| 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. |
- 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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| 3. |
- 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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| 4. |
- Bennett, Elena M., et al.
(författare)
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Understanding relationships among multiple ecosystem services.
- 2009
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 12:12, s. 1394-1404
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Tidskriftsartikel (refereegranskat)abstract
- Ecosystem management that attempts to maximize the production of one ecosystem service often results in substantial declines in the provision of other ecosystem services. For this reason, recent studies have called for increased attention to development of a theoretical understanding behind the relationships among ecosystem services. Here, we review the literature on ecosystem services and propose a typology of relationships between ecosystem services based on the role of drivers and the interactions between services. We use this typology to develop three propositions to help drive ecological science towards a better understanding of the relationships among multiple ecosystem services. Research which aims to understand the relationships among multiple ecosystem services and the mechanisms behind these relationships will improve our ability to sustainably manage landscapes to provide multiple ecosystem services.
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| 5. |
- Borrvall, Charlotte, et al.
(författare)
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Early onset of secondary extinctions in ecological communities following the loss of top predators
- 2006
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 9:4, s. 435-442
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Tidskriftsartikel (refereegranskat)abstract
- The large vulnerability of top predators to human-induced disturbances on ecosystems is a matter of growing concern. Because top predators often exert strong influence on their prey populations their extinction can have far-reaching consequences for the structure and functioning of ecosystems. It has, for example, been observed that the local loss of a predator can trigger a cascade of secondary extinctions. However, the time lags involved in such secondary extinctions remain unexplored. Here we show that the loss of a top predator leads to a significantly earlier onset of secondary extinctions in model communities than does the loss of a species from other trophic levels. Moreover, in most cases time to secondary extinction increases with increasing species richness. If local secondary extinctions occur early they are less likely to be balanced by immigration of species from local communities nearby. The implications of these results for community persistence and conservation priorities are discussed.
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| 6. |
- Cornelissen, Johannes H C, et al.
(författare)
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Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:7, s. 619-627
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Tidskriftsartikel (refereegranskat)abstract
- Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
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| 7. |
- Cornwell, William K., et al.
(författare)
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Plant species traits are the predominant control on litter decomposition rates within biomes worldwide
- 2008
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 11:10, s. 1065-1071
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Tidskriftsartikel (refereegranskat)abstract
- Worldwide decomposition rates depend both on climate and the legacy of plant functional traits as litter quality. To quantify the degree to which functional differentiation among species affects their litter decomposition rates, we brought together leaf trait and litter mass loss data for 818 species from 66 decomposition experiments on six continents. We show that: (i) the magnitude of species-driven differences is much larger than previously thought and greater than climate-driven variation; (ii) the decomposability of a species' litter is consistently correlated with that species' ecological strategy within different ecosystems globally, representing a new connection between whole plant carbon strategy and biogeochemical cycling. This connection between plant strategies and decomposability is crucial for both understanding vegetation-soil feedbacks, and for improving forecasts of the global carbon cycle.
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| 8. |
- Elmhagen, Bodil, 1973-, et al.
(författare)
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Trophic control of mesopredators in terrestrial ecosystems: top-down or bottom-up?
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:3, s. 197-206
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Tidskriftsartikel (refereegranskat)abstract
- It has been argued that widespread extinctions of top predators have changed terrestrial ecosystem structures through mesopredator release, where increased abundances of medium-sized predators have detrimental effects on prey communities. This top-down concept has received much attention within conservation biology, but few studies have demonstrated the phenomenon. The concept has been criticized since alternative explanations involving bottom-up impacts from bioclimatic effects on ecosystem productivity and from anthropogenic habitat change are rarely considered. We analyse the response of a mesopredator (the red fox) to declines in top predators (wolf and Eurasian lynx) and agricultural expansion over 90 years in Sweden, taking bioclimatic effects into account. We show a top-down mesopredator release effect, but ecosystem productivity determined its strength. The impacts of agricultural activity were mediated by their effects on top predator populations. Thus, both top-down and bottom-up processes need to be understood for effective preservation of biodiversity in anthropogenically transformed ecosystems.
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| 9. |
- Englund, Göran, et al.
(författare)
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Predation leads to assembly rules in fragmented fish communities
- 2009
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 12, s. 663-671
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Tidskriftsartikel (refereegranskat)abstract
- Diamond [Assembly of species communities. In: Ecology and Evolution of Communities (eds Cody, M.L. & Diamond, J.M.). Harvard University Press, Cambridge, pp. 342–444] proposed that resource competition leads to checkerboard-like distributions of competing species. This proposal prompted research that revealed checkerboard patterns within a wide range of communities, but the mechanisms that generate such patterns are still poorly understood. Here we present whole-lake natural experiments and analyses of species–environment relationships in small coastal lake fish communities that were fragmented when land uplift isolated these lakes from the Baltic Sea, showing that a combination of predation and habitat suitability generated checkerboard distributions. Checkerboard patterns developed because two piscivores, northern pike and Eurasian perch, caused the extinction of several prey species in deep lakes. Conversely, low oxygen levels in shallow lakes caused extinction of the piscivores, and these areas served as a refuge for tolerant prey species. Based on these findings, we suggest that habitat suitability and biotic interactions should be viewed simultaneously in null models of assembly rules.
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| 10. |
- Englund, Göran, et al.
(författare)
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Scaling up the functional response for spatially heterogeneous systems.
- 2008
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 11:5, s. 440-9
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Tidskriftsartikel (refereegranskat)abstract
- Scale transition theory is a framework for predicting regional population dynamics from local process functions and estimates of spatial heterogeneity. Using this framework, we estimated regional scale functional responses for a benthic predator-prey system in the Baltic Sea. Functional responses were based on laboratory experiments or field observations of stomach contents, and prey densities measured at a local scale (0.1 m(2)) or a regional scale (300 km(2)). Laboratory data overestimated consumption at high prey densities, whereas predictions based on local scale data tallied closely with consumption observed at the regional scale. The predicted regional functional response was different for increasing and decreasing prey densities, reflecting that predator and prey densities, as well as the covariance between them, exhibit oscillatory dynamics. We conclude that it is important to validate laboratory data with small-scale field observations and that scale transition is a powerful tool for scaling-up process functions in heterogeneous systems.
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