| 1. |
- Antonsen, H, et al.
(författare)
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Relative importance of burning, mowing and species translocation in the restoration of a former boreal hayfield: responses of plant diversity and the microbial community
- 2005
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 42:2, s. 337-347
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Tidskriftsartikel (refereegranskat)abstract
- 1. The extensive loss of species-rich grasslands in Europe as a result of agricultural intensification has triggered a desire to recreate more diverse and natural grassland systems in set-aside fields. Appropriate management and species introductions are necessary to overcome residual soil fertility, lack of suitable plant propagules and dominance of undesirable invasive species. 2. A field experiment was performed in a boreal former hayfield to test the effect of turf inoculation, mowing (twice annually) and spring burning. We surveyed changes in plant diversity, composition and productivity over a 3-year period. Signature fatty acids and soil respiration measurements were employed to survey changes in the soil community. 3. Few changes in the vegetation and soil communities could be related to inoculation of turf monoliths. Most of the measured variables in mown plots differed from the set-aside (control) plots, while burned plots displayed mainly similar responses. Mowing increased plant species richness and diversity, mainly by enhancing the number and frequency of forb species. Small-statured forb species were promoted by mowing, whereas tall leafy grasses declined. Effects of mowing on soil communities comprised an increased soil respiration and stimulation of arbuscular mycorrhizal fungi. 4. Synthesis and applications. The results demonstrate the importance of reducing sward height in order to promote plant species coexistence in former boreal hayfields. In such systems, eliminating accumulated litter by spring burning has little influence on species composition when the sward is allowed to grow tall. Mowing is therefore the most efficient way of enhancing biodiversity. The results also show that mowing-mediated changes in above-ground plant communities may stimulate below-ground symbiotic micro-organisms, potentially resulting in a positive feedback on ecosystem development.
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| 2. |
- Eschen, R, et al.
(författare)
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Carbon addition alters vegetation composition on ex-arable fields
- 2007
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 44:1, s. 95-104
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Tidskriftsartikel (refereegranskat)abstract
- 1. Recent changes in European agricultural policy have led to measures to reverse the loss of species-rich grasslands through the creation of new areas on ex-arable land. Ex-arable soils are often characterized by high inorganic nitrogen (N) levels, which lead to the rapid establishment of annual and fast-growing perennial species during the initial phase of habitat creation. The addition of carbon (C) to the soil has been suggested as a countermeasure to reduce plant-available N and alter competitive interactions among plant species. 2. To test the effect of C addition on habitat creation on ex-arable land, an experiment was set up on two recently abandoned fields in Switzerland and on two 6-year-old restoration sites in the UK. Carbon was added as a mixture of either sugar and sawdust or wood chips and sawdust during a period of 2 years. The effects of C addition on soil parameters and vegetation composition were assessed during the period of C additions and 1 year thereafter. 3. Soil nitrate concentrations were reduced at all sites within weeks of the first C addition, and remained low until cessation of the C additions. The overall effect of C addition on vegetation was a reduction in above-ground biomass and cover. At the Swiss sites, the addition of sugar and sawdust led to a relative increase in legume and forb cover and to a decrease in grass cover. The soil N availability, composition of soil micro-organisms and vegetation characteristics continued to be affected after cessation of C additions. 4. Synthesis and applications. The results suggest that C addition in grassland restoration is a useful management method to reduce N availability on ex-arable land. Carbon addition alters the vegetation composition by creating gaps in the vegetation that facilitates the establishment of late-seral plant species, and is most effective when started immediately after the abandonment of arable fields and applied over several years.
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| 3. |
- Gårdmark, Anna, et al.
