Research Branch


See below to download Technical Report 032 PDF file.
   

Effects of Variable Aspen Retention on Stand Development, Aspen Sucker Production, and Growth of Lodgepole Pine in the SBSdw1 Variant of South-central British Columbia

Author(s) or contact(s): T.A. Newsome, J.L. Heineman, and A.F. Linnell Nemec
Source: Research Branch
Subject: Growth and Yield
Series: Technical Report
Other details:  Published 2006. Hardcopy is available.
 

Abstract

In 1999, an experiment was established to examine the effects of reducing aspen density on stand-level lodgepole pine and aspen growth in the SBSdw1 biogeoclimatic variant of the Cariboo-Chilcotin. Aspen retention treatments of 0, 500-800, 1000-1500, and 2000-2800 stems ha-1 were applied in an 11-year-old mixed-species stand of aspen and lodgepole pine. One year after cutting, aspen basal area in these retention treatments was 0, 1.25, 3.05, and 2.89 m2 ha-1, respectively, compared with 5.36 m2 ha-1 in the control. Four years after treatment, based on stand-level measurements taken in permanent measurement plots, pine vigour tended to be better in treatments where <1000 aspen stems ha-1 had been retained but there were no significant differences in mean stand-level lodgepole pine height, stem diameter, quadratic mean diameter, or basal area as a result of the aspen retention treatments.

Aspen suckering was assessed 2 and 4 years after cutting. Sucker densities differed significantly between aspen retention treatments after 2 years, ranging from 28 187 stems ha-1 in the complete aspen removal treatment to 344 stems ha-1 in the 2000-2800 stems ha-1 treatment. Sucker densities appear to have declined naturally by approximately 35% between years 2 and 4 after cutting; however, this apparent decline may be partly due to a change in the sampling method. There were no significant differences between treatments in sucker height in either year 2 or 4 after cutting.

In addition to stand-level measurements, the ongoing performance of target lodgepole pine that had, or had not, met existing British Columbia Ministry of Forests free-growing requirements at a stand age of 12 years was assessed. By 2003, pine in the free-growing group were larger than those in the not free-growing group according to all measurement criteria. Regression analysis showed that tall aspen (i.e., aspen at least as tall as the target pine) within a 1.78-m radius were more important competitors with the target pine than aspen that were further away. When the stand was 13 years old, tall broadleaf basal area explained 25.7% of the variation in 2000-2003 lodgepole pine stem diameter increment.

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Updated May 11, 2007