Animals exhibit a diversity of movement tactics [1]. Tracking resources that change across space and time is predicted to be a fundamental driver of animal movement [2]. For example, some migratory ungulates (i.e., hooved mammals) closely track the progression of highly nutritious plant green-up, a phenomenon called "green-wave surfing" [3-5]. Yet general principles describing how the dynamic nature of resources determine movement tactics are lacking [6]. We tested an emerging theory that predicts surfing and the existence of migratory behavior will be favored in environments where green-up is fleeting and moves sequentially across large landscapes (i.e., wave-like green-up) [7]. Landscapes exhibiting wave-like patterns of green-up facilitated surfing and explained the existence of migratory behavior across 61 populations of four ungulate species on two continents (n = 1,696 individuals). At the species level, foraging benefits were equivalent between tactics, suggesting that each movement tactic is fine-tuned to local patterns of plant phenology. For decades, ecologists have sought to understand how animals move to select habitat, commonly defining habitat as a set of static patches [8, 9]. Our findings indicate that animal movement tactics emerge as a function of the flux of resources across space and time, underscoring the need to redefine habitat to include its dynamic attributes. As global habitats continue to be modified by anthropogenic disturbance and climate change [10], our synthesis provides a generalizable framework to understand how animal movement will be influenced by altered patterns of resource phenology.© 2020 Elsevier Inc.

Liming programmes aiming to restore fish populations are being implemented in many acidified aquatic systems in northern Europe. We studied Odonata communities in 47 forest lakes in SW Sweden, 13 that are currently being limed, and 8 that have previously been limed. Thirty-one species were recorded, with the highest mean number in untreated lakes, followed by previously treated lakes and currently treated lakes. Species communities differed between untreated and limed lakes, but only few rare species found in the untreated lakes were absent in the treated lakes. Likewise, species known to thrive in acid environments were either rare or showed no preferences. Comparing the number of records of odonate species within a large regional area to the proportion of lakes inhabited in our study, we found that seven of the most commonly observed species occurred less frequently in limed lakes than in the untreated ones, including two of the three most common taxa. Reduced species numbers in limed lakes might be due to conditions on other trophic levels, including fish predation. We argue that Odonata should be considered when developing new biological indices of water quality, although the causes of the observed occurrence patterns need to be studied further. © 2016 Springer International Publishing Switzerland

Alpine and polar regions are predicted to be among the most vulnerable to changes in temperature, precipitation, and nutrient availability. We carried out a seven-year factorial experiment with warming and nutrient addition in two alpine vegetation communities. We analyzed the relationship between fruit production and monthly mean, maximum, and min temperatures during the fall of the pre-fruiting year, the fruiting summer, and the whole fruit production period, and measured the effects of precipitation and growing and thawing degree days (GDD & TDD) on fruit production. Nutrient addition (heath: 27.88 ± 3.19 fold change at the end of the experiment; meadow: 18.02 ± 4.07) and combined nutrient addition and warming (heath: 20.63 ± 29.34 fold change at the end of the experiment; meadow: 18.21 ± 16.28) increased total fruit production and fruit production of graminoids. Fruit production of evergreen and deciduous shrubs fluctuated among the treatments and years in both the heath and meadow. Pre-maximum temperatures had a negative effect on fruit production in both communities, while current year maximum temperatures had a positive impact on fruit production in the meadow. Pre-minimum, pre-mean, current mean, total minimum, and total mean temperatures were all positively correlated with fruit production in the meadow. The current year and total precipitation had a negative effect on the fruit production of deciduous shrubs in the heath. GDD had a positive effect on fruit production in both communities, while TDD only impacted fruit production in the meadow. Increased nutrient availability increased fruit production over time in the high alpine plant communities, while experimental warming had either no effect or a negative effect. Deciduous shrubs were the most sensitive to climate parameters in both communities, and the meadow was more sensitive than the heath. The difference in importance of TDD for fruit production may be due to differences in snow cover in the two communities. © 2022 The Authors

Global warming is expected to have large impacts on high alpine and Arctic ecosystems in the future. Here we report effects of 18 years of experimental warming on two contrasting high alpine plant communities in subarctic Sweden. Using open-top chambers, we analysed effects of long-term passive experimental warming on a heath and a meadow. We determined the impact on species composition, species diversity (at the level of rare, common and dominant species), and phylogenetic and functional diversity. Long-term warming drove differentiation in species composition in both communities; warmed plots, but not control plots, had distinctly different species composition in 2013 compared with 1995. Beta diversity increased in the meadow, while it decreased in the heath. Long-term warming had significant negative effects on the three orders of phylogenetic Hill diversity in the meadow. There was a similar tendency in the heath, but only phylogenetic diversity of dominant species was significantly affected. Long-term warming caused reductions in forbs in the heath, while evergreen shrubs increased. In the meadow, deciduous and evergreen shrubs showed increased abundance from 2001 to 2013 in warmed plots. Responses in species and phylogenetic diversity to experimental warming varied over both time (medium (7 years) vs long-term (18 years)) and space (between two neighbouring plant communities). The meadow community was more negatively affected in terms of species and phylogenetic diversity than the heath community. A potential driver for the changes in the meadow may be decreased soil moisture caused by long-term warming. © 2021

Premise: Climate change is having major impacts on alpine and arctic regions, and inter-annual variations in temperature are likely to increase. How increased climate variability will impact plant reproduction is unclear. Methods: In a 4-year study on fruit production by an alpine plant community in northern Sweden, we applied three warming regimes: (1) a static level of warming with open-top chambers (OTC), (2) press warming, a yearly stepwise increase in warming, and (3) pulse warming, a single-year pulse event of higher warming. We analyzed the relationship between fruit production and monthly temperatures during the budding period, fruiting period, and whole fruit production period and the effect of winter and summer precipitation on fruit production. Results: Year and treatment had a significant effect on total fruit production by evergreen shrubs, Cassiope tetragona, and Dryas octopetala, with large variations between treatments and years. Year, but not treatment, had a significant effect on deciduous shrubs and graminoids, both of which increased fruit production over the 4 years, while forbs were negatively affected by the press warming, but not by year. Fruit production was influenced by ambient temperature during the previous-year budding period, current-year fruiting period, and whole fruit production period. Minimum and average temperatures were more important than maximum temperature. In general, fruit production was negatively correlated with increased precipitation. Conclusions: These results indicate that predicted increased climate variability and increased precipitation due to climate change may affect plant reproductive output and long-term community dynamics in alpine meadow communities. © 2021 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America