(författare)
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Density-dependent body growth reduces the potential of marine reserves to enhance yields
- 2006
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 43:1, s. 61-69
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Tidskriftsartikel (refereegranskat)abstract
- 1. Some models of marine no-take reserves predict that reserves can enhance fishery yield. However, empirical evidence of this remains inconclusive. One reason for this may be the disregard for density-dependent body growth in most models. Density-dependent body growth links the number and size of individuals, and thus could influence the biomass of fishery yield. 2. We developed an age- and size-structured model of an exploited population and analysed the effect of implementing a no-take reserve of varying size. 3. Protecting part of a population from exploitation in a no-take reserve results in a rapid build-up of biomass inside the reserve because of increased survival. However, when body growth is density-dependent it also results in reduced length at a given age within the no-take reserve because of crowding effects. This prediction is backed up by empirical observations. 4. If there is export of individuals (here larvae) from the no-take reserve, length at a given age will also decrease in the fished part of the population outside the reserve. An increase in the number of exploitable individuals thus results in decreased individual body mass. The positive effect of larval drift on fished population size and catch numbers will therefore rarely translate into an increase in equilibrium yield biomass. 5. Synthesis and applications. When body growth is density-dependent, implementation of no-take reserves affects the body size of both protected and exploitable individuals. Although reserves can have several benefits besides increasing yields, our study shows that, if density-dependent somatic effects are important, a general increase in yield biomass cannot be expected. In populations with density-dependent body growth, reserves are more likely to decrease yield biomass unless the population is severely overexploited. Analyses of the efficiency of marine reserves as a means of enhancing the yield of fisheries need to account for ecological processes, and density-dependent body growth is likely to be key.
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| 4. |
- Loman, Jon, et al.
(författare)
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Does pond quality limit frogs Rana arvalis and Rana temporaria in agricultural landscapes? A field experiment
- 2006
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 43:4, s. 690-700
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Tidskriftsartikel (refereegranskat)abstract
- 1. When assessing the cause of population absence or decline, it is important to understand the relative effect of local, regional and global factors. In this study we evaluated the first of these factors for two frog populations. 2. Amphibians are often absent from intensively farmed areas. There could be several reasons for this, one of them being the quality of the aquatic habitat available for reproduction. 3. In order to test why common frogs Rana temporaria and moor frogs Rana arvalis are absent from most ponds in the intensively agricultural areas of southern Sweden, we performed a field experiment. Spawn of both species were introduced into 18 ponds surrounded by intensively cropped fields. 4. Tadpole performance generally did not differ from that in a set of reference ponds in various other habitat types where one or both of these frog species occurs naturally. 5. In the same experimental ponds and in a number of reference ponds, we also introduced tadpoles of the two species into enclosures that protected them from predation and thus increased recapture rate. This experiment revealed that the water quality of farmland ponds is rarely unsuitable for successful frog reproduction. 6. Having measured abiotic and biotic variables in the experimental and reference ponds, we assessed the importance of different parameters to tadpole performance. While farmland ponds generally had higher pH, higher conductivity and higher nitrate and nitrite concentrations than our reference ponds, these factors had no discernible effects on tadpole performance under the ranges found across all pond types. None of the other parameters differed between the two groups of ponds, nor did they have any strong or obvious effects on tadpole performance or survival. 7. Synthesis and applications. The results indicate that water quality alone is not responsible for the scarcity of amphibians in farmland areas of southern Sweden. To understand better the cause of their rarity, future studies should also focus on the quality of the terrestrial habitat surrounding the ponds and the metapopulation structure.
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| 5. |
- McKie, Brendan G., et al.
