No description available.

This project aimed to reanalyse two large historical data sets from two different locations in New Zealand (Fiordland in the South Island and Pureora Forest Park in the North Island). The data describe populations of mice (Mus musculus), rats (Rattus rattus and R. norvegicus), and stoats (Mustela erminea) collected using standard monitoring techniques from five distinct types of forest habitat. The new analysis methods selected were an index of patchiness and Site Occupancy analysis. The objectives of the analysis were (1) to evaluate whether the patchiness index and Site Occupancy analysis methods might contribute to improved protocols for monitoring small mammal populations in the future, and (2) to use formal tests of five hypotheses to evaluate two of the assumptions made by the conventional density index often used in small mammal studies. I describe the results of the analyses for each species, including any problems encountered (such as the inability of the Site Occupancy method to analyse very sparse data sets). I also describe the results pooled from each of the two study locations and potential consequences for small mammal monitoring and control. This analysis has suggested that in most cases the density index is not a rigorous measure of small mammal populations. However, both the index of patchiness and Site Occupancy analysis provided useful, new information about these populations of rodents and stoats, despite the fact that these historical data sets were not designed for use with modern methods of analysis. Please note: some figures and tables were printed separately and added to the thesis as unnumbered pages. These can be found in the file 03Plates_and_Tables.pdf.

The geographical distribution of the Gulf of Bothnia zooplankton species is presented together with observations of abundancies and vertical distributions. The historical development of this plankton community in the last 70 years is discussed.Spring and summer development of the plankton fauna was studiedin the Bothnian Bay. Compared to in southern parts of the Balticit could be shown that the start of development in spring formany species was only moderately later in the Bothnian Bay. Theperiod of maximal biomass was in late summer and autumn.In a study of horizontal distribution large between-station variations were found. These variations were not random as close stations formed homogenous groups. Several cases of patchiness were established. Systematically appearing differences in age-distributions were proposed as a factor in the formation of patchiness.The selective prédation on zooplankton by Baltic herring was studied in the Bothnian Bay. Besides chosing certain species herring selects the older and larger stages of these species. Egg-bearing Eurytemora females were more heavily preyed upon than the males.From literature information and own observations it was proposed that in sence of production the Bothnian Bay and the Bothnian Sea are two very different systems. Climatic effects cause a delay of primary production in spring enabling the pelagic consumers to develop in phase with the producers in the Bothnian Bay. Contrary to systems with a spring peak in phytoplankton growth this situation will lead to high pelagial efficiency leaving little to feed the benthic communities. / digitalisering@umu

abstract: Many animals thermoregulate to maximize performance. However, interactions with other animals, such as competitors or predators, limit access to preferred microclimates. For instance, an animal may thermoregulate poorly when fighting rivals or avoiding predators. However, the distribution of thermal resources should influence how animals perceive and respond to risk. When thermal resources are concentrated in space, individuals compete for access, which presumably reduces the thermoregulatory performance while making their location more predictable to predators. Conversely, when thermal resources are dispersed, several individuals can thermoregulate effectively without occupying the same area. Nevertheless, interactions with competitors or predators impose a potent stress, often resulting in both behavioral and physiological changes that influence thermoregulation. To assess the costs of intraspecific competition and predation risk during thermoregulation, I measured thermoregulation, movement, and hormones of male lizards (Sceloporus jarrovi) in experiment landscapes, with clumped to patchy distributions of microclimates. I found lizards aggressively competed for access to microclimates, with larger males gaining priority access when thermal resources were aggregated. Competition reduced thermoregulatory performance, increased movements, and elevated plasma corticosterone in large and small males. However, the magnitude of these responses decreased as the patchiness of the thermal environment increased. Similarly, under simulated predation risk, lizards reduced thermoregulatory performance, decreased movements, and elevated plasma corticosterone. Again, with the magnitude of these responses decreased with increasing thermal patchiness. Interestingly, even without competitors or predators, lizards in clumped arenas moved greater distances and circulated more corticosterone than did lizards in patchy arenas, indicating the thermal quality of the thermal landscape affected the energetic demands on lizards. Thus, biologists should consider species interactions and spatial structure when modeling impacts of climate change on thermoregulation. / Dissertation/Thesis / Doctoral Dissertation Biology 2017

