| 1. |
- Tyler, Torbjörn, et al.
(författare)
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Climate warming and land-use changes drive broad-scale floristic changes in Southern Sweden
- 2018
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 24:6, s. 2607-2621
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Tidskriftsartikel (refereegranskat)abstract
- Land-use changes, pollution and climate warming during the 20th century havecaused changes in biodiversity across the world. However, in many cases, the environmental drivers are poorly understood. To identify and rank the drivers currentlycausing broad-scale floristic changes in N Europe, we analysed data from two vascularplant surveys of 200 randomly selected 2.5 9 2.5 km grid-squares in Scania,southernmost Sweden, conducted 1989–2006 and 2008–2015, respectively, andrelated the change in frequency (performance) of the species to a wide range ofspecies-specific plant traits. We chose traits representing all plausible drivers ofrecent floristic changes: climatic change (northern distribution limit, flowering time),land-use change (light requirement, response to grazing/mowing, response to soildisturbance), drainage (water requirement), acidification (pH optimum), nitrogendeposition and eutrophication (N requirement, N fixation ability, carnivory, parasitism,mycorrhizal associations), pollinator decline (mode of reproduction) andchanges in CO2 levels (photosynthetic pathway). Our results suggest that climatewarming and changes in land-use were the main drivers of changes in the flora duringthe last decades. Climate warming appeared as the most influential driver, withnorthern distribution limit explaining 30%–60% of the variance in the GLMM models.However, the relative importance of the drivers differed among habitat types,with grassland species being affected the most by cessation of grazing/mowing andspecies of ruderal habitats by on-going concentration of both agriculture and humanpopulation to the most productive soils. For wetland species, only pH optimum wassignificantly related to species performance, possibly an effect of the increasinghumification of acidic water bodies. An observed relative decline of mycorrhizal species may possibly be explained by decreasing nitrogen deposition resulting in lesscompetition for phosphorus. We found no effect of shortage or decline of pollinatinglepidopterans and bees.
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| 2. |
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| 3. |
- Ekroos, Johan, et al.
(författare)
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Sparing land for biodiversity at multiple spatial scales
- 2016
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- A common approach to the conservation of farmland biodiversity and the promotion of multifunctional landscapes, particularly in landscapes containing only small remnants of non-crop habitats, has been to maintain landscape heterogeneity and reduce land-use intensity. In contrast, it has recently been shown that devoting specific areas of non-crop habitats to conservation, segregated from high-yielding farmland (“land sparing”), can more effectively conserve biodiversity than promoting low-yielding, less intensively managed farmland occupying larger areas (“land sharing”). In the present paper we suggest that the debate over the relative merits of land sparing or land sharing is partly blurred by the differing spatial scales at which it is suggested that land sparing should be applied. We argue that there is no single correct spatial scale for segregating biodiversity protection and commodity production in multifunctional landscapes. Instead we propose an alternative conceptual construct, which we call “multiple-scale land sparing,” targeting biodiversity and ecosystem services in transformed landscapes. We discuss how multiple-scale land sparing may overcome the apparent dichotomy between land sharing and land sparing and help to find acceptable compromises that conserve biodiversity and landscape multifunctionality.
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| 4. |
- Bahram, Mohammad, et al.
(författare)
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Structure and function of the global topsoil microbiome
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 560:7717, s. 233-7
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Tidskriftsartikel (refereegranskat)abstract
- Soils harbour some of the most diverse microbiomes on Earth and are essential for both nutrient cycling and carbon storage. To understand soil functioning, it is necessary to model the global distribution patterns and functional gene repertoires of soil microorganisms, as well as the biotic and environmental associations between the diversity and structure of both bacterial and fungal soil communities(1-4). Here we show, by leveraging metagenomics and metabarcoding of global topsoil samples (189 sites, 7,560 subsamples), that bacterial, but not fungal, genetic diversity is highest in temperate habitats and that microbial gene composition varies more strongly with environmental variables than with geographic distance. We demonstrate that fungi and bacteria show global niche differentiation that is associated with contrasting diversity responses to precipitation and soil pH. Furthermore, we provide evidence for strong bacterial-fungal antagonism, inferred from antibiotic-resistance genes, in topsoil and ocean habitats, indicating the substantial role of biotic interactions in shaping microbial communities. Our results suggest that both competition and environmental filtering affect the abundance, composition and encoded gene functions of bacterial and fungal communities, indicating that the relative contributions of these microorganisms to global nutrient cycling varies spatially.
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| 5. |
- Bao, Xiaozhe, et al.
