Swedish Research Council for Environment Agricultural Sciences and Spatial Planning

Background Traditionally managed semi-natural pastures are recognised for their high biodiversity. One drawback is that these pastures are often low in fodder production and hence rather unprofitable, which may lead to abandonment. Two ways to increase production and profitability and maintain grazing are to (i) offer the grazers supplementary feed, or (ii) co-enclose the semi-natural pasture with an improved pasture. Both practices may transfer nutrients to the semi-natural pasture, with potential negative effects on biodiversity. This systematic review aimed to analyse the available evidence concerning the following primary question: “What is the effect of giving grazers access to additional nutrient sources on biodiversity in semi-natural pastures?” (Q1). We also used two supporting questions: “What is the effect of giving grazers access to additional nutrient sources on nutrient status of the soils of semi-natural pastures?” (Q2) and “How do the grazers of semi-natural pastures behave while having access to additional nutrient sources?” (Q3). Methods Searches for peer-reviewed and grey literature were made using bibliographic databases, search engines, specialist websites, and stakeholder contacts. Literature was screened for relevance according to predefined eligibility criteria, and critical appraisal was performed using the tool CEECAT. A database of the relevant studies was compiled. Descriptive information about the evidence base is presented in tables and an interactive evidence atlas. Because of absent study setup replication, Q1 and Q2 were not analysed quantitatively. However, sample size allowed the use of mixed modelling to quantitatively analyse Q3 regarding the effects of (i) co-enclosing an improved pasture on grazers’ electivity for the improved area, and (ii) supplementary feed on the forage intake of grazers. Review findings A total of 12 articles on the effects of supplementary feeding and 19 on the effects of co-enclosing an improved pasture were included, of which some targeted multiple review questions. Because of the limited literature, it is not possible to draw any conclusions concerning the effects on biodiversity (Q1) or nutritional status (Q2) in semi-natural pastures. For Q3, 28 studies fulfilled our criteria, of which 18 investigated the behaviour of grazers related to co-enclosing an improved pasture, and 10 investigated their forage intake while having access to supplementary fodder. The results show that all grazer species except goats preferred grazing in the improved areas regardless of whether they were grazing together with other grazer species or not. We found no effect of supplementary feeding on forage intake of the grazers. Conclusions We detected a knowledge gap concerning the effects of the two additional nutrient sources on semi-natural pasture biodiversity (Q1) and nutrient status (Q2), which points toward further research needs. Analysis of Q3 showed that grazers prefer to graze improved compared to semi-natural pasture areas. However, how this behaviour subsequently affects nutrient transport and biodiversity is unclear and cannot be translated into management recommendations. To gain better knowledge about the primary question of our review, research focusing specifically on this question is needed. We provide suggestions for how such studies could be designed, including spatio-temporal setup, and key management and environmental conditions to consider. Supplementary Information The online version contains supplementary material available at 10.1186/s13750-024-00343-4.

