| 1. |
- Hagenberg, Liyenne Wu Chen, et al.
(författare)
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Vegetation change on mountaintops in northern Sweden: Stable vascular-plant but reordering of lichen and bryophyte communities
- 2022
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Ingår i: Ecological Research. - : Wiley. - 0912-3814 .- 1440-1703. ; 37:6, s. 722-737
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Tidskriftsartikel (refereegranskat)abstract
- Alpine ecosystems harbor remarkably diverse and distinct plant communities that are characteristically limited to harsh, and cold climatic conditions. As a result of thermal limitation to species occurrence, mountainous ecosystems are considered to be particularly sensitive to climate change. Our understanding of the impact of climate change is mainly based on vascular plants however, whereas cryptogams (i.e., lichens and bryophytes) are generally neglected or simply considered as one functional group. Here we aimed to improve our understanding of the drivers underlying temporal changes in vegetation of alpine ecosystems. To this end, we repeatedly surveyed the vegetation on four mountain summits along an elevational gradient in northern Sweden spanning a 19-year period. Our results show that the vascular plant communities remained relatively stable throughout the study period, despite fluctuations in terms of ground cover and species richness of shrubs and graminoids. In contrast, both lichens and bryophytes substantially decreased in cover and diversity, leading to alterations in community composition that were unrelated to vascular plant cover. Thermophilization of the vascular plant community was found only on the two intermediate summits. Our findings are only partially consistent with (long-term) climate-change impacts, and we argue that local non-climatic drivers such as herbivory might offset vegetation responses to warming. Hence, we underline the importance of considering local non-climatic drivers when evaluating temporal vegetation change in biologically complex systems.
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| 2. |
- Abeli, Thomas, et al.
(författare)
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Geographical pattern in the response of the arctic-alpine Silene suecica (Cariophyllaceae) to the interaction between water availability and photoperiod
- 2015
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Ingår i: Ecological research. - : Wiley. - 0912-3814 .- 1440-1703. ; 30:2, s. 327-335
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Tidskriftsartikel (refereegranskat)abstract
- We hypothesized a geographical pattern of the plant performance (seedling development, biomass production, relative water content and chlorophyll content) as a result of response to the interaction between photoperiod and water availability in populations of the arctic-alpine Silene suecica from different latitudes, thus experiencing different photoperiods during the growing season. Particularly, we expected a lower drought sensitivity in northern compared to southern populations as a consequence of harsher conditions experienced by the northern populations in terms of water availability. The experiment was carried out under common garden conditions, manipulating the water availability (wet and dry) and the photoperiod (21 and 16 h). We found an interaction between photoperiod and water availability on plant height, leaves, growth, biomass and total chlorophyll. However, the photoperiod neither counteracted nor intensified the effect of drought. Plants exposed to drought compensated for decreasing water availability by reducing their shoot growth. Changes in the chlorophyll content and chlorophyll a/b ratio were observed. Northern populations showed a higher basal growth performance and a greater response to the changed water regime (from wet to dry) than the southern populations. Southern populations showed a reduced ability to respond to drought, but their low basal performance may be advantageous under low water availability, avoiding water loss. In contrast, northern populations showed a stronger plastic response that limited the negative effects of reduced water availability. This study highlights the possibility that the plant response to environmental constraints (specifically water availability) may follow a geographical pattern.
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| 3. |
- Ali, A., et al.
