A dendroecological investigation of inter-annual variability in growth, competition, and spatial pattern of jack pine forests

In this thesis, I studied the growth, competition and spatial pattern of mature, fire-origin, natural jack pine (Pinus banksiana Lamb.) forests along an ecoclimatic gradient in the boreal plains and boreal shield ecozones of Saskatchewan and Manitoba, Canada. The magnitude and causes of inter-annual variation in these processes requires further study. I used a dendroecological approach to obtain annual data on these processes, which provides more information than periodic data obtained from permanent sample plots. Understanding the magnitude and causes of inter-annual variability in these processes will be needed to adapt forest management practices to climate change effects. At each of 10 study plots, I measured and cross-dated ring widths on samples obtained from a complete census of all living and dead trees detectable at the time of sampling. I found that ring-width data at breast height could be scaled to tree level volume increment with a mean error of less than 10%, and that stand reconstructions were reliable for up to 50 years into the past in this region. I examined inter-annual variation in competition in relation to stand characteristics, disturbances, and inter-annual variation in both growth rate and growing conditions. Size and growth rate were considered independently using the Gini and Lorenz asymmetry coefficients, and concurrently with an index of competition asymmetry. Inter-annual variations in competition and growth rate were significantly related, suggesting that variation in growing conditions influences competition, a possibility that is not presently accounted for in forest growth and stand development models. I also examined temporal changes in the spatial distribution of live and dead trees, and these results did not support the hypothesis that competition always leads to spatial regularity.