Climate change is expected to affect alpine and Arctic tundra communities. Most previous long-term studies have focused on impacts on vascular plants, this study examined impacts of long-term warming on bryophyte communities. Experimental warming with open-top chambers (OTCs) was applied for 18 years to a mesic meadow and a dry heath alpine plant community. Species abundance was measured in 1995, 1999, 2001 and 2013. Species composition changed significantly from original communities in the heath, but remained similar in mesic meadow. Experimental warming increased beta diversity in the heath. Bryophyte cover and species richness both declined with long-term warming, while Simpson diversity showed no significant responses. Over the 18-year period, bryophyte cover in warmed plots decreased from 43 % to 11 % in heath and from 68 % to 35 % in meadow (75 % and 48 % decline, respectively, in original cover), while richness declined by 39 % and 26 %, respectively. Importantly, the decline in cover and richness first emerged after 7 years. Warming caused significant increase in litter in both plant communities. Deciduous shrub and litter cover had negative impact on bryophyte cover. We show that bryophyte species do not respond similarly to climate change. Total bryophyte cover declined in both heath and mesic meadow under experimental long-term warming (by 1.5-3 °C), driven by general declines in many species. Principal response curve, cover and richness results suggested that bryophytes in alpine heath are more susceptible to warming than in meadow, supporting the suggestion that bryophytes may be less resistant in drier environments than in wetter habitats. Species loss was slower than the decline in bryophyte abundance, and diversity remained similar in both communities. Increased deciduous shrub and litter cover led to decline in bryophyte cover. The non-linear response to warming over time underlines the importance of long-term experiments and monitoring. © 2020 The Author(s) 2020. Published by Oxford University Press on behalf of the Annals of Botany Company.

Picophytoplankton in the Baltic Sea includes the simplest unicellular cyanoprokaryotes (Synechococcus/Cyanobium) and photosynthetic picoeukaryotes (PPE). Picophytoplankton are thought to be a key component of the phytoplankton community, but their seasonal dynamics and relationships with nutrients and temperature are largely unknown. We monitored pico- and larger phytoplankton at a coastal site in Kalmar Sound (K-Station) weekly during 2018. Among the cyanoprokaryotes, phycoerythrin-rich picocyanobacteria (PE-rich) dominated in spring and summer while phycocyanin-rich picocyanobacteria (PC-rich) dominated during autumn. PE-rich and PC-rich abundances peaked during summer (1.1 × 105 and 2.0 × 105 cells mL–1) while PPE reached highest abundances in spring (1.1 × 105 cells mL–1). PPE was the main contributor to the total phytoplankton biomass (up to 73%). To assess nutrient limitation, bioassays with combinations of nitrogen (NO3 or NH4) and phosphorus additions were performed. PE-rich and PC-rich growth was mainly limited by nitrogen, with a preference for NH4 at >15°C. The three groups had distinct seasonal dynamics and different temperature ranges: 10°C and 17–19°C for PE-rich, 13–16°C for PC-rich and 11–15°C for PPE. We conclude that picophytoplankton contribute significantly to the carbon cycle in the coastal Baltic Sea and underscore the importance of investigating populations to assess the consequences of the combination of high temperature and NH4 in a future climate. Copyright © 2021 Alegria Zufia, Farnelid and Legrand.

In a world where we utilize increasing amounts of pesticides and develop new ones to deal with pests that have grown resistant to pesticides in circulation, studies such as this one need to be conducted to increase our knowledge about how pesticides interact with other risk factors such as global warming. This study investigated the relationship between the butenolide pesticide Flupyradifurone and different temperatures that are predicted to become norm in northern Europe and their effect on bumblebees (Bombus terrestris). There was a significant increase in consumption of sugar solution when bumblebees were fed Flupyradifurone at higher temperatures, whereas control bees had higher consumption at low temperatures. The increase in consumption could indicate that the higher temperatures in the experiment resulted in an increase in toxicity thus resulting in an increase in energy spent due to detoxification. Bumblebees exposed to Flupyradifurone had aberrations in their behaviour such as increased aggressiveness and responsiveness to stimuli, as well as a decrease in movement speed. As a study investigating the synergistic effects of Flupyradifurone and increasing temperatures have not previously been conducted, the findings in this study are new and further testing might be necessary to cement the results.

When planning optimal conservation strategies for wild and cultivated types of a plant species, a number of influencing biological and environmental factors should be considered from the outset. In the present study Brassica rapa was used to illustrate this: to develop Scandinavian conservation strategies for wild and cultivated B. rapa, DNA-marker analysis was performed on 15 cultivated and 17 wild accessions of B. rapa plus 8 accessions of the cross compatible B. napus. The B. rapa cultivars were bred in Sweden and Finland in 1944-1997 and the wild B. rapa material was collected from Denmark, Sweden and United Kingdom. The B. napus accessions were bred within the last 20 years in the Scandinavian countries. Results were based on scoring of 131 polymorphic ISSR markers in the total plant material. A Bayesian Markov chain Monte Carlo (MCMC) approach implemented in NewHybrids demonstrated a clear distinction of B. rapa and B. napus individuals except for three individuals that seemed to be backcrosses. The backcrossed hybrids descended from two Swedish populations, one wild and one escaped. The overall pattern of genetic variation and structure in B. rapa showed that cultivated and wild B. rapa accessions formed two almost separated clusters. Geographical origin and breeding history of cultivars were reflected in these genetic relationships. In addition, wild populations from Denmark and Sweden seemed to be closely related, except for a Swedish population, which seemingly was an escaped cultivar. The study point to that many processes, e.g. spontaneous introgression, naturalisation, breeding and agricultural practise affected the genetic structure of wild and cultivated B. rapa populations. © 2008 Springer Science+Business Media B.V.

In our thesis we investigated the invasive alien species Japanese knotweeds’ potential spread by seeds in the urban areas of Halmstad. The Japanese knotweed origins from the East of Asia and has spread to Europe where its invasive cumulative effect presents a threat to the domestic flora and cities infrastructure. In the species native environment Japanese knotweed can reproduce both vegetative by rhizomes and by sexual reproduction of seeds. Most likely, the majority of Japanese knotweed in Europe spreads only through its rhizomes, and successful establishment of seedlings is currently unknown. In Sweden, no published studies have been conducted on the sexual reproduction of Japanese knotweed. With this thesis we want to investigate the possibility of sexual reproduction of Japanese knotweed in Sweden, with focus on the species populations in the urban areas of Halmstad. By testing the Japanese knotweed seeds in controlled laboratory experiments we were able to test the seeds germination in both petri dishes and in pots of soil. The experiment showed that the seeds were vital. The majority of the seeds sown in petri dishes managed to germinate during the 14 days of the experiment (78,13%), and several seeds also germinated in the pots with soil (15%). The result of our experiment showed that the distance between the Japanese knotweed stands and potential pollen donators stand were not of importance for the germination rate of the seeds. Nor was the number of potential pollen donators in a 2 km radius from the Japanese knotweed stands. How effective Japanese knotweed sexual reproduction is in the wild is still unknown, but our thesis provides evidence on the possibility.

Invasiva främmande arter utgör idag ett av de största hoten mot biologisk mångfald, både nationellt och globalt. Sveriges geografiska läge har medfört en relativt begränsad utbredning av invasiva främmande arter men problematiken förväntas öka med framtida klimatförändringar. SLU ArtDatabanken har därför riskklassificerat arter i Sverige utifrån deras potentiella ekologiska effekt på ekosystem samt deras invasionspotential. ArtDatabankens rapport ska ligga till grund för en framtida nationell förteckning där de invasiva främmande arterna med störst skadeverkan nationellt kommer att omfattas av svensk lagstiftning.