Background The bacterium Bacillus thuringiensis serovar israelensis (Bti) is commercially produced in various formulations for use as a larvicide worldwide, targeting especially the aquatic larval stage of mosquitoes. However, there is a concern that repeated Bti treatments may have both direct and indirect impacts on non-target organisms (NTOs) and the ecosystems they inhabit. This review evaluates the evidence for such impacts. Methods Literature was searched using six bibliographic databases, two search engines, and on specialist web sites. Eligibility screening was performed in two steps on (1) title/abstract, with consistency among reviewers assessed by double-screening 557 articles and (2) full text. Articles included after full text screening were critically appraised independently by two reviewers. Disagreements were reconciled through discussions. Key parameters of included studies are presented in narrative synthesis tables, including risk of bias assessments. Meta-analyses comparing treated with untreated ecosystems and using either the raw mean difference or log response ratio as effect size were performed. Review findings Ninety-five articles covering 282 case studies were included in the review. From these, we identified 119 different response variables, which were divided into nine outcome categories. Most studies investigated NTO abundance or life history (reproduction related outcomes), but diversity and community composition are also well represented as outcome categories. The studies are highly variable in methodology, rigor, and spatio-temporal scale, spanning 1 day to 21 years and from < 1m ² to > 10,000 m ² . Our metanalyses revealed a consistent negative effect of Bti treatment on abundances of Chironomidae and Crustacea, and also on chironomid emergence, although from a more restricted set of studies and regions. For most remaining response variables, we judged meta-analysis unfeasible, due to low study numbers or insufficient reporting of methods and results. Conclusions There is now a significant body of studies documenting effects of mosquito control using Bti on NTOs or other ecosystem properties, especially associated with negative effects on Chironomidae, as apparent from our meta-analyses. Accordingly, we suggest the potential for negative NTO or other ecosystem effects of Bti treatment should not be discounted a priori. Once a decision to proceed with Bti treatment has been taken, priority should be given to a well-designed program of ongoing monitoring and assessment. The paucity of rigorous studies conducted with low bias risk for most response variables undermines our capacity for evaluating how common many of the effects documented might be. Future research would benefit from a rigorous and well-replicated approach to studying Bti impacts in semi-field mesocosms or in the field, combined with a greater rigor in reporting key methodological details. A greater focus is needed on understanding the environmental factors which regulate the wider effects of mosquito control using Bti on NTOs and ecosystems, to enhance our capacity for predicting where and when Bti is most likely to have additional, negative and indirect ecological impacts.

Background Cultivated peatlands are widespread in temperate and boreal climate zones. For example, in Europe about 15% of the pristine peatland area have been lost through drainage for agricultural use. When drained, these organic soils are a significant source of greenhouse gas (GHG) emissions. To reach climate goals, the agricultural sector must reduce its GHG emissions, and one measure that has been discussed is changing land use from cropland to ley production or perennial green fallow. This management change leads to lower reported emissions, at least when using the IPCC default emission factors (EF) for croplands and grasslands on organic soils (IPCC 2014). However, there was a limited background dataset available for developing the EFs, and other variables than management affect the comparison of the land use options when the data originates from varying sites and years. Thus, the implications for future policies remain uncertain. This protocol describes the methodology to conduct a systematic review to answer the question of whether ley production or perennial green fallow can be suggested as a valid alternative to annual cropping to decrease GHG emissions on organic soils in temperate and boreal climate. Methods Publications will be searched in different databases and bibliographies of relevant review articles. The comprehensiveness of the search will be tested through a list of benchmark articles identified by the protocol development team. The screening will be performed at title and abstract level and at full text level, including repeatability tests. Eligible populations are organic agricultural soils in temperate and boreal climate regions. Interventions are grasslands without tillage for at least 3 years, and comparators are annual cropping systems within the same study as the intervention. The outcome must be gas fluxes of either carbon dioxide (CO 2 ), nitrous oxide (N 2 O), or methane (CH 4 ), or any combination of these gases. Studies will go through critical appraisal, checking for internal and external validity, and finally data extraction. If possible, a meta-analysis about the climate impact of perennial green fallow compared to annual cropping on organic soils will be performed.

