In this thesis, I have studied long shoot performance in the monoecious, deciduous tree Betula pubescens ssp. czerepanovii. In field studies and a common garden experiment, I have a) studied how environmental variations affect the performance of long shoots in mountain birch, and b) described the relationship between long shoot performance and characteristics of the parent long shoot. I have shown that difference in long shoot performance to some extent can be explained by environmental variables such as temperature, precipitation and global radiation the current and previous summer, annual soil and air temperatures, and the length of growing season. For example, a low summer temperature the previous summer had a negative effect on a majority of long shoot characteristics. Variation in shoot characteristics was of the same magnitude along the regional east-western gradient as along the local altitudinal gradient. Variation among individual trees was of the same magnitude as variation among years. Further, long shoot performance was affected by the parent shoot characteristics and reflects that primordia of different organs are formed in the previous summer. On several occasions, freezing damage to mountain birch has been observed on Mt Njulla in northernmost Sweden. Following such damage, fewer but larger leaves emerge. Damages were compensated for with increased number of buds on long shoots produced the same year and one year after damage. Moreover, there were more new long shoots born on short shoots among damaged trees. Dormant buds and short shoots fulfil important functions in a fluctuating environment and as an adaptation to recurring damages of different origin and severity. Differences in the performance among mountain birch saplings grown in a common-garden at Abisko could to a large degree be explained by their origin. Further, saplings from Sweden and from Iceland responded differently to defoliation, and fertilization did not alter the responses to defoliation.

Omställningen till förnybar energi går fort, vindkraften har utvecklats snabbt i Sverige desenaste åren. Vindkraftsanläggningar har effekt på omgivande fågelliv såsom förändring avbiotoper, bullerstörningar och risk för kollision med rotorblad. Uppsatsen undersöker vilkafaktorer som styr kungsörnens rörelsemönster, samt vilken effekt vindkraften har på kungsörnen,biotoper, födoval och häckning. Kan vindkraft och kungsörn kombineras i ett område?Exempel finns på dåligt placerade vindkraftverk, vilka har skördat många fågelliv, orsakadeav kollisioner med rotorblad, här är det inte bara rovfåglar utan också andra fågelarter somutsätts för risker.Kungsörnen är en känslig art som har uppmärksammats vid miljöprövningar inför vindkraftsbyggen.Kungsörnen har långsam reproduktion, men också att den är beroende av just debiotoper som hotas och förändras vid en större utbyggnad av vindkraft. Kungsörnen i Sverigebygger bon på klipphyllor eller i äldre skog med branter, miljöer som ofta är potentiellaområden för vindkraftsparker. Kungsörnen rör sig över stora hemområden, områdenas storlekberor på hur tät skogen är och om det finns gamla bo-träd. Kungsörnen jagar på öppna ytorsom kalhyggen, men den föredrar en kombination av gammal skog och kalhyggen.För att skydda kungsörnen vid vindkraftsetablering, kan verken etableras i samklang medskogsbruket, för att bevara värdefulla biotoper för kungsörnen. Skogsbruket ska vara hållbartoch framblickande för att bäst skydda arter som kungsörn. Kollisionsrisker med fågeldöd,beteendeförändring och habitatförlust, biotopförlust, barriäreffekter är exempel på olikafaktorer som påverkar artens fortlevnad på platser med vindkraftverk.Studier av kungsörnens rörelsemönster och utbredning har gjorts i Sverige. Örnarna märktesmed GPS-sändare i början av häckningssäsongen. Resultatet från dessa studier visade attkungsörnarna flög över långa sträckor efter häckning, det vill säga att de kan ha stora jakt- ochhäckningsområden. Vissa örnar flög längre än andra. Orsakerna var att häckningen misslyckadesoch att det kan ha varit ont om mat. Kunskaper om den hotade fågelartens beteendeoch häckning kan öka möjligheter till anpassningar vid vindkraftsanläggningar. Utformningenav vindkraft har skett i en balansgång mellan effektiv energiproduktion och miljöhänsyn. Fördet senare har olika mätmetoder påverkat utformningen av vindkraftverk, exempelvisklassning av höjdintervaller fåglarna flyger i. Kompromisser har gjorts för att lösa vissaintressekonflikter, det vill säga att man har klassificerat kungsörnspopulationer utifrån desslivskraft.Rekommendationer var vindkraft ska placeras är i kuperade områden med ungskog, då det ären biotop som kungsörnen undviker. Kungsörnens val av hemområden är väldigt individuella,vilket bör tas i beaktning vid etablering av skyddszoner intill en potentiell störningskälla som vindkraft.