<p>For a complete picture of the lake ecosystem, it is necessary to understand the mechanisms regulating biomass and nutrient status (nutrient limitation, optimal supply, or surplus) of benthic algae, which are important primary producers and a food resource for grazers. This thesis gives an overview of the natural variation of benthic algae at different scales of space and time and on different substrates, and unravels some of the underlying factors. Algal nutrient status was assessed using the C:N:P (carbon:nitrogen:phosphorus) ratio of the entire natural benthic community. A review, observations, and experiments confirmed that a C:N:P ratio of about 158:18:1 (molar basis) represented an optimal nutrient supply, and that substantially higher C:N, N:P, or C:P ratios reflected algal growth limitation caused by an N or P nutrient deficiency. </p><p>Horizontal variation of benthic algal biomass and nutrient status was patchy, of similar amount for all investigated distances, substrates, and lakes, and constituted a dominant proportion of the total variation. For example, patches of nutrient limited algae were found within only 10 m distance from patches with a nutrient surplus. Thus, horizontal variation should not be neglected when sampling benthic algae in lakes. Field observations suggested an impact of wind, nutrients, and grazers on the horizontal variation. Light and nutrients might have caused the observed vertical and temporal variation. Field experiments confirmed a simultaneous control of benthic algal biomass by nutrients and grazing, mediated by light and temperature. Grazing effects were larger than nutrient effects, but the comparison of natural communities in lakes of different trophy suggested that benthic algal biomass was controlled by nutrients in the long run. </p><p>An important nutrient supply was animal excretions, causing a low C:N:P ratio of epizoon on zebra mussels, and algal communities associated with macrograzers. A field experiment revealed that 15N circulated one week longer in epizoon associated with a sessile caddisfly than in surrounding epilithon. In conclusion, the regulation of benthic algal biomass and nutrient status in lakes is complex, and benthic animals should be looked at not only as grazers, but also as a nutrient source.</p>

For a complete picture of the lake ecosystem, it is necessary to understand the mechanisms regulating biomass and nutrient status (nutrient limitation, optimal supply, or surplus) of benthic algae, which are important primary producers and a food resource for grazers. This thesis gives an overview of the natural variation of benthic algae at different scales of space and time and on different substrates, and unravels some of the underlying factors. Algal nutrient status was assessed using the C:N:P (carbon:nitrogen:phosphorus) ratio of the entire natural benthic community. A review, observations, and experiments confirmed that a C:N:P ratio of about 158:18:1 (molar basis) represented an optimal nutrient supply, and that substantially higher C:N, N:P, or C:P ratios reflected algal growth limitation caused by an N or P nutrient deficiency. Horizontal variation of benthic algal biomass and nutrient status was patchy, of similar amount for all investigated distances, substrates, and lakes, and constituted a dominant proportion of the total variation. For example, patches of nutrient limited algae were found within only 10 m distance from patches with a nutrient surplus. Thus, horizontal variation should not be neglected when sampling benthic algae in lakes. Field observations suggested an impact of wind, nutrients, and grazers on the horizontal variation. Light and nutrients might have caused the observed vertical and temporal variation. Field experiments confirmed a simultaneous control of benthic algal biomass by nutrients and grazing, mediated by light and temperature. Grazing effects were larger than nutrient effects, but the comparison of natural communities in lakes of different trophy suggested that benthic algal biomass was controlled by nutrients in the long run. An important nutrient supply was animal excretions, causing a low C:N:P ratio of epizoon on zebra mussels, and algal communities associated with macrograzers. A field experiment revealed that 15N circulated one week longer in epizoon associated with a sessile caddisfly than in surrounding epilithon. In conclusion, the regulation of benthic algal biomass and nutrient status in lakes is complex, and benthic animals should be looked at not only as grazers, but also as a nutrient source.

No description available.

This collection of research examines how changes in the sensory landscape, mediated by both odor and hydrodynamic properties, impact odor-mediated predator-prey interactions in salt marsh communities. I approached this research using an interdisciplinary framework that combined field and laboratory experimentation to address issues of scale and make connections between predator behavior and patterns of predation in the field. I explored a variety of interactions mediated by changes in the sensory landscape including; indirect effects of biotic structure on associated prey, predator responses to patches of prey with differing density and distribution, and dynamic interactions between predators and prey distributions. I found that biotic structure (oyster reefs [Crassostrea virginica]) has negative indirect effects on associated hard clam prey (Mercenaria mercenaria) through the addition of oyster reef odor cues that attract predators (blue crabs [Callinectes sapidus] and knobbed whelks [Busycon carica])and increase foraging success near the structural matrix. Variation in the structure of patch-scale prey odor plumes created by multiple prey results in predator-specific patterns of predation as a function of patch density and distribution which are mediated by differences in predator sensory ability. There is a potential negative feedback loop between blue crab predators and hard clam prey distributions; clam patches assume random within-patch distributions after exposure to blue crab predators, making the detection of patches by future blue crab predators more difficult. Sensory landscapes are also mediated by water flow, which transports prey odor plumes downstream to predators. Characterization of water flow in small-scale estuary systems indicates that values of turbulent flow parameters are highly context specific and depend on both tidal type (spring, neap, normal) and site. Wind and tidal range seem to be good predictors for wave components and turbulent components of fluctuating flow parameters, respectively, although the strength of their predictive ability is dependent on time scale. Modifications of the sensory landscape through changes in structurally-induced turbulence, mixing of individual plumes from multiple prey, and bulk velocity and turbulence characteristics need to be considered when formulating predictions as to the impact of predators on naturally occurring prey populations in the field.