I vår rapport undersöks vilka invasiva främmande landbaserade växter som utgör de största hoten mot ekskogar i Västra Götalands län. Resultatet kan ge ett underlag för att prioritera vilka invasiva främmande växtarter som Länsstyrelsen, i ett tidigt skede, bör rikta åtgärder mot för att bevara och skydda ekskogar i länet. Ek är särskilt skyddsvärt då släktet är ett av Europas viktigaste trädslag och utgör habitat för en stor mängd arter. Invasiva främmande växter kan utgöra ett hot mot ekskogar genom exempelvis beskuggning och konkurrens vilket kan påverka träden negativt. 

Vi har i vår rapport baserat urvalet av invasiva främmande arter på ArtDatabankens risklista samt EU:s förteckning över invasiva främmande arter av unionsbetydelse. Arbetet utfördes som en GIS-analys och en fältstudie. GIS-analysen baserades på observationer i SLU Artportalen och i fältstudien inventerades 4 skyddade ekskogar i länet. De olika resultaten kan indikera på ett bristfälligt underlag i SLU Artportalen. Resultatet av GIS-analysen visade att det största hotet, både nutida och framtida, mot undersökta ekskogar var parkslide (Reynoutria japonica), medan fältstudien visade att druvfläder (Sambucus racemosa) utgjorde det största nutida hotet i inventerade ekskogar. Antalet observationer av invasiva främmande växter från vår artlista i tätortsnära ekskogar, med tillhörande buffertzoner om 2 kilometer, var fler än i ekskogar och dess buffertzoner som klassades som icke tätortsnära. Skillnaden i antal observationer var signifikant. Resultatet kan bekräfta att invasiva främmande växter är mer förekommande i och kring tätorter, varför hoten mot tätortsnära ekskogar kan vara större än mot icke tätortsnära. Detta överensstämmer med tidigare forskning som visar att spridning av invasiva främmande växter gynnas av mänskliga aktiviteter såsom trädgårdsodling samt hantering och transport av massor.

Clearcutting is the most common method for forestry in Sweden. However research shows that this type of intense management can have a negative impact on biological biodiversity as it interferes with an area’s natural characteristics. Previous studies have mainly focused on biological effects on land. In this study dragonflies were used as biological indicators to investigate the impact of clearcutting in aquatic environments. The result from this study indicate that the use of clearcutting as a method for forestry can, with a certain postponement in time, negatively affect the species diversity of Odonata, and thus also the aquatic biodiversity in lakes in the immediate surroundings of a clearcut area, although it is still unclear exactly how and by which mechanisms. It is also uncertain if the effects are only temporarily, or long-term. If Sweden is to reach the environmental goal of Flourishing Lakes and Streams, it is essential to adopt further safety measures when conducting clearcutting near waters to avoid negative impact on the aquatic biological diversity.

Sammanfattning

Nattfjärilar är en utsatt grupp när det kommer till nattbelysning, eftersom nattbelysning påverkar processer som födosök och reproduktion samt ökar deras mortalitet genom stress och ökad risk för predation. Mörka och belysta lokaler i Halmstads urbana grönområden undersöktes för att studera nattbelysningens påverkan på nattfjärilars individantal och artdiversitet. I studien visade vi på signifikanta skillnader hos både nattfjärilars individantal samt artdiversitet mellan de mörka och belysta lokalerna, där tillhörande analyser visade signifikant färre antal individer och likaså negativ trend för artdiversiteten. Analyserna visade att minskad artdiversitet och individantal i belysta lokaler inte var signifikant korrelerat med belysningsstyrkan i lokalerna. Dock finns det indikationer på att belysningsstyrkan eventuellt haft en negativ påverkan på individantalet och artdiversiteten av nattfjärilar i denna studie. Det fanns en belyst lokal som utmärkte sig med ovanligt hög diversitet där artdiversiteten var det tredje högsta uppmätta värdet i hela studien. Detta kan eventuellt bero på förekomsten av blommande buskage vilket återfanns i direkt anslutning till inventeringsområdet. Vi föreslår därför att blommande växter och buskage kan implementeras som åtgärd för att förebygga nattbelysningens påverkan på nattfjärilspopulationer. Kompletterande samt uppföljande studier av ämnet kring vilka växter som passar specifikt för nattfjärilar behövs, då det i dagsläget är ett ämne som i Sverige behöver utvecklas innan implementering av passande växter kan bli en lämplig åtgärd.

Vresrosen, Rosa rugosa, är en kraftigt invasiv art med en oerhörd konkurrenskraft i sanddominerademiljöer såsom sanddyner och sandblottor. Ofta leder etableringen av R. rugosa i dessasanddominerade miljöer till total igenväxning av området med en starkt negativ påverkan på deninhemska floran och faunan. Då merparten av arterna i dessa habitat är beroende av den unika miljönsom den skiftande sanden skapar så innebär igenväxningen ett mycket stort hot. När området bindsupp till en mer stabil miljö utan det permanent tidiga successionsstadium som den vanligtvis befinnersig i så påverkar det även näringsmängden i sanden med ökade näringshalter samt att de varma, öppnamicrositesen försvinner tillsammans med sandens förmåga att röra sig. Eftersom många av deovanliga och hotade arterna kräver en väldigt specifik miljö så försvinner de ofta också närigenväxningen nått så här långt. Denna studie fokuserar på vresrosens etablering och påverkan isanddominerade miljöer. Studien går även in forskning kring samt hur man praktiskt bekämparväxten, då den hotar många ekologiskt viktiga områden. Dessutom hanterar rapporten mina egnaresultat efter inventeringar i Gullbranna/Tönnersa, ett område som historiskt sett varit mycket hårtpåverkat av vresrosen.

ABSTRACT

Seven islands in the lake Kolsnaren have been investigated. I have inventoried saproxylic insects and investigated what characters on dead wood and characters at the islands that have affected species number of beetles (Coleoptera) and true bugs (Hemiptera). This study shows a relatively low number of species of beetles and true bugs but the study was too small to estimate a proper result. Probably there is many more species, especially more rare/threatened species. The characters vary between islands, but even the individual islands had different tree species, thickness, degradation stage and sun exposure of dead wood. Therefore there were favourable conditions for many different saproxylic species that have different demands of the habitat to find suitable substrate. The islands are partly isolated by water but no longer distances. With that in mind it was important that there is plenty of dead wood with varying characters around Kolsnaren so they get the opportunity to disperse and recolonise the islands when even the habitats are changing in time. The dead woods thickness and degradation stage was the characters with most impact of the number of species.

