The aim of this study was to determine if the occurrence, thalli length and cover of the epiphytic lichens Alectoria sarmentosa, Bryoria capillaris and Usnea dasypogea differ between sites with inland and coastal climate in Norrbotten county, Sweden. The trunk and branch diameter of the Picea abies trees, on which the lichens were inventoried, were measured as well. B. capillaris was the most common lichen species in both habitats. B. capillaris and A. sarmentosa had significant higher percentage occurrence in inland sites, while the occurrence of U. dasypogea was higher in the coastal sites. For B. capillaris, the percentage cover per branch was also higher in inland than in coastal sites. No significant difference in thallus lengths were found for any species. Obtained climate data suggest that humidity is higher inland, which is favourable for B. capillaris. Litterateur suggest that of all studied species, B. capillaris is the most common species in colder climates while A. sarmentosa is an intermediate and U.dasypogea is a lichen species normally occurring in warmer climates, which might explain their observed occurrence pattern outcome of the study. Linear regression was executed as well where only A.sarmentosa had significant and positive relationships to branch diameter. Other studies support the correlation with branch diameter but not with trunk diameter.

Forest fires occur frequently in the boreal forest of North America and greatly affect vegetation dynamics, biogeochemical cycles and resident human populations. Estimates of the frequency of boreal forest fires would be useful for understanding boreal ecosystems and managing the affects of fires on human populations. The objectives of this work were to investigate relations between fire frequency and climate change, vegetation)n type and waterbreaks in Wood Buffalo National Park (WBNP), located in northern Alberta. To address these objectives, four hypotheses were tested: 1) tree ring-width records from the boreal forest can provide a proxy climate record; 2) annual area burned in the boreal forest varies in response to climate changes; 3) boreal fores: fire frequency varies with differences in forest type and the proximity to waterbreaks and 4) fossil pollen and macroscopic charcoal records from massive lake sediments can provide meaningful estimates of local fire frequency. The first hypothesis was tested by constructing tree ring chronologies from 3 white spruce and two jack pine sites in WBNP. All five chronologies were significantly positively correlated with June precipitation in the growth year or the previous year, and were significantly negatively correlated with historical records of fire weather and annual area burned. The second hypothesis was tested by analyzing historical records of annual area burned and climate. and tree ring records of fire history and climate. Annual area burned was significantly negatively correlated with seasonal means of fire weather indices. The time since last fire was estimated using tree ring records from 166 sites located throughout WBNP. These records exhibited decadal and centennial scale variations in fire frequency. Comparisons with tree ring other proxy climate records suggest that the~e variations are related to climatic changes. The third hypothesis was tested using survival analysis of the time since last fire records, disaggregated by dominant vegetation and the mean distance to waterbreaks. Sites dominated by jack pine (Pinus banksiana) and aspen (Populus tremuloides) exhibited significantly higher fire frequencies than did sites dominated by black spruce (Picea mariana) or white spruce (Picea glauca). Fire frequency increased with increased mean distance to waterbreaks. The fourth hypothesis was tested by analyzing fossil pollen and charcoal records from two lakes at -5 year resolution for 600 years. I compared their fire history records with local tree ring records of fire, and their mean fire intervals with regional fire frequency estimates for sites with similar vegetation and mean distances to waterbreaks. One lake exhibited a meaningful fire frequency estimate and the other lake did not. The poor fire frequency estimate was related to high sediment mixing and the lack of homogenous vegetation around the lake. The results indicate that: 1) area burned and fire frequency in the boreal forest of northern Alberta varies temporally at the annual, decadal and centennial scales; 2) fire frequency varies spatially in relation to vegetation type and mean waterbreak distance; and 3) lakes with massive sediments can provide meaningful estimates of local fire frequency. / Thesis / Doctor of Philosophy (PhD)

