Epiphytic lichens are important species in the forest ecosystem. The Swedish forestry model affects them by fragmenting large old continuous forests. These fragments could be used as islands in a test of MacArthur and Wilsons theory of island biogeography. This study investigates if island biogeographic factors such as area and distance from nearest continuous forest affects lichen diversity in forest fragments, In addition time since logging to investigate if the populations will reach equilibrium and also if differences in habitats such as forest volume affects lichen diversity in addition to island biogeography. The number of lichen species were examined in 15 boreal forest fragments north of Storuman municipality, Västerbotten.   According to the results, positive significant correlations were observed between the number of lichen species and island biogeographic variables in the area of the islands. No positive correlations could be observed between the number of lichen species and distance to the nearest continuous forest.  There were also significant correlations between number of species and time since logging around the forest islands. However, there were positive correlations between the number of lichen species and forest volume, which tells us that more than island biogeographic factors that affect lichens in the form of habitat changes. This study indicates that in order to favor lichen diversity in forest landscapes it is important to maintain larger forest fragments with older trees. Clearly forest management agencies should consider the complex ecology of lichens when planning and performing forestry practices.

Predators play a critical role in regulating the structure and function of ecosystems by exhibiting top-down forces on lower trophic levels. Despite their important contributions in maintaining ecosystem health, lethal predator control remains a global wildlife management strategy to reduce predation on livestock, culturally and/or economically important species, and species at risk, as well as to reduce conflict with humans. Predator control has received criticism due in part to a paucity of rigorous research on the community-level impacts of this practice, beyond the target prey species. Specifically, there is a lack of understanding of the behavioural consequences of predator control on the wider ecological community. In this thesis, I used a multi-year camera trap dataset to evaluate how government-mandated grey wolf (Canis lupus) population reduction to conserve boreal woodland caribou (Rangifer tarandus caribou) could impact the resource selection of the carnivore community in northeast Alberta, Canada. In my second chapter, I investigated whether perceived persecution risk due to predator control may alter wolf habitat selection. I found that wolves switched from positively associating with roads before predator control to avoiding anthropogenic linear features and selecting for block features after predator control. These results suggest that lethal control may prompt wolves to prioritize local prey acquisition near block features over movement on linear features. In my third chapter, I examined whether coyote, lynx, and black bear exhibited shifts in co-occurrence with habitat features, competitors, and prey consistent with a release from top-down suppression in response to predator control. I found that predator control triggered unexpected behavioural changes among coyote and lynx consistent with a release from top-down suppression, but not among black bears. Non-apex predator response to predator control may depend on the strength of competition between the apex and non-apex predator, emphasizing the need to consider bottom-up processes when trying to understand the indirect effects of predator control. This research demonstrates that predator control can have trickle-down effects within the larger ecological community, specifically affecting how species utilize resources. As predator control continues to be a recommended wildlife management strategy, it is imperative to continue investigating its unintended consequences throughout the ecological community. / Graduate