(författare)
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Diversity-productivity dependent resistance of an alpine plant community to different climate change scenarios
- 2016
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Ingår i: Ecological Research. - : Wiley. - 0912-3814 .- 1440-1703. ; 31:6, s. 935-945
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Tidskriftsartikel (refereegranskat)abstract
- Here we report from a experiment imposing different warming scenarios [control with ambient temperature, constant level of moderate warming for 3 years, stepwise increase in warming for 3 years, and one season of high level warming (pulse) simulating an extreme summer event] on an alpine ecosystem to study the impact on species diversity-biomass relationship, and community resistance in terms of biomass production. Multiple linear mixed models indicate that experimental years had stronger influence on biomass than warming scenarios and species diversity. Species diversity and biomass had almost humpback relationships under different warming scenarios over different experimental years. There was generally a negative diversity-biomass relationship, implying that a positive diversity-biomass relationship was not the case. The application of different warming scenarios did not change this tendency. The change in community resistance to all warming scenarios was generally negatively correlated with increasing species diversity, the strength of the correlation varying both between treatments and between years within treatments. The strong effect of experimental years was consistent with the notion that niche complementarity effects increase over time, and hence, higher biomass productivity over experimental years. The strongest negative relationship was found in the first year of the pulse treatment, indicating that the community had weak resistance to an extreme event of one season of abnormally warm climate. Biomass production started recovering during the two subsequent years. Contrasting biomass-related resistance emerged in the different treatments, indicating that micro sites within the same plant community may differ in their resistance to different warming scenarios.
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| 4. |
- Angeler, David
(författare)
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Phytoplankton community similarity in a semiarid floodplain under contrasting hydrological connectivity regimes
- 2010
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Ingår i: Ecological Research. - : Wiley. - 0912-3814 .- 1440-1703. ; 25, s. 513-520
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Tidskriftsartikel (refereegranskat)abstract
- In this study we compare phytoplankton community similarity between sites in a semiarid floodplain wetland over a 6-year period with variable hydroperiod and connectivity regimes. Phytoplankton communities showed a relatively high site idiosyncrasy during most parts of the study; however, during situations of low connectivity when individual sites were highly fragmented, phytoplankton communities occasionally became more similar between sites. This suggests that mass effects related to dispersal-mediated processes could be important. Viewed from a metacommunity perspective, phytoplankton community assembly at the wetland scale involves complex hierarchical processes that can act independently at different spatial extents. The main conclusion of this study is that the well-known effects of environmental variability associated with hydrological disturbance alone may not be sufficient for explaining, and by extension predicting, community assembly in this wetland. Other processes, perhaps involving overland dispersal, may eventually add a new dimension to, and complicate our understanding of, community processes in fluctuating wetlands.
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| 5. |
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| 6. |
- Bommarco, Riccardo
(författare)
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Assessing bee species richness in two Mediterranean communities: importance of habitat type and sampling techniques
- 2011
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Ingår i: Ecological Research. - : Wiley. - 0912-3814 .- 1440-1703. ; 26, s. 969-983
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Tidskriftsartikel (refereegranskat)abstract
- The decline of bees has raised concerns regarding their conservation and the maintenance of ecosystem services they provide to bee-pollinated wild flowers and crops. Although the Mediterranean region is a hotspot for bee species richness, their status remains poorly studied. There is an urgent need for cost-effective, reliable, and unbiased sampling methods that give good bee species richness estimates. This study aims: (a) to assess bee species richness in two common Mediterranean habitat types: semi-natural scrub (phrygana) and managed olive groves; (b) to compare species richness in those systems to that of other biogeographic regions, and (c) to assess whether six different sampling methods (pan traps, variable and standardized transect walks, observation plots and trap nests), previously tested in other European biogeographic regions, are suitable in Mediterranean communities. Eight study sites, four per habitat type, were selected on the island of Lesvos, Greece. The species richness observed was high compared to other habitat types worldwide for which comparable data exist. Pan traps collected the highest proportion of the total bee species richness across all methods at the scale of a study site. Variable and standardized transect walks detected the highest total richness over all eight study sites. Trap nests and observation plots detected only a limited fraction of the bee species richness. To assess the total bee species richness in bee diversity hotspots, such as the studied habitats, we suggest a combination of transect walks conducted by trained bee collectors and pan trap sampling.
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| 7. |
- De Frenne, Pieter, et al.
(författare)
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The use of open-top chambers in forests for evaluating warming effects on herbaceous understorey plants
- 2010
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Ingår i: Ecological research. - : Wiley. - 0912-3814 .- 1440-1703. ; 25:1, s. 163-171
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Tidskriftsartikel (refereegranskat)abstract
- Open-top chambers (OTCs) are widely used experimental warming devices in open-field ecosystems such as tundra and alpine heath. However, knowledge of their performance in temperate deciduous forest ecosystