Little research has been conducted on the sensitivity of earlywood vessel in ring-porous tree species in response to flooding. The impact of flooding and climate on vessel characteristics in black ash (Fraxinus nigra Marsh.) was studied in the boreal region of Lake Duparquet, northwestern Quebec. In addition to standard tree-ring measurements, numbers and cross-sectional area of earlywood vessels were examined and measured using an image analyzing program. Interestingly, among all Spearman rank correlations between chronologies and hydrologic/climatic variables, the strongest associations were found between earlywood vessel chronologies from floodplain trees and spring river discharge data. High water discharge in the spring was negatively correlated to earlywood vessel area and inversely correlated to number of vessels. The mean earlywood vessel area chronology developed from floodplain trees was found to be the best proxy for high magnitude flood events and it has potential to be used for flood reconstructions.

In the boreal forests of northeastern Alberta and northwestern Saskatchewan, one of the most abundant and reliable sources of lithic material was the Quarry of the Ancestors. This Quarry is located 50 km northwest of Ft. McMurray, AB and is the primary source of Beaver River Sandstone; a lithic raw material that dominates the archaeological stone tool and debitage assemblages in this region. Other lithic materials, such as quartzite, chert, and quartz, were accessible in gravel and glacial tills and in lakeshore and river beds scattered across northern Alberta and Saskatchewan. The analysis of stone tools from 31 archaeological sites spanning 260 km from the Quarry into the Descharme River system, in northwestern Saskatchewan, suggests that as pre-contact people moved across the landscape and away from the Quarry, they maintained and recycled their tools and used whatever other lithic resources were available. In contexts where there were issues with the availability, quality and abundance of lithic raw materials, the mobility of pre-contact hunter-gatherers may have been strongly influenced by the distribution of these lithic sources. However, the availability of food resources may have also been a strong influence over mobility patterns in circumstances where these lithic raw material issues were less marked. Northern Dene groups of this region are known to have travelled hundreds of kilometers seasonally following barren-ground caribou whose wintering grounds extended well into northwestern Saskatchewan. Through the distribution of lithic raw material and the analysis of lithic tool technology, I explore the role these two important resources had in shaping the overall organization of pre-contact hunter-gatherer mobility strategies employed in these two regions.

主催：JST/CREST，Vrije University, ALTERRA, IBPC

During oil-sands mining all vegetation cover, soil, overburden and oil-sand is removed, leaving pits several kilometres wide and hundreds of metres deep. These pits are reclaimed by a variety of treatments using mineral soil or a mixed peat and mineral soil as the capping layer and planted with trees with natural colonisation from adjacent sites. A number of reclamation treatments covering different age classes were compared with a range of natural forest ecotypes to identify the age at which the treatments become similar to a natural site with respect to vegetation composition and key soil attributes relevant to nutrient cycling. Ecosystem function was estimated from plant community composition, litter decomposition, development of an organic layer and bio-available nutrients. Key response variables including moisture, pH, C:N ratios, bio-available nutrients and ground-cover were analysed by non-metric multidimensional scaling and cluster analysis to discover which reclamation treatments were moving towards or merging with natural forest ecotypes and at what age this occurs. On reclaimed sites, bio-available nutrients including nitrate generally were above the natural range of variability but ammonium, phosphorus, potassium, sodium and manganese were generally very low and limiting to ecosystem development. Plant diversity was similar to natural sites from 5 years to 30 years after reclamation, but declined as reclaimed sites approached canopy closure. Grass and forb leaf litters decomposed faster than aspen or pine in the first year, but decomposition on one reclamation treatment fell below the natural range of variability. Development of an organic layer appeared to be facilitated by the presence of shrubs, while forbs correlated negatively with first-year decomposition of aspen litter. The better restoration amendments for tailings sands involved repeated fertilisation of peat: mineral mixtures in the early years of plant establishment, these became similar to a target ecotype at about 25 years. Good results were also shown by subsoil laid over non-saline overburden and fertilised once, these became similar to a target ecotype at about 15 years. Other treatments receiving a single application of fertiliser remain entrenched in the early reclamation phase for up to 25 years.