The use of satellite and airborne remote sensing data to predict foliar macronutrients and pigments for a boreal mixedwood forest composed of black and white spruce, balsam fir, northern white cedar, white birch, and trembling aspen was investigated. Specifically, imaging spectroscopy (IS) and light detection and ranging (LiDAR) are used to model the foliar N:P ratio, macronutrients (N, P, K, Ca, Mg) and chlorophyll. Measurement of both foliar macronutrients and foliar chlorophyll provide critical information about plant physiological and nutritional status, stress, as well as ecosystem processes such as carbon (C) exchange (photosynthesis and net primary production), decomposition and nutrient cycling. Results show that airborne and spaceborne IS data explained approximately 70% of the variance in the canopy N:P ratio with predictions errors of less than 8% in two consecutive years. LiDAR models explained more than 50% of the variance in the canopy N:P ratio with similar predictions errors. Predictive models using spaceborne Hyperion IS data were developed with adjusted R2 values of 0.73, 0.72, 0.62, 0.25, and 0.67 for N, P, K, Ca and Mg, respectively. The LiDAR model explained 80% of the variance in canopy Ca concentration with an RMSE of less than 10%, suggesting strong correlations between forest height and Ca. Two IS derivative indices emerged as good predictors of chlorophyll across time and space. When the models of these two indices with the same parameters as generated from Hyperion data were applied to other years' data for chlorophyll concentration prediction, they could explain 71, 63 and 6% and 61, 54 and 8 % of the variation in chlorophyll concentration in 2002, 2004 and 2008, respectively with prediction errors ranging from 11.7% to 14.6%. Results demonstrate that the N:P ratio, N, P, K, Mg and chlorophyll can be modeled by spaceborne IS data and Ca can only be predicted by LiDAR data in the canopy of this forest. The ability to model the N:P ratio and macronutrients using spaceborne Hyperion data demonstrates the potential for mapping them at the canopy scale across larger geographic areas and being able to integrate them in future studies of ecosystem processes. / Ph. D.

The environmental problems facing the world today are largely attributable to anthropogenic activities and landscape change. Addressing these challenges in an evidence-based way requires an understanding of precisely how species and ecosystems are responding to human impacts. Discerning linkages between stressors and their ecological repercussions, and using this to inform conservation, can be challenging due to the complexity and uncertainty of ecological research. I focused on the responses of five wide-ranging large mammal species – gray wolf (Canis lupus), Canada lynx (Lynx canadensis), coyote (Canis latrans), white-tailed deer (Odocoileus virginianus) and moose (Alces alces) – to human footprint (measure of human infrastructure and landscape change), using 12 years (2001-2013) of snowtrack surveys conducted across the boreal forest of Alberta. I explored three key challenges to discerning the linkages between ecological dynamics and management actions. First, I asked whether the direction and magnitude of species responses vary depending on the spatial extent and grain of the study. Second, I asked whether these species respond more strongly to individual footprint features or to the cumulative effects of footprint (measured as total footprint), and whether responses to footprint are consistent across species. Third, I evaluated the utility of thresholds for large mammal management and asked whether there is evidence for consistent threshold responses to total footprint across scales. In addressing the first two questions, I evaluated a set of generalized linear mixed effects models (GLMM) relating the relative abundance of each species to individual and cumulative effects of human footprint, using an information-theoretic approach. I compared the direction of species responses across our regional study area (approximately 400,000 km2) to those reported in previous smaller-extent studies (median 1,525 km2), and compared responses across three spatial grains (250m, 1500m, and 5000m transect buffers). In addressing the third question, I conducted a review on the utility of ecological thresholds, described as abrupt changes in the response to a continuous driver, for large mammal management. I further tested for thresholds in species responses to total footprint by comparing linear models (logistic regression) to piecewise regression models. I compared threshold values between two grains (approximately 33km2 - 1500m transect buffer, and 5500km2 - grouping transects into clusters), and across four regions (boreal forest extent, three landscape planning units). I found that the direction of species responses varied with spatial extent, but not grain, and that species responded strongly to a broad suite of footprint features, indicating the need to manage for cumulative effects. Despite the appeal of ecological thresholds, using these as targets is challenging and the success of doing so has rarely been evaluated. I found threshold models to be better supported than linear ones across species, but due to variability and uncertainty in threshold values, the results are more suited as guidelines or hypotheses to be further tested, as opposed to specific management targets. Translating research on complex ecological systems into management actions is a continuing challenge, yet, ongoing biodiversity monitoring and adaptive management may refine our existing tools, and ultimately lead to better environmental stewardship. / Graduate / 2017-09-05 / 0329