(författare)
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Mitigation or disturbance? Effects of liming on macroinvertebrate assemblage structure and leaf-litter decomposition in the humic streams of northern Sweden
- 2006
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Ingår i: Journal of Applied Ecology. - Oxford : Blackwell. - 0021-8901 .- 1365-2664. ; 43:4, s. 780-791
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Tidskriftsartikel (refereegranskat)abstract
- Stream liming can alleviate the effects of anthropogenic acidification but itself constitutes a substantial ecosystem-level perturbation. Acidity in the humic streams of northern Sweden largely arises from natural causes but liming is extensively practised, with uncertain ecological outcomes.We investigated macroinvertebrate assemblage structure and leaf-litter decomposition in seven humic Swedish streams, each of which is limed at a single point using a dosing tower. Grey alder Alnus incana leaves were enclosed in replicate fine (mesh size 0·5 mm) and coarse (10 mm) mesh bags at three locations in each stream: upstream of the dosing tower, in the transitional ‘mixing zone’ immediately downstream of the tower, and at a site further downstream where the lime powder is completely dissolved, with marked changes to water chemistry. Benthic macroinvertebrate assemblages were characterized from each site via five replicate Surber samples.Alkalinity, pH, conductivity and calcium (Ca) concentrations increased following liming, whereas dissolved organic carbon and aluminium concentrations decreased.Decomposition in fine mesh bags, primarily mediated by microbes, was positively associated with pH and Ca and was significantly elevated by liming, probably attributable to stimulation of fungal pectin-degrading enzymes that require Ca as a cofactor.Decomposition attributable to detritivorous insects (shredders), assessed by subtracting decomposition observed in fine mesh bags from that observed in coarse bags, was reduced following liming, in concert with changes to shredder assemblages. Abundance of large caddisfly shredders declined in limed stream sections, whereas some smaller stoneflies increased in number. Shredder diversity declined following liming during spring. Species evenness fell overall, and richness was reduced in four of six streams.Synthesis and applications. Water chemistry changes following stream liming in northern Sweden appear to overcompensate for the limited acid deposition observed in the region, with important ecosystem consequences. The potential deleterious impacts of liming need to be balanced against its desired outcomes in regions where acidity is largely attributable to natural causes.
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| 6. |
- Rundlöf, Maj, et al.
(författare)
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Local and landscape effects of organic farming on butterfly species richness and abundance
- 2008
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 45:3, s. 813-820
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Tidskriftsartikel (refereegranskat)abstract
- 1. Agri-environmental schemes (AES) are commonly adopted in Europe to reduce the loss of farmland biodiversity. These schemes have, however, been criticized as not fulfilling this goal, partly because their effectiveness is thought to differ depending on external factors such as landscape heterogeneity, the focal organism and scale of application. 2. We used one AES, organic farming, as a landscape-scale experiment to test whether its effect on butterflies depends on the spatial scale at which it is applied. Our study system consisted of organically and conventionally managed fields within eight pairs of matched landscapes, differing in the proportion of land under organic management at the landscape scale. Butterflies and their nectar and host-plant resources were surveyed along the fields and adjacent field borders. 3. Butterfly species richness and abundance were significantly increased by organic farming at the local scale. However, local butterfly species richness was also positively affected by a large proportion of organic farming in the surrounding landscape, independent of the local farming practice. Local and landscape farming practices interacted such that the farming practice within fields had a larger effect on butterfly abundance if surrounded by conventionally rather than organically managed fields. These results could only partly be explained by variation in local availability of nectar and host-plant resources. 4. The total observed species richness (γ-diversity) was higher in organically managed landscapes, mainly because of higher within-field diversity (α-diversity), whereas the between-field diversity (β-diversity) tended to be similar in both landscape types. 5. Synthesis and applications. Butterflies were positively affected by organic farming at a local scale, but the amount of organic farming in the surrounding landscape had either an additive (species richness) or interactive (abundance) effect. Therefore, the spatial distribution of AES must be taken into account to maximize their potential to increase farmland biodiversity. We have shown that organic farming affected butterfly species richness on nearby conventionally managed land. This suggests a landscape effect of organic farming that may indicate a wider benefit of AES for biodiversity conservation.
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| 7. |
- Rundlöf, Maj, et al.
