Basal area and diameter growth in high-graded eastern temperate mixedwood forests: the influence of acceptable growing stock, species, competition and climate
AbstractHarvesting practices in temperate mixedwoods of eastern North America have a history of diameter-limit cuts, which have often resulted in degraded residual stands. In this study, we examined the factors influencing stand basal area (BA) and tree diameter growth in previously high-graded mixedwood forests, to understand which stands are more likely to recover from high-grading. Over 15 years, we monitored tree growth, recruitment and stem quality of 532 sample plots that were located in high-graded stands of Quebec’s mixedwood forest. We found that diameter growth rates were positively correlated with precipitation-related variables for balsam fir (Abies balsamea) and for yellow birch (Betulla alleghaniensis) but opposing trends for temperature-related variables were found. Conversely to balsam fir, yellow birch growth was positively correlated to temperature variables. Our results also show that BA growth was greater for plots with a larger acceptable growing stock (AGS: trees with potential sawlog production) and that the increase in AGS was greater for plots with larger amount of conifer BA. These result highlights the importance to maintain a proportion of conifer trees in these mixed stands. Moreover, the significant effect of asymmetric competition in our study underscores the relevance of considering the spatial distribution when choosing crop trees.