Conversion of dense lodgepole pine stands in west-central British Columbia into young lodgepole pine plantations using prescribed fire. 2. Effects of burning treatments on tree seedling establishment

Abstract

The ecological effects of different treatments used to convert dense logdepole pine (Pinusconforta Dougl.) stands into young lodgepole pine plantations are being determined. The treatments used were bulldozing the trees and either broadcast burning the slash or bulldozing the slash into windrows, which were then burned. Burns were conducted under different fuel moisture conditions and state of fuel curing to achieve four classes of fire severity. Lodgepole pine seedling survival was affected by both site preparation and fire severity. Five years after outplanting, survival was significantly (p < 0.05) greater for areas between windrows (81%) than for areas beneath windrows (65%) or for broadcast-burned areas (67%). Survival was greatest after 5 years for low-severity burns in fresh slash (80%) compared with low-severity burns in cured slash and higher severity burns (67–69%). Seedling total height and height increment 5 years after outplanting were significantly greater (p < 0.05) in areas beneath windrows than in areas between windrows or in broadcast-burned areas. However, stem diameter was similar among all site preparation treatments. Fire severity had no effect on lodgepole pine total height, height increment, and basal diameter growth in any year after outplanting. Lodgepole pine seedling foliar nutrient levels were generally consistent with trends in seedling growth in that foliar concentrations generally tended to be higher when growth was higher (in the case of site preparation); however, no significant differences in growth were found (in the case of fire severity). This suggested that foliar nutrient levels could at least partly explain seedling growth results. Surface mineral soil (0–15 cm) chemistry exhibited similar trends to seedling foliar chemistry when site preparation treatments were compared, but not when fire severity classes were compared. This was attributed to foliar chemistry being controlled by factors other than soil chemistry alone.