosa pine to pre-commercial thinning, particularly on drier sites.

The primary aim of this study is to describe the growth and mortality response trajectories of ponderosa pine stands in a pre-commercial thinning experiment established on the Nez Perce and Spokane Tribal Forests in the Inland Northwest.  Secondary objectives include the comparison of observed responses to stand projections (e.g., from the Forest Vegetation Simulator) and the joint characterization of height growth, basal area increment, and crown rise.

Scope & Design

The study was initiated in the fall of 1997 on the Nez Perce reservation (ID) and in the fall of 1998 on lands managed by the Spokane Tribes (WA).  Four spacing treatments (5 ft × 5 ft, 7 ft × 7 ft, 10 ft × 10 ft, and 14 ft × 14 ft) and a control were distributed across 7 sites according to a randomized block design.  The selected sites constituted dense, naturally regenerated ponderosa pine stands on drier Douglas-fir and Ponderosa pine habitat types. Sample trees at each site (30 per treatment) were tagged and measured prior to spacing, then re-measured at +1, +3, and +5 years post-treatment.  The sample trees were remeasured again in 2011, corresponding to +13 (Spokane Tribe sites) and +14 (Nez Perce sites) growth years post-treatment.

Timeline

Field data were collected in summer 2011. 
Analysis and reporting will be completed by May 2013.
Preliminary results will be presented at the INGY Technical Meeting in March 2013; final results in March 2014.

Publications & Reports

Ferguson, D.E., J.C. Byrne, W.R. Wykoff, B. Kummet, and T. Hensold (2011) Response of ponderosa pine stands to pre-commercial thinning on Nez Perce and Spokane Tribal Forests in the Inland Northwest, USA.  Research Paper RMRS-RP-88, USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO.

Data

Available upon request.