| 1. |
- Bengtson, Per, et al.
(författare)
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Rapid turnover of DOC in temperate forests accounts for increased CO2 production at elevated temperatures
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:9, s. 783-790
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The evidence for the contribution of soil warming to changes in atmospheric CO2 concentrations and carbon stocks of temperate forest ecosystems is equivocal. Here, we use data from a beech/oak forest on concentrations and stable isotope ratios of dissolved organic carbon (DOC), phosphate buffer-extractable organic carbon, soil organic carbon (SOC), respiration and microbial gross assimilation of N to show that respired soil carbon originated from DOC. However, the respiration was not dependent on the DOC concentration but exceeded the daily DOC pool three to four times, suggesting that DOC was turned over several times per day. A mass flow model helped to calculate that a maximum of 40% of the daily DOC production was derived from SOC and to demonstrate that degradation of SOC is limiting respiration of DOC. The carbon flow model on SOC, DOC, microbial C mobilization/immobilization and respiration is linked by temperature-dependent microbial and enzyme activity to global warming effects Of CO2 emitted to the atmosphere.
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| 2. |
- Berggren, Martin, et al.
(författare)
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Lake secondary production fueled by rapid transfer of low molecular weight organic carbon from terrestrial sources to aquatic consumers
- 2010
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 13:7, s. 870-880
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Tidskriftsartikel (refereegranskat)abstract
- P>Carbon of terrestrial origin often makes up a significant share of consumer biomass in unproductive lake ecosystems. However, the mechanisms for terrestrial support of lake secondary production are largely unclear. By using a modelling approach, we show that terrestrial export of dissolved labile low molecular weight carbon (LMWC) compounds supported 80% (34-95%), 54% (19-90%) and 23% (7-45%) of the secondary production by bacteria, protozoa and metazoa, respectively, in a 7-km2 boreal lake (conservative to liberal estimates in brackets). Bacterial growth on LMWC was of similar magnitude as that of primary production (PP), and grazing on bacteria effectively channelled the LMWC carbon to higher trophic levels. We suggest that rapid turnover of forest LMWC pools enables continuous export of fresh photosynthates and other labile metabolites to aquatic systems, and that substantial transfer of LMWC from terrestrial sources to lake consumers can occur within a few days. Sequestration of LMWC of terrestrial origin, thus, helps explain high shares of terrestrial carbon in lake organisms and implies that lake food webs can be closely dependent on recent terrestrial PP.
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| 3. |
- Hansson, Bengt, et al.
(författare)
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Heritability of dispersal in the great reed warbler
- 2003
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 6:4, s. 290-294
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Tidskriftsartikel (refereegranskat)abstract
- Dispersal is commonly considered to be a condition-dependent behaviour with no or low heritability. Here, we show that dispersal in the great reed warbler (Acrocephalus arundinaceus ) has a high heritability. Analyses of capture-recapture data of male great reed warblers gathered from the species' whole Swedish breeding range revealed a remarkable offspring-parent resemblance in dispersal behaviour (philopatry vs. inter-population dispersal). Also, the degree of dispersal differed between cohorts, which shows that dispersal was partly conditionally dependent. The offspring to mid-parent estimate of heritability was 0.50. In a previous study of the same data set of male offspring, we did not detect associations between dispersal and several relevant environmental, parental and offspring condition factors. Thus, our results indicate that variation in dispersal partly has a genetic basis in great reed warblers.
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| 4. |
- Järemo, Johannes, et al.
(författare)
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Flee or fight uncertainty : Plant strategies in relation to anticipated damage
- 1999
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 2:6, s. 361-366
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Tidskriftsartikel (refereegranskat)abstract
- In order to cope with damage, plants have evolved a number of strategies. We incorporate two of those strategies, compensatory regrowth and escaping damage in time, into a mathematical model in an attempt to outline under what circumstances one or the other of these phenotypic traits will evolve. Escaping damage in time is accomplished by flowering and setting seeds at a point of time when the risk of damage is low, whereas a compensatory capacity is made possible by activating a proportion of meristems that are left dormant. Our analysis suggests that damage that is predictable in time will favour phenotypes that flower late in the season and that have a good compensatory capacity. As damage becomes less predictable in time, a strategy that implies flowering as early as possible in the season and with no compensatory capacity at all, becomes advantageous.
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| 5. |
- Lundberg, Per, et al.