Background In Sweden there are nearly one million soil-based on-site wastewater treatment systems (OWTSs). OWTSs may contribute to eutrophication of surface waters, due to the discharge of phosphorus (P). Hence, in certain cases, a high P removal rate (up to 90%) of OWTSs is required by Swedish authorities. Since these requirements may have costly consequences to property owners, it is debated whether they are too strict. In this debate, it is often claimed that the soil retention of P occurring in the natural environments may be underestimated by authorities. Soil retention is the inhibition of the transport of P through the ground, due to different chemical, physical and biological processes occurring there. These processes make the P transport slower, which may reduce the unwanted impact on receiving water bodies. However, the efficiency of soil retention of P remains unclear. The objective of this systematic map was to collect, code, organise and elucidate the relevant evidence related to the topic, to be able to guide stakeholders through the evidence base, and to support future research synthesising, commissioning, and funding. The systematic map was carried out in response to needs declared by the Swedish Agency for Marine and Water Management but the conclusions should be valid for a wider range of countries across boreo-temperate regions. Methods Searches were made for peer-reviewed and grey literature using bibliographic databases, search engines, specialist websites, and stakeholder contacts. The references were screened for relevance according to a predefined set of eligibility criteria. A detailed database of the relevant studies was compiled. Data and metadata that enable evaluation and discussion of the character and quality of the evidence base were extracted and coded. Special focus was placed on assessing if existing evidence could contribute to policy and practice decision making. Descriptive information about the evidence base was presented in tables and figures. An interactive evidence atlas and a choropleth were created, displaying the locations of all studies. Review findings 234 articles out of 10,797 screened records fulfilled the eligibility criteria. These articles contain 256 studies, performed in the field or in the laboratory. Six different study types were identified, based on where the measurements were conducted. Most studies, including laboratory studies, lack replicates. Most field studies are observational case studies. Conclusions It is not possible to derive valid generic measures of the efficiency of soil retention of P occurring in the natural soil environment from available research. Neither does the evidence base allow for answering the question of the magnitude of the potential impact of OWTSs on the P concentration in recipients on a general basis, or under what conditions OWTSs generally have such an impact. A compilation of groundwater studies may provide examples of how far the P may reach in x years, but the number of groundwater studies is insufficient to draw any general conclusions, given the complexity and variability of the systems. Future research should strive for replicated study designs, more elaborate reporting, and the establishment of a reporting standard.

Accurate, unbiased and concise synthesis of available evidence following clear methodology and transparent reporting is necessary to support effective environmental policy and management decisions. Without this, less reliable and/or less objective reviews of evidence could inform decision making, leading to ineffective, resource wasteful interventions with potential for unintended consequences. We evaluated the reliability of over 1000 evidence syntheses (reviews and overviews) published between 2018 and 2020 that provide evidence on the impacts of human activities or effectiveness of interventions relevant to environmental management. The syntheses are drawn from the Collaboration for Environmental Evidence Database of Evidence Reviews (CEEDER), an online, freely available evidence service for evidence users that assesses the reliability of evidence syntheses using a series of published criteria. We found that the majority of syntheses have problems with transparency, replicability and potential for bias. Overall, our results suggest that most recently published evidence syntheses are of low reliability to inform decision making. Reviews that followed guidance and reporting standards for evidence synthesis had improved assessment ratings, but there remains substantial variation in the standard of reviews amongst even these. Furthermore, the term ‘systematic review’, which implies conformity with a methodological standard, was frequently misused. A major objective of the CEEDER project is to improve the reliability of the global body of environmental evidence reviews. To this end we outline freely available online resources to help improve review conduct and reporting. We call on authors, editors and peer reviewers to use these resources to ensure more reliable syntheses in the future.