Journal of Vegetation Science published by John Wiley & Sons Ltd on behalf of International Association for Vegetation Science.Aims: Understanding fine-grain diversity patterns across large spatial extents is fundamental for macroecological research and biodiversity conservation. Using the GrassPlot database, we provide benchmarks of fine-grain richness values of Palaearctic open habitats for vascular plants, bryophytes, lichens and complete vegetation (i.e., the sum of the former three groups). Location: Palaearctic biogeographic realm. Methods: We used 126,524 plots of eight standard grain sizes from the GrassPlot database: 0.0001, 0.001, 0.01, 0.1, 1, 10, 100 and 1,000 m2 and calculated the mean richness and standard deviations, as well as maximum, minimum, median, and first and third quartiles for each combination of grain size, taxonomic group, biome, region, vegetation type and phytosociological class. Results: Patterns of plant diversity in vegetation types and biomes differ across grain sizes and taxonomic groups. Overall, secondary (mostly semi-natural) grasslands and natural grasslands are the richest vegetation type. The open-access file ”GrassPlot Diversity Benchmarks” and the web tool “GrassPlot Diversity Explorer” are now available online (https://edgg.org/databases/GrasslandDiversityExplorer) and provide more insights into species richness patterns in the Palaearctic open habitats. Conclusions: The GrassPlot Diversity Benchmarks provide high-quality data on species richness in open habitat types across the Palaearctic. These benchmark data can be used in vegetation ecology, macroecology, biodiversity conservation and data quality checking. While the amount of data in the underlying GrassPlot database and their spatial coverage are smaller than in other extensive vegetation-plot databases, species recordings in GrassPlot are on average more complete, making it a valuable complementary data source in macroecology. © 2021 The Authors.

We examined the effect of thermal shock on the germination of seeds of three conifers, two introduced (Pseudotsuga menziesii and Pinus ponderosa), and one native to Patagonia (Araucaria araucana). Previous research has suggested increased susceptibility to invasions in burnt areas, and therefore, the effect of simulated fire (heat) on seed germination in these native and introduced species was compared. Seeds were heated to two different heat intensities (50°C and 100°C) for 1 or 5 min, which is within the temperature range reached in the upper soil layers during forest fires. Germination tests were then carried out in a growth chamber. The heat treatments had a negative effect on the germination of P. menziesii at temperatures of 100°C, and a negative effect on the germination of P. ponderosa at the temperature of 100°C and the exposure of 5 min. The heat treatments had no affect at all on A. araucana. The species with larger seeds (A. araucana) had higher survival rates after the thermal shocks. Also intraspecific differences in seed sizes possibly point at larger seeds surviving thermal shocks better than smaller seeds. In addition, thermal shock caused a delay in the onset of germination in the two introduced species, while it did not change the time for germination in A. araucana. © The Authors. Journal compilation © Nordic Journal of Botany 2010.

Faced with rapid environmental changes, individuals may express different magnitude and plasticity in their response to a given stressor. However, little is known about the causes of variation in phenotypic plasticity of the stress response in wild populations. In the present study, we repeatedly captured individual roe deer (Capreolus capreolus) from two wild populations in Sweden exposed to differing levels of predation pressure and measured plasma concentrations of stress-induced cortisol and behavioral docility. While controlling for the marked effects of habituation, we found clear between-population differences in the stress-induced cortisol response. Roe deer living in the area that was recently recolonized by lynx (Lynx lynx) and wolves (Canis lupus) expressed cortisol levels that were around 30% higher than roe deer in the human-dominated landscape free of large carnivores. In addition, for the first time to our knowledge, we investigated the stress-induced cortisol response in free-ranging newborn fawns and found no evidence for hypo-responsiveness during early life in this species. Indeed, stress-induced cortisol levels were of similar magnitude and differed between populations to a similar extent in both neonates and adults. Finally, at an individual level, we found that both cortisol and docility levels were strongly repeatable, and weakly negatively inter-correlated, suggesting that individuals differed consistently in how they respond to a stressor, and supporting the existence of a stress-management syndrome in roe deer. © 2018, The Author(s).

This article describes two observations from the outer archipelago of SW Finland on how adult white-tailed sea eagles (Haliaeetus albicilla) actively train their post-fledged offspring to identify, catch and handle prey outside the nest. This involves synchronized and deliberate behaviour from the adults. Adult-juvenile training may be fundamental, as the food sources are shifting, the competition for abundant food items is strong, and the dependence of alternative prey is increasing.

The loss of submerged macrophytes during eutrophication of shallow takes is a commonly observed phenomenon. The proximate reason for this decline is a reduction of available light due to increasing phytoplankton and/or epiphyton biomass. Here we argue that the ultimate cause for the transition from a macrophyte-dominated state to a phytoplankton-dominated state is a change in fish community structure. A catastrophic disturbance event (e.g. winterkill) acting selectively on piscivores, cascades down food chains, eventually reducing macrophyte growth through shading by epiphyton, an effect that is reinforced by increasing phytoplankton biomass. The transition back from the phytoplankton to the macrophyte state depends on an increase in piscivore standing stock and a reduction of planktivores. A conceptual model of these mechanisms is presented and supported by literature data and preliminary observations from a field experiment. © 1992 Kluwer Academic Publishers.

Food chain theory provides explicit predictions for equilibrium biomasses among trophic levels in food chains of different lengths. Empirical studies on freshwater benthic food chains have typically been performed on chains with up to three levels and in field experiments with limited spatial and temporal scale. Here we use a ‘’natural snapshot experiment” approach to study equilibrium biomass and abundance among trophic levels in natural ponds differing only with respect to fish assemblage structure. Forty-four ponds were surveyed for their density and biomass of fish, snails and periphyton. Ponds were divided into three categories based on fish assemblage: ponds with no fish (two trophic levels), ponds with molluscivorous fish (three trophic levels), ponds with molluscivorous fish (three trophic levels) and ponds that also had piscivorous fish (four trophic levels). Ponds without fish had a high density and biomass of snails and a low biomass of periphyton, whereas snails with molluscivorous fish. In the presence of piscivores, molluscivore populations consisted of low numbers of large individuals. Snail assemblages in piscivore ponds were characterised by relatively high densities of small-bodied detritivorous species and periphyton biomass was not significantly different from ponds with three trophic levels. Thus, predictions from classic food chain theory were upheld in ponds with up to three trophic levels. In ponds with four trophic levels, however, there was a decoupling of the trophic cascade at the piscivore-molluscivore level. Gape-limited piscivory, predation on snails by molluscivores that have reached an absolute size refuge from predation, and changes in food preferences of the dominant snails are suggested to explain the observed patterns.

In order to better understand the potential effects of climate change on the Peregrine Falcon, we investigated the relationship between extreme weather events and Peregrines’ breeding success in South Greenland. We defined three variables – number of days with extremely low temperatures, extreme precipitation, consecutive rainy days – and an additive variable, total days with extreme weather, and tested their relationship with Peregrines’ breeding success (measured as young per site and nest success) over a 33 year study period. Breeding success was negatively influenced by the number of days with extreme weather and extremely low temperature. The strongest relationship found was total days with extreme weather in the entire breeding season, which explained 22% and 27% of the variation in nest success and young per site, respectively. The number of days with extreme weather in our study related to fluctuations in the North Atlantic Oscillation (NAO). Thus, with a strengthening of the NAO, linked to climate change, more extreme weather may occur in the Arctic and induce increased variation in Peregrines’ breeding success. Our data did not allow us to pinpoint when in the breeding cycle inclement weather was particularly harmful, and we recommend finer-scale research (e.g. automated nest cameras) to better monitor the species-specific effects of rapidly changing climate.