(författare)
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The effect of organic farming on butterfly diversity depends on landscape context
- 2006
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 43:6, s. 1121-1127
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Tidskriftsartikel (refereegranskat)abstract
- The recent dramatic decline in farmland biodiversity is often attributed to agricultural intensification and structural changes in the agricultural landscape. One suggested farm practice seen to benefit biodiversity and reverse declines is organic farming. Because organic farming is viewed as a more sustainable form of agriculture it is currently subsidized by European agri-environment schemes. However, the efficiency of agri-environment schemes to preserve biodiversity has recently been questioned, partly because their uptake has been highest in extensively farmed more heterogeneous landscapes. We investigated the effect of farming practice on butterfly species richness and abundance along cereal field headlands and margins on 12 matched pairs of organic and conventional farms in contrasting landscapes (homogeneous and heterogeneous landscape diversity). Both organic farming and landscape heterogeneity significantly increased butterfly species richness and abundance. There was also a significant interaction between farming practice and landscape heterogeneity, because organic farming only significantly increased butterfly species richness and abundance in homogeneous rather than heterogeneous landscapes. An analysis of the distribution of organic farming in Sweden in relation to productivity of the arable land (yield of spring barley, kg ha(-1)) indicated that the distribution of organic farms was skewed towards extensively farmed agricultural areas. Synthesis and applications. The species richness and abundance of butterflies can be enhanced by actions aimed at both promoting organic farming and increasing landscape heterogeneity. However, the beneficial effect of organic farming was only evident in intensively farmed homogeneous landscapes. Currently, the majority of organic arable land in Sweden is located in heterogeneous landscapes where changing the type of farming practice adds little to the existing biodiversity. We therefore propose that the interaction between landscape heterogeneity and farming practice must be considered when promoting farmland biodiversity, for example in Europe by developing context-based agri-environment schemes to increase the amount of organic farming in intensively farmed landscapes. We also propose that in homogeneous agricultural landscapes, organic farming could be used as a more efficient tool to restore landscape heterogeneity if the creation of semi-natural landscape elements was mandatory in the regulations associated with organic agri-environment schemes.
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| 8. |
- Wretenberg, Johan, et al.
(författare)
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Linking agricultural policies to population trends of Swedish farmland birds in different agricultural regions
- 2007
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 44:5, s. 933-941
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Tidskriftsartikel (refereegranskat)abstract
- 1. The widespread declines of farmland birds have generally been linked to agricultural intensification. We tested the hypotheses that (i) changes in agricultural policy, through its effects on agricultural intensification and (ii) regional differences in agricultural intensification affect temporal and spatial population trends of farmland birds in Sweden. 2. We analysed regional bird population trends (1976–2003) for seven common farmland bird species: the migratory lapwing Vanellus vanellus, skylark Alauda arvensis, starling Sturnus vulgaris and linnet Carduelis cannabina and the resident tree sparrow Passer montanus, house sparrow P. domesticus and yellowhammer Emberiza citrinella. We identified three periods of agricultural policy in Sweden between 1976 and 2003: the intensification period (i.e. 1976–87; promoting increased production), the set-aside period (1987–95; promoting extensification of farming) and the Common Agricultural Policy (CAP) period (1995–2003; promoting increased production). Population trends were compared between three types of Swedish farmlands: open plains (intensive farming with a marked intensification), mosaic farmlands (i.e. farmland-dominated forest mosaics, less intensive farming, but show moderate intensification) and forest regions (i.e. forest-dominated farmlands with low intensity farming and extensification/abandonment). 3. The four migrants displayed clear significant trend switches between the policy periods, with declines in the ‘intensification period’ and the ‘CAP period’ and less negative or even positive population trends in the ‘set-aside period’. The population trends of the three resident species showed no clear pattern in relation to agricultural policy periods. 4. All species except tree sparrow displayed significantly different population trends between farmland regions. Four species (lapwing, skylark, linnet and house sparrow) declined most in the open plains and the forest regions, whereas two species (starling and yellowhammer) declined most in the mosaic farmlands. 5. Synthesis and applications. Large-scale changes in agriculture policy have a strong potential to change the present poor state of farmland biodiversity as shown by the generally positive population trends in the ‘set-aside period’. It also suggests extensification to be beneficial to farmland birds. However, in regions of low profitability and an already ongoing extensification, a further extensification will lead to loss of both farmland habitat and bird diversity. In such regions mixed farming needs to be retained and hence should be supported.
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| 9. |
- Wretenberg, J, et al.