Background Drainage activities have caused widespread wetland loss, groundwater drawdown and impairment of ecosystem services. There are now several national programs for wetland restoration, primarily focused on reintroducing ecosystem services such as habitats and nutrient retention. In Sweden, recent dry summers have also reinforced interest in hydrological functions such as the potential for enhanced groundwater storage, both in and around the wetland. However, there are several knowledge gaps regarding groundwater storage effects of restoration, including if they extend beyond the wetland and how they vary with local conditions. Therefore, we have systematically reviewed groundwater storage effects from the interventions of restoring, constructing or draining boreo-temperate wetlands. Drainage was included primarily to evaluate to what degree restoration can reverse drainage effects. Methods We searched 8 databases for scientific journal publications in English, Swedish, Norwegian, Danish, French, German and Polish. Gray literature was searched in English and Swedish. Articles were included based on their relevance for Swedish conditions, i.e., in previously glaciated areas with boreal or temperate climate. Extracted outcome data were groundwater level changes, along with other variables including type of wetland and intervention and, when reported, distance between sampling point and intervention. Meta-analyses were conducted separately for studies that reported groundwater levels at different distances and studies that reported overall effects. Included studies were subject to critical appraisal to evaluate their susceptibility to bias, primarily selection bias, performance bias, and detection bias. Critical appraisal results were used in sensitivity analysis. Review findings Out of 11,288 screened records, 224 articles fulfilled the criteria, and from these, 146 studies were included in meta-analysis. Most studies (89%) investigated peatlands, primarily from Finland, the UK and Canada. Restoration and drainage studies were equally common. Only nine studies reported measurements beyond the wetland area. Our synthesis is therefore primarily focused on effects within wetlands. In peatland restoration, the observed groundwater level rise decreased exponentially with distance from the restored ditch and was reduced to 50% after 9 [95% confidence interval: 5, 26] m. Drainage reached somewhat farther, with 50% of the groundwater drawdown remaining at 21 [11, 64] m. On average, restoration increased groundwater levels by 22 [16, 28] cm near the intervention, whereas drainage caused a drawdown of 19 [10, 27] cm. Assuming that sampling was unbiased, effects were similar for bogs, fens and mires. Restricting the meta-analysis to the 58% of studies that were of high validity did not alter conclusions. Conclusions Effects of peatland restoration and drainage were of similar magnitudes but opposite directions. This indicates that, on average, rewetting of drained peatlands can be expected to restore groundwater levels near the ditch. However, restoration may not reach all the area affected by drainage, and there was a strong dependence on local context. For managers of wetland projects, it is thus important to follow up and monitor restoration effects and reinforce the intervention if necessary. Our results also point to a need for better impact evaluation if increased storage beyond the restored wetland area is desired.

Background Wetlands in many parts of the world have been degraded, as use of the land for food production and forestry for human needs have taken precedence. Drainage of wetlands has led to deteriorated wetland conditions and lowered water tables. Across the world, there are several programs for wetland restoration and construction, primarily to reintroduce lost habitats for wildlife, and to obtain nutrient retention functions. In Sweden, recent dry and hot summers have reinforced interest in the hydrological functions that wetlands may have, in particular as potential support for water storage in the landscape and added groundwater storage during dry periods. However, the agreement on substantial effects on groundwater is limited, and there are several critical knowledge gaps, including the extent to which such effects extend outside the wetland itself, and how they vary with local conditions, such as topography, soil, and climate. Therefore, this review will address the groundwater storage effect of restoring, constructing or draining wetlands in the boreo-temperate region. Methods We will conduct a systematic review of the evidence, drawing on both peer-reviewed and grey literature. Articles in English, Swedish, Norwegian, Danish, French, German and Polish will be retrieved from academic databases, Google Scholar, and websites of specialist organizations. We will screen literature in two stages, first at the title and abstract level and then in full text, the latter with blinded decisions by two independent reviewers for all articles. Articles will be included based on relevance criteria for a Swedish context: wetlands on previously glaciated soils in boreal and temperate climates. Data will be extracted from all included articles, including wetland type, intervention type, and hydrogeological setting. Studies will be subject to critical appraisal to evaluate their susceptibility to bias. Provided enough evidence of sufficient reliability, we will carry out meta-analyses of effect sizes in relation to various factors. The review will include a narrative synthesis in which we summarize the results of the review.

Background Soil-based on-site wastewater treatment systems (OWSs) are suspected to contribute to eutrophication of surface waters, due to the discharge of phosphorus (P). However, along the flow path between the facilities and surface waters, different processes contribute to delay the transport of phosphorus through the ground. This may reduce the unwanted impact on receiving water bodies. However, the strength and significance of this so-called soil retention remains unclear. In Sweden, there are nearly one million OWSs. To protect surface waters, a high P removal rate (up to 90%) is often required by the local municipalities. However, since these requirements may have costly consequences to property owners, it is debated as to whether they are too strict. In this debate, it is often claimed that the retention of P occurring in natural environments may be underestimated by authorities. Accordingly, there is a need for a scrutiny of the available evidence related to soil retention of phosphorus from OWSs. This is the objective of the planned systematic map. Focus will be on boreal and temperate climate zones. Methods Searches will be made for peer-reviewed articles and grey literature using bibliographic databases, search engines, specialist websites and stakeholder contacts. The references will be screened for relevance according to a predefined set of eligibility criteria. At stage one, after testing and clarifying the eligibility criteria, the references will be single-screened based on title and abstract. At stage two, potentially relevant references will be screened in full-text independently by two reviewers. We will compile a detailed database of the relevant studies. Moreover, a narrative report will be produced, describing the research landscape in general terms. This will be carried out with a conceptual model, describing the processes involved in P retention in natural environments, as a foundation. It will be discussed where the respective studies/study types fit into the conceptual model, and also evaluated how each study/study type can be related to the overarching question of eutrophication. Moreover, we will describe identified knowledge gaps that warrant further primary research effort, as well as identified knowledge clusters that could be suitable for systematic reviews.

Water quality in freshwater lakes and coastal areas has deteriorated in many densely populated areas with increasingly intensive agriculture. For example, eutrophication of aquatic environments has become a major environmental problem in large parts of the world. Biogeochemical transformations occurring in wetlands generally result in reduced nutrient content of water, but quite commonly these ecosystems have been drained or filled to create new forest and arable land. In recent decades efforts have been made to compensate for the losses of natural wetlands by creating new wetlands or restore drained wetlands. However, the large variation in measured nutrient removal rates in such wetlands has made it difficult to assess the effectiveness of such interventions. In this chapter we discuss the role of created wetlands in regulating water quality at the catchment scale. First, we pay attention to a recent systematic review of nitrogen and phosphorus removal in single wetlands in boreal, temperate and sub-tropical regions. Second, in a more focused case study, we evaluate the efficacy of large numbers of constructed wetlands in southern Sweden to remove nutrients from runoff in the context of the eutrophication of the Baltic Sea. The removal efficiency of total nitrogen and total phosphorus in single wetlands is in general relatively high (median values are 37% and 46%, respectively). However, to make a significant difference on a catchment scale, more and larger wetland areas need to be created, and they need to be wisely placed where nutrient loading rates are high.

For many reasons, which also depend on the historical and social context in which they occur, in many occasions women have been excluded from the history or they have secondary roles. The architecture has supported its recognition in the life of the ‘great masters’ and their works, as ‘historic lighthouses’ able to legitimize almost all of a discipli-nary discourse. So, once unraveled this male scenario, it includes both a brief history of architects (worldwide) and the phenomenon of the feminization of higher education in this subject. Concerning the profession, it is exposed which the current features of this, especially in Portugal, taking into account the unemployment, the conciliation of the work-family-personal-social levels, the concept of «career», the expectations and the management of time in the work-leisure binomial, using literature review as research met-hodology.

The increasing focus on urban diffuse sources of Priority Pollutants (PPs) has highlighted stormwater as an important contributor to contamination of natural water bodies. This study presents an example of an integrated model developed to be able to quantify PP loads discharged by stormwater systems. The integrated model includes three submodels that simulate (a) stormwater pollutant sources in the catchments, (b) runoff quality and quantity and (c) stormwater treatment. These submodels employ all the generic available information that can be retrieved without extensive on-site data collection campaigns. Given the general lack of data regarding stormwater PPs and the inherent uncertainty of stormwater quality models, the Generalized Likelihood Uncertainty Estimation (GLUE) technique was applied to estimate the results’ uncertainty. The integrated model was used to estimate the total suspended solids (TSS) and copper (Cu) loads discharged from an industrial/residential catchment in Albertslund (Denmark). The results of the runoff estimation were affected by a high level of uncertainty, which was consequently transferred to the other submodels. The estimation of the model uncertainty and its inclusion in the results enables a wider application of this model and provides a tool for assessing PPs pollution reduction strategies.Graphical abstractHighlights► An integrated model for estimation of stormwater Priority Pollutants was developed. ► The model was applied to estimate TSS and copper loads from a stormwater system. ► Generalized Likelihood Uncertainty Estimation was used for uncertainty analysis. ► Input data uncertainty affected the uncertainty of model’s results. ► The integrated model can be used to evaluate different pollution control scenarios.

