Field performance of young forest trees in British Columbia has been related to their light environment (Carter and Klinka 1992; Chen 1997; Chen and Klinka 1998; Coates and Burton 1999; Drever and Lertzman 2001; Klinka et al. 1992; Mailly and Kimmins 1997; Mitchell and Arnott 1995; Wang et al. 1994; Wright et al. 1998). Survival and growth of understory trees, or trees adjacent to forest edges, can be substantially less than that of open-grown trees (Hansen et al. 1993; Mitchell 2001). Reduced field performance of these trees at or near forest edges may have important negative consequences for future stand growth and yield. This is particularly the case where partial cutting or variable retention harvesting systems are used as alternatives to traditional clearcut ? single cohort forest management practices. With partial cutting and variable retention harvesting, greater portions of regenerating stands are under the influence of residual stand trees. It is, therefore, of practical importance to develop a means of predicting the forest growth and yield consequences of forest practices that result in more spatially complex stands. In British Columbia, a spatially explicit model used to estimate growth and yield for simple, single species and single cohort stands (i.e. the Tree and Stand Simulator [TASS] see https://www.for.gov.bc.ca/research/gymodels/TASS/ ; Mitchell 1975) is now being modified for use with more complex forest stands containing multiple species and/or cohorts. In the new model (TASS-III), larger overstory trees exert a competitive influence on smaller (younger) understory trees by modifying the light available to the smaller trees, and hence affect their mortality and growth rates. Central to the development of TASS-III is the generation of predictive relationships between light, mortality, and growth for the economically important species in British Columbia, and, the development and linking of light models that can provide spatially explicit light estimates.
David G. Simpson.
Simpson, David G.. 2006. Light and tree growth in complex forest stands: FY 2005-06 annual progress report - April 2006. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2006MR148