This thesis aims at bringing about a greater awareness of the interpretive nature of forestry sciences by examining the ethics and values underlying the “Emulation of Natural Disturbance” (END) forest management approach in Canada. The thesis contains four main manuscripts. The first manuscript reports on a mental models analysis of the meaning of the END for academic forestry scientists across Canada. The results of this study indicate inconsistencies and contradictions between scientists’ mental model of the END, which puts into question the utility and appropriateness of the END for forestry policy. The second manuscript discusses the ethics underlying the END and critiques its policy implications from a pragmatic perspective. In the third manuscript the ethics and values underlying the END are put in relation with Holmes Rolston III’s ethics of “Following Nature”. The last manuscript reports on a survey of forestry curricula across North America conducted to ascertain the level of formal training in ethics afforded to professional foresters and natural resource managers. This manuscript contains a proposed course syllabus in forestry ethics. The curricula study complements the other manuscripts in that it is meant as another means by which to promote interdisciplinary dialogue among forestry scientists, environmental ethicists, and social scientists. In this thesis, in addition to trying to illustrate how ethics shape our interpretations of forests, a pragmatic approach is used to dissolve the fact/values and Nature/Culture dichotomies in forestry sciences and to argue for a more democratic approach to forestry policy.

Forest management practices in Ontario are required to emulate natural disturbance in an effort mitigate the anthropological impact on the environment. This is enforced by the Crown Forest Sustainability Act, initiated in 1994, yet inadequate research has been done to support management techniques that satisfy the legislation in regards to the plant diversity and community composition. A series of 435 plots on 139 sites were established in Northern Ontario, consisting of stands of various ages and disturbance origins. Plant diversity and community composition were estimated with a variety of diversity indices and multivariate community analyses. My results show that managed stands are more diverse than those with a natural disturbance origin based on multiple diversity indices. Detrended Canonical Correspondence Analyses revealed considerable variation in community composition among all stands. Plant communities differ between the stands of different disturbance origins (managed/unmanaged), and these differences are influenced by stand age. These results reject the hypothesis that current forest management practices emulate natural disturbance. / Forest Ecosystem Science Coop Inc NSERC CRD Program NSERC Strategic Grant Progam Ontario Ministry of Natural Resources Canadian Forest Service

This thesis aims at bringing about a greater awareness of the interpretive nature of forestry sciences by examining the ethics and values underlying the “Emulation of Natural Disturbance” (END) forest management approach in Canada. The thesis contains four main manuscripts. The first manuscript reports on a mental models analysis of the meaning of the END for academic forestry scientists across Canada. The results of this study indicate inconsistencies and contradictions between scientists’ mental model of the END, which puts into question the utility and appropriateness of the END for forestry policy. The second manuscript discusses the ethics underlying the END and critiques its policy implications from a pragmatic perspective. In the third manuscript the ethics and values underlying the END are put in relation with Holmes Rolston III’s ethics of “Following Nature”. The last manuscript reports on a survey of forestry curricula across North America conducted to ascertain the level of formal training in ethics afforded to professional foresters and natural resource managers. This manuscript contains a proposed course syllabus in forestry ethics. The curricula study complements the other manuscripts in that it is meant as another means by which to promote interdisciplinary dialogue among forestry scientists, environmental ethicists, and social scientists. In this thesis, in addition to trying to illustrate how ethics shape our interpretations of forests, a pragmatic approach is used to dissolve the fact/values and Nature/Culture dichotomies in forestry sciences and to argue for a more democratic approach to forestry policy.

