Forest Investment Account (FIA) - Forest Science Program
FIA Project Y073022

    Competitive effects of broadleaf trees on conifer performance over a range of ecosystems
Project lead: Newsome, Teresa
Author: Newsome, Teresa A.
Imprint: Williams Lake, BC : BC Ministry of Forests, 2007
Subject: Forest Investment Account (FIA), Pinus Contorta, Populus Tremuloides, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Program: Timber growth and value (Strategic Goal #2) Theme: #1 Basic research on tree growth and stand development Topic: #1.1 Complex stands This project was initiated to study competitive relationships between lodgepole pine (Pinus contorta) and trembling aspen (Populus tremuloides) and to provide scientifically based and operationally useful information about the management of mixed stands. Conifer timber production is usually the primary management objective for forest plantations and the effects of broadleaves within these plantations are not well understood. Pine and aspen were chosen for study because they are the most common conifer-broadleaf mixture to occur in the Cariboo-Chilcotin. The initial retrospective study provided results that have been used to update free growing guidelines for some of the IDF and SBS subzones; however, longer-term information is needed to refine these guidelines. Data is also needed for other biogeoclimatic subzones to determine whether guidelines require modification. We have established four long-term studies regarding pine-aspen competition in the IDFxm, SBSdw1, SBSdw2 and SBPSxc to address these issues. Increasingly, the value of mixed species stands for other values such as maintaining biodiversity and long-term ecosystem health are being recognized and it is important that accurate growth and yield information is available for timber supply estimates. This proposal best meets strategic goal number 2 'To improve knowledge based science in support of improving timber growth and value'. Under this goal it addresses the first theme 'Basic research on tree growth and stand development' under the topic of complex stands. The main focus of the research is on species interactions between pine and aspen. Neighbourhood studies looking at the influence of aspen on pine growth and development have been established in all the long term trials across a variety of subzones. Except for the initial retrospective trial, all of the 4 replicated trials include treatments where variable densities of aspen were retained along with pine. Growth and yield plots are installed in two of the trials and will be established in one more trial. These data can be used to calibrate and/or verify tree growth models such as PrognosisBC that predict the growth of these complex stands. In addition, light levels in aspen stands have been assessed and documented in a variety of subzones across different stand ages and aspen densities so that models can be developed to predict light availability based on easily measured stand parameters (Comeau 2002). There are 3 groups of experiments within this proposal: 1. A 'retrospective study’ (Newsome et al. 2003) was initiated in 1992 in naturally regenerated pine aspen forests in the IDFdk and SBSdw1 (EP1152). Some of the results have already been used to develop the existing free growing guidelines (BC MOF, 2000). 2. Based on findings from the retrospective study, 4 'variable density studies’ were established in the SBSdw1, SBSdw2, IDFxm, and SBPSxc subzones to provide information about the effects of aspen density and spatial arrangement on pine growth (EP1152). 3. A 'light study’ investigates the relationship between aspen basal area and light availability in aspen stands of different ages across a range of subzones. All the above studies are focused on providing scientifically based information to assist in the management of mixed species stands. The overall objectives for this project are: 1. To investigate and quantify the effects of trembling aspen competition on lodgepole pine growth and performance by (a) assessing established stands, and (b) manipulating aspen densities and spatial arrangement within young stands. 2. To use the above results to produce scientifically-based guidelines for developing silviculture prescriptions and implementing operational treatments. 3. To gather growth and yield data from mixed species stands as they mature. 4. To determine whether models developed by Comeau (2002) to predict understory and within canopy light availability from aspen abundance are suitable for application in Cariboo-Chilcotin SBS, IDF, and SBPS stands. This project provides options for maximizing timber production within mixed species stands while reducing health risks and enhancing biodiversity. The information from the trials is ecologically-based, scientifically credible, and contributes to forest policy decisions. Extension of long-term results has been provided through publications, presentations, consultations and field tours
Related projects:  FSP_Y051022FSP_Y062022
Contact: Newsome, Teresa, (250) 398-4408,


Executive summary (65Kb)

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Updated August 16, 2010 

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