STANDING CROP, BIOMASS ALLOCATION PATTERNS AND SOIL-PLANT WATER RELATIONS IN SYMPHORICARPOS-OCCIDENTALIS HOOK - FOLLOWING AUTUMN OR SPRING BURNING

The impacts of autumn or spring burning on Symphoricarpos occidentalis were studied in Fescue Prairie in central Saskatchewan. Symphoricarpo s density increased two- to three-fold over preburn density in the lst 2 growing seasons following a burn. Individual shoot weights were app roximately one-third those of plants in reference (unburned) sites. Le aves that were approximately two to three times larger, combined with increased stem densities, enabled plants in burned stands to re-establ ish a leaf area index equal to reference sites within 2 mo of growth i n the lst growing season. Total standing crop of S. occidentalis was r educed only for the early part of the 1 st growing season following bu rning. In the lst growing season following burning, xylem water potent ials and stomatal conductance of burned plants equalled or exceeded th ose of reference sites. A delayed effect of burning was expressed in t he 2nd growing season, with soil moisture, xylem water potentials and turgor potentials being lower in burned plants than in the reference. Flexibility in resource allocation, with a larger proportion of biomas s in leaves, and unaffected or improved water status are adaptive feat ures that enable S. occidentalis to regain its position in the plant c ommunity the 1st growing season following disturbance by burning. One- time burning in autumn or spring should not reduce the dominance of S. occidentalis in this region.