Afin de mieux appréhender l’ouverture actuelle de la forêt boréale au nord du Québec et d’identifier les facteurs qui en sont responsables, cette thèse a étudié la dynamique, la stabilité et la résilience des deux types d’écosystèmes forestiers en jeu dans la zone de transition, au cours du temps. Ces écosystèmes, les pessières à mousses, denses, et les pessières à lichens, beaucoup moins denses (dites « ouvertes »), partagent la même espèce ligneuse dominante (Picea mariana). La thèse s’est concentrée sur le développement d’outils géochimiques innovants en paléoécologie permettant de retracer la structure et la composition présentes et passées des écosystèmes terrestres, puis sur la reconstruction du régime des feux par analyses de charbons. Elle démontre dans un premier temps que les deux écosystèmes ont des sols aux propriétés physico-chimiques distinctes, et sont entretenus par les interactions sol-végétation-climat. Le deuxième volet montre que les enregistrements chimiques sont également différents dans les sédiments récents de lacs d’étude, selon s’ils sont entourés de pessières à mousses ou à lichens. Grâce aux proxys géochimiques calibrés, le troisième chapitre reconstruit l’histoire de la végétation et des feux au cours de l’Holocène. Il met en évidence une rupture majeure dans la structure des écosystèmes, observée vers 4500-4000 ans calibrés avant présent, et permet de conclure à une ouverture de la forêt boréale à cette période en raison d’une augmentation de la fréquence de feux. La stabilité précaire des états actuels est mise en perspective avec le contexte présent d’augmentation des feux dans la région et les mesures d’aménagement à adapter en conséquence. / In order to better figure out the ongoing transition of the boreal forest in northern Quebec and to identify the responsible factors, this thesis studied the dynamics, stability and resilience of the two forest ecosystems at stake, over time. These ecosystems, the closed-canopy dense moss forest and the open lichen woodland, share the same dominant tree species (black spruce, Picea mariana). The thesis focused on the development of innovative geochemical tools in palaeoecological studies that could track present and past terrestrial ecosystem structure and composition, and then focused on the reconstruction of past fire regimes through lacustrine charcoal analyses. A first step demonstrated that the soils of both ecosystems displayed distinct physical and chemical properties and are maintained by the feedback interactions in the soil-vegetation-climate system. The second step showed that modern sediments of study lakes recorded variations in their chemical composition depending on whether they were surrounded by moss forest or lichen woodland. Using the so calibrated geochemical proxies, the third chapter reconstructed the vegetation and fire histories during the Holocene. A major disruption in ecosystem structure was evidenced 4500-4000 years calibrated before present and led to the conclusion of a boreal forest opening at that time due to an increase in fire frequency. The precariousness of the present states stability is discussed in light with the current context of fire increase in the study region and suggests that forest management should be adapted consequently.

Le feu est la principale perturbation en forêt boréale mixte. La sévérité des feux n'est pas spatialement homogène et épargne souvent partiellement ou entièrement des parties de la forêt appelées îlots résiduels. Ces îlots forestiers résiduels après feux sont étudiés depuis de nombreuses années, et ces études se sont surtout intéressées aux facteurs déterminant leur occurrence à l'échelle du paysage. Cependant, les travaux réalisés en Fennoscandinavie et aux États-Unis ont révélé la présence de peuplements forestiers (appelés refuges) ayant la capacité de se maintenir dans le territoire pendant plusieurs millénaires. L'objectif principal de cette thèse était de caractériser la dynamique temporelle et la structuration d'îlots forestiers localisés au sein de la forêt boréale mixte de l'est du Canada. Treize îlots forestiers qui ont échappé au dernier feu ont été échantillonnés. Des carottes de sols ont été extraites dans chacun des sites pour réaliser des analyses paléoécologiques (charbons et macrorestes). Les caractéristiques stationnelles de chaque site ont été échantillonnées pour déterminer si les refuges se distinguent des autres îlots résiduels. La charge en combustible des îlots a également été mesurée. Les données ont également servi à alimenter des modèles numériques de comportement du feu (Fire Behavior Prediction System, BehavePlus, FlamMap3) qui ont été utilisés afin de déterminer les caractéristiques stationnelles qui permettent aux refuges d'échapper au feu de façon récurrente. Les résultats ont mis en évidence l'existence de deux types d'îlots résiduels en forêt boréale mixte : les refuges et les autres îlots résiduels. Les refuges sont moins susceptibles au feu comparativement aux îlots résiduels qui ont échappé uniquement au dernier feu, probablement de façon fortuite. Les refuges ont en revanche la capacité de persister dans le paysage forestier durant plusieurs millénaires, ne brûlant uniquement durant des feux particulièrement sévères. Les analyses macrofossiles des refuges soulignent des changements majeurs au sein de la végétation locale, avec comme événement remarquable le passage de formations dominées par Larix laricina/Picea sp. vers des formations dominées par Abies balsamea/Thuja occidentalis. Ce changement de végétation s'est produit à différentes périodes selon les sites, soulignant un processus endogène