Target diameter harvesting (TDH) is a forest management system in which all stems above a set minimum diameter are harvested on a periodic basis. There is evidence in the literature that TDH can achieve a rate of return on a similar scale to a clearfelling regime, with added benefits of regular cash flow from partial harvests, and preservation of non-timber values. Economic analysis was carried out on 12 years of TDH using permanent sample plot (PSP) data from Woodside Forest, a 30ha plantation of radiata pine (Pinus radiata). The Woodside Forest management regime has a target diameter of 60cm, and a harvest cycle of two years. Economic analysis considered the option to partial harvest or clearfell every two years, and compared the outcome of each option in terms of land expectation value (LEV). Comparisons are made between regimes with different numbers of partial harvests, assessing the effect of TDH on stand LEV. Results show that in three of four applicable stands, LEV reached a maximum at ages 30 – 32, (near the time when partial harvesting commenced), and reduced slowy with increased numbers of partial harvests. This shows there is a small opportunity cost associated with choosing TDH over a clearfell system. The effect of revenue from early partial harvesting operations on LEV was small as the majority of stand value is still in the standing crop. This limited the conclusions that can be drawn form this study due to the short time frame analyzed. The study was limited by a small dataset which did not accurately represent average stand values. Because of this, no attempt to quantify the value of the opportunity costs was made. Despite this, the results support the notion that TDH can achieve economic returns similar to clearfelling in radiata pine forests.

Bringing together field-based empirical studies, a simulation modelling experiment, and a critical analysis of the natural disturbance emulation paradigm, this thesis evaluates partial harvesting in the black spruce boreal forest. Forest management in Ontario is required to emulate natural disturbances, but in regions of the boreal forest where fire cycles are long, regulated even-aged management by clearcutting has truncated forest age-class distributions. Partial harvesting has been proposed as a means to maintain the structural complexity and biodiversity associated with old forests while allowing continued timber production. Despite the potentially important role of partial harvesting in a strategy for sustainable boreal forest management, little research has examined post-harvest stand development, a critical determinant both of habitat and timber supplies.I used a chronosequence approach in combination with dendroecological techniques, a neighbourhood modelling framework, and maximum likelihood statistical methods to quantify stand dynamics over the first decade after partial harvest in the black spruce (Picea mariana) boreal forest of northeastern Ontario, Canada. Residual trees displayed large but time-lagged growth responses to partial harvest. The largest responses were found in young trees, while old trees were largely unable to react to improved post-harvest resource availability. Growth responses were offset by elevated rates of residual-tree mortality, which peaked in the first year after harvest at nearly 13 times the pre-harvest level. Proximity to harvest machinery trails severely escalated the risk of mortality for residual trees. Considering growth and mortality responses together in a forest simulator model, I found that stand development proceeded most rapidly where skidding intensity was reduced and retention areas were aggregated. Given appropriate prescriptions, my results indicate that partial harvesting can be a viable silvicultural option for black spruce boreal forests. However, the ability of partially harvested stands to emulate natural disturbance is questionable, particularly given the strong influence of harvest machinery impacts on post-harvest stand development. I argue that the natural disturbance emulation framework has important flaws and falls short of a justifiable approach for forest management in Ontario.

Bringing together field-based empirical studies, a simulation modelling experiment, and a critical analysis of the natural disturbance emulation paradigm, this thesis evaluates partial harvesting in the black spruce boreal forest. Forest management in Ontario is required to emulate natural disturbances, but in regions of the boreal forest where fire cycles are long, regulated even-aged management by clearcutting has truncated forest age-class distributions. Partial harvesting has been proposed as a means to maintain the structural complexity and biodiversity associated with old forests while allowing continued timber production. Despite the potentially important role of partial harvesting in a strategy for sustainable boreal forest management, little research has examined post-harvest stand development, a critical determinant both of habitat and timber supplies.I used a chronosequence approach in combination with dendroecological techniques, a neighbourhood modelling framework, and maximum likelihood statistical methods to quantify stand dynamics over the first decade after partial harvest in the black spruce (Picea mariana) boreal forest of northeastern Ontario, Canada. Residual trees displayed large but time-lagged growth responses to partial harvest. The largest responses were found in young trees, while old trees were largely unable to react to improved post-harvest resource availability. Growth responses were offset by elevated rates of residual-tree mortality, which peaked in the first year after harvest at nearly 13 times the pre-harvest level. Proximity to harvest machinery trails severely escalated the risk of mortality for residual trees. Considering growth and mortality responses together in a forest simulator model, I found that stand development proceeded most rapidly where skidding intensity was reduced and retention areas were aggregated. Given appropriate prescriptions, my results indicate that partial harvesting can be a viable silvicultural option for black spruce boreal forests. However, the ability of partially harvested stands to emulate natural disturbance is questionable, particularly given the strong influence of harvest machinery impacts on post-harvest stand development. I argue that the natural disturbance emulation framework has important flaws and falls short of a justifiable approach for forest management in Ontario.