Methane (CH4) tree stem-atmosphere flux is viewed as a new frontier in the global carbon cycle and may be of great importance. The effect on flux from different tree species, forest ecosystems and seasons is still uncertain. This study aims to investigate how CH4 flux from stems of spruces and birches in a boreal riparian zone in northern Sweden was affected during the spring flood. Spatial and temporal patterns were examined in combination with tree species differences. A closed stem chamber system was applied to estimate CH4 flux from 28 trees during pre-snowmelt and snowmelt conditions. A three-way ANOVA analysis and Tukey´s HSD test was applied to test for main effects and interaction effects from “Field day”, “Distance to the stream” and “Species”. The study revealed that i) there was a significant increase in stem flux over the course of the spring flood while not unequivocal, ii) spruces and birches displayed no significant difference in flux, iii) the distance to the stream had no undisputable significant effect on stem flux. However, a trend in flux variation was observed with distance to the stream. No significant interaction effects were detected. Cumulative seasonal environmental changes or natural variability might explain temporal patterns. Spatial patterns may be connected to hot spots close to the stream. Results for species and interaction effects might facilitate estimations of fluxes in forested ecosystems. Methane flux rates are affected over the course of the spring flood, but further studies are needed to determine the cause for it.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第23523号 / 農博第2470号 / 新制||農||1087(附属図書館) / 学位論文||R3||N5354(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)准教授 岡田 直紀, 教授 神﨑 護, 教授 北島 薫 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Anthropogenic activities perturb the global carbon and nitrogen cycle with large implications for the earth’s climate. Land use activities deliver excess carbon and nitrogen to aquatic ecosystems. In the boreal biome, this is mainly due to forestry and atmospheric deposition. Yet, impacts of these anthropogenically mediated inputs of carbon and nitrogen on the processing and emissions of greenhouse gases from recipient streams and lakes are largely unknown. Understanding the ecosystem-scale response of aquatic greenhouse gas cycling to land use activities is critical to better predict anthropogenic effects on the global climate system and design more efficient climate change mitigation measures. This thesis assesses the effects of forest clearcutting and nitrate enrichment on greenhouse gas emissions from boreal inland waters. It also advances methods to quantify sources and sinks of these emissions. Short-term clearcut and nitrate enrichment effects were assessed using two whole-ecosystem experiments, carried out over four years in nine headwater catchments in boreal Sweden. In these experiments, I measured or modeled air-water fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), combining concentration, ebullition and gas-transfer velocity measurements in groundwater, streams and lakes. By using Swedish national monitoring data, I also assessed broad-scale effects of forest clearcutting by relating CO2 concentrations in 439 forest lakes to the areal proportion of catchment forest clearcuts. To improve quantifications of CO2 sources and sinks in lakes, I analyzed time series of oxygen concentrations and water temperature in five lakes on conditions under which whole-lake metabolism estimates can be inferred from oxygen dynamics given the perturbing influence of atmospheric exchange, mixing and internal waves. The experiments revealed that aquatic greenhouse gas emissions did not respond to nitrate addition or forest clearcutting. Importantly, riparian zones likely buffered clearcut-induced increases in groundwater CO2 and CH4 concentrations. Experimental results were confirmed by monitoring data showing no relationship between CO2 patterns across Swedish lakes and clearcut gradients. Yet, conclusions on internal vs. external CO2 controls largely depended on whether spatially or temporally resolved data was used. Partitioning CO2 sources and sinks in lakes using time series of oxygen was greatly challenged by physical transport and mixing processes. Conclusively, ongoing land use activities in the boreal zone are unlikely to have major effect on headwater greenhouse gas emissions. Yet, system- and scale specific effects cannot be excluded. To reveal these effects, there is a large need of improved methods and design of monitoring programs that account for the large spatial and temporal variability in greenhouse gas dynamics and its controls by abiotic and biotic factors.

Boreal old-growth forests are key determinants in the global carbon cycle. It is unknown how the role of persistent old-growth forests will be in the carbon cycle in the face of predicted climatic changes. Eddy-covariance measurements are commonly used to quantify carbon exchange between ecosystems, such as forests, and the atmosphere. Error due to gap-fill method is of particular interest in these datasets. Here we filled a 15-year eddy covariance dataset from the Northern Old-Growth Boreal Black Spruce (Picea mariana) site located near Thompson, in central Manitoba, Canada using four different gap-fill methods. Our objectives were to determine if choice of gap-fill method affected annual NEP and if these errors compounded to even greater differences over the 15-year study period. Most significant differences in NEP among methods occurred from September to December, but variations during the growing season were responsible for most of the annual differences. / October 2016