Our Swedish forests have always been under the exposure of fire, more or less. The historical influence of fires, have made some species bound to these habitats or temporarily using them. Among these species, beetles (Coleoptera) are numerous. One of the tree species with the most historic influence of fire as well as inhabiting a great beetle-fauna is the oak (Quercus sp.). An area with an especially rich beetle-fauna tied to the oak and a extensive history of fire is the Hornsö-area in Smaland. 

The purpose of this study is to investigate how the beetle-fauna and number of individuals differs between newly dead oaks in burnt areas and outside them, in the Hornsö area. The two studied families was long-horn beetles (Cerambycidae) and bark beetles (Scolytinae). The beetles were reared from hatching boxes. The study aims to fil in knowledge gaps about which species that are pyrophilous respectively fire-favoured. In the future this could contribute to a better knowledge about how to manage the oakforests and it`s associated species.

The results shows that bark beetles are more numerous on burned oaks, that have died recently where the fire have been limited to the ground. It also seems like bark beetles are more numerous on smaller diameter trees. Future studies should focus on studying wood a wider range of diameters as well as more trees and samples. A longer time for rearing the insects would also be desirable. 

Grasslands represent canopies with a complex structure where sources and sinks of ammonia (NH3) may coexist at the plant level. Moreover, management practices such as mowing, hay production and grazing may change the composition of the sward and hence the source-sink relationship at the canopy level as well as the interaction with the atmosphere. There is therefore a need to understand the exchange of ammonia between grasslands and the atmosphere better, especially regarding the location and magnitude of sources and sinks. Fluxes of atmospheric NH3 within a grassland canopy were assessed in the field and under controlled conditions using a dynamic chamber technique (cuvette). These cuvette measurements were combined with extraction techniques to estimate the ammonium (NH+4 ) concentration and the pH of a given part of the plant or soil, leading to an estimated ammo- nia compensation point (Cp ). The combination of the cuvette and the extraction techniques was used to identify the poten- tial sources and sinks of NH3 within the different compart- ments of the grassland: the soil, the litter or senescent “litter leaves”, and the functioning “green leaves”. A set of six field experiments and six laboratory experiments were performed in which the different compartments were either added or removed from the cuvettes.The results show that the cuvette measurements agree with the extraction technique in ranking the strength of compartment sources. It suggests that in the studied grassland the green leaves were mostly a sink for NH3 with a compensation point around 0.1–0.4 μg m−3 and   an NH3 flux of 6 to 7 ng m−2 s−1. Cutting of the grass did not increase the NH3 fluxes of the green leaves. The litter was found to be the largest source of NH3 in the canopy, with a Cp of up to 1000μgm−3 NH3 andanNH3 fluxupto90ngm−2 s−1. The litter was found to be a much smaller NH3 source when dried (Cp =160 μg m−3 and FNH3 =35 ng m−2 s−1 NH3 ). Moreover emissions from the litter were found to vary with the relative humidity of the air. The soil was a strong source of NH3 in the period immediately after cutting (Cp =320 μg m−3 and FNH3 =60 ng m−2 s−1 ), which was nevertheless always smaller than the litter source. The soil NH3 emissions lasted, however, for less than one day, and were not observed with sieved soil. They could not be solely explained by xylem sap flow extruding NH+4 . These results indicate that future research on grassland-ammonia relationships should focus on the post-mowing period and the role of litter in interaction with meteorological conditions.

Genom en kombinerad linjetaxering och revirkartering av nyanlagd våtmark i Stjärnarpsdalen utanför Halmstad under april-juni 2018 har jag undersökt artsammansättning, antal individer och par samt häckningskriteria hos fågelarter på plats. En jämförelse har gjorts med fem andra våtmarker i Halland i fråga om artsammansättning och häckninggskriteria för att undersöka om ålder eller storlek hos våtmarker har en effekt på dessa. Efter flertalet besök i Stjärnarp observerades totalt 55 arter varav 31 nyttjade våtmarken för antingen häckning, födosök eller rastade. Totalt 19 arter visade tecken på häckning inom våtmarkens gränser, varav endast fem arter slutligen fick ut avkomma. Hos samtliga undersökta våtmarker varierade antal arter mer under 2018, när de var av olika ålder, jämfört med när de alla var ungefär ett år gamla. Jag fann inga signifikanta korrelationer, beroenden eller skillnader mellan undersökta variabler, med undantag för signifikant korrelation och beroende mellan antal möjliga häckningar och area hos våtmarker. Enligt flera källor kan våtmarkers egenskaper och utformning ha stor betydelse för fåglars förekomst, t ex våtmarkens storlek, ålder, vattendjup, skötsel, placering, närvaro av fisk och mycket mer. I denna studie har Stjärnarp visats hysa arter som bl a häckar, och flera dessa arter indikerar på egenskaper som tidig succession, näringsrikt vatten, öppna strandängar och mer. Beroende på vad för fåglar och annan biologisk mångfald man vill gynna här i framtiden är planering och kontinuerligt uppföljningsarbete viktigt för att se om och hur fågelfaunan förändras samt vad det kan bero på.

Clonal plants from poor habitats benefit less from morphologically plastic responses to heterogeneity than plants from more productive sites. In addition, physiological integration has been suggested to either increase or decrease the foraging efficiency of clonal plants. We tested the capacity for biomass production and morphological response in two closely related, rhizomatous species from habitats that differ in resource availability, Carex arenaria (from poor sand dunes) and C. disticha (from nutrient-richer, moister habitats). We expected lower total biomass production and reduced morphological plasticity in C. arenaria, and that both species would produce more ramets in high nutrient patches, either in response to signals transported through physiological integration, or by locally determined responses to nutrient availability. To investigate mineral nutrient heterogeneity, plants were grown in boxes divided into two compartments with homogeneous or heterogeneous supply of high (H) or low (L) nutrient levels, resulting in four treatments, H-H, H-L, L-H and L-L. Both C. arenaria and C. disticha produced similar biomass in high nutrient treatments. C. disticha responded to high nutrients by increased biomass production and branching of the young parts and by altering root:shoot ratio and rhizome lengths, while C. arenaria showed localised responses to high nutrients in terms of local biomass and branch production in high nutrient patches. The results demonstrated that although it has a conservative morphology, C. arenaria responded to nutrient heterogeneity through morphological plasticity. An analysis of costs and benefits of integration on biomass production showed that young ramets of both species benefited significantly from physiological integration, but no corresponding costs were found. This suggests that plants from resource-poor but dynamic habitats like sand dunes respond morphologically to high nutrient patches. The two species responded to nutrient heterogeneity in different traits, and this is discussed in terms of local and distant signalling of plant status. © 2010 German Botanical Society and The Royal Botanical Society of the Netherlands.