dans cette transformation de la végétation. Le développement de Larix laricina s'est accompagné dans certains assemblages macrofossiles de taxons typiques de milieux humides (tels que les characées). L'importante couche de matière organique qui caractérise les refuges semble entraver le développement d'espèces de début de succession telles que Betula papyrifera et Populus tremuloïdes. Les îlots refuges doivent leur persistance dans le paysage forestier à un certain nombre de facteurs biotiques et abiotiques qui limitent le passage du feu. Les résultats issus des simulations du comportement du feu, suggèrent un rôle mineur des coupe-feu (lacs, tourbières, et monticules rocheux essentiellement), de la charge en combustible et de la topographie dans l'occurrence des refuges. L'humidité semble être le seul facteur déterminant leur développement au sein de la mosaïque paysagère. Les refuges se mettent en place au sein de faibles dépressions humides qui favorisent l'accumulation de la matière organique. La structure des refuges et des autres îlots résiduels révèle deux principales caractéristiques permettant de les distinguer sur le terrain : le diamètre moyen des arbres et l'épaisseur de la matière organique. Les arbres des refuges ont un plus petit diamètre que ceux des autres îlots résiduels. L'importante épaisseur de la matière organique des refuges affecte négativement la croissance des arbres. Ces caractéristiques pourront être utilisées comme outils d'aide à la décision dans les stratégies d'aménagement forestier. / Fire is the main natural disturbance shaping boreal forest landscapes. In North American boreal ecosystems, wildfires contribute to the creation of a complex mosaic of stands of varying age, composition, and structure, within which other disturbances and processes can interact. A burned area usually includes tree patches that partially or entirely escaped fire, called post-fire residual patches. The spatially occurrence of post-fire residual patches has been extensively described. However, the presence of fire refuges has been reported in Fennoscandia and in United-States, which can escape fire for several millennia. The aim of this study was to characterize temporal dynamics in post fire residual patches in mixedwood boreal forest of eastern Canada. The analyses concern the reconstruction of fire and forest dynamics history though Holocene and identify characteristics features of these patches. This research aimed to contribute significantly to the objectives of ecosystemic management to preserve biological diversity in the forest mosaics.Thirteen post-fire residual patches which escaped the last fire have been sampled. At each stand, cores and monoliths were extracted for paleoecological analyses. The reconstitution of fire history and forest dynamics were studies by using macroscopic charcoals and macroremains. The characteristics features of stands were also sampled, to differentiate fire refuges from other post-fire residual patches. The fuel load was also measured, and all these data were used as inputs for fire behavior modeling (Fire Behavior Prediction System, BehavePlus, FlamMap3), to identify stand characteristics prevent fire refuges to burn in comparison with other residual stands and forest matrix.The results showed the presence in the landscaped of two types of post-fire residual patches in mixedwood boreal forest: fire refuges and other post-fire residual patches. The fire refuges present less fire susceptibility than other post-fire residual patches, which escape only the last fire probably by chance. On the other hand, fire refuges can persist in the landscape for several millennia, burning in the most severe fires. The forest dynamics reconstruction in fire refuges, highlight major shift in the vegetation from Larix laricina/Picea sp. to late successional species Abies balsamea/Thuja occidentalis. Occuring at all stands, but at different periods of Holocene, these changes can be attributed to internal processes. The presence of Larix laricina was associated to the occurrence of aquatic taxa (e.g. Characear). The late successional species (Abies balsamea/Thuja occidentalis) can persist in the landscape for several centuries due to moisture conditions. The thickness of organic matter recorded in fire refuges seems to inhibit the recruitment of early successional species such as Betula papyrifera et Populus tremuloïdes.The fire refuges owe their persistence in the landscape to abiotoc and biotic factors that limit fire occurrence. Then results obtained from fire behavior simulations, suggest a minor role of fire breaks (lakes, rocks), fuel load and topography in persistence of fire refuges. Local moisture condition seems to be key factor in their occurrence in the landscape. The fire refuges occur likely in depressions, which favor organic matter accumulation. The structure of fire refuges and other residual patches revealed two main characteristics, which distinguish between the two types of residual patches: Mean diameter of trees and thickness of organic matter. The trees of fire refuges present smaller tree diameter than other post-fire residual patches. The thickness of organic matter accumulation in fire refuges affects negatively the growth of trees. These features can be used as tools for decision support in forest management strategies.