Strategies for reduction of micropollutant (MP) discharges from stormwater drainage systems require accurate estimation of the potential MP removal in stormwater treatment systems. However, the high uncertainty commonly affecting stormwater runoff quality modelling also influences stormwater treatment models. This study identified the major sources of uncertainty when estimating the removal of copper and zinc in a retention pond and a biofilter by using a conceptual dynamic model which estimates MP partitioning between the dissolved and particulate phases as well as environmental fate based on substance-inherent properties. The two systems differ in their main removal processes (settling and filtration/sorption, respectively) and in the time resolution of the available measurements (composite samples and pollutographs). The most sensitive model factors, identified by using Global Sensitivity Analysis (GSA), were related to the physical characteristics of the simulated systems (flow and water losses) and to the fate processes related to Total Suspended Solids (TSS). The model prediction bounds were estimated by using the Generalized Likelihood Uncertainty Estimation (GLUE) technique. Composite samples and pollutographs produced similar prediction bounds for the pond and the biofilter, suggesting a limited influence of the temporal resolution of samples on the model prediction bounds. GLUE highlighted model structural uncertainty when modelling the biofilter, due to disregard of plant-driven evapotranspiration, underestimation of sorption and neglect of oversaturation with respect to minerals/salts. The results of this study however illustrate the potential for the application of conceptual dynamic fate models base on substance-inherent properties, in combination with available datasets and statistical methods, to estimate the MP removal in different stormwater treatment systems and compare with environmental quality standards targeting the dissolved MP fraction.

1. The goals of this study were to assess which environmental gradients can be important in predicting viral abundance (VA), the frequency of virus-infected cells (FVIC) and burst size (BS), and to assess which lake characters favour viral-induced bacterial mortality (VBM) as opposed to potential grazer-induced bacterial mortality (PGBM). 2. The epilimnion and hypolimnion of 21 lakes differing in trophic status and humic content were investigated. Samples were obtained for viral and bacterial abundance, the FVIC and burst size, flagellate and ciliate abundances and water chemistry. The potential importance of VBM in relation to PGBM was calculated based on data on FVIC and flagellate and ciliate abundance. 3. Partial least squares regression (PLS) analysis showed that VA as well as the ratio between viral and bacterial abundance were positively related to inorganic nutrient concentrations, dissolved organic carbon concentration, chlorophyll-a concentration and bacterial production. 4. The PLS model also revealed that FVIC decreased with increasing trophic status whereas BS increased. Furthermore, potential grazing was positively related to increasing trophic status and decreasing humic content. PGBM appeared to be dominating over VBM in the majority of lakes sampled, especially in the epilimnion. 5. Thus, the relative importance of viruses for bacterial mortality was potentially highest in humic lakes of medium trophic status and it was also greater in the hypolimnion than in the epilimnion.

1. The goal of this study conducted in three lakes differing in nutrient content and size was to assess the temporal variation in viral community composition and possible co-variation with compositional changes in bacterial communities. 2. The viral community composition differed among lakes and changed over the season. Changes could also be detected on short-time scales, i.e. over a few days. These changes were comparable in magnitude to the changes detected between months or seasons. 3. The most important environmental factors co-varying with viral community composition, as determined by multivariate analysis, differed over the year and among lakes. Temperature and concentrations of dissolved organic carbon (DOC), total phosphorus and soluble reactive phosphorus were the most important factors. 4. Bacterial community composition also varied over the season and among lakes. The most important factors co-varying with bacterial community composition, as determined by multivariate analysis, were also temperature and DOC concentration. 5. Correlation between viral and bacterial community composition was weak and appeared to be a result of an indirect connection rather than a direct relationship between bacteria and viruses.

