Environmental conditions on wintering or spring-staging areas may influence subsequent reproductive performance in migratory birds. These cross-seasonal effects may result from habitat loss and degradation (e.g., via contamination) which in turn reduce reproductive success, particularly in waterfowl that use stored nutrients for reproduction. North American lesser scaup (<i>Aythya affinis</i>) and white-winger scoter (<i>Melanitta fusca</i>) numbers have declined over the past 20 years, particularly in the boreal forest, and remain well below conservation goals, whereas ring-necked duck (<i>A. collaris</i>) numbers have increased. Environmental changes on scaup and scoter wintering and staging areas have raised concern about possible cross-seasonal effects on birds arriving on breeding grounds. The spring condition hypothesis (SCH) purports that many female scaup fail to acquire sufficient nutrients in late winter and spring, causing a decrease in breeding propensity and productivity. The contaminant hypothesis proposes that increased exposure to contaminants (particularly selenium [Se]) on wintering and staging areas has decreased scaup productivity. Accordingly, I compared body condition and studied Se concentrations in scaup, scoters and ringnecks to test the condition and contaminant hypotheses. <p>Scaup had similar body condition to ringnecks, and had similar body mass compared to scaup collected near Yellowknife, NT, in 1968-70. There was no relationship between scaup and ringneck nutrient levels and claw tip carbon, nitrogen or hydrogen isotope values, suggesting that arrival body condition likely was not related to location or diet several months prior. Instead, scaup and ringnecks nutrient levels may be more affected by feeding or habitat conditions on or near the breeding grounds. Scaup had slightly higher liver Se concentrations than ringnecks, but levels in both species were below recognized harmful threshold concentrations; I found no relationship between Se and breeding propensity, or between Se and somatic lipid or protein stores. Scoters had much higher Se concentrations, yet contrary to predictions, there were positive relationships between Se and both lipid stores and breeding status. Follicle [Se] in scaup was below threshold concentrations; despite high liver Se in scoters, egg and follicle levels also were well below threshold concentrations. Using both body composition analysis and stable-isotope analysis I determined that scoters derive egg protein from their breeding ground diet, which likely prevents Se deposition from somatic protein to eggs, and egg lipids are apparently derived from somatic tissues. In all three species, liver Se concentrations were significantly correlated with claw tip ä15N. As the claw tip likely represents assimilated diet from 2-5 months prior to sampling, this correlation suggests that Se in these boreal breeding species is carried over from wintering and staging areas. <p>Overall, results did not support either the spring condition or contaminant hypotheses. Scaup and scoters are late-nesting species, with highest pair densities occurring at the northern extent of their range. Maximum ring-neck pair densities occur at more southern latitudes. Ring-necks also nest earlier and appear to be more flexible in timing of nest initiation. Therefore, it is possible that due to climate change, early spring conditions alter the optimal timing of nest initiation to the detriment of late-nesting species such as scaup and scoters, and favour earlier nesters like ringnecks. Further research into this mismatch hypothesis is warranted.

Albertas oil sands are located in the boreal forest where surface mining disturbs huge tracts of land. One such area, Syncrude Canada Ltd.s Mildred Lake mine, contains waste overburden (OB) piles which can be saline and sodic (SSOB). The objectives of this research were to 1) determine SSOB material impacts on planted tree root distributions, 2) quantify root activity to identify plant species growing at depth, and 3) document coarse woody root structure for planted trees. Root distributions for three mixedwood stands on reclaimed OB in relation to electrical conductivity (EC) and sodium absorption ratio (SAR) were examined using soil cores. Root distributions followed a similar pattern with soil depth as those from undisturbed boreal forest stands and appeared unaffected by the SSOB at this stage; however, future monitoring will be required as the stands mature. Root activity was assessed for jack pine (jP) and white spruce (wS) stands on tailings sand (TS) and OB using a strontium (Sr) chloride tracer. Understory and tree foliage was collected prior to and after application to measure Sr concentration in the control, broadcast, and depth treatments. A small proportion of roots grew in the OB material regardless of its chemical properties. Results from the Sr tracer study suggested that these roots were probably from the clover, sow thistle, and grasses. Planted trees showed little to no change in Sr tissue content suggesting that there were little to no roots in the treatment zones, the understory species out-competed the trees for Sr accessibility, or the tracer was diluted in the tree biomass to undetectable levels. Root systems of planted jP trees older than 10 years and older than 20 years on TS and OB were excavated and the number and diameter of lateral roots, the degree of kinking and coiling, and the presence of a taproot were recorded. Excavated trees showed poor taproot development on 70% of the trees and numerous root deformities, suggesting that more emphasis is needed in correct planting techniques and good planting stock to ensure proper root development. Roots are critical components of boreal forest ecosystems; without healthy root systems productivity may decline, stands may be susceptible to windthrow, and general forest health may suffer.