This thesis aims to increase our understanding of mechanisms that influence larval dispersal in marine benthic invertebrates, particularly in the absence of strong oceanographic features (e.g. estuarine plumes, upwelling events, or markedly different water masses). Laboratory experiments identified behavioural mechanisms that regulate the vertical distribution of larvae in response to thermal stratification, and field studies in St. George’s Bay, Nova Scotia (NS), Canada, examined the relationship between larval abundance and physical variables (temperature, salinity, fluorescence, etc) and identified mechanisms that regulate larval distributions in situ. In the laboratory, I demonstrated that thermal stratification affects the vertical distribution of larvae by acting as a barrier to migration, or through temperature-dependent vertical swimming velocities. I also developed a random walk based model which highlighted that the key to successfully simulating larval response to temperature was 1) determining the temperature-dependent distribution of vertical swimming velocities and 2) the temporal autocorrelation in these velocities. In the field, the most striking pattern was that the larval distributions for species with similar swimming abilities were significantly correlated to one another at all scales (0.5 to 40 km). This suggests a common mechanism, related to larval swimming ability, which greatly influences the horizontal larval distribution. I found that the spatial scale of variability in larval distributions (~ 3 km) matches that in both the environmental variables and of coherent structures in current velocities (i.e. the tidal excursion). Results from an aggregation-diffusion model suggest that horizontal larval swimming could not be responsible for the observed level of aggregation in the larval horizontal distributions. I suggest that these horizontal patterns are the result of 1) an aggregative process (i.e. larvae swimming against a vertical current and maintaining their vertical position) and 2) a diffusive process which scales the aggregations to the scale of the coherent structures in current velocity (i.e. tidal excursion). In conclusion, this thesis increases our understanding of larval behaviour and its effects on larval dispersal. The results will be particularly useful to those who are interested in mechanisms regulate population connectivity, particularly those using bio-physical models to model dispersal trajectories.

A case study of a prehistoric site named Ängesviken, in eastern Jämtland, is presented in this thesis. Ängesviken is situated in a region that traditionally has been understood as peripheral and without a significant history prior to the Late Iron Age or even the mediaeval period. The site appears to have a continuous presence of human activities through a period of 3000 years, manifested through a horizontal stratigraphy. In order to study this site of abstruse character a multidisciplinary approach is used, where archaeology, paleoecology, and spatiality are combined. The conceptual framework of the study is that landscapes are the result of socio-ecological processes over time. To frame the data provided by chosen methods, theoretical frameworks of cultural niche construction theory and landscape patchiness applied, which provide insight of the socio-ecological systems present at Ängesviken during the last 3000 years. During the Iron Age, the site was used for pastoralism, combined with hunting. The archaeological and geographical context of Ängesviken indicate that the site might have been connected with other regions through networks of trade during this period. During the mediaeval period there is a reorganisation of the outlands, leading to a phase of regrowth, but the site could possibly still have been utilised as hunting grounds as there are mediaeval villages in the region. In the early modern period and modern period, the site is once again used for pastoralism. Today, the utilisation of the site has changed towards modern forestry and occasional hunting of elk. The continuous presence at Ängesviken could be explained by the resources the outlands provided. This case study indicates that the far-reaching networks of trade during the Iron Age led to a process of local modification of the ecosystem driven by an external market. This study shows that the anthropogenic modification of the boreal forest's ecosystem has a longer history in eastern Jämtland than traditionally has been thought. The investigation of Ängesviken highlights the importance of researching abstruse and previously uncertain sites from a multidisciplinary approach, as the different datatypes complement each other and results in a deeper knowledge of the site and the socio-ecological systems in a long-term perspective. / Uppsatsen består av en fallstudie av en arkeolgosik lokal vid namn Ängesviken i östra Jämtland. Platsen ligger i ett område som vid första anblick ter sig perifeiellt placerat i utmarkerna till medeltida byar och tidigmoderna fäbodar. Tidigare har en vikingatida byggnad sam en intilligande grav undersökts arkeologiskt. Arkeologiska undersökningar har visat att människor tycks ha använt platsen under en 3000-års period, men hur platsen använts eller påverkats av denna användning har arkeologin inte kunnat påvisa. För att undersöka mänskliga aktiviteter vid Ängesviken under de senaste 3000 åren, samt hur dessa aktiviteter påverkat landskapet, undersöks platsen från ett tvärvetenskapligt perspektiv. Arkeologi kombineras med paleoekologi och rumslig analys. Det konceptuella ramverket för undersökningen bygger på historisk ekologi där kulturell nische konstruktion kombineras med "landscape patchiness". "Landscape patchiness" har sitt ursprung ur ekologin och lägger fokus på lakala vegetationsstrukturer. De äldsta praktikerna på platsen är ännu inte fullt ut klargjorda men platsens läge i landskapet ter sig som en trolig orsak till de första aktiviteterna. Pollenanalysen visar att området används för djurhållning under järnåldern, en aktivitet som kom att förändra landskapets struktur och platsens ekologi. Järnålderns kulturella nische ter sig multifunktionell där djurhållning har kombinerats med andra nyttjanden av utmarksresurser. Pollenanalysen visar att platsen verkar överges under medeltid för att sedan åter brukas för djurhållning under tidigmodern och modern tid. Undersökningen visar på vikten av tvärvetenskapliga undersökningar av otydliga och tidigare svårtolkade arkeologiska lokaler och sammanhang inom det Skandinaviska inlandet.