(författare)
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Arbuscular mycorrhiza under water — Carbon‒phosphorus exchange between rice and arbuscular mycorrhizal fungi under different flooding regimes
- 2019
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 129, s. 169-177
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Tidskriftsartikel (refereegranskat)abstract
- Arbuscular mycorrhizal fungi (AMF) are commonly present in wetlands, but their functional role there is not well understood. We have quantified the carbon (C) allocation from rice to AMF under different flooding regimes, using stable isotope labeling (13CO2), and assessed the potential phosphorus (P) delivery from AMF to rice by profiling the expression of plant and fungal P transporter genes. The results showed that the plant-assimilated C was allocated to AMF under all flooding regimes, as evidenced by the significant enrichment of 13C in the AMF signature fatty acids. The plant C allocation to AMF declined at increased flooding intensity, and was strikingly greater at the growth stage when the rice plants had a higher nutrient requirement. The gene expression profiles and rice P levels strongly indicated that a considerable amount of P was transported to plants via the mycorrhizal pathway under wetland conditions, although AMF colonization did not improve rice growth. This work provides the first solid evidence of C‒P exchange in AM symbiosis under flooded conditions, although it is reduced compared to non-flooded conditions. Nonetheless, this means that AMF may have an important function in wetlands, which opens new perspectives on the application of symbiotic AMF in wetlands.
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| 6. |
- Barin, Mohsen, et al.
(författare)
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Salinity-induced differences in soil microbial communities around the hypersaline Lake Urmia
- 2015
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Ingår i: Soil Research. - 1838-675X. ; 53:5, s. 494-504
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Tidskriftsartikel (refereegranskat)abstract
- Lake Urmia in north-western Iran is one of the largest hypersaline lakes in the world, and agricultural production in the surrounding area is limited by soil salinity. We investigated the effects of salinity on belowground microbial communities in soils collected from fields of cultivated onions (Allium cepa L.) and lucerne (Medicago sativa L.), and sites with the native halophyte samphire (Salicornia europaea L.). We tested the hypotheses that salinity reduces microbial biomass and changes the structure of the microbial community. The physical and chemical properties of soil samples were analysed, and phospholipid fatty acids were identified as signatures for various microbial groups. We found that the organic carbon (OC) content was the dominant determinant of microbial biomass. We also found linear relationships between OC and the biomass of various groups of organisms across the wide salinity gradient studied. Salinity, on the other hand, caused changes in the microbial fatty acid composition that indicated adaptation to stress and favoured saprotrophic fungi over bacteria, and Gram-negative bacteria over Gram-positive. Principal component analysis showed that salinity variables and microbial stress indices formed one group, and OC and microbial biomass another. The importance of OC for high microbial biomass in severely stressed soils indicates that OC amendment may be used to mitigate salt stress and as a method of managing saline soils.
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| 7. |
- Birgander, Johanna, et al.
(författare)
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The responses of microbial temperature relationships to seasonal change and winter warming in a temperate grassland
- 2018
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 24:8, s. 3357-3367
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Tidskriftsartikel (refereegranskat)abstract
- Microorganisms dominate the decomposition of organic matter and their activities are strongly influenced by temperature. As the carbon (C) flux from soil to the atmosphere due to microbial activity is substantial, understanding temperature relationships of microbial processes is critical. It has been shown that microbial temperature relationships in soil correlate with the climate, and microorganisms in field experiments become more warm-tolerant in response to chronic warming. It is also known that microbial temperature relationships reflect the seasons in aquatic ecosystems, but to date this has not been investigated in soil. Although climate change predictions suggest that temperatures will be mostly affected during winter in temperate ecosystems, no assessments exist of the responses of microbial temperature relationships to winter warming. We investigated the responses of the temperature relationships of bacterial growth, fungal growth, and respiration in a temperate grassland to seasonal change, and to 2 years’ winter warming. The warming treatments increased winter soil temperatures by 5–6°C, corresponding to 3°C warming of the mean annual temperature. Microbial temperature relationships and temperature sensitivities (Q10) could be accurately established, but did not respond to winter warming or to seasonal temperature change, despite significant shifts in the microbial community structure. The lack of response to winter warming that we demonstrate, and the strong response to chronic warming treatments previously shown, together suggest that it is the peak annual soil temperature that influences the microbial temperature relationships, and that temperatures during colder seasons will have little impact. Thus, mean annual temperatures are poor predictors for microbial temperature relationships. Instead, the intensity of summer heat-spells in temperate systems is likely to shape the microbial temperature relationships that govern the soil-atmosphere C exchange.
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| 8. |
- Birgander, Johanna, et al.