Despite the spatial significance of Canadas boreal forest, there is very little known about greenhouse gas emissions within it. The primary objective of this project was to study the atmosphere-soil exchange of CH4 and N2O in the boreal forest of central Saskatchewan. In the summers of 2006 and 2007, greenhouse gas emissions were measured along transects in three different mature forest stands (trembling aspen, black spruce and jack pine) using a sealed chamber method. In addition, the gross rates of mineralization and nitrification, and the relative contribution of nitrification and denitrification to N2O emissions, were measured at the trembling aspen site using a stable isotope technique in which 15N-enriched nitrate and ammonium were injected into intact soil cores. The amount of 14N found in the labeled pools was used to measure the gross rates, and the amount of 15N found in the emitted N2O was used to determine the relative contribution of the different N pathways to total N2O emissions. Results indicated that the jack pine and black spruce sites were slight sinks of CH4 (-1.23 kg CH4-C ha-1 yr-1and -0.17 kg CH4-C ha-1 yr-1 respectively in 2006 and -0.95 kg CH4-C ha-1 yr-1and 0.45 kg CH4-C ha-1 yr-1 respectively in 2007), whereas the trembling aspen site was a net source (46.7 kg CH4-C ha-1 yr-1 in 2006 and 196.0 kg CH4-C ha-1 yr-1 in 2007). All three sites had very low cumulative N2O emissions, ranging from -0.02 to 0.14 kg N2O-N ha-1 yr-1 in both years. Of the environmental controls examined for CH4, consumption at the jack pine site was correlated positively with organic carbon and negatively with water-filled pore space. Black spruce CH4 emissions were correlated negatively with both organic carbon and clay content, and emissions at the trembling aspen site were positively correlated with soil temperature and organic carbon, while also related to the presence of standing water (2006 and 2007 had very high precipitation, causing a high water table and ponding in depressions). The N2O emissions were not correlated with any of the environmental parameters measured at the jack pine or black spruce sites, but clay content was positively related to emissions at the trembling aspen site. The 15N results indicated that N cycling at the trembling aspen site was very rapid, allowing little N to escape the system as N2O; the majority of emissions that did occur were due to a nitrification-related process.

Thesis (Ph. D.)--Bryn Mawr college. / Bibliography; p. 145-152.

The Slate Islands caribou (Rangifer tarandis caribou) is an insular population which has experienced several population crashes and has been described as likely to succumb to extirpation. While a great deal of research has been conducted on mainland woodland caribou, factors which influence caribou distributions may differ between island and main land populations. In this thesis, I investigate relationships between habitat, landscape, anthropogenic features, population size, predation and spatial distribution of woodland caribou across the Slate Islands Provincial Park (Ontario) at the forest-patch spatial scale. Generalized linear models were used to compare observed caribou locations to available locations across the park, based on data from 1978 to 1995. Results indicated that the Slate Islands caribou selected deciduous cover, larger forest patches, areas further to water, flatter areas, lower elevations and areas closer to anthropogenic features. Population size had a limited effect on caribou distributions. / October 2015

Anthropogenic climate change is expected to dramatically affect boreal forests, not only through warming effects, but through changes in seasonal and diurnal temperature patterns, precipitation, cloud-cover, and direct effects of rising CO2. My doctoral research examines the impact of these changes on dominant boreal forest conifer species, using dendrochronological methods. Through my analysis of white spruce (Picea glauca) and lodgepole pine (Pinus contorta) tree rings across five Yukon Territory sites, I found that white spruce growth is showing growth declines in response to all three measured climate changes, with negative correlations between tree ring increment and spring and summer temperature, spring frost events, and growing season cloud cover. Lodgepole pine populations exhibited growth enhancement with increasing spring maximum daily temperatures, but generally neutral responses to warming summers, higher frost event frequency and increased cloud cover. To evaluate the effect of rising CO2 on boreal forest growth, I examined three representative managed forest stands across Canada, first building a model of climate effects, and examining temporal trends in the residual growth patterns. I found evidence for CO2 fertilization in Ontario black spruce (Picea mariana) and Manitoba white spruce populations, particularly at younger ages, but no growth enhancement in Yukon lodgepole pine. These results taken together suggest that Yukon white spruce may suffer pronounced growth declines under continued climate change, but more eastern spruce populations may be better able to benefit from increased carbon availability. Yukon lodgepole pine populations are less vulnerable to the impacts of climate change, but are also unlikely to exhibit significant growth increases in response to increasing temperature, frost events, cloud cover or rising CO2. The results from this thesis have important implications for future management of the Canadian boreal forest under progressive climate change.