I assessed the relationship between natural disturbances and climate in Douglas-fir forests in western North America. I quantified synchrony within disturbance types, explored the potential for synergism between disturbance types, and analyzed changes in disturbance dynamics that have occurred following Euro-American settlement of western North America. I used new and previously published dendrochronological reconstructions of disturbance histories and climatic variability to explore these complex interactions at multiple spatial scales over the last three centuries. I used dendroentomological methods to reconstruct western spruce budworm outbreaks at thirteen sites along a transect running from central Oregon to western Montana. These forests experienced repeated, often decadal-length western spruce budworm outbreaks over the last three centuries. I compared my records with previously published outbreak reconstructions and found widespread synchrony of outbreaks at stand-level, regional, and sub-continental scales. At ten of my sites, I also reconstructed or obtained previously published reconstructions of fire dates. I compared these disturbance histories with dendroclimatological drought records to quantify the influence of moisture availability on disturbances. I found that fires were more likely to occur during drought years, while western spruce budworm outbreaks were most likely to begin near the end of droughts. After approximately 1890, fires were largely absent from these sites and western spruce budworm outbreaks became longer-lasting, more frequent, and more synchronous, likely due to land-use induced changes in the structure and composition of forests. My results show no discernible impact of defoliation events on subsequent fire risk. Any effect from the addition of fine and coarse fuels during defoliation events was too small to detect given the overriding influence of climatic variability. If there is any relationship between the two disturbances, it is a subtle synergistic relationship wherein each disturbance type dampens the severity but does not alter the probability of occurrence of the other disturbance type over long time scales. This dissertation includes unpublished co-authored material. / 10000-01-01

This thesis aims at bringing about a greater awareness of the interpretive nature of forestry sciences by examining the ethics and values underlying the “Emulation of Natural Disturbance” (END) forest management approach in Canada. The thesis contains four main manuscripts. The first manuscript reports on a mental models analysis of the meaning of the END for academic forestry scientists across Canada. The results of this study indicate inconsistencies and contradictions between scientists’ mental model of the END, which puts into question the utility and appropriateness of the END for forestry policy. The second manuscript discusses the ethics underlying the END and critiques its policy implications from a pragmatic perspective. In the third manuscript the ethics and values underlying the END are put in relation with Holmes Rolston III’s ethics of “Following Nature”. The last manuscript reports on a survey of forestry curricula across North America conducted to ascertain the level of formal training in ethics afforded to professional foresters and natural resource managers. This manuscript contains a proposed course syllabus in forestry ethics. The curricula study complements the other manuscripts in that it is meant as another means by which to promote interdisciplinary dialogue among forestry scientists, environmental ethicists, and social scientists. In this thesis, in addition to trying to illustrate how ethics shape our interpretations of forests, a pragmatic approach is used to dissolve the fact/values and Nature/Culture dichotomies in forestry sciences and to argue for a more democratic approach to forestry policy. / Forestry, Faculty of / Graduate