(författare)
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Warmer winters increase the rhizosphere carbon flow to mycorrhizal fungi more than to other microorganisms in a temperate grassland
- 2017
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 23:12, s. 5372-5382
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Tidskriftsartikel (refereegranskat)abstract
- A decisive set of steps in the terrestrial carbon (C) cycle is the fixation of atmospheric C by plants and the subsequent C-transfer to rhizosphere microorganisms. With climate change winters are expected to become milder in temperate ecosystems. Although the rate and pathways of rhizosphere C input to soil could be impacted by milder winters, the responses remain unknown. To address this knowledge-gap, a winter-warming experiment was established in a seminatural temperate grassland to follow the C flow from atmosphere, via the plants, to different groups of soil microorganisms. In situ 13CO2 pulse labelling was used to track C into signature fatty acids of microorganisms. The winter warming did not result in any changes in biomass of any of the groups of microorganisms. However, the C flow from plants to arbuscular mycorrhizal (AM) fungi, increased substantially by winter warming. Saprotrophic fungi also received large amounts of plant-derived C—indicating a higher importance for the turnover of rhizosphere C than biomass estimates would suggest—still, this C flow was unaffected by winter warming. AM fungi was the only microbial group positively affected by winter warming—the group with the closest connection to plants. Winter warming resulted in higher plant productivity earlier in the season, and this aboveground change likely induced plant nutrient limitation in warmed plots, thus stimulating the plant dependence on, and C allocation to, belowground nutrient acquisition. The preferential C allocation to AM fungi was at the expense of C flow to other microbial groups, which were unaffected by warming. Our findings imply that warmer winters may shift rhizosphere C-fluxes to become more AM fungal-dominated. Surprisingly, the stimulated rhizosphere C flow was matched by increased microbial turnover, leading to no accumulation of soil microbial biomass.
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| 9. |
- Henriksson, Natalie D., et al.
(författare)
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Topsoil removal enhances plant target species occurrence in sandy calcareous grassland
- 2019
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Ingår i: Flora: Morphology, Distribution, Functional Ecology of Plants. - : Elsevier BV. - 0367-2530. ; 256, s. 7-15
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Tidskriftsartikel (refereegranskat)abstract
- Species-rich sandy calcareous grasslands are threatened by land use change, eutrophication and acidification. Disturbance is vital for the persistence of characteristic sandy calcareous grassland species because it provides habitats with low competition, and can lead to increased pH and decreased nutrient availability, which favour many threatened species. Today many sandy calcareous grasslands lack a proper disturbance regime. The outcome of topsoil removal, applied as restoration measure, was investigated in a multi-site study. Successful restoration was associated with colonisation of plants representing conservation target species, as well as increased pH and reduced amounts of nutrients and organic matter. The impact of topsoil removal on plant species composition and soil properties was examined, with adjacent degraded plots serving as controls. Non-degraded target vegetation was included as reference areas. Restored plots had a significantly higher mean proportion of target species compared to control plots. However, control plots had higher species richness. Topsoil removal increased the pH value and decreased contents of ammonium and organic matter in the newly established topsoil layer, while no effect was seen on nitrate, phosphate and lime. Restored plots had a high cover of bare sand, but in contrast to target plots, a rather low proportion of forbs in relation to graminoids. Control plots had a higher vegetation cover, mainly represented by graminoids, forbs and the dwarf shrub species Calluna vulgaris (L.) Hull. Our study suggests that topsoil removal is an effective restoration measure due to its positive influence on soil characteristics and target species. However, the degraded sandy grasslands that were chosen as controls in this study should also be recognised as important habitats with conservation values due to the high species richness, suggesting that a mosaic pattern of the different successional stages is desirable.
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| 10. |
- Hydbom, Sofia, et al.
(författare)
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Reduced tillage stimulated symbiotic fungi and microbial saprotrophs, but did not lead to a shift in the saprotrophic microorganism community structure
- 2017
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Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393 .- 1873-0272. ; 119, s. 104-114
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Tidskriftsartikel (refereegranskat)abstract
- The need for sustainable agricultural systems, which for example enhance soil organic carbon (SOC) content, has increased the interest for management with reduced tillage. In this study we used a Swedish long-term (20 yrs.) systems experiment, including reduced tillage (harrowing 10 cm) and plowing (moldboard plow 0–20 cm) combined with three levels of nitrogen (N) fertilization. With this setup we tested if (1) the arbuscular mycorrhizal fungi (AMF) concentration and (2) the fungi to bacteria (F:B) ratio would be higher under reduced tillage than under conventional tillage, and if this would be associated with higher SOC concentrations. We also tested if (3) the microbial biomass C close to the surface would be higher under reduced tillage than conventional tillage. Furthermore, since disturbance can reduce respiration and microbial growth we tested if (4) this occurred in our reduced tillage system. In addition, we tested if (5) fertilization increased the growth rate of fungi and decreased that of bacteria. We collected soil samples in July and October and found that the microbial biomass C, measured in October only, was higher close to the surface in the reduced tillage treatment and so was the microbial respiration. The fungal and bacterial growth rate, on the other hand, were not affected by tillage treatment. Fertilization did not affect the bacterial growth rate but did have a positive effect on fungal growth rate. In accordance with our expectations reduced tillage had a stimulating effect on AMF and saprotrophic fungi, and contrary to our expectation, also bacteria were positively affected by reduced tillage. In line with the unchanged F:B ratio, we found no indication that even 20 years of reduced tillage increased SOC concentrations in the long term.
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