(författare)
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Population trends of farmland birds in Sweden and England: similar trends but different patterns of agricultural intensification
- 2006
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 43:6, s. 1110-1120
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Tidskriftsartikel (refereegranskat)abstract
- Studies, mainly from the UK, show that many farmland birds have declined as a result of recent agricultural intensification. We tested this idea by analysing farmland bird population trends in Sweden, a country displaying less dramatic agricultural changes and less intensive agriculture. Specifically we investigated whether (i) farmland specialists have declined more than generalists, (ii) population declines in Sweden are less marked than in England and (iii) Swedish population trends are associated with changes in the amount of autumn-sown crops, and inputs of pesticides and fertilizers. Data on population trends for 21 farmland bird species collected from the Swedish Breeding Bird Survey 1976-2001 were analysed in relation to agricultural changes in Sweden. Fifteen (71%) farmland bird species declined significantly in number (P < 0.05) over the 26 years. Farmland specialists displayed a significantly stronger average decline (55%) as a group than farmland generalists (7%). For seven species the declines were significantly steeper between 1976 and 1988 than between 1988 and 2001. Farmland bird populations have declined at least as much in Sweden as in England. Several specialist species displayed similar temporal patterns in population change in both countries. The area of autumn-sown crops has remained stable in Sweden, whereas use of pesticides and fertilizers has declined. There are no clear associations between these factors and observed farmland bird population declines. The similarities in bird population trends in Sweden and England, despite large differences in patterns of agricultural change in Sweden and England, may be explained by: (i) common wintering grounds, (ii) similar negative effects of agricultural intensification (England) and intensification/abandonment (Sweden) and (iii) a simultaneous loss of landscape heterogeneity. Synthesis and applications. Farmland birds in Sweden have declined by at least as much as in England, despite clear differences between the two countries in the degree of agricultural intensification over the last 30 years. We suggest that the marked declines in Swedish populations are caused by (i) the dual negative effects of intensification and abandonment of farmland at breeding grounds, and (ii) Swedish populations partly sharing wintering grounds with English populations. We conclude that agri-environmental schemes need to be flexible enough to address the negative effects both of intensification and the abandonment of farming. In addition, our results emphasize that farmland bird conservation is an issue without country borders.
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| 10. |
- Bommarco, Riccardo, et al.
(författare)
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Cereal aphid populations in non-crop habitats show strong density dependence
- 2007
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Ingår i: Journal of Applied Ecology. - : John Wiley & Sons. - 0021-8901 .- 1365-2664. ; 44:5, s. 1013-1022
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Tidskriftsartikel (refereegranskat)abstract
- 1.Few studies have addressed how density-dependent and density-independent regulation of population growth and abundance varies among habitats for a species that requires multiple habitat types to complete its life cycle. Understanding such relationships, however, are of direct relevance to the control of crop pest insects that regularly move between crop and non-crop habitats.2.We used autoregressive models to analyse a series of seasonal catches of the cereal aphid Rhopalosiphum padi. The data were collected from regional suction traps and egg counts on the overwintering host, over a period of 14–31 years, at four locations in Sweden. R. padi is an obligate host-alternating species in Sweden and seasonal catches reflect habitat use in a year: the primary woody host in winter and spring, the cereal crops in summer, and the perennial grasslands in the autumn.3.Strong direct density dependence acting within the year was found, but the strength varied between seasons depending on habitat use by the aphids during the year. Only a weak indication or no indication at all of density dependence was found during the period of residency on the primary host in the winter and spring periods.4.Density dependence occurred when R. padi utilized summer cereals (42% of the variation was explained), and even stronger density dependence occurred in the perennial grasslands in the autumn (70% variation explained). Stochastic fluctuations in the winter and spring were balanced by a strong density dependence in the cereal and grassland habitats in the summer and autumn periods, which reduced variability in population fluctuations.5.Weather, measured as seasonal average temperature and accumulated precipitation, did not affect aphid abundance fluctuations much, explaining only 1–9% of the variability.6.Synthesis and applications. Our results suggest that density-dependent regulation of R. padi occurs in late summer grasslands and early summer cereals. The mechanisms causing these patterns are not understood, making it difficult to provide specific pest management recommendations at this stage. The results do indicate, however, that pest management needs to involve a landscape-level approach, taking into account mechanistic information about the plant, herbivore and predator interactions in multiple habitats visited by the herbivorous pest.
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