Worldwide, riparian areas are considered among the most biologically productive and species-rich habitats on the landscape and provide important breeding areas for many bird species. In the Boreal Plain ecozone of western Canada, forests adjacent to riparian areas are generally protected from forest harvesting through the retention of treed buffer strips. <p>Riparian buffer strips are expected to provide habitat for wildlife including many passerine bird species. Recently, non-conventional methods of riparian management have been implemented in parts of the Boreal Plain with the intent of aligning forestry more closely with natural disturbance processes. How bird communities associated with these management scenarios diverge from natural disturbances and how riparian birds interact with disturbances in the adjacent upland habitat are key questions in the conservation of boreal riparian bird communities. To answer these questions, I surveyed birds inhabiting riparian areas with adjacent naturally disturbed (burned) and harvested forest to determine how bird communities differ early (1-5 years) post-disturbance and, separately, in a before-and-after harvesting study. <p>Riparian species associated with burned merchantable shoreline forests and riparian areas included Common Yellowthroat (<i>Geothlypis trichas</i>) and Eastern Kingbird (<i>Tyrannus tyrannus</i>). Le Contes Sparrow (<i>Ammodramus leconteii</i>) was associated with burned riparian habitats adjacent to non-merchantable forests (e.g., bog, fen), while Alder Flycatcher (<i>Empidonax alnorum</i>) and Wilsons Warbler (<i>Wilsonia pusilla</i>) were indicative of harvested sites with larger buffers (30 m). Riparian species richness was highest in burned non-merchantable sites. Multivariate Redundancy Analysis of post-disturbance bird communities showed greater divergence in overall (riparian and upland) community composition than one with only riparian species. This suggests reduced sensitivity of riparian birds to disturbances in forested areas compared to upland bird communities. However, a higher natural range of variability was exhibited in riparian bird community composition in post-fire sites than in post-harvested sites. This emphasizes that forest management practices do not currently fully approximate natural disturbance for boreal riparian birds. <p>To assess the response of bird communities in riparian habitats to forestry, I studied bird communities one year (2004) prior to forest harvest and two years (2005 and 2006) after harvest. One of three treatments, 1) 5-35% retention (0 m buffer), 2) 35-75% retention (10 m buffer with variable retention in the next 30 m), 3) 75-100% retention (50 m buffer) and unharvested reference sites, was randomly assigned to 34 wetlands. Treatments were designed to represent buffer management strategies currently applied in the Boreal Plain. Eight of 22 species showed a significant response (p<0.1) to treatment, year or year*treatment effects including two riparian species, the Common Yellowthroat and Song Sparrow (<i>Melospiza melodia</i>) that increased in abundance in harvested sites. Overall pre-disturbance communities diverged (p<0.05) over the three-year study period as shown using Multiple-response Permutation Procedures (MRPP). However, riparian bird communities did not diverge from pre-disturbance or from reference sites providing further evidence that riparian bird communities are less impacted by forestry in the adjacent upland habitats than overall bird communities. Therefore, alternative forest harvesting methods should be explored that encompass landscape-scale management including total buffer removal to maximize conservation objectives for boreal forest bird communities while attempting to maintain natural disturbance processes.

Worldwide, riparian areas are considered among the most biologically productive and species-rich habitats on the landscape and provide important breeding areas for many bird species. In the Boreal Plain ecozone of western Canada, forests adjacent to riparian areas are generally protected from forest harvesting through the retention of treed buffer strips. <p>Riparian buffer strips are expected to provide habitat for wildlife including many passerine bird species. Recently, non-conventional methods of riparian management have been implemented in parts of the Boreal Plain with the intent of aligning forestry more closely with natural disturbance processes. How bird communities associated with these management scenarios diverge from natural disturbances and how riparian birds interact with disturbances in the adjacent upland habitat are key questions in the conservation of boreal riparian bird communities. To answer these questions, I surveyed birds inhabiting riparian areas with adjacent naturally disturbed (burned) and harvested forest to determine how bird communities differ early (1-5 years) post-disturbance and, separately, in a before-and-after harvesting study. <p>Riparian species associated with burned merchantable shoreline forests and riparian areas included Common Yellowthroat (<i>Geothlypis trichas</i>) and Eastern Kingbird (<i>Tyrannus tyrannus</i>). Le Contes Sparrow (<i>Ammodramus leconteii</i>) was associated with burned riparian habitats adjacent to non-merchantable forests (e.g., bog, fen), while Alder Flycatcher (<i>Empidonax alnorum</i>) and Wilsons Warbler (<i>Wilsonia pusilla</i>) were indicative of harvested sites with larger buffers (30 m). Riparian species richness was highest in burned non-merchantable sites. Multivariate Redundancy Analysis of post-disturbance bird communities showed greater divergence in overall (riparian and upland) community composition than one with only riparian species. This suggests reduced sensitivity of riparian birds to disturbances in forested areas compared to upland bird communities. However, a higher natural range of variability was exhibited in riparian bird community composition in post-fire sites than in post-harvested sites. This emphasizes that forest management practices do not currently fully approximate natural disturbance for boreal riparian birds. <p>To assess the response of bird communities in riparian habitats to forestry, I studied bird communities one year (2004) prior to forest harvest and two years (2005 and 2006) after harvest. One of three treatments, 1) 5-35% retention (0 m buffer), 2) 35-75% retention (10 m buffer with variable retention in the next 30 m), 3) 75-100% retention (50 m buffer) and unharvested reference sites, was randomly assigned to 34 wetlands. Treatments were designed to represent buffer management strategies currently applied in the Boreal Plain. Eight of 22 species showed a significant response (p<0.1) to treatment, year or year*treatment effects including two riparian species, the Common Yellowthroat and Song Sparrow (<i>Melospiza melodia</i>) that increased in abundance in harvested sites. Overall pre-disturbance communities diverged (p<0.05) over the three-year study period as shown using Multiple-response Permutation Procedures (MRPP). However, riparian bird communities did not diverge from pre-disturbance or from reference sites providing further evidence that riparian bird communities are less impacted by forestry in the adjacent upland habitats than overall bird communities. Therefore, alternative forest harvesting methods should be explored that encompass landscape-scale management including total buffer removal to maximize conservation objectives for boreal forest bird communities while attempting to maintain natural disturbance processes.

Temperate forests are an important global carbon sink. However, various environmental disturbances can impact carbon sequestration capabilities of these forests. In 2021, a record-breaking defoliation, caused by the spongy moth (Lymantria dispar L., formerly knows as the gypsy moth) occurred in eastern North America. In this study, we assess the impact of this spongy moth defoliation on carbon uptake in a mature oak-dominated temperate forest in the Great Lakes region in Canada, using eddy covariance flux data from 2012 to 2022. The forest is more than 90 years old and known as CA-TPD site in the AmeriFlux and global FLUXNET networks. Study results showed that prior to spongy moth defoliation the forest was a carbon sink with mean annual gross ecosystem productivity (GEP) of 1,367 ± 104, ecosystem respiration (RE) of 1,201 ± 145 and, net ecosystem productivity (NEP) of 197 ± 74 g C m−2 yr−1 over the 2012–2020 period. However, due the defoliation in the early growing season in 2021, GEP declined to 959 g C m-2 yr-1 and RE increased to 1,345 g C m-2 yr-1 causing the forest to became a large source of carbon with annual NEP of -351 g C m-2 yr−1. This large decline in annual NEP was a result of both reduced GEP (30%) and elevated RE (12%). However, in 2022, forest carbon fluxes recovered to pre-infestation levels, with a GEP value of 1,671 g C m-2 yr-1, an RE value of 1,287 g C m-2 yr-1, and an NEP value of 298 g C m-2 yr-1, indicating that the forest was once again a large carbon sink. This research demonstrates that major transient natural disturbances such as the 2021 spongy moth defoliation can have a significant impact on forest carbon dynamics in a future warmer climate. The extent to which North American temperate forests will remain a major carbon sink will depend on the severity and intensity of these disturbance events and rate of recovery of forests following the disturbance. / Thesis / Master of Science (MSc) / Temperate deciduous forests play an important role in carbon sequestration from the atmosphere. However, the impact of climate change, extreme weather, and disturbance events can alter the extent to which these forests sequester carbon, in some cases shifting their role from being a carbon sink to becoming a carbon source to the atmosphere. In 2021, a spongy moth infestation severely defoliated a mature oak-dominated temperate forest north of Lake Erie, Ontario, Canada, turning the forest from a carbon sink to a carbon source. Our analysis indicates that meteorological conditions during the early spring might have influenced the severity of this infestation. Specifically, the prevalence of dry and warm weather conditions enabled the moth to survive and thrive longer. This study shows the significant influence of natural disturbances on forest carbon dynamics as temperatures continue to rise due to climate change. The future role forests play in carbon sequestration will be determined by the severity of disturbance events and the effectiveness of forests to recover in the aftermath of these events.

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.