A dendrochronological study was used to evaluate growth impacts on White Spruce (Picea glauca (Moench)) resulting from the 1982 Lodgepole sour gas well blowout. Stem analysis was evaluated from four ecologically similar monitoring sites located on a 10 kilometre downwind gradient and compared to a control site. Incremental volume was calculated, standardized using running mean filters and analyzed using one-way ANOVA. Pre and post-blowout growth trends were analyzed between sites and were also evaluated over a height profile in order to assess growth impact variability within individual trees.
Growth reductions at the two sites closest the wellhead were statistically significant for five post-blowout years. Growth at these condensate impacted sites was reduced to 9.8 % and 38.1 % in 1983. Differences in growth reductions reflect a gradient of effects and a dose-response relationship. Recovery of surviving trees was been rapid but is leveling off at approximately 80 % of pre-blowout growth. Growth reductions were greater and recovery rates slower than those previously predicted by other authors.
Statistically significant differences in height profile growth responses were limited to the upper portions of the trees. Growth rates over a tree height profile ranged from 10 % less to 50 % more than growth rates observed at a 1.3 metres. Analytical methodologies detected and described growth differences over a height profile but a larger sample size was desirable.
As is always the case in catastrophic events, obtaining pre-event baseline data is often difficult. Dendro-chronological methods described herein offer techniques for determining pre-blowout growth and monitoring impacts and recovery in forested areas.