My study confirms that there are phenotypic plastic traits in blue mussels (Mytilus edulis) inresponse to predatory pressure from shore crabs (Carcinus maenas) and sea stars (Asteriasrubens) and a combination of them. Blue mussels can sense predators by olfactory cues fromthe predators themselves, or by alarm cues from attacked conspecifics, and then developinducible defences. In this experimental study, blue mussels were exposed to either nopredator (control) or to enclosed predators in terms of two shore crabs, two sea stars or thecombination of one shore crab and one sea star, over a period of six weeks. According to previous studies a good defence against predation from shore crabs should be athicker and also a more circular mussel shell, and a good defence against sea stars should be astrong posterior adductor muscle. All three predatory treatments resulted in mussel individuals with significantly heavier shells.When exposed to sea stars, individuals grew less lengthwise and showed a significantly lowerend volume, as well as a significantly heavier posterior adductor muscle. These mussels alsoshowed a tendency to survive sea star predation better in the predation test. Thus, induciblephenotypic defences against predation by sea star predation, were clearly demonstrated. Theexposure to shore crabs resulted in a significantly higher height of the mussels, whencontrolling for mussel length. The mussels exposed to shore crabs also showed end volumessimilar to control mussels, whereas an exposure to a combination of a crab and a sea starresulted in intermediate end volumes. This supports a phenotypic plasticity in traits related topredator threat. Individuals in all three predatory treatments were harder attached by morebyssus threads at the end of the experiment. Control mussels and those exposed to a singlecrab and sea star were repeatedly found to be more aggregated (i.e. fewer solitary mussels)over the course of the experiment, whereas the mussels presumably exposed to more olfactorycues from two shore crabs or two sea stars were more often found solitary and attached bybyssus threads. This study demonstrated inducible defences in how blue mussel allocate their resources todifferent dimensions of growth, shell weight, adductor muscle weight, as well as aggregationand byssus attachment, depending on predatory threat.

Species constantly experience changes in their environmental conditions owing to natural or human induces reasons. Understanding how species respond to these fluctuations are important for ecology, especially given the ongoing climate change. Empirical studies have shown that species respond differently to the same disturbance. However, our knowledge of what create these differences in the environmental response is limited and in most cases based on studies focusing on single species. In this thesis, I have taken a theoretical approach and used dynamical models to investigate how the population dynamics of species are affected by species-species interactions and environmental fluctuations.   In the first paper (Paper I) I investigated how a species respond to environmental fluctuations when isolated or embedded in a food web. The study showed that species-species interactions had an effect in temporally positively autocorrelated environments (red noise) but not in uncorrelated environments (white noise). This was owing to species following their equilibrium densities in red environments which in turn enabled species-species interactions to come into play. Red environmental variables are more prominent in nature than white. Thus, these results show the importance of using a food web approach when analyzing species response to environmental fluctuations.   The most commonly discussed effect of climate change is an elevated mean temperature. This shift is expected to affect the growth rate of many species. However, there is no robust theory of how we should expect species in food webs to respond to a rise in temperature. In the second paper (Paper II) I defined and studied the dynamic rate of food webs (DR) acting analogously to single species growth rate. I found that the higher DR the easier for species population densities to follow their equilibrium over time. Both DR and noise color changed the temporal relationship between the population and the environmental noise. Thus, it is of major importance to take the scale of time into consideration when investigating species response to environmental fluctuations.   Another important factor which affect population dynamics is species spatial distributions. Dispersal between subpopulations enable individuals to rescue or prolong the time to extinction for the population seen as a whole. In the third paper (Paper III), I investigated how species in food webs respond to environments that varies both in time and space and compared the results with the one from single species. I found that single species were stabilized by an increased dispersal rate independent of the noise color. Species-species interactions had an effect for some of the species in these landscapes. At red asynchronous noise, one resource species in each food web had a local minimum in stability at low dispersal rate. Here, dispersal decoupled local population dynamics and prevented species from tracking their equilibriums. At high dispersal rates, all resource species and their single species counterparts were stabilized by dispersal as local patch dynamics lost its importance. Environmental noise together with the spatial dimension does seem to explain much of the stability properties of species on our planet.   However, natural ecosystems are much more complex and species rich than the food web models I have used so far. Theoreticians have previously had a hard time describing stable complex systems that survive environmental fluctuations. Thus, in my fourth and last project (Paper IV) I investigated how species population dynamics are affected by environmental fluctuations when embedded in larger food webs. These systems were built by connecting food web modules with periodic boundary conditions (PBC). The PBC method has previously helped physicists to understand the nature of waves and particles by removing the edges in systems. I found that food web size does not have to have a negative effect on food web stability. I showed that by removing the destabilizing effect of edges it is possible to describe large stable food webs, more similar to natural ecosystems.   Overall, the research presented here give new insights into species responses to environmental fluctuations. They especially highlight the importance of considering both species interactions and environmental noise color when studying population dynamics in a fluctuating environment. A food web approach is necessary when analyzing species population dynamics and planning for conservation actions, especially when studying the effects of climate change on biodiversity.

