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This project is a continuation of the two year Y082001. In that project critical long-term data from a set of 10 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). In this next phase we plan to collect critical data from additional established sites and continue 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 three smaller scale (~40ha) experimental areas were recently established (2001+) across Western Forest Products landbase (Beese et al. 2005). The intent is to examine the effects of different amounts and patterns of variable retention on the response of retained and planted trees and natural regeneration. This includes 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. Each site permanently monitors 3000- 5000 planted trees, 3000+ tagged natural regeneration trees and 500-1500 retained trees measured on a 1,3,5,8 and 10 year cycle (+/- 1 year).
Within these experimental areas ?sector plots? have been established to examine the effects of forest edge on growth (Iles and Smith, 2006, Smith et al., 2008). The sector plots are designed to sample growth response gradients across variable retention edges; 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 natural and planted seedling and retained tree responses at the two sites including previously collected data. Results to date show that seedling and natural regeneration growth peaks at a distance (generally 15-20m) from edges, patches or individual trees. A light model run alone does not fully explain this response but it is hypothesized that it may be additionally linked to moisture or other below ground effects. Data collected using separate funding include light (direct and diffuse), soil moisture and soil temperature. These variables and distance from edge will be used to examine the responses of the trees and seedlings measured as part of this project. Note that Y081210 is a complementary project aimed at measuring additional experimental and edge sites and includes a more thorough and comprehensive analysis of growth responses across all sites measured to date. (See Experimental Design).
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 ...
Smith, Nick J., Iles, Kim; Raynor, Kurt. 2009. Effects of variable retention on planted and natural regeneration in Coastal BC. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2009MR029
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), British, Columbia
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