There is a range of detailed research on edge effects using field data at local scales. However, the scientific literature lacks studies that aim to understand its characteristics in forest fragments using larger scales. Also, few works have considered the influences that each fragment of the landscape imposes on its neighbour. Since biological processes linked to fragmentation and degradation commonly start at edges and influence the dynamics of forest communities, studies on edge effects are crucial for the development of management and conservation plans. Lidar technologies have been used in several studies on forest structure, but few have investigated edge effects. This dissertation presents two distinct applications of lidar for studying anthropogenic-caused edges in different scenarios and ecosystems. In the first study, edge effects in commercial Eucalyptus plantations and fragments of the Atlantic Forest, located in the State of São Paulo, were evaluated by quantifying the differences in height and understory density in the edge vegetation vs core. We also sought to understand the influences that each type of adjacent fragment (Eucalyptus, native forest or pasture) imposes on the neighbouring vegetation. Edge effects, regarding height and understory density, on fragments of native vegetation adjacent to Eucalyptus plantations and vice-versa were more attenuated than nearby pastures. The results indicated that the protection of native forests in silviculture areas besides favouring the maintenance of local ecosystem services (provision and maintenance of water flow, diversity of flora and fauna species, natural pest control, etc.) could help maintain the homogeneity of the stands due to their ability to minimise edge effects. This protection could favour the occurrence of border Eucalyptus more similar to the ones in the core. In the second study, edge effects caused by seismic lines, i.e. corridors cut through the forest during the process of exploration of gas and oil, in areas of Boreal Forest in the central region of Alberta is addressed. Besides quantifying the effects of distance from seismic lines over height and fractional cover on the neighbouring vegetation, the interactions between these variables and primary vegetation growth factors related to the topographic position, incident radiation and surface geology were evaluated. The results showed that significant changes in vegetation structure adjacent to forest edge occur close to seismic lines, including reduced tree height and cover. Random Forest analyses revealed that the distance from the seismic line, incident radiation and surface water accumulation potential (inferred from the topographic position index) are the most critical variables for height and fractional cover prediction. Overall, lidar proved to be a robust tool for assessing the spatial and ecological dimensions of edge effects in different scenarios. With this in mind, management and conservation strategies for fragmented areas could benefit from this technology to reduce the impact from edge effects on ecosystems. / Há uma gama de pesquisas detalhadas sobre efeitos de borda usando dados de campo em escalas locais. No entanto, a literatura científica carece de trabalhos que visem compreender suas características em fragmentos florestais utilizando escalas maiores. Além disso, poucos estudos levaram em conta as influências que cada fragmento da paisagem impõe sobre seu vizinho. Uma vez que processos biológicos ligados à fragmentação e degradação geralmente se iniciam pelas bordas e influenciam a dinâmica das comunidades florestais, estudos sobre efeitos de borda são cruciais para o desenvolvimento de planos de manejo e conservação. Tecnologias lidar têm sido usadas em diversos estudos sobre a estrutura de florestas, mas poucos trabalhos investigaram efeitos de borda. Esta dissertação apresenta duas aplicações distintas do lidar para o estudo de bordas criadas pelo homem em diferentes cenários e ecossistemas. No primeiro estudo, efeitos de borda em plantios comerciais de eucalipto e fragmentos de Mata Atlântica, no Estado de São Paulo, foram avaliados por meio da quantificação das diferenças na altura e densidade do sub-bosque na vegetação da borda vs. interior. Buscou-se também compreender as influências que cada tipo de fragmento adjacente (eucalipto, floresta nativa ou pasto) impõe sobre a vegetação vizinha. Os efeitos de borda, em termos de altura e densidade do sub-bosque, em fragmentos de vegetação nativa adjacentes aos plantios de eucalipto e vice-versa foram mais atenuados do que próximo às pastagens. Os resultados indicaram que a proteção de florestas nativas em áreas de silvicultura além de favorecer a manutenção de serviços ecossistêmicos locais (provisão e manutenção do fluxo de água, diversidade de espécies da flora e fauna, controle natural de pragas etc.) poderia ajudar a manter a homogeneidade dos talhões devido à sua capacidade de minimizar os efeitos de borda. Esta proteção poderia favorecer a ocorrência de eucaliptos de borda mais semelhantes aos de interior. No segundo estudo, foram abordados efeitos de borda causados pela abertura de linhas sísmicas durante o processo de exploração de gás e petróleo em áreas de Floresta Boreal, na região central de Alberta. Além da quantificação dos efeitos da distância das linhas sísmicas na altura e cobertura arbórea da vegetação vizinha, foram avaliadas as interações entre tais variáveis e fatores de crescimento primário da vegetação relacionados a posição topográfica, radiação e superfície geológica. Os resultados mostraram que variações significativas na estrutura da vegetação adjacente à borda da floresta ocorrem próximas às linhas sísmicas, incluindo altura e cobertura arbórea reduzidas. Análises por meio de florestas aleatórias (random forest) revelaram que a distância da linha sísmica, a radiação incidente e o potencial de acumulação de água superficial (inferida a partir do índice de posição topográfica) são as variáveis mais importantes para predição de altura e cobertura arbórea. No geral, o lidar se mostrou uma ferramenta robusta para avaliar as dimensões espaciais e ecológicas dos efeitos de borda em diferentes cenários. Com isso em mente, estratégias de manejo e conservação para áreas fragmentadas poderiam se beneficiar desta tecnologia para redução do impacto de efeitos de borda nos ecossistemas.

