Tree diversity and treatment cost effectiveness responses of vegetation release ten years after treatment

This thesis synthesizes two papers in journal article format, on the effects of vegetation release treatments on boreal tree species. For both papers, field data was collected 10-years after alternative vegetation release. The first paper investigates tree diversity responses for six early seral boreal forest plantations in Ontario, Canada, representing three conifer species; black spruce [Picea mariana (Mill) B.S.P.], white spruce [Picea glauca (Moench) Voss] and jack pine (Pinus banksiana Lamb.), 14 release treatments and 94 experimental units. Dominance-diversity curves and Simpson's indices of diversity and evenness indicate tree alpha diversity. I propose a new method for assessing diversity, percentage of theoretical species maximum (%TSM); which is determined by comparing post-disturbance richness (S) with a theoretical species maximum (TSM). Results support the hypothesis that, "alternative vegetation release treatments generally do not significantly reduce diversity levels (%TSM) when compared to untreated plots (a priori planned comparisons)." Results also support the hypothesis that "tree monocultures do not develop after vegetation release." Only one out of 94 experimental units developed into a tree layer monoculture (Simpson's reciprocal diversity index = 1) at a site that was intensively treated with annual applications of herbicide.;Key words. Biodiversity, glyphosate, herbicide alternatives, plantation, mixedwood, orthogonal contrasts, pesticide, rank abundance plots, triclopyr, vegetation release, weed;The second paper utilizes a cost effectiveness analysis to investigate the relationship between white spruce gross total volume, and estimated current treatment costs based on detailed treatment time study data at the white spruce site. Only the white spruce site was included in the cost effectiveness analysis because detailed time-study data was only available for that site. This study is important, since very few cost-effectiveness studies of vegetation management in conifer plantations are reported in the literature. Individual treatment costs were estimated by pricing out 2003 values by consulting silviculture vegetation release companies. The most cost effective treatment was the aerial application of herbicide Vision (...