One of the most widely established invasive alien plant species in Sweden is the Japanese knotweed. A range of control measures exist, and there is great need of methods to evaluate their effectiveness. No single method currently guarantees eradication of the Japanese knotweed, hence there is considerable interest to develop more efficient techniques. One is heat treatment using steam or hot water. The effects of heat on above-ground biomass are easy to evaluate but it has proven to be more problematic to evaluate vitality of below-ground rhizomes, which can stay dormant under unfavorable conditions. We have therefore evaluated rhizome vitality using combined greenhouse trials and fluorescence microscopy observations with the vital stains fluorescence diacetate (FDA) and propidium iodide (PI). Fluorescence diacetate was effective in separating live rhizomes from rhizomes that were autoclaved at 121°C. However, while propidium iodide is routinely used to identify dead cells by staining their nuclei, unexpectedly few nuclei were stained in the heat-treated rhizomes. When temperature was reduced to 80°C for 1 hour, FDA indicated some live meristems. However, at 80°C for longer periods, no fluorescence was visible which indicated dead rhizomes. This shows the importance of treatment longevity in order to terminate persistent rhizomes of Japanese knotweed. Type of presentation: Flash talk. 

Coexistence between genetically modified (GM) and non-GM plants is a field of rapid development and considerable controversy. In crops, it is increasingly important to understand and predict the GM volunteer emergence in subsequent non-GM crops. Theoretical models suggest recruitment from the seedbank over extended periods, but empirical evidence matching these predictions has been scarce. Here, we provide evidence of long-term GM seed persistence in conventional agriculture. Ten years after a trial of GM herbicide-tolerant oilseed rape, emergent seedlings were collected and tested for herbicide tolerance. Seedlings that survived the glufosinate herbicide (15 out of 38 volunteers) tested positive for at least one GM insert. The resulting density was equivalent to 0.01 plantsm-2, despite complying with volunteer reduction recommendations. These results are important in relation to debating and regulating coexistence of GM and non-GM crops, particularly for planting non-GM crops after GM crops in the same field. © 2008 The Royal Society.

We test the hypothesis that the expansive horizontal clonal growth of Carex arenaria may provide a method of escape from soil-borne pathogens (fungi and nematodes) by growing away from the site of infection. Plants were grown in non-sterilized or sterilized dune sand, i.e., with or without soil-borne pathogens. The effects of soil-borne pathogens were studied on the whole genet, on the mother alone, and on the first primary rhizome. Genets with the mother plant infected produced less total biomass and had less biomass allocated to roots than genets with uninfected mothers. Infected genets had fewer primary rhizomes and lower total rhizome length, but rhizome specific weight or the distance between shoots did not decrease in infected plants. In C. arenaria, uninfected mothers with an infected first primary rhizome produced shorter and fewer rhizomes than uninfected genets. The infected first rhizome continued to grow at the same speed as uninfected rhizomes, probably by support from the uninfected mother plant. However, secondary rhizome branching was affected only by direct exposure to soil pathogens and not by the status of the mother plant. The results provide evidence that clonal growth may facilitate escape from soil-borne pathogens. The rhizome explores a patchy environment by supporting the growth of young tillers when passing pathogenic patches.

Naturvårdsverket har i regleringsbrevet för år 2009 fått i uppdrag av regeringen att redovisa vilka element som verket bedömer bör ingå i övervakningen av GMO som introduceras i miljön för försök eller i kommersiell odling. I samråd med Miljödepartementet har uppdraget avgränsats till att inte inkludera försök, utan enbart beröra kommersiell odling. Denna rapport utgör redovisningen av uppdraget.

I enlighet med EU:s direktiv 2001/18/EC skall övervakning av genmodifierade grödor utföras i samband med kommersiell odling. Övervakningsplanen utgörs av en allmän del med syfte att upptäcka oförutsedda effekter, och en fallspeci-fik del där risker som har framkommit vid miljöriskbedömningen övervakas. Om inga sådan risker framkommer görs ingen fallspecifik övervakning. Natur-vårdsverket presenterar i denna rapport förslag på parametrar som bör ingå vid övervakning av kommersiell odling av genmodifierade grödor. Förslagen gäller herbicidtoleranta grödor som i nuläget anses relevanta för svenska förhållanden (majs, raps och sockerbeta), potatis med förändrad stärkelsesammansättning, sockerbeta med virusresistens mot Rhizomania samt insektsresistenta (Bt) grö-dor. 

Vad gäller herbicidtoleranta grödor är övervakning av miljöeffekter orsakade av förändringar i herbicidanvändning viktigt. En förändrad herbicidanvändning kan leda till förändringar i ogräsförekomst och -sammansättning, vilket i sin tur kan ge effekter också på högre trofinivåer. Även uppkomst av resistens hos ogräs är en viktig riskfaktor. Herbicidtolerans anses normalt inte medföra någon förhöjd fitness i naturliga habitat, men förekomst av resistenta plantor (spill-plantor eller korsningar med vilda släktingar) utanför åkern bör övervakas med avseende på effekter av förhöjd fitness i habitat som kan påverkas av herbici-der, såsom åkerrenar, vägkanter och banvallar. 

Rhizomaniaresistens hos sockerbeta är en potentiellt fitnesshöjande egenskap, men endast om viruset förekommer i marken. Övervakning av eventuella resi-stenta spillplantor föreslås därför. För att undersöka potentialen för förändrad fitness hos eventuella hybrider med strandbeta behöver studier göras av Rhizo-mania-förekomst i strandbetans habitat. För att kunna bedöma risken för pol-lenflöde mellan sockerbetsodlingar och strandbeta behöver förekomsten av lokaler med strandbeta undersökas. 

För potatis med förändrad stärkelsesammansättning anses att potentialen för spridning är liten och att de potentiella riskerna med egenskapen är små, varför allmän övervakning föreslås vara tillräcklig. 

Vid odling av insektsresistenta grödor (Bt) måste åtgärder som förhindrar upp-komst av resistens hos målorganismerna utföras. Utöver detta bör möjliga effek-ter på icke-målorganismer övervakas samt studeras vidare inom oberoende studier. Oberoende studier behövs också på effekten av insektsresistens på bio-geokemiska kretslopp, liksom på spridning av insektsresistens via spillplantor eller genflöde till vilda släktingar, eftersom modifieringen i dessa fall kan med-föra en förhöjd fitness.

Möjligheterna att knyta GMO-övervakning till befintliga övervakningsprogram i Sverige diskuteras i rapporten. Generellt kan konstateras att inga program direkt verkar kunna användas för GMO-övervakning i sin nuvarande form. Potentiellt skulle fågeltaxeringens data för allmän övervakning kunna utnyttjas vid GMO-övervakning. Det är viktigt att främst de organismgrupper som kan komma att påverkas och därmed bättre användas som indikatorer i första ledet (framförallt växter och insekter) vid en eventuell miljöeffekt ingår i relevant miljöövervak-ning. Eftersom kunskap ofta saknas om effekter på markorganismer och mark-funktion kommer övervakning av dessa att behöva genomföras i relevanta fall. Övervakningen bör kompletteras av oberoende vetenskapliga studier relevanta för svenska förhållanden. 