Northern peatlands are an important carbon store, with carbon dynamics and hydrology intrinsically linked. The riparian zone is the interface between the terrestrial and aquatic systems, situated adjacent to the stream and characterised by periodic flooding, near surface water tables and unique soil and plant species composition. Due to its unique biogeochemical environment, the riparian zone has the potential to modify significantly the production, mobilisation and transport of carbon via the land-atmosphere and aquatic pathways. Two contrasting headwater catchments, an ombrotrophic peatland (Auchencorth Moss, SE Scotland) and a forested, till dominated catchment (Västrabäcken, N Sweden), were investigated. In each carbon concentrations in soil and stream water and hydrological parameters were measured in transects connecting the wider catchment, riparian zone and stream. The overarching aim was to investigate the role of the riparian zone on the hydrological and bio-geochemical functioning of peatland and forested catchments, focusing on carbon export via the aquatic pathway. Specific objectives were to: a) examine the importance of soils, water table and vegetation composition on riparian biogeochemical cycling, b) investigate riparian-stream hydrological connectivity and the transport of carbon across the soil-water interface and c) assess riparian processes in relation to the net ecosystem carbon balance (NECB) across northern latitude ecosystems. Porewater total carbon (TC) concentrations (sum of dissolved organic and inorganic carbon (DOC, DIC), CO2 and CH4) were on average higher in Auchencorth Moss (78.8-140 mg C L-1) than the Västrabäcken (27.7-63.2 mg C L-1) catchment. In both catchments, higher TC concentrations were observed in the riparian zone compared to the wider catchment. The dominant control for differentiating between catchment and riparian biogeochemical processes was the higher average riparian water table with each carbon species displaying a positive relationship with water table height. A range of other factors, including soil temperature and the carbon content of catchment and riparian soils, also contributed to the complexity of riparian carbon biogeochemical cycles. Catchment specific phenomena, including the presence of aerenchymous vegetation and stream sediment deposition onto the riparian zone, modified riparian carbon dynamics in the Auchencorth Moss catchment. Isotopically, porewater DOC, CO2 and CH4 had a 14C content >100 %modern, indicating that the modern plant derived DOC is being transported down the soil profile, providing the source for CO2 and CH4 production at depth. In both catchments the riparian zone represented an important and dynamic source of carbon to stream waters. Total annual CO2 export from the riparian zone of the Västrabäcken catchment to the stream channel over the hydrological year was 2.7 g CO2-C m2 yr-1 with export predominantly from between 40 and 55 cm depth within the soil. Two monthly peaks in CO2 export occurred over the hydrological year related to either storm events or the spring snow melt period which accounted for 19 % of annual export, highlighting the temporal variability in soil-stream linkages, especially during high flow periods. In the generally wetter peatland catchment, riparian-stream linkages were driven by antecedent conditions and variation in riparian water table, with changes in water input, rather than changes in CO2 source concentrations, controlling stream water composition. The negative CO2 concentration-discharge relationship in the stream suggested that event water dominated, with small but important inputs from high concentration soil water during individual events. The importance of event water in transporting carbon was confirmed through the isotope result. CO2, CH4 and DOC exported via the aquatic pathway predominantly contained modern, plant derived carbon from the near surface soil horizons but with a small contribution (5-28 %) from deeper geological sources leading to aged evasion CH4 (310-537 years BP) and CO2 (36 years BP to modern). In both catchments the riparian zone was more important, relative to the wider catchment, in controlling the export of carbon via the aquatic pathway. At Auchencorth Moss, the riparian zone, plus an area of the catchment extending ~20 m from the stream, were hotspots for land-atmosphere fluxes of CH4, with mean flux of 1.08-7.70 mg m2 hr-1 in comparison to the catchment overall (0.05 mg m2 hr-1). In both catchments, combining detailed catchment hydrological models with high temporal resolution carbon concentration measurements, especially in riparian zone soils, has the potential to improve estimates of downstream and evaded carbon export in headwater catchments. Riparian zones should therefore be included more in studies investigating hydrological and biogeochemical processes in northern latitude headwater catchments. The processes within riparian zones suggest that despite the relatively small area that riparian zones represent, in relation to the wider catchment, they may play an important role in the NECB of peatland and forested catchments under future management and climate change scenarios.