Post-fire survival, composition and regeneration of understory species in the boreal forest have shown to be affected by several factors, where consumption of the organic soil layer together with altered soil properties play important parts. There has however also been shown that the pre-fire site characteristics affect the post-fire understory vegetation. This study aimed to investigate the effects of fire and pre-fire site characteristics on understory regeneration and composition at a local scale in a boreal forest. Classification of species richness of the understory species together with measurements of biomass in terms of leaf area index (LAI) and normalized difference vegetation index (NDVI) were performed in a Pinus sylvestris forest in the Gärsjön catchment area, three years after a stand-replacing wildfire. Data of site index, fire severity on soil and moss, fire severity on shrubs, stand age, and remaining humus depth were also used. A total of 36 species of vascular plants (10 forbs, 14 graminoids, 5 dwarf shrubs, 2 ferns, 1 shrub and 4 trees) together with 3 species of bryophytes were recorded in the area. The study revealed that understory species composition was explained by remaining humus depth and site index. The regeneration of the understory was affected differently, where LAI was affected by site index, and NDVI was connected to both site index and fire severity on soil and moss. LAI and NDVI differed in their sensitivity in capturing differences among plant species, where higher values of LAI were associated to species such as E. sylvaticum, P. erecta, C. arundinacea and J. conglomeratus, while NDVI was related to both the ground and field layer, with high values associated to a high abundance of C. canescens and C. ovalis. According to my result, it can be concluded that NDVI is a more appropriate measure of post-fire re-establishment and recovery of understory vegetation in the boreal forest.

During oil-sands mining all vegetation cover, soil, overburden and oil-sand is removed, leaving pits several kilometres wide and hundreds of metres deep. These pits are reclaimed by a variety of treatments using mineral soil or a mixed peat and mineral soil as the capping layer and planted with trees with natural colonisation from adjacent sites. A number of reclamation treatments covering different age classes were compared with a range of natural forest ecotypes to identify the age at which the treatments become similar to a natural site with respect to vegetation composition and key soil attributes relevant to nutrient cycling. Ecosystem function was estimated from plant community composition, litter decomposition, development of an organic layer and bio-available nutrients. Key response variables including moisture, pH, C:N ratios, bio-available nutrients and ground-cover were analysed by non-metric multidimensional scaling and cluster analysis to discover which reclamation treatments were moving towards or merging with natural forest ecotypes and at what age this occurs. On reclaimed sites, bio-available nutrients including nitrate generally were above the natural range of variability but ammonium, phosphorus, potassium, sodium and manganese were generally very low and limiting to ecosystem development. Plant diversity was similar to natural sites from 5 years to 30 years after reclamation, but declined as reclaimed sites approached canopy closure. Grass and forb leaf litters decomposed faster than aspen or pine in the first year, but decomposition on one reclamation treatment fell below the natural range of variability. Development of an organic layer appeared to be facilitated by the presence of shrubs, while forbs correlated negatively with first-year decomposition of aspen litter. The better restoration amendments for tailings sands involved repeated fertilisation of peat: mineral mixtures in the early years of plant establishment, these became similar to a target ecotype at about 25 years. Good results were also shown by subsoil laid over non-saline overburden and fertilised once, these became similar to a target ecotype at about 15 years. Other treatments receiving a single application of fertiliser remain entrenched in the early reclamation phase for up to 25 years. / Forestry, Faculty of / Graduate

Biodiversity has been heavily impacted by anthropogenic landscape changes associated with natural resource extraction. Terrestrial mammals, which disproportionately maintain ecosystem functions, are among the species most affected by anthropogenic landscape changes. In turn, it is important that we incorporate mammal conservation into natural resource extraction to mitigate biodiversity change, for which we must better understand the dynamics of mammal communities. I used data from motion-activated camera traps deployed in the northwest Nearctic to investigate two aspects of mammal communities: how the environment shapes fine-scale mammal diversity and how mammalian predator species coexist. In my first study, I compared how well natural and anthropogenic landscape features explain fine-scale mammal diversity within and between six variably industrialized landscapes. I found that anthropogenic landscape features explain fine-scale mammal diversity better than natural features in heavily industrialized landscapes, where they may increase or decrease diversity. In my second study, I examined whether prey partitioning facilitates the coexistence of mammalian predator species in an industrialized boreal landscape. My findings suggest that sympatric predator species only partially partition prey, as some predator species had identical prey associations. Strikingly, though, I also found that all predators were positively associated with white-tailed deer, an invasive prey species made abundant by industrial landscape changes. Together, these findings reveal that industrial landscape changes significantly alter both the spatial distributions and predator–prey dynamics of mammal communities. This work can inform conservation and restoration strategies for slowing biodiversity change. / Graduate