(författare)
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Spatial population dynamics and the design of marine reserves
- 1999
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 2:3, s. 129-134
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Tidskriftsartikel (refereegranskat)abstract
- The failure of many fisheries world-wide, and the concern about marine biodiversity, has sparked a growing interest in the spatial aspects of harvested populations. If a population conforms to the Ideal Free Distribution and that one of the habitats is set aside as a reserve free from harvesting, the design of reserves may be problematic. If a substantial proportion of the unharvested population is to be preserved, then the reserve area must be unrealistically large, or have a much higher expected fitness than the unprotected area. Interestingly, the optimal harvest rate will be unaffected by both the size of the reserve and the quality of it relative to the harvested area. Even if the Ideal Free Distribution model is extended to include simple age-structure and "spillover" of recruits from the reserve, these conclusions largely remain intact. In a model that also includes spillover, the habitat quality of the reserve may also affect the catch.
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| 6. |
- Lundberg, Per, et al.
(författare)
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Species loss leads to community closure
- 2000
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 3:6, s. 465-468
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Tidskriftsartikel (refereegranskat)abstract
- Global extinction of a species is sadly irreversible. At a local scale, however, extinctions may be followed by re-invasion. We here show that this is not necessarily the case and that an ecological community may close its doors for re-invasion of species lost from it. Previous studies of how communities are assembled have shown that there may be rules for that process and that limitations are set to the order by which species are introduced and put together. Instead of focusing on the assembly process we randomly generated simple competitive model communities that were stable and allowed for two to 10 coexisting species. When a randomly selected single species was removed from the community, the cascading species loss was recorded and frequently the resulting community was more than halved. Cascading extinctions have previously been recorded, but we here show that the relative magnitude of the cascade is dependent on community size land not only trophic structure) and that the reintroduction of the original species lost often is impossible. Hence, species loss does not simply leave a void potentially refilled, bur: permanently alters the entire community structure and consequently the adaptive landscape for potential re-invaders.
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| 7. |
- Olsson, Pål Axel, et al.
(författare)
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Tracking carbon from the atmosphere to the rhizosphere
- 2005
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 8:12, s. 1264-1270
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Tidskriftsartikel (refereegranskat)abstract
- Turnover rates of arbuscular mycorrhizal (AM) fungi may influence storage of soil organic carbon (SOC). We examined the longevity of AM hyphae in monoxenic cultures; and we also used C-13 incorporation into signature fatty acids to study C dynamics in a mycorrhizal symbiosis involving Glomus intraradices and Plantago lanceolata. C-13 enrichment of signature fatty acids showed rapid transfer of plant assimilates to AM fungi and a gradual release of C from roots to rhizosphere bacteria, but at a much slower rate. Furthermore, most C assimilated by AM fungi remained 32 days after labelling. These findings indicate that C-13 labelled fatty acids can be used to track C flux from the atmosphere to the rhizosphere and that retention of C in AM fungal mycelium may contribute significantly to SOC.
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| 8. |
- Perez-Tris, Javier, et al.
(författare)
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Dispersal increases local transmission of avian malarial parasites
- 2005
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 8:8, s. 838-845
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Tidskriftsartikel (refereegranskat)abstract
- The relationships between dispersal and local transmission rate of parasites are essential to understanding host-parasite coevolution and the emergence and spread of novel disease threats. Here we show that year-round transmission, as opposed to summer transmission, has repeatedly evolved in malarial parasites (genera Plasmodium and Haemoproteus) of a migratory bird. Year-round transmission allows parasites to spread in sympatric host's wintering areas, and hence to colonize distantly located host's breeding areas connected by host-migration movements. Widespread parasites had higher local prevalence, revealing increased transmission, than geographically restricted parasites. Our results show a positive relationship between dispersal and local transmission of malarial parasites that is apparently mediated by frequent evolutionary changes in parasite transmission dynamics, which has important implications for the ecology and evolution of infectious diseases.
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| 9. |
- Ripa, Jörgen, et al.
(författare)
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Linear analysis solves two puzzles in population dynamics : the route to extinction and extinction in coloured environments
- 1999
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 2:4, s. 219-222
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we give simple explanations to two unsolved puzzles that have emerged in recent theoretical studies in population dynamics. First, the tendency of some model populations to go extinct from high population densities, and second, the positive effect of autocorrelated environments on extinction risks for some model populations. Both phenomena are given general explanations by simple, linear, stochastic models. We emphasize the predictive and explanatory power of such models.
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| 10. |
- Råberg, Lars, et al.
(författare)
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The cost of an immune response: vaccination reduces parental effort
- 2000
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 3:5, s. 382-386
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental assumption of theories of the ecology and evolution of inducible defences is that protective responses to attacks by parasites or predators should not only have benefits, but also costs. The vertebrate immune system is by far the best studied example of an inducible defence, yet little is known about the costs of an immune response, especially in natural populations. To test: if an immune response per se is costly, we induced an antibody response in female blue tits, Parus caeruleus, by immunising them with human diphtheria-tetanus vaccine, and compared their nestling-feeding rate with that of saline-injected controls. We found that vaccinated females reduced their nestling feeding rate, thus demonstrating a cost of the immune response in the currency of parental effort.
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