Forest Investment Account (FIA) - Forest Science Program
FIA Project Y113064

    Effects of variable retention on planted and natural regeneration in Coastal BC
Project lead: N.J. Smith (Western Forest Products Inc)
Contributing Authors: Smith, Nick J.; Iles, Kim; Raynor, Kurt
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
This project is a continuation Y102064. There are no significant deviations to the original project plan. In that project critical long-term data from a set of 11 large-area variable retention experiments were collected. In addition statistical and practical fundamentals of ‘sector sampling’ were developed resulting in the publication of two articles in Forest Science (Iles and Smith, 2006, Smith, et al., 2008) and one submitted journal paper (Smith et al. 2008). In this next phase we plan to continue to collect critical data from additional established sites and summarise the development of sector sampling methodology and statistical properties.
This study is designed to examine the effects of retained forest edge on the growth of regenerating trees in Coastal BC. Seven large scale (~100 ha) and four smaller scale (~11ha-40ha) experimental areas were recently established (2000+) across the former Weyerhaeuser BC Coastal Group’s, now mostly Western Forest Products land base (Beese et al. 2005). The intent was to examine the effects of different amounts and patterns of variable retention on the response of retained and planted trees and natural regeneration. This included measuring establishment, survival and growth over the long-term (20 years +). A variety of other indicators are tracked in complementary Adaptive Management and Monitoring projects (Beese et al. 2001) such as plant and animal populations (Beese et al., 2005). The experimental sites are established on homogenous areas, with clearcut and uncut controls and up to 3 treatments comprised of different types and levels of variable retention, all randomly allocated. Note that each site examines only one of these treatment types. Treatment types are group retention, group size, dispersed retention, group removal and mixed retention. Within each site the treatments are varied at three levels, for instance: 5%, 10% and 30% dispersed retention (the small scale experiments only examine two levels, for instance 5% and 15% for dispersed retention). Each site permanently monitors 2000- 5000 planted trees, 3000+ tagged natural regeneration trees and 500-1500 retained trees measured on a, generally, 1,3,5,8,10, then 5 year cycle (+/- 1 year).
Within these experimental areas ‘sector plots’ have been established to examine the effects of forest edge on tree growth (Iles and Smith, 2006, Smith et al., 2008, Smith et al., 2009). Planted, natural and retained trees are spatially located within the sector plots. The sector plots are randomly placed and oriented but sample N,S,E and W facing edges from a central pivot-point outward to the extent of the sampled strata. In dispersed experiments, clearcuts and uncut areas ~0.1ha ‘sector’ plots with a central angle of 36 degrees are established randomly. For group retention or group removal treatments four 9 degree sectors tied to a central 'pivot-point' are established with random angles in a minimum of 3 patches per treatment. The sector plots overcome the edge effect biases entailed by establishing traditional fixed area or prism plots (Iles, 2003 p614).
An analysis will examine planted trees at TM128. This is a replicate of three dispersed tree experiments (TM188, LL55 and TM128) and will ensure all replicates have similar length remeasurements (TM188=8 year, LL55=6 year and TM128=9 year post planting). Results to date show that tree response is only significantly impacted at higher retention levels. Data collected using separate funding includes light (direct and diffuse), soil moisture and soil temperature.
Forest management issues addressed: effects of variable retention on the survival and growth of the next crop across a wide range of sites and conditions. An analysis and modelling framework that integrates numerous components including retained trees, natural regeneration and planted trees. We expect our results to have some influence on timber supply sensitivity analyses and silvicultural prescriptions at stand edges. The development of a new unbiased sampling system, sector sampling was specially designed to sample variable retention.
The intent of this final year is to summarize our findings on sector sampling, measure critical data in a dispersed experiment and maintain field experimental data so that we may enable future measurement ("data protection"). As part of this project we request assistance in:1) Measuring one dispersed retention study at TM128 (with a random allocation of clearcut, 5% and 15% dispersed retention) we will measure planted trees only: maintenance at 5599 (a group size experiment- small (0.1ha), medium (0.25ha) and large (1ha) retention); OP0185 (a group removal with small (0.1ha,), medium (0,25ha) and large (1ha) patch removal); Nanaimo Lakes 45-104 (a dispersed retention (0%, 5% and 15% retention) experiment and MH4902 a mixed retention experiment. At TM128 we will measure planted trees and remove Elk protection cages and remove deciduous brush as needed. Maintenance includes maintaining Elk-protection cages/vexar at OP0185, tag maintenance at 5599 and general plot maintenance at Nanaimo Lakes 45-104 and MH4902. We will submit a dispersed comparison paper looking at 5 year response and have a short eight year response paper in draft form. 2) Updating our sector sampling work by generalizing all findings to date into a general sector sampling paper to form the basis of a journal aricle. This will include sector sampling and sub-sampling.
Related projects:  FSP_Y091064FSP_Y102064


Final technical report (0.4Mb)
Conference presentation on sector sampling (1.8Mb)

To view PDF documents you need Adobe Acrobat Reader, available free from the Adobe Web Site.

Updated May 19, 2011 

Search for other  FIA reports or other Ministry of Forests and Range publications.

Please direct questions or comments regarding publications to