| 1. |
- Birkhofer, Klaus, et al.
(författare)
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Conventional agriculture and not drought alters relationships between soil biota and functions
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Soil biodiversity constitutes the biological pillars of ecosystem services provided by soils worldwide. Soil life is threatened by intense agricultural management and shifts in climatic conditions as two important global change drivers which are not often jointly studied under field conditions. We addressed the effects of experimental short-term drought over the wheat growing season on soil organisms and ecosystem functions under organic and conventional farming in a Swiss long term trial. Our results suggest that activity and community metrics are suitable indicators for drought stress while microbial communities primarily responded to agricultural practices. Importantly, we found a significant loss of multiple pairwise positive and negative relationships between soil biota and process-related variables in response to conventional farming, but not in response to experimental drought. These results suggest a considerable weakening of the contribution of soil biota to ecosystem functions under long-term conventional agriculture. Independent of the farming system, experimental and seasonal (ambient) drought conditions directly affected soil biota and activity. A higher soil water content during early and intermediate stages of the growing season and a high number of significant relationships between soil biota to ecosystem functions suggest that organic farming provides a buffer against drought effects.
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| 2. |
- Bracht Jörgensen, Helene, et al.
(författare)
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Collembolan dietary specialisation on soil grown fungi
- 2003
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Ingår i: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 39:1, s. 9-15
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Tidskriftsartikel (refereegranskat)abstract
- Preferences of six collembolans for eight species of microfungi grown in soil have been investigated. Collembolans (Folsomia fimetaria, Isotoma anglicana, Isotama notabilis, Heteromurus nitidus, Protaphorura armata, Pseudosinella alba) and microfungi where chosen for the experiment on the basis of their abundance and vertical distribution in an organically grown field where all organisms and soil were collected. Collembolans were tested with pairs of different species of microfungi and a control (sterile soil) in petri dishes and their position determined after 90 min. Based on the first two axes in a Principal Component Analysis we could identify two main feeding patterns in the collembolans: (1) their general acceptance of the fungi (the mean value of the preference indices for all eight fungi), and (2) their alternating preference for Cladosporium herbarum and Fusarium culmorum (high preference index for C. herbarum and low for F. culmorum or vice versa). The six collembolan species in our study combined these two feeding patterns with an intraspecific preference for the eight fungal species and seemed to minimise food competition among collembolans co-occurring in the same soil horizons. Our data suggest that differences in preference between collembolan species may help to explain the coexistence of many species in the same microhabitats of the soil.
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| 3. |
- Bracht Jörgensen, Helene
(författare)
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Food selection and fitness optimisation in insects
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To optimise fitness is a continuous process which assists species survival in changing environments. Choosing an optimal diet is an essential part of the optimisation process and a key element of optimal foraging theory. The relationship between food choice and fitness optimisation has been tested on three ground beetles and several collembolan species by using food items naturally occurring in the same habitat as the animals. The ground beetles Harpalus rufipes and Amara similata are considered being seed-eaters but can include insects in their diet in the field. An addition of insect species to a mixture of seeds did not improve beetle fitness, though a seed mixture was of a higher quality to the beetles than seeds of single plant species. However the beetles did not show a high degree of selectivity between the specific seed species and their choice was not always in agreement with the quality of the seeds. The collembolans, on the other hand, showed a high degree of selectivity and Folsomia fimetaria, Protaphorura armata and Heteromurus nitidus preferred fungi that optimised their growth, survival and fecundity. Folsomia fimetaria could even select the optimal food when a fungal species was grown in different soil substrates. The high degree of selectivity corresponding to food quality that was seen in the collembolans might be due to a production of fungal odour that can be detected by the collembolans. Plants producing proteinase inhibitors experience reduced attacks by herbivores thus the effect on predators feeding on the herbivores was studied. The herbivorous caterpillar Helicoverpa armigera was fed an artificial diet containing a proteinase inhibitor and the ground beetle Harpalus affinis was fed with H. armigera. H. affinis reduced its feeding when the caterpillars had been fed the proteinase inhibitor containing diet. This indicates that changes in food quality at the plant trophic level cascaded to the predator trophic level. In spite of the many laboratory studies we still lack knowledge of selection of food in the field for this insects. A PCR-based method to detect DNA of ingested food species has been developed. Diversity of fungi found in the gut of collembolans was low compared to that of whole animals. This might be due to the dissection method where the head with mouthparts and the uppermost part of the gut was discharged, which presumably contains most undigested fungal material. This method will make it possible to study food selective behaviour of cryptic soil organisms in the future.