Naturvårdsverket har i regleringsbrevet för år 2009 fått i uppdrag av regeringen att redovisa vilka uppgifter som verket bedömer behövs i miljöriskbedömningen av genmodifierade (GM) grödor för att kunna ta naturvårdshänsyn till långsiktiga effekter och effekter på icke-målorganismer. Denna rapport utgör redovisningen av uppdraget.

Utveckling och användning av genetiskt modifierade organismer (GMO) är förknippat med potentiella risker. En genomgång har gjorts av de grödor som i dagsläget är intressanta för svenska förhållanden (raps, sockerbeta, potatis och majs), vilka genmodifieringar som finns för varje gröda, och vilka potentiella effekter dessa genmodifierade grödor kan ha. Målen har varit att identifiera potentiella risker vid kommersiell odling och försöksodling av de aktuella grö-dorna, definiera vilka uppgifter som behövs för att kunna utföra en miljörisk-bedömning och undersöka kunskapsläget för dessa uppgifter. 

Enligt gällande EU-lagstiftning och inom vetenskaplig litteratur framhålls att miljöriskbedömningar ska genomföras baserat på ett fall till fall-förfarande. Nya transgena egenskaper utvecklas dock ständigt och det råder stor variation mellan medlemsländerna exempelvis avseende förekomst av icke-målorganismer och frööverlevnad. Detta innebär att det i praktiken är sällan som tillräckliga kunskaper finns om den aktuella grödan och miljön där den är tänkt att odlas kommersiellt, för att fullständigt kunna utvärdera de eventuella negativa effekterna i det specifika fallet. Här måste en rimlighetsavvägning göras av vilka uppgifter som anses nödvändiga mot bakgrund av de identifierade riskerna.

Jordbruksverkets beslut avseende försöksodling av genmodifierade grödor visar att merparten av försöksodlingarna gäller potatis, raps och sockerbeta, medan försöksodling av majs har förekommit två gånger. Genflödesproblematiken skiljer sig mellan grödorna. Majs har inga vilda släktingar som den kan korsa sig med i Sverige och potatis korsar sig inte med de befintliga svenska vilda släktingarna, medan sockerbeta och raps har vilda släktingar till vilka genspridning kan ske. 

För att kunna genomföra miljöriskbedömningar av genmodifierade grödor med hänsyn till långsiktiga effekter och effekter på icke-målorganismer anser Naturvårdsverket att det finns ett behov av ytterligare kunskap avseende odling av GM-grödor under svenska förhållanden. Med utgångspunkt från de identifierade riskernas storlek anser Naturvårdsverket att det är särskilt angeläget att öka kunskaperna kring effekter på icke-målorganismer vid odling av herbicidtoleranta och insektsresistenta grödor, liksom kring resistensutveckling hos ogräs och spillplantor vid odling av herbicidtoleranta grödor. För detta krävs oberoende vetenskapliga studier.

Although sexual reproduction appears to be rare in many clonal plant species, the majority of clonal species show similar levels of genetic variation to non-clonal plant species. Aegopodium podagraria is a noxious garden weed and has become a successful invader in many natural habitats. Earlier studies have demonstrated population differentiation in life-history traits between different A. podagraria populations in Sweden. In this study, we used three methods to assess genetic variation in this species. Using analyses of molecular markers (chloroplast DNA PCR-RFLP and allozyme electrophoresis) we did not detect any variation between different A. podagraria clones. However, a multivariate analysis of leaflet shape in five populations from central Sweden revealed considerable variation both within and between populations. The variation found in leaflet shape is suggested to be genetically based because the leaves were collected from plants grown from seed under similar conditions in a common garden environment. These relatively high levels of variation within and between populations indicate that there is likely to be repeated seedling recruitment within established populations. © The Authors. Journal compilation.

Invasive alien species are one of the biggest threats to biodiversity today, they push away native species and contribute to the loss of natural habitats and biodiversity. American skunk cabbage (Lysichiton americanus), is on the EU “Consolidated List of Invasive Alien Species of Union concern” since 2016 and is locally a problem in Sweden. A pre-study mapping the occurrence and preferred living conditions for L. americanus along Vinån in Falkenberg municipality found about 30,000 individuals. As digging them up with roots, situated 30 cm down in the ground, is the only suitable way of eradication, restoration will probably be necessary, especially areas with high natural values. According to numerous studies, restoration should be done with native species that have the same community traits as the invader. Other studies also indicate that there should be native species that are more resistant to invasions. The aim of the main study was to see if there were plants along Vinån, that are native to Sweden and seemed to have a higher resistibility to L. americanus. The results indicate that Polypodiopsida, Equisetum, Scirpus sylvaticus L., Filipendula ulmaria L. and Phalaris arundinacea L. are in competition with L. americanus and might have a higher resistibility to it. More research is needed before the findings can be implemented in restorations, but by using this study as a stepping stone, the hope is to find an ideal mix of species that could both offer resistance against new invasions of L. americanus and help restore invaded areas with native species. The traits of the species with possible higher resistance is discussed as are the benefits of using native species.

We have examined the role of microbial communities on the surface of submersed macrophytes and in the underlying sediment for nitrification and denitrification in light and dark in NH(4)(+)-enriched microcosm systems using isotope pairing and dilution techniques. Potamogeton pectinatus L. and intact sediment cores were collected in a shallow reservoir receiving treated municipal wastewater and containing dense submersed vegetation. Chambers containing P. pectinatus shoots, sediment, or both P. pectinatus shoots and sediment were exposed to 6 h of darkness, 6 h of light, and 6 h of darkness. (14)NH(4)(+) and (15)NO(3)(-) were added at ambient concentrations of 15 and 5 mg N liter(-1), respectively. NH(4)(+) was primarily nitrified in the epiphytic microbial communities, and NO; was denitrified in the underlying sediment. In chambers containing macrophytes, there was a net production of O(2) and NO(3)(-) in light and a net consumption in dark, and nitrification was higher in light than in dark. In chambers with only sediment, there was always a net consumption of NO(3)(-), and nitrification was similar in light and dark. The results show that submersed macrophytes can be important for the N metabolism in NH(4)(+)-rich freshwaters (e.g., wastewater treatment systems) by stimulating nitrification through providing surfaces for attached nitrifying bacteria and possibly also through diurnal changes in the water chemistry.

1. The denitrifying capacity of epiphyton was used to evaluate differences in the function of epiphytic microbial communities on submersed macrophytes in nutrient-rich freshwater ecosystems. The denitrifying capacity of epiphyton on Patamogeton perfoliatus shoots of different age and with different epiphytic abundances from a eutrophic lake was investigated in laboratory microcosms in the Light and dark. Additionally, differences between epiphyton on shoots of Potamogeton pectinatus grown under different in Situ nutrient and hydraulic conditions were investigated by examining their denitrifying capacity. 2. Denitrification was registered in well-developed epiphytic layers on both mature and senescent shoots in the dark, with activities 3- to 10-fold higher in the epiphytic communities of senescent shoots. No activity was detected on young shoots with sparse epiphyton or on shoots from which loosely attached epiphyton had been removed. Denitrification never occurred during illumination. 3. Even though the epiphytic abundance was similar in magnitude, the denitrifying capacity of epiphyton adapted to high nutrient loadings was about a hundred times higher than that of epiphyton adapted to lower nutrient levels. Additionally, epiphytic abundance and denitrifying capacity were higher at sites less exposed to wave turbulence or water currents, than at sites with more water turbulence. 4. The results illustrate how the hydraulic and nutrient conditions of the surrounding water affect both the quantity and function of epiphytic microbial communities in nutrient-rich freshwater ecosystems.