We added dissolved organic carbon (C) in various amounts to 6 enclosures in an oligotrophic subarctic lake to assess how bacterioplankton growth on dissolved organic C affects the growth of calanoid copepod (Eudiaptomus graciloides) and cladoceran (Daphnia longispina) zooplankton. Organic C was added as glucose (12.5 to 400 µgC L−1d−1) and was isotopically distinct (−11.7 ‰) from lakewater organic C (<−27.2‰). All enclosures were also enriched with the same amounts of inorganic nitrogen (30 µgN L−1d−1 as NH4NO3) and inorganic phosphorus (2 µgP L−1d−1 as Na3PO4). The results showed a direct relationship between bacterial growth on dissolved organic C and incorporation of bacterial biomass into crustacean zooplankton. After 9 days, D. longispina and E. graciloides contained glucose-C in all treatments and the incorporation of glucose-C by zooplankton was strongly correlated with bacterial growth on glucose-C.δ15N data revealed different trophic positions of the two crustaceans, suggesting that D. longispina fed directly on bacteria while E. graciloides incorporated bacterial C by consumption of bacterivorus protozoans. Greater incorporation of glucose-C in D. longispina than in E. graciloides was explained by higher individual growth rates in D. longispina, and this difference between the two zooplankters increased as the bacterial production increased. Thus, the results show that the transfer of dissolved organic C through the food web can be more efficient via cladocerans than via calanoid copepods and that the effect becomes more pronounced as bacterial energy mobilization increases.

"The problem of fit is about the interplay between the human and ecosystem dimensions in social-ecological systems that are not just linked but truly integrated. This interplay takes place across temporal and spatial scales and institutional and organizational levels in systems that are increasingly being interpreted as complex adaptive systems. In 1997, we were invited to produce one of three background papers related to a, at that time, new initiative called Institutional Dimensions of Global Environmental Change (IDEG), a research activity of the International Human Dimensions Program of Global Environmental Change (IHDP). The paper, which exists as a discussion paper of the IHDP, has generated considerable interest. Here we publish the original paper 10 years later with an extended introduction and with reflections on some of the issues raised in the original paper concerning problems of fit."

The responses of aquatic bacteriophages to (1) P additions in P-limited batch cultures and (2) separate P and N additions in batch cultures that were both P- and N-limited were monitored. Possible connections between the abundance of non-nucleoid-containing cells (non-Nu CC) and viral abundance were also examined. The water used in the experiments was collected from the mesotrophic Lake Erken (Sweden) in late autumn. In both experiments, nutrient addition resulted in increases in viral abundance and non-nucleoid-containing bacterial cells. However, in the P- and N-limited cultures, P addition resulted in increases in viral abundance and non-nucleoid-containing bacterial cells, but no increase in bacterial abundance. In contrast, in the cultures to which N was added, increases in viral abundance were accompanied by increases in the abundance of both bacteria and non-nucleoid-containing cells. The results show that there is a connection between changes in the abundance of viruses and non-nucleoid-containing cells. However, there are indications that viral abundance can change in response to changes in the P status of the environment without any increase in bacterial abundance.

Wood-ash applications have been proposed to promote the long-term sustainability of forest production at increased harvest intensities. Effects of wood-ash and nitrogen (N) application on soil-solution chemistry were studied for 9 years following application in a coniferous stand in Sweden. Crushed, self-hardened wood ash was applied at 3, 6, and 9 Mg.ha(-1) alone, the lowest dosage both with and without 150 kg N.ha(-1). Pelleted wood ash (3 Mg.ha(-1)) and N were also applied alone. The soil solution was sampled by suction cups at 50 cm depth. The crushed, self-hardened ash readily dissolved in water, as reflected in increased soil-solution concentrations of sodium and sulphate. Significant (p < 0.05) elevations were also found for potassium, calcium, aluminum, and total organic carbon. Vanadium, chromium, manganese, nickel, copper, zinc, arsenic, and lead were not significantly affected by the ash treatments, but cadmium tended to increase in the treatments with ash alone. From the fourth year onwards, the pH of the soil solution was lowered and the aluminum concentration raised in the plots given 9 Mg crushed ash.ha(-1). Fertilization with N alone temporarily increased concentrations of inorganic N, cadmium, aluminum, and zinc and decreased the pH. The crushed ash generally had longer lasting effects than N fertilization.