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| 4. |
- Bracht Jørgensen, Helene, et al.
(författare)
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Life-history traits of soil collembolans in relation to food quality
- 2008
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Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393. ; 38:2, s. 146-151
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Tidskriftsartikel (refereegranskat)abstract
- Preference studies of many different collembolan species have categorised collembolans being selective in their food choice. To clarify whether collembolan food selectivity is related to fitness parameters, three species, Folsomia fimetaria, Protaphorura armata and Heteromurus nitidus, were fed three fungal species, Alternaria infectoria, Mucor hiemalis and Penicillium hordei, representing fungi of high, medium and low preference. The fungal diets were grown on soil and collembolan growth, survival and fecundity were measured. The fungus A. infectoria supported growth, survival and reproduction best in all three species of collembolans, while the fungus P. hordei was of low food quality. M. hiemalis was of medium quality and F. fimetaria was the only collembolan reproducing on M. hiemalis. F. fimetaria favoured reproduction over growth when confined to M. hiemalis. When P. armata was fed M. hiemalis it reached a size where reproduction normally starts, but no young were produced. This suggests that M. hiemalis lacks nutrients necessary for reproduction. H. nitidus did not perform well on any of the fungi offered, which were generally of low food quality for this species. In this study, where the fungal growth substrate is soil, there is a clear relationship between collembolan fitness and their food choice in contrast to some other studies where substrates optimised for fungal growth had been used. We show that specific fungal species are important for resource allocation to growth or reproduction and closely connected with food choice. Further, we argue that natural fungal growth substrates, such as soil, should be used in experiments of this kind.
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| 5. |
- Bracht Jörgensen, Helene, et al.
(författare)
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Organic amendment and fungal species in combination can alter collembolan fitness
- 2013
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 65, s. 316-321
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Tidskriftsartikel (refereegranskat)abstract
- Organic material of different origin is commonly used as fertiliser in agricultural practices. Clover and wheat straw are here used to determine the importance of organic amendment for population development of fungal feeding collembolans. Two fungal species, Alternaria infectoria and Mucor hiemalis, were inoculated in three growth substrates, clover amended soil, straw amended soil and non-amended soil, where both amendments and the soil originated from agricultural fields. Food choice as well as growth rate, survival and fecundity of the collembolan, Folsomia fimetaria, were measured when fed fungi grown in the three substrates. The type of amendment altered food quality of the two fungi, which was reflected in the collembolan food preference. Growth and fecundity of F. fimetaria were enhanced when fed M. hiemalis grown in both types of plant amended soils. F. fimetaria had a slightly higher fitness when fed A. infectoria grown in the straw amended soil, whereas it's fitness decreased when fed with A. infectoria grown in clover amended soil. We also examined how the predatory mite, Hypoaspis aculeifer, was attracted towards the two fungi as it uses the fungal odour as a potential cue of a prey habitat. H. aculeifer was attracted to both fungi when they were grown in clover amended soil where fungal growth also was observed to be massive. Thus, we conclude that amendment applications can cause effects that cascade through several trophic levels. (C) 2013 Elsevier Ltd. All rights reserved.
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| 6. |
- Bracht Jörgensen, Helene, et al.
(författare)
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Selective foraging of fungi by collembolans in soil
- 2005
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Ingår i: Biology letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 1:2, s. 243-246
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Tidskriftsartikel (refereegranskat)abstract
- Soils contain highly diverse communities of microorganisms and invertebrates. The trophic interactions between these species are largely unknown. Collembolans form an abundant part of the invertebrate community in soils. A prevailing view is that soil collembolans are generalist feeders on fungi, lichens, fragmented litter and bacteria. However, in laboratory food choice experiments, it has been shown that collembolans preferentially select certain taxa of fungi. To examine this apparent contradiction, we developed a molecular technique based on the analysis of 18S ribosomal DNA (rDNA) sequences to explore the diversity of fungi in soils and in the guts of collembolans. We report that the diversity of fungi found in the natural soil was 33 times higher than that in the guts of the collembolan Protaphorura armata. The data support the view that collembolan species can be highly selective when foraging on fungi in soils.
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| 7. |
- De Vries, Franciska T., et al.