The aim of this study was to investigate the importance of winter season for the production of carbon dioxide (CO2) and methane (CH4) in humic and clear-water boreal aquatic systems. The study was conducted in 16 experimental ponds in northern Sweden during the winter of 2013. Half of the ponds had a higher concentration of dissolved organic carbon (DOC). CO2, CH4, DOC and dissolved inorganic carbon (DIC) were measured repeatedly under the ice from January to April. The results show that CO2 was accumulated continually during winter. No difference in winter accumulation were found between humic and clear ponds. CH4 was rarely accumulated in neither humic nor clear ponds, and was not an important part of the gas flux at spring ice melt. At ice melt, the flux from humic ponds accounted for 1.6 g C m-2 and 1.7 g C m-2 from clear ponds, which was equivalent for 15.6% respective 100% of the annual gas emissions. On a whole-year basis humic ponds acted as a source of 10.3 g C m-2, while clear ponds acted as a sink of 14.7 g C m-2. 76 mg m-2 d-1 DOC was consumed in humic and 59 mg m-2 d-1 DOC in clear ponds while the DIC accumulation was 125 mg m-2 d-1 in humic and 118 mg m-2 d-1 in clear ponds. This study stresses the importance of ice-covered boreal aquatic systems as a significant parts of the global carbon cycling.

Anthropogenic climate change is expected to dramatically affect boreal forests, not only through warming effects, but through changes in seasonal and diurnal temperature patterns, precipitation, cloud-cover, and direct effects of rising CO2. My doctoral research examines the impact of these changes on dominant boreal forest conifer species, using dendrochronological methods. Through my analysis of white spruce (Picea glauca) and lodgepole pine (Pinus contorta) tree rings across five Yukon Territory sites, I found that white spruce growth is showing growth declines in response to all three measured climate changes, with negative correlations between tree ring increment and spring and summer temperature, spring frost events, and growing season cloud cover. Lodgepole pine populations exhibited growth enhancement with increasing spring maximum daily temperatures, but generally neutral responses to warming summers, higher frost event frequency and increased cloud cover. To evaluate the effect of rising CO2 on boreal forest growth, I examined three representative managed forest stands across Canada, first building a model of climate effects, and examining temporal trends in the residual growth patterns. I found evidence for CO2 fertilization in Ontario black spruce (Picea mariana) and Manitoba white spruce populations, particularly at younger ages, but no growth enhancement in Yukon lodgepole pine. These results taken together suggest that Yukon white spruce may suffer pronounced growth declines under continued climate change, but more eastern spruce populations may be better able to benefit from increased carbon availability. Yukon lodgepole pine populations are less vulnerable to the impacts of climate change, but are also unlikely to exhibit significant growth increases in response to increasing temperature, frost events, cloud cover or rising CO2. The results from this thesis have important implications for future management of the Canadian boreal forest under progressive climate change.

Freshwater ecosystems have long been neglected as an important part of the global carbon cycle. However, research shows that most of the world’s lakes are net-heterotrophic and consequently emitters of greenhouse gases to the atmosphere. In many boreal and north-temperate lakes, most of the yearly emissions usually occur in spring, shortly after ice-thaw. The aim of this study was to quantify the flux of carbon dioxide (CO2) and methane (CH4) in three boreal lakes, during this annual event. In order to do this, water samples were collected before and after ice-thaw, and the flux was estimated as the difference in mass of carbon between the two sampling occasions. The results showed that the lakes had accumulated high amounts of carbon over the winter, with higher concentrations generally at higher depths. The fluxes during ice-thaw ranged from 234–380 (mean: 302) and -1.15–15.12 (mean: 8.64) mmol m-2 y-1 for CO2 and CH4, respectively. Given their small sizes, the lakes emitted less carbon, per unit area, than expected. This was assumed to be due to the lakes’ rather isolated locations and since the heating of the water rapidly caused them to become highly stratified, thus preventing the wind from releasing deeper stored carbon. Presumably, this holds true for other similar boreal lakes as well, which suggests that attention – in such ecosystems – also needs to be brought to other mixing periods.

The main aim of this study was to analyse the long-term effects on epiphytic lichen dry mass development, diversity and community structure after exposure to a simulated nitrogen deposition gradient. A whole tree experiment was set up in a boreal forest in the County of Västerbotten in Sweden, whereby 15 trees were artificially irrigated and nitrogen fertilized during seven consecutive years (2006-2012). The treatments were equal to an additional deposition of 0.6, 6, 12.5, 25 and 50 kg N ha-1 yr-1. Branches from the trees were collected in October 2012 and the lichen material was harvested and further analysed during the spring 2013. The results from this study showed that the lichens were directly affected by the long-term increased nitrogen deposition. Generally, lichen dry mass and species richness declined at high nitrogen loads and the initial positive effects of low nitrogen loads reported in a preceding study had thus depressed with time. The results from this study also showed that the composition of the lichen community changed benefitting nitrogen-tolerant species, probably not because of competition but more likely because of nitrogen-sensitive species disappearance. This study strongly indicates that it takes more than a few years to detect changes in lichen communities exposed to enhanced nitrogen loads. In addition low concentrations seem to have a cumulative impact. Consequently, this study stresses the importance of also considering the cumulative effect of low nitrogen loads when determining critical values. The critical load for lichen communities in boreal forests might be below 6 kg N ha-1 yr-1.