<p>Soils of Northern Hemisphere forests contain a large part of the global terrestrial carbon (C) pool. Even small changes in this pool can have large impact on atmospheric [CO2] and the global climate. Soil respiration is the largest terrestrial C flux to the atmosphere and can be divided into autotrophic (from roots, mycorrhizal hyphae and associated microbes) and heterotrophic (from decomposers of organic material) respiration. It is therefore crucial to establish how the two components will respond to changing environmental factors. In this thesis I studied the effect of elevated atmospheric [CO2] (+340 ppm, ¹³C-depleted) and elevated air temperature (2.8-3.5 oC) on soil respiration in a whole-tree chamber (WTC) experiment conducted in a boreal Norway spruce forest. In another spruce forest I used multivariate modelling to establish the link between day-to-day variations in soil respiration rates and its δ¹³C, and above and below ground abiotic conditions. In both forests, variation in δ¹³C was used as a marker for autotrophic respiration. A trenching experiment was conducted in the latter forest in order to separate the two components of soil respiration. The potential problems associated with the trenching, increased root decomposition and changed soil moisture conditions were handled by empirical modelling. The WTC experiment showed that elevated [CO2] but not temperature resulted in 48 to 62% increased soil respiration rates. The CO2-induced increase was in absolute numbers relatively insensitive to seasonal changes in soil temperature and data on δ¹³C suggest it mostly resulted from increased autotrophic respiration. From the multivariate modelling we observed a strong link between weather (air temperature and vapour pressure deficit) and the day-to-day variation of soil respiration rate and its δ¹³C. However, the tightness of the link was dependent on good weather for up to a week before the respiration sampling. Changes in soil respiration rates showed a lag to weather conditions of 2-4 days, which was 1-3 days shorter than for the δ¹³C signal. We hypothesised to be due to pressure concentration waves moving in the phloem at higher rates than the solute itself (i.e., the δ¹³C–label). Results from the empirical modelling in the trenching experiment show that autotrophic respiration contributed to about 50% of total soil respiration, had a great day-to-day variation and was correlated to total soil respiration while not to soil temperature or soil moisture. Over the first five months after the trenching, an estimated 45% of respiration from the trenched plots was an artefact of the treatment. Of this, 29% was a water difference effect and 16% resulted from root decomposition. In conclusion, elevated [CO2] caused an increased C flux to the roots but this C was rapidly respired and has probably not caused changes in the C stored in root biomass or in soil organic matter in this N-limited forest. Autotrophic respiration seems to be strongly influenced by the availability of newly produced substrates and rather insensitive to changes in soil temperature. Root trenching artefacts can be compensated for by empirical modelling, an alternative to the sequential root harvesting technique.</p>

Forest management practices have changed the over-all structure of the Fennoscandian forest landscape resulting in a lack of suitable substrates for many wood-inhabiting species. The objectives of this thesis was to describe the colonization patterns of wood-inhabiting fungi, including the potential role of beetles as dispersal vectors, on different types of dead wood substrate and assess the importance of active measures in the forest landscape in order to restore biodiversity i.e. to increase the amount of dead wood and the use of restoration fire. The results clearly demonstrate the importance of restoration fire for wood-inhabiting fungi in a dry Pinus sylvestris forest. The general pattern for the majority of the species was a drastic decline the first two years after fire. However, after four years most of the species had recovered and were frequently found on logs strongly affected by the fire. The early fungal colonization patterns on fresh experimental Picea abies logs revealed no differences between managed forest stands and stands associated with nature reserves. After five years the species assemblage on the experimental logs was affected by stand age, forest site type, and distance to forest reserves. However, very few red-listed species colonized the logs in spite of being fairly common in the reserve stands. We conclude that the experimental period of only five years was too short to fully evaluate the possibilities to use experimental logs for threatened and red-listed species. We assessed the colonization patterns of different fungal functional groups based upon their different nutritional strategies namely mycorrhizal, saprotrophic on litter and humus, saprotrophic on wood causing white rot, and saprotrophic on wood causing brown rot. The results show that the fungal community undergoes a marked change in dominant nutritional strategies during the initial stage of the colonization process both after fire disturbance and on fresh un-colonized experimental logs. To which extent, saproxylic beetles are involved as passive or active vectors in the dispersal and colonization of wood-inhabiting fungi occurring on dead wood is poorly understood. The results clearly showed that some beetle species do discriminate between different fungal substrates and in particular, the bark beetle Dryocoetes autographus showed significant preference for wood with Fomitopsis rosea mycelium.

Disturbances are ubiquitous features of most northern forest ecosystems. The subsequent response of plant assemblages on both short (resistance or not) and long term (recolonization or not) will depend on a number of factors operating at several spatial scales. In boreal forest ecosystems, bryophyte assemblages are a conspicuous and species rich group of plants for which these processes are poorly understood. Using a combination of experimental and observational approaches this thesis explores these questions for closed-canopy bryophyte assemblages in relation to a) microtopography (both for the initial and long-term response), b) environmental constrains during post-logging succession and c) disturbance type. My results clearly show that the shade and shelter provided by microtopographic surface structures can increase survival rates of bryophytes following clear-cut logging by decreasing mortality from microclimatic stress and mechanical disturbance. Following clear-cutting, the recovery of forest floor and dead wood living bryophytes seems to be a relatively steady and progressive process without any major bottleneck episodes in the young or semi-mature forest stages with much of the pre-disturbance composition recovered after 50 years. Although boulders were found to increase the initial survival on clear-cuts and hence increase disturbance resistance, we found no evidence that boulders influenced the subsequent recolonization process. Lastly, strong compositional dissimilarities were found in young forests (40 years) following clear-cut logging, wildfire and insect outbreak, indicating divergent trajectories to occur following different disturbances. Hence, early seral stages of forest ecosystems regenerating after natural disturbances seem to compliment young managed forests in maintaining landscape level diversity. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Manuscript. Paper 4: Manuscript.