The aim of this study was to examine the importance of epiphytic denitrifying bacteria on submersed vegetation in removing N from a shallow nutrient-enriched freshwater ecosystem. The investigation was conducted during the summer of 1994 in a surface now reservoir receiving municipal tertiary-treated wastewater. The submersed vegetation in the reservoir was dominated by Potamogeton pectinatus L. and filamentous green algae (FGA). The N loading was 2300 mg N h(-1) m(-2) and the N removal, calculated as the mean difference between influent and effluent N, was 190 mg N h(-1) m(-2) (8%). The majority of influent N consisted of NH4+, but the main part of the N removal was due to the removal of NO3- whereas no net retention of NH4+ was found. Mean total soluble solids and BOD7 retention was 69 and 38%, respectively, Denitrification measurements were conducted in darkness at in situ temperature in microcosms with P. pectinatus, FGA, or infect sediment cores. Epiphytic denitrification ranged between 0.21 to 7.0 mg N h(-1) m(-2) reservoir surface area depending on the abundance of the submersed vegetation (5-140 g DW m(-2)). Sediment denitrification was 4.7 mg N h(-1) m-L reservoir surface area. The mean assimilative N uptake of the submersed vegetation and epiphyton was 3.4 and 1.6 mg N h(-1) m(-2) reservoir surface area, respectively. Measured N removal rates through plant uptake and denitrification could only account for a minor part of the N removal observed by mass balance. However, microcosm denitrification measurements underestimate actual denitrification. Thus, the major part of the N removal was most likely due to denitrification. In conclusion, this study indicates that denitrification in epiphytic microbial communities on submersed vegetation can be of significant importance for the N removal in nutrient-enriched freshwater ecosystems.

The aim of the present study was to investigate seasonal and spatial patterns of soil oxygen consumption, nitrification, denitrification and fluxes of dissolved inorganic nitrogen (DIN) in a tidal salt marsh of the Lagoon of Venice, Italy. In the salt marsh, intact soil cores including overlying water were collected monthly at high tide from April to October in salt marsh creeks and in areas covered by the dominant vegetation, Limonium serotinum. In May, cores were also collected in areas with vegetation dominated by Juncus maritimus and Halimione portulacoides. In laboratory incubations at in situ temperature in the dark, flux rates of oxygen and DIN were monitored in the overlying water of the intact cores. 15N-nitrate was added to the overlying water and nitrification and denitrification were measured using isotope-dilution and -pairing techniques. The results show that highest soil oxygen consumption coincided with the highest water temperature in June and July. The highest denitrification rates were recorded in spring and autumn coinciding with the highest nitrate concentrations. Soil oxygen consumption and nitrification rates differed between sampling sites, but denitrification rates were similar among the different vegetation types. The highest rates were recorded in areas covered with L. serotinum. Burrowing soil macrofauna enhanced oxygen consumption, nitrification and denitrification in April and May. The data presented in this study indicate high temporal as well as spatial variations in the flux of oxygen and DIN, and nitrogen transformations in the tidal salt marshes of the Venice lagoon during the growth season. The results identify the salt marshes of the Venice lagoon as being metabolically very active ecosystems with a high capacity to process nitrogen.

Benthic macroinvertebrates are usually small animals living in our lentic and lotic ecosystems, they have been used as indicators of water quality and biodiversity for a long time. Dam removals have become one of the “go-to” conservation methods for restoring connectivity in lotic ecosystems and thereby enabling passage upstream for migrating species. In Sweden, a large part of rivers and streams have dams present which act as migration barriers. Hushållningssällskapet Halland runs a project, LIFE-Goodstream in which a dam considered a migration barrier was removed in the stream Trönningeån. This report has three focus areas 1) the ecological effects of the dam removal while 2) considering the effect on the species composition of the orders Ephemeroptera (Mayflies), Plecoptera (Stoneflies), Trichoptera (Caddisflies) and Odonata (Dragonflies) in the stream Trönningeån with two tributaries and finally 3) suggest appropriate conservation methods for the future. By examining the benthic macroinvertebrate community our study showed that a small dam removal can have a clear positive effect on water quality, changing the water status classification from low water quality to high. Although there was no effect on the species diversity by the dam removal, a turnover in species composition became obvious after the examination. Moreover, we learned that Trichoptera was the most present order in two out of the three streams while Odonata was the least represented order. Also, bottom substrate, velocity and riparian zone have larger impact on species composition than adjacent environments. Re-meandering streams to further increase biodiversity while also ensuring water quality, is an essential method for a thriving conservation work in the future.

Seasonal changes in rhizome concentrations of total nonstructural carbohydrates (TNC), water soluble carbohydrates (WSC), and mineral nutrients (N, P and K) were monitored in two Phragmites australis stands in southern Sweden. Rhizome biomass, rhizome length per unit ground area, and specific weight (weight/ length ratio) of the rhizomes were monitored in one of the stands. Rhizome biomass decreased during spring, increased during summer and decreased during winter. However, changes in spring and summer were small (< 500 g DW m-2) compared to the mean rhizome biomass (approximately 3000 g DW m^-2). Winter losses were larger, approximately 1000 g DW m-2, and to a substantial extent involved structural biomass, indicating rhizome mortality. Seasonal changes in rhizome length per unit ground area revealed a rhizome mortality of about 30% during the winter period, and also indicated that an intensive period of formation of new rhizomes occurred in June. Rhizome concentrations of TNC and WSC decreased during the spring, when carbohydrates were translocated to support shoot growth. However, rhizome standing stock of TNC remained large (> 1000 g m^-2). Concentrations and standing stocks of mineral nutrients decreased during spring/ early summer and increased during summer/ fall. Only N, however, showed a pattern consistent with a spring depletion caused by translocation to shoots. This pattern indicates sufficient root uptake of P and K to support spring growth, and supports other evidence that N is generally the limiting mineral nutrient for Phragmites. The biomass data, as well as increased rhizome specific weight and TNC concentrations, clearly suggests that "reloading" of rhizomes with energy reserves starts in June, not towards the end of the growing season as has been suggested previously. This resource allocation strategy of Phragmites has consequences for vegetation management. Our data indicate that carbohydrate reserves are much larger than needed to support spring growth. We propose that large stores are needed to ensure establishment of spring shoots when deep water or stochastic environmental events, such as high rhizome mortality in winter or loss of spring shoots due to late season frost, increase the demand for reserves. © 1992 SPB Academic Publishing.