(författare)
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Disentangling plant and soil microbial controls on carbon and nitrogen loss in grassland mesocosms
- 2015
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Ingår i: Journal of Ecology. - : Wiley. - 1365-2745 .- 0022-0477. ; 103:3, s. 629-640
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that plant-soil interactions play an important role in determining the impact of global change phenomena on biodiversity and ecosystem functioning. Little is known, however, about the individual and relative importance for carbon (C) and nitrogen (N) cycling of non-random changes in plant and soil communities that result from global change phenomena, such as fertilization and agricultural intensification. We set up a field-based mesocosm experiment in which we re-inoculated soil with contrasting microbial communities taken from extensively managed and from intensively managed grasslands. In a full-factorial design, we subsequently established plant communities representative of intensively and extensively managed grasslands and imposed a fertilization treatment. We then measured plant biomass and diversity, and leaching of C and N as key measures of C and N loss. We hypothesized that non-random changes in both microbial and plant communities would impact C and N leaching, but via different mechanisms. We predicted that plant communities representative of extensively managed grassland would reduce C and N leaching directly through increased water or N uptake, or indirectly via promoting microbial communities that immobilize C and N, whereas plant communities of intensively managed grassland would have the opposite effect. We also hypothesized that microbial communities of extensively managed grassland would feed back positively to plant diversity and that matching' plant and microbial communities would reduce C and N leaching. We found that both plant and microbial communities from extensively managed grassland reduced C and N leaching, especially when matched'. Plant community effects on C and N leaching operated directly through root C inputs and N uptake, rather than through changes in soil microbial communities. In contrast, microbial communities modified C and N leaching both directly by immobilization and indirectly through modifying plant community composition. Synthesis. Our results show that changes in plant and microbial communities both individually and interactively modify C and N loss from grasslands. Moreover, our results suggest that soil microbial communities typical of extensively managed grassland might counteract, or delay, the negative consequences of fertilization on plant diversity and ecosystem functioning.
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| 8. |
- de Vries, Franciska T., et al.
(författare)
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Soil food web properties explain ecosystem services across European land use systems
- 2013
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Ingår i: Proceedings of the National Academy of Sciences. - Washington, DC : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 110:35, s. 14296-14301
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Tidskriftsartikel (refereegranskat)abstract
- Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic locations, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world.
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| 9. |
- Dänhardt, Juliana, et al.
(författare)
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Ekosystemtjänster i det skånska jordbrukslandskapet
- 2013
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Rapport (populärvet., debatt m.m.)abstract
- Jordbrukslandskapet tillhandahåller ekosystemtjänster som utgör förutsättningen för en uthållig jordbruksproduktion och är till nytta för samhället i stort. Bakom dessa finns ekologiska processer som beror av samspel mellan en mångfald av organismer. Skånes jordbruk har genomgått betydande förändringar som förändrat landskapet och livsmiljön för många av dessa. För att bevara och förvalta ekosystemtjänsterna krävs en förståelse för sambanden mellan jordbruk, landskap och ekosystemprocesser. Rapporten beskriver ekologiska processer som ligger till grund för några viktiga ekosystemtjänster i Skånes jordbrukslandskap och visar betydelsen av biologisk mångfald för deras funktion. Där så är möjligt beskrivs hur de kan värderas. Slutligen redovisas praktiska åtgärder som gynnar dem. Rapporten visar att ekosystemtjänster inte enkelt går att ersätta med teknologiska lösningar, utan att förvaltning av dessa tjänster lönar sig. Detta kräver ökad ekologisk kunskap och anpassade styrmedel vilket kräver ökat samråd och regelbunden återkoppling mellan lantbrukare, myndigheter och forskare. Förhoppningen är att rapporten, framtagen av Lunds universitet och Region Skåne, inspirerar till detta!
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| 10. |
- Gagic, Vesna, et al.
(författare)
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Combined effects of agrochemicals and ecosystem services on crop yield across Europe
- 2017
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 20:11, s. 1427-1436
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneously enhancing ecosystem services provided by biodiversity below and above ground is recommended to reduce dependence on chemical pesticides and mineral fertilisers in agriculture. However, consequences for crop yield have been poorly evaluated. Above ground, increased landscape complexity is assumed to enhance biological pest control, whereas below ground, soil organic carbon is a proxy for several yield-supporting services. In a field experiment replicated in 114 fields across Europe, we found that fertilisation had the strongest positive effect on yield, but hindered simultaneous harnessing of below- and above-ground ecosystem services. We furthermore show that enhancing natural enemies and pest control through increasing landscape complexity can prove disappointing in fields with low soil services or in intensively cropped regions. Thus, understanding ecological interdependences between land use, ecosystem services and yield is necessary to promote more environmentally friendly farming by identifying situations where ecosystem services are maximised and agrochemical inputs can be reduced.
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