Graduate Students:
Chad Wardman Msc Graduate, 1997
Chad Wardman completed a General Arts Diploma at the University College of the Okanagan in 1992 and received his B.A. in Geography from Simon Fraser University in 1994. Chad completed his M.Sc. in Geography (forest ecology) at Simon Fraser University in 1997. He is currently working at Hugh Hamilton Consultants, specializing in forestry.
Summary of Research:
Growth Responses of Douglas-Fir and Western Hemlock Around Vine Maple Priority Gaps in Southwestern British Columbia
Vine maple is a shade-tolerant, multi-stemmed, deciduous tree of the understory of conifer forest in the Pacific Northwest. Vine maple is distinct in its ability to establish ‘priority gaps’ -- gaps that establish at the time of stand initiation and persist through several stages of forest development. Priority gaps represent distinct microenvironments within the forest ecosystem and provide a diversity of resources to flora and fauna.
On 20 paired plots, I examined the gap size, morphology of conifers, site chronologies and site productivity in 75 year old, Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) stands. For both species, trees on the edge of gaps had significantly larger crowns (182% for Douglas-fir and 132% for western hemlock) and boles (46% and 69%) than trees in the closed canopy. I found no differences in the patterns of radial growth between the sites for Douglas-fir or western hemlock sapling growth (~ 1 - 13 years breast-height age). For Douglas-fir on the edge of gaps, significantly higher annual basal area increments did occur in the years after 1945 due to the higher radial growth rates compared to Douglas-fir in the closed canopy. Western hemlock on the edge of gaps had consistently higher BAIs than hemlock in the closed canopy for 1945-1995, but the initial difference between the sites may have been due to the differing sizes of seedlings and saplings that occupied each site immediately after logging. Site index was significantly higher for Douglas-fir adjacent to the gap (42.6 m) than for Douglas-fir in the closed canopy (40.2 m), indicating vine maple may play an important role in the log-term productivity of these stands.
Median priority gap size was 79.9 m2 in Douglas-fir stands and 197.1 m2 in western hemlock stands. On Douglas-fir priority gap sites, potential growing space was 61% greater than that of closed canopy trees, but current BA productivity and site BA did not significantly differ from the adjacent canopy sites. The current BA productivity for western hemlock around the gap was only 62% that of western hemlock in the adjacent canopy, as western hemlock around the gap occupy 150% the potential growing space of western hemlock in the closed canopy.
Priority gaps offer an excellent opportunity for B.C. silviculturalists to meet biological and structural diversity goals by incorporating distinct microhabitats into management prescriptions. Integrating priority gaps into the stand mosaic was not associated with significant losses to timber production in the Douglas-fir stand, but was associated with losses in timber production in the western hemlock stand.
PUBLICATIONS
Wardman, C.W., and Schmidt, M.G. 1998. Growth and form of Douglas-fir adjacent to persistent vine maple gaps in southwestern British Columbia. For.Ecol.Mgmt. 106: 223-233.
Wardman, C.W. 1997. Growth responses of conifers around vine maple priority gaps in southwestern British Columbia. M. Sc. thesis. Department of Geography, Simon Fraser University. Burnaby, British Columbia.