Trophic cascades, together with other indirect interactions are important aspects in shaping the composition and abundance of species in the food web. Theoretically, movement of energy between systems, and coupling between habitats by mobile predators have been suggested as being important for food web stability and evenness. Individual diet specialisations have been shown to be widespread in many animal taxa. Although not widely studied, some studies have indicated that mobile predators that display individual specialisations, may have a reduced ability to couple habitats. In this thesis, by using field studies and an experimental study, my aim was to assess the individual specialisation displayed by Eurasian perch (Perca fluviatilis) and its influence on the ability of the perch to couple habitats. In the experiment, we also investigated the effect of habitat coupling, or the lack of habitat coupling, on the dynamics and stability of the resources in the ecosystem. We show that habitat diversity and resource availability influenced perch individual specialisation and morphological variation. We found that the perch total niche width decreased with decreasing habitat switching ability. We demonstrate asymmetrical habitat coupling ability in perch across pelagic and littoral habitats, providing evidence that not all individuals within a species respond in the same way when it comes to spatial coupling and thereby providing stability within a food web. Our results expand on previous work and suggest that habitat coupling ability can influence individual specialisations and niche width. Furthermore, we show the importance of individual specialisations in relation to habitat coupling. Finally, we provide evidence for the theory that a food web dominated by a food specialist should exhibit more variable resource dynamics than a food web dominated by a generalist predator by showing a greater indirect effect of predation on the phytoplankton levels when no habitat coupling occurs. While many models and theoretical concepts have proposed a stabilising effect of cross movement of energy and mobile predators, little empirical evidence exists that confirms this mechanism. In conclusion, my thesis gives some support for the theoretical predictions that habitats coupled by a generalist predator should be more stable.

Data över förekomst av två storleksklasser (0-150 mm och >150 mm) av Europeisk ål (Anguilla anguilla) i vattendrag på svenska västkusten hämtades från SERS (Svenskt ElfiskeRegiSter vid SLU). Dessa analyserades genom logistisk regression för att avgöra vilka olika makrohabitat-, landskaps- och hindervariabler som bäst kunde användas för att förutspå förekomst av ål. Resultatet visade att det för makrohabitatvariablerna var vattendragets bredd, vattenhastighet och vegetationsmängd som bäst förutspådde förekomst av båda storleksklasserna. För landskapsvariablerna var det avstånd till mynningen, fosforkoncentration och vattentemperatur som bäst förutspådde förekomsten av båda storleksklasserna. Därtill var även sjöprocent en viktig variabel för att förklara förekomsten av den större klassen ål. För variabler som beskriver vandringshinder var det dammar, ålyngelledare och naturlika fiskvägar som bäst förutspådde ålförekomst av båda storleksklasserna. Därtill var även avstånd till uppströms hinder viktigt för att förklara förekomsten av större ål (>150 mm). Mängden lämpliga tillväxthabitat för ålen kan därför troligtvis ökas genom åtgärder riktade mot lokalens vattendragsbredd, vattenhastighet och vegetationsmängd.

No description available.

