Production Ecology and Stand Dynamics of Young Acadian Forest Stands in Response to Silvicultural Intensity and Compositional Objectives

Early successional stands are common across the Acadian forests of eastern Canada and the Northeastern US. However, productivity and dynamics of these stands, as well as the underlying mechanisms influencing these processes, under different management scenarios are poorly understood. To address this need, I used a factorial experiment that controlled silvicultural intensity and species composition to quantify the effects of varying treatments on early stand dynamics, and the physiological and morphological factors influencing tree performance . Specifically, I studied: 1) species differences in aboveground allometrics, 2) light capture, light-use efficiency (LUE; growth/light capture), and foliar carbon isotope composition (δ13C) of white spruce across a range of growing conditions, and 3) stand growth and yield in response to combinations of silvicultural intensity and compositional objectives. In Chapter 1, a new set of aboveground component biomass equations were developed for sapling-sized trees. In addition, I found that the Forest Inventory and Analysis (FIA) sapling biomass equations underestimated biomass between 10% and 36%, which corresponded to the loss of forest biomass in Maine when FIA switched to new equations. In Chapter 2, I found that aboveground productivity of white spruce seedlings was negatively correlated to competition and positively correlated to light capture. LUE was not correlated with inter-tree competition, suggesting the stands had not reached a density-dependent sorting stage, where use-efficiency tends to increase for dominant trees. δ13C was negatively correlated with competition suggesting that assimilation declined as trees became more light-limited. In Chapter 3, I found that a Populus nigra × P. maximowiczii clone outperformed three P. deltoides × P. nigra clones at the rocky, somewhat poorly drained site, while white spruce yield was negatively correlated with hybrid poplar yield in mixed plantations. Compositional objectives strongly influenced the productivity of naturally regenerated stands over a seven-year period after treatment in Chapter 4, indicating that stands can be directed into distinctly different trajectories depending on the silvicultural treatment. The approach used to study forest productivity in this experiment revealed that hierarchical responses (physiological, tree, and stand) to silviculture-induced growing conditions may influence the long-term trajectories of young Acadian forest stands in the region.

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