Forest Investment Account (FIA) - Forest Science Program
FIA Project Y072051

    Modelling boreal mixedwoods (spruce-aspen-pine) with TASS
Project lead: Harper, George
Contributing Authors: Harper, George J.; Polsson, Ken R.; O'Neill, Meghan
Imprint: Victoria, BC : Ministry of Forests and Range, 2007
Subject: Forest Investment Account (FIA), Pinus, Picea, Populus Tremuloides, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
'best fit' theme: 3.1 Growth and yield modeling/predictions - Complex Stands. Project summary: We propose to develop TASS III understory spruce and pine height and diameter growth relationships to enable TASS simulations of aspen-spruce and aspen-pine boreal mixedwoods. This work will initially be based on a compilation of best available information from various published and unpublished sources. Further assessment and refinement of the TASS model will occur through comparison with field data obtained from specific boreal and sub-boreal mixedwood case studies. This is an incremental approach with early first approximation results in the first year and data collection and model refinements in the following two years. Background: The BC MoF Research Branch supports the development and maintenance of the Tree and Stand Simulator (TASS) and the extension tool TIPSY (Table Interpolations for Projecting Stand Yields (TASS yield tables)). TASS v. II is a spatially explicit, individual tree based model driven by height growth, crown expansion and bole increment (Mitchell 1975, For. Sc. Monograph 17). TASS III is a multi-canopy version of TASS II that includes a light model thereby enabling the simulation of understory light levels and plant growth. With the recent addition of aspen to TASS II, research will now focus on the biology of understory tree growth, light relationships and developmental patterns of species mixtures in boreal mixedwoods. Relationships between growth and light are becoming established in the literature and much new information is being made available on boreal forest dynamics. Light has been recognized as one of the key determinants of understory growth and survival (Williams et al. 1999, Chen et al. 1996, Kaufmann and Ryan 1986). The spatial modelling of both light and tree growth are not unique to TASS III. Other research groups have developed models linking light and forest growth (Lieffers et al. 2002, Comeau 2001, Gond et al. 1999). Recent TASS III developments have incorporated work by Carter and Klinka (1992) on the shade tolerance of coastal Douglas-fir, western hemlock and western redcedar. As well, work in progress by D. Simpson, BC MoF (FSP project # Y051092) is developing growth relationships for Interior Douglas-fir across a range of understory light conditions. First year project activities; 1) compile all available information from published and unpublished sources linking understory tree growth with the light dynamics of aspen-spruce and aspen-pine boreal mixedwoods, 2) summarize this information in a technical report with a gap analysis and recommendations for future data collection, 3) create first approximation TASS III growth curves for aspen-spruce and aspen-pine mixedwood simulations and, 4) incorporate TASS II aspen yields into the TIPSY database. Year 2 - 3 activities; 5) Based on the first year gap analysis, additional field data will be collected that relates tree growth and light levels. For this purpose, we will follow methods similar to those used by earlier researchers (Simpson et. al. 2003, Wright et. al. 1998) focusing efforts at previously established boreal and sub-boreal mixedwood research sites. (Deliverables: refinement of TASS III growth response functions and publication of an extension note describing the model). FSP objectives: This proposal is consistent with the vision of the FIA Forest Science Program (FSP) through addressing the strategic objectives of enhancing knowledge based science in support of sustainability and timber growth and yield. Currently TASS output (via TIPSY) is widely used for allowable annual cut determinations (managed stands) in BC. It is also used to determine the economic impacts of various management alternatives by predicting their effect on timber yield and quality. TASS/TIPSY can be used for any decisions requiring managed stand yield tables (e.g. timber supply analysis, development of silviculture strategies, development of stand management guidelines, habitat supply decisions). The anticipated outcomes of this research proposal include: Incorporation of aspen yields into the TIPSY database thereby enhancing estimation and evaluation of aspen management decisions (Aspen is the predominant leading species within boreal mixedwoods). A summary of understory growth patterns for spruce and pine within boreal mixedwood stands. This will improve our knowledge and understanding of boreal mixedwood dynamics and support science-based management decisions. TASS III understory growth calibration will support the development of biologically defensible growth and yield estimates for boreal mixedwoods and complex stands.
Related projects:  FSP_Y061051FSP_Y083051


Executive Summary (31Kb)
Report (0.2Mb)
Extension Note (5.1Mb)

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Updated August 16, 2010 

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