Although the autumn phenology of plants is important for a wide range of processes including primary production, carbon sequestration and food availability for herbivores, few studies have addressed spatial variation of autumn phenology and how it changes with climate change. The greatest increase of temperature is predicted near the pole and therefor it is important to estimate how this change will affect Arctic ecosystems. The phenology of vegetation is a valuable indicator of climate change and knowledge about phenology will give indications how the Arctic terrestrial ecosystems will react on climate changes. So far, the spring phenology is well-known compared to the autumn phenology. The aim of this study was to examine how autumn phenology varies among and within locations in forest-tundra ecotone in Northwestern Sweden. The phenology of the plant communities was measured spectrally with the Normalized Difference Vegetation Index [NDVI]. This allow me to directly compare the results of this study with the results from large scale studies using satellite-derived indices. I found that the timing of the autumn senescence varies among locations, topographic positions and vegetation types. These results are important because they contribute to a more nuanced understanding of the processes regulating primary production and food availability for herbivores in the Scandinavian mountains, and provide important information for forecasting the responses of these ecosystems to future climate changes.

Hornborgasjön är en grund och näringsrik slättsjö och är en av Sveriges viktigaste rastlokaler för sjöfåglar. Varje vår och höst samlas stora mängder av bl.a. rastande änder och svanar. Kransalger (Chara spp) är den dominerande undervattensväxten i sjön men där finns också axslinga (Myriophyllum spicatum) och olika typer av nate (Potamogeton spp) som vanligt förekommande. Syftet med den här studien var att ta reda på om det finns något samband mellan rastande sjöfåglar och den undervattensvegetation som finns i Hornborgasjön. Resultaten är framtagna utifrån data från simfågelräkningen och inventeringarna av undervattensvegetationsom utfördes mellan åren 1993–2015. Även sjöfåglarnas samband med abiotiska faktorer som vattenstånd och nederbörd var av intresse att undersöka. Tidigare studier har visat att vattenståndet spelar roll för sjöfåglars tillgänglighet på föda i sjöar och våtmarker. Högre vattennivåer under långa perioder gör att födan troligtvis inte blir lika lättillgängligt för vissa fågelarter men gynnar andra. I längden kanske detta också påverkar mängden och utbredningen av undervattensväxter. Eftersom vattenståndet verkar spela roll för tillgängligheten på föda för en del fågelarter så var det intressant att undersöka om även nederbördsmängden under perioder har en påverkan på mängden tillgänglig föda. Åtta arter av sjöfåglar som i viss utsträckning betar undervattensvegetation samt sex vegetationstyper ingick i studien. Resultaten pekar på att det finns ett signifikant samband mellan antalet rastande sjöfåglar och undervattensvegetation framförallt med kransalger och nate. Knölsvan (Cygnus olor), vigg (Aythya fuligula), brunand (Aythya ferina), snatterand (Anas strepera), och sothöna (Fulica atra) var de arter som påvisade starkast samband med den totala andelen undervattensvegetation. Inget signifikant samband mellan sjöfåglar och vattenstånd eller nederbörd kunde konstateras. / Lake Hornborga is a shallow and nutrient-rich floodplain lake and is one of Sweden's most important stopover points for waterfowl. Every spring and autumn large quantities of migrating ducks and swans gather. Stoneworts (Chara spp) is the dominant underwater plant in the lake,but there are also spiked water-milfoil (Myriophyllum spicatum) and various types of pondweed (Potamogeton spp) as common. The purpose of this study was to find out whether there is any relationship between the migrating waterfowl and the underwater vegetation found in Lake Hornborga. The results are derived from data from bird counts and inventories of underwatervegetation carried out between the years 1993-2015. Even waterfowl associated with abiotic factors such as water levels and precipitation was of interest to investigate. Previous studies have shown that water levels play a role in the availability of seabirds on food in lakes and wetlands. Higher levels of water for long periods make the feed probably less accessible to some bird species but benefit others. In the long run, this may also affect the amount and extent of underwater plants. Since water levels seem to play a role in the availability of food for some bird species, it was interesting to investigate whether the amount of precipitation during periods also has an effect on the amount of available food. Eight species of waterfowl that to some extent graze submerged vegetation and six vegetation types were included in the study. The results indicate that there is a significant correlation between the number of migrating waterfowl and underwater vegetation especially with stoneworts and pondweed. Mute Swan (Cygnusolor), tufted duck (Aythya fuligula), pochard (Aythya ferina), Gadwall (Anas strepera), and the coot (Fulica atra) were the species that showed the strongest relationship with the total percentage of underwater vegetation. No significant correlation between waterfowl and waterlevel or precipitation was found.

No description available.