Swedish forests are mostly used for timber harvesting and 96 % of this harvesting is made by clear cutting while only 4 % is effected through other methods such as single tree harvesting. All species are not affected by forestry to same magnitude. Some specifically generalists are not affected at all. Hence, this study, had its aim to find out vascular plant species that persist, disappear or colonize other species as a result of anthropogenic disturbances in different production forests, so as to determine not only if canopy openness affects the species distribution but also the magnitude of the effects. I examined 10 different forest localities during May and June 2008. Three of these localities were made up of clear cut forest plots, 3 with partially cut down forest plots and 4 with undisturbed production forest plots. Species composition and diversity were then compared between these plots. A total of 34 different species were found. Statistical Analysis was made on how well the species in the partially cut down forest plots fitted into the undisturbed forest group as well as comparing this results with results of how counterpart species in the clear cut forest plots fitted into the undisturbed forest groups. These results showed that there was no significant difference, ANOVA values of P = 0.839, 0.602 and 0.564 respectively among the species composition between the forest, partially cut down and clear cut forest groups between the forest, partially cut down and clear cut forest plots. However, among the 54 species found in all study plots, 11 were common between the forest and partially logged sites whereas only Carex sp in the clear cut forest was common to those in the forest plots implying that canopy openness did not affect the total species number but had an effect in species composition. Clear cutting seems to kill off everything but trees and generalists. Hence, resiliency of vegetation should be increased by management practices that ensure the maintenance of prior species.

Den här avhandlingen belyser hur avverkning och markberedning påverkar markfloran i den svenska barrskogen. Dessutom utvärderas två inventeringsmetoder som används inom växtekologin. Vid arbetet har både rikstäckande inventeringsdata och fältförsök använts och de likartade resultaten tyder på att rikstäckande inventeringar är en underutnyttjad resurs i forskningen. Ju större andel av träden som avverkas desto större blir förändringen av markflorans sammansättning. Vissa arter, som lingon, ljung, etc., verkar dock inte påverkas i nämnvärd omfattning, medan andra, som blåbär, minskar i relation till hur mycket som avverkats. Gräs och mjölkört ökar efter avverkning, dock visar sig vissa gräs och mjölkört inte reagera om inte avverkningen överskrider ett tröskelvärde på ca 80 %. Avverkning har en liten, men signifikant, effekt på antalet arter, medan artomsättning, d.v.s. arters etablering på och/eller försvinnande från provytorna, framförallt påverkas av andel gran innan avverkning, markens produktionsförmåga och först därefter av hur stor andel av träden som avverkas. Det var också uppenbart att markberedning har en stark effekt som skiljer sig från avverkning. Framförallt gynnas björnmossor av markberedning men även vårfryle, kruståtel och mjölkört. Arter som missgynnas av markberedning var bl.a., en levermossa, lingon, väggmossa och kråkbär. I växtekologi är visuell täckningsbedömning, d.v.s. hur stor del av en provyta som täcks av en växtart, och registrering av förekomst/icke förekomst, d.v.s. finns en växtart på en provyta eller inte, de två vanligaste metoderna vid vegetationsinventering. Vid registrering av förekomst/icke förekomst missas upp till en tredjedel av förekomsterna, vanligaste orsaken till missade registreringar verkar vara att man inte upptäcker arten snarare än att den inte kan identifieras. Det var stora variationer mellan arter, där arter med få exemplar på provytan missas oftare. Både den visuella täckningsbedömningen och förekomst/icke förekomst visar sig ha personberoende fel, d.v.s. att olika personer genomgående ger högre eller lägre värden än andra. Trots det personberoende felet visar sig täckningsbedömningar ha ett större informationsvärde än registrering av förekomst/icke förekomst när det gäller att särskilja olika typer av vegetation. Erfarenhet har en förvånansvärt liten effekt på kvaliteten av täckningsbedömningar. / This thesis has two main focuses; first, the response of forest ground layer flora on forestry, mainly harvesting and secondly, the quality of the vegetation assessment methods, cover estimates by eye and presence/absence data. The effect of harvesting intensity was evaluated with survey data from permanent plots as well as vegetation data from a field trial fourteen years after harvesting. Both data sets confirmed that response of ground layer flora increased with increasing logging intensity. Thereby, indicating that survey data is possible to use in research. From the survey data set, existence of a time lag was evident for several species and also a threshold level was evident in cutting intensity needed to affect a number of species. Logging had a modest, but significant positive effect on the change in species number per plot. Species turnover was influenced by the proportion of Picea abies in the tree canopy; site productivity; and logging intensity. In the field trial scarification had a strong effect that was different from the one created by cutting. In plant ecology cover estimate by eye and presence/absence recording are the two most frequent methods used. The methods were evaluated with survey data and a field trial. In the first data set vegetation was recorded independently by two observers in 342 permanent 100-m2 plots. Overall, one third of each occurrence was missed by one of the two observers, but with large differences among species. Species occurring at low abundance tended to be frequently overlooked. Observer-explained variance in cover estimates was <10% in 15 of 17 species. In the second data set, 10 observers independently estimated cover in sixteen 100-m2 plots in two different vegetation types. The bias connected to observer varied substantially between species. The estimates of missing field and bottom layer had the highest bias, indicating that missing layers are problematic to use in analysis of change. Experience had a surprisingly small impact on the bias connected to observer. Analyses revealed that for the statistical power, cover estimates by eye carries a higher information value than do presence/absence data when distinguishing between vegetation types, differences between observers is negligible, and using more than one observer had little effect.

Two small bordering catchments in Bispgården, Central Sweden, wereinvestigated in regard to soil solution and stream water chemistry during the frostfree seasons of 2003-2007. Both catchments were drained by first order streams,Fanbergsbäcken and Gråbergsbäcken, and in Fanbergsbäckens catchment anextensive investigation of the soil and soil solution chemistry was conducted bylysimeter and centrifugation sampling. The area of intensive soil solutioninvestigation was situated in a slope towards a stream incorporating a rechargearea, with podzolic soil, and a discharge area close to the stream with an arenosolsoil. Samples were continuously taken in both the recharge- and the discharge areaof the slope, and stream water was sampled in the streams of both catchments. Themain variables of interest of the study were the interactions, the influence ofdissolved organic carbon and the effects of wood ash application to soil solutionand stream water.The natural variations and the interactions between soil solution and streamwater were monitored during 2003-2004. In soil solution, most of the investigatedsubstances tended to increase during the growing season, due to weathering andmicrobial degradation of biota. Ca, Mg, Al and Fe were highly associated todissolved organic carbon (DOC) throughout the catchment. The low molecularfraction of DOC seemed to have a higher impact on the soil processes in therecharge area, while high molecular DOC was more important for transport ofcations in the discharge area and the stream water.The concentration of different substances in the two streams differedsignificantly, even though the catchments were similar in size, shape