Anthropogenic activities have increased nitrogen (N) emissions. However, higher N deposition is associated with negative fallouts in ecosystems, highlighting the necessity to define its critical load (CLO). Lichens, with their lack of roots, stomata, and cuticles, are helpful air pollution indicators and can be used to establish N CLO. Several studies report epiphytic lichens’ reaction to N deposition, but few have also focused on their recovery. In this study, I reproduced a deposition gradient to investigate epiphytic lichen biomass response to long-term N deposition. As such, whole trees were fertilized with 0.6, 6, 12.5, 25, or 50 kg N/ha/year from 2006 to 2012. In 2012, after six years of irrigation, Hypogymnia species and A. sarmentosa had altered biomass, and based on those results, a CLO below 6 kg N/ha/year is recommended for epiphytic lichens in the boreal forest. I also investigated the recovery of epiphytic lichens nine years after the simulated N deposition ceased. In 2021, a high increase in lichen biomass was recorded, suggesting that lichen growth rate is faster than previously assumed by other studies. However, biomass recovery was lower in high N treatments in Hypogymnia sp., Bryoria sp., and A. sarmentosa, suggesting those species recall the historical treatments possibly due to retained impairments. Since differences among treatments increased in the nine years after the simulated N deposition ceased, my results indicate that short-term negative effects of N deposition can have long-lasting effects on the epiphytic lichen community. Thus, I stress the importance of considering the recovery capability of different species during CLO determination to avoid underestimating the impact of N deposition.

Soil nutrient availability is a key component to understanding the boreal ecosystems, as it directly relates to plant productivity and ecosystem diversity. There is however little known about how the nutrient availability changes seasonally in the boreal forest. This study aimed to understand how soil temperature and nutrient availability changed seasonally as well as with or without reindeer grazing. This was done through measuring NH4, NO3, PO4, total N, and C:N ratio in soil samples taken in- and outside a reindeer exclosure in northern Sweden and then analyzing for differences over sampling time, grazing treatment, and the interaction of both. Differences in soil temperature were more extreme in the grazed areas, giving higher summer temperatures and lower winter temperatures, due to a decreased layer of insulating lichens. Increased soil temperatures also resulted in lowering the C:N ratio, possibly by enhancing the microbial activity leading to larger amounts of CO2 being released. No nutrients differed by grazing treatments, possibly due to the system being complex enough to contain contradicting effects. No systematical differences in seasonal nutrient levels could be found, which was deemed as surprising, but opens for the possibility of sampling one time being sufficient to have an approximation of nutrient levels all year round

A 7.09 m lacustrine sediment core was taken from Mariana Lake, Alberta (55º57'N, 112º01'W) to determine if the regional vegetational complex had been affected by the mid-Holocene Hypsithermal. Dating control was provided by 6 radiocarbon dates, with a second degree polynomial fitted to the dates to give an age to depth curve. The basal date of the core is 11 300 ± 110 yr BP. Fossil pollen analysis of the core revealed five distinct pollen zones. Between 11 856 and 10 434 yr BP the study site supported a sparse herb dominated vegetation. A spruce and shrub birch assemblage followed, from 10 434 to 9 100 yr BP, with increased vegetation density. The climate was likely similar to today. This was replaced by a paper birch and spruce complex from 9 100 to 7 638 yr BP likely as a result of warming climate. A mild Hypsithermal effect is recorded between 7 638 and 5 623 yr BP. A forest of decreased crown density was created, with spruce, paper birch and poplar being the major vegetational components. Modern conditions have existed at the site from 5 623 yr BP onwards, though it is hypothesised the regional water budget may have increased slightly around 2 228 yr BP; increased peat development appears to have occurred at this time. Through the use of difference diagrams the site is compared to three other published sites which, along with Mariana Lake, form a north-south transect from the southern Boreal Forest to the northern Alberta Boreal Forest. The hypsithermal vegetation changes varies with distance to the Parkland-Boreal Forest ecotone boundary. It is concluded the parkland did not reach Mariana Lake during the mid-Holocene, though conditions at the site became similar to those at the southern edge of the Boreal Forest that is proximal to the parkland. / Thesis / Bachelor of Arts (BA)