Forest Investment Account

Abstract of FIA Project Y051286

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Montane alternative silvicultural systems (MASS): growth limitations on regenerating conifers

Author(s): Mitchell, A. K.
Imprint: B.C. : Canadian Forest Service, 2005
Subject: Forest Investment Account (FIA), Silvicultural Systems, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program


Montane forests contain a large part of the British Columbia potential coastal timber harvest for the next 25 years. Local and global demand to sustain non-timber values has raised concerns with clearcut-based silviculture. Coastal forest managers need to know where alternatives to clearcutting are operationally feasible, and whether they are economically and ecologically sound. In response to these concerns and to address the implementation and applicability of alternative silvicultural systems in coastal montane forests, a multi-agency cooperative, the Montane Alternative Silvicultural Systems (MASS) Partnership (Arnott and Beese 1997) was established in 1993. One of the primary objectives of the MASS partnership is to test new approaches for regeneration in silvicultural systems that retain different amounts and densities of overstory trees in the Montane Moist Maritime Coastal Western Hemlock biogeoclimatic variant (CWHmm2) of east Vancouver Island (Green and Klinka 1994). Coastal montane climates are characterized by a short growing season, winter snow pack, and slow decomposition rates that place unique biological and physical demands on regeneration (Koppenaal and Mitchell 1992). Studies investigating the relationship between the size of forest opening and growth of conifer regeneration in British Columbia have found that growth response and survival is influenced by regional climate (Wright et al. 1998b), species shade tolerance (Mitchell and Arnott 1995, Chen 1997, Kobe and Coates 1997), soil moisture (Carter and Klinka 1992), substrate (Wright et al. 1998a), nutrition (Hawkins et al., 2002) and temperature (Minore 1986). In accordance with the influence of residual overstory trees on regeneration microclimate we expected that differences in the size of forest opening and amount and distribution of retained trees among the silvicultural systems [Clearcut (CC), Green tree (GT), Patch cut (PC), and Shelterwood (SW)] would provide a wide range of light, temperature, evaporative demand, and to a lesser extent moisture, all of which can affect conifer growth and productivity directly or indirectly through competition for and availability (via changes in decomposition and mineralization rates) of soil nutrients (Prescott 1997). As part of the MASS project the three studies reported here build on long-term silviculture studies established since 1993 to provide scientific information on which to base management decisions for the regeneration of montane forests (Mitchell et al 2004). The regeneration studies reported here compare: 1. a) the effects of silvicultural alternatives on the growth and survival of planted dominant species (western hemlock and amabilis fir). b) the effects of vegetation competition and nutrient availability on the growth and survival of planted dominant species (western hemlock and amabilis fir) in relation to silvicultural alternatives. 2. the effects of silvicultural alternatives on the growth and survival of planted alternative species (Douglas-fir, western red cedar, yellow cedar). 3. the effects of soil disturbance resulting from harvesting in silvicultural alternatives on the growth and survival of western hemlock and amabilis fir.

For further information, please contact A. K. Mitchell, Canadian Forest Service (

Updated September 08, 2005 

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