andforestation. The seasonal patterns of most of the substances measured weresignificantly correlated between the streams, however. Cations and pH correlatedwell with DOC and flow. The flow pattern driven by precipitation seems to be thedriver of the stream water chemistry.Wood ash was applied at a dosage of 3 ton/ha to one of the catchments in theautumn of 2004, to investigate the initial effects on the soil solution- and streamwater chemistry. WAA is recommended by the Swedish Forest Agency tocounteract acidification in soil and runoff that may be caused by an intensivebiomass harvesting. The impact of the WAA was studied during 2005-2006.Compared to the control temporarily higher concentrations of K, Ca and SO4 wereobserved in the soil solution of the ashed area. In the stream water the effects of theWAA were easier to distinguish due to higher sampling frequency. The strongesteffect was seen for K, but increases in the stream water were also noted for DOC,Ca, Mg, Si, Cl and malonate. No increase in pH could be statistically verifiedhowever, and overall the initial effects of the WAA seem mild. / Två angränsande avrinningsområden i Bispgården i centrala Sverigeundersöktes under den snöfria säsongen 2003-2006. Båda avrinningsområdenadränerades av första ordningens bäckar och i det ena, Fanbergsbäckensavrinningsområde, gjordes en omfattande undersökning av mark och markvattenkemin.Markvatten provtogs genom centrifugering och med lysimetrar.Provtagningen gjordes i inströmningsområdet där jordmånen var en typiskpodzol samt närmare bäcken, i utströmningsområdet, där jordmånen var enarenosol. Bäckvatten provtogs i båda avrinningsområdena. Interaktioner mellanmark, markvatten och bäckvatten undersöktes med särskilt fokus på inverkan avorganiskt kol samt påverkan av askåterföring.De naturliga variationerna i markkemin samt interaktionerna mellan mark- ochbäck vatten undersöktes 2003-2004. I markvatten ökade merparten av de studeradeämnena under provtagningssäsongen beroende av ökad vittring och recirkulationav biota och fallförna. Ca, Al och Fe var i stor utsträckning associerade till löstorganiskt kol (DOC). Den lågmolekylära fraktionen av DOC hade en störreinverkan på markprocesserna i inströmningsområdet, medan den högmolekyläradelen var viktigare för transport av katjoner i utströmningsområdet samt ibäckvattnet.Koncentrationsnivåerna av olika substanser i bäckarna uppvisade skillnadertrots avrinningsområdenas yttre likheter med avseende på storlek, form ochbeskogning. Trots de kvantitativa skillnaderna erhölls emellertid liknandesäsongsvariationer i koncentrationerna, vilket indikerade att kemin i huvudsakstyrdes av mängden DOC som i sin tur berodde av avrinningen som drevs avnederbörden. Höga halter av Ca, Mg, Al och Fe återfanns associerade tillhögmolekylärt DOC i bäckvattnet i en utsträckning som inte rapporterats tidigare.På hösten 2004 spreds 3 ton aska/ha till Fanbergsbäckens avrinningsområde föratt undersöka de initiala effekterna på mark- och bäckvatten kemin. Askåterföringbör ske minst en gång per omloppstid vid helträdsavverkning, i enlighet medSkogsstyrelsens rekommendationer, främst för att motverka försurning i mark ochavrinnande vatten som antas uppstå vid intensivt uttag av biomassa. De initialaeffekterna av askåterföringen på mark- och bäckvattnets kemi studerades under2005-2006 och Gråbergsbäcken kunde användas som obehandlad kontroll vidundersökning av vattenkemin i Fanbergsbäcken. I undersökningen av markvattenviåterfanns stora säsongsvariationer, vilket gjorde det svårt att urskilja eventuellaeffekter av askåterföringen. Tillfälligt högre värden av K, Ca och SO4 återfannsdock i det askade området i jämförelse med kontrollområdet. På grund av högreprovtagningsfrekvens i bäckvattnet var det lättare att påvisa förändringar ibäckvatten kemin. Framförallt märktes en signifikant ökning av K jämfört medkontrollbäcken. Sådana ökningar, om än inte lika markanta återfanns också förDOC, Ca, Mg, Si, Cl och malonat. En tendens till ökat pH kunde observeras, mendenna kunde inte verifieras statistiskt. De initiala effekterna av askåterföringen varsåledes till synes milda, och den eftertraktade pH-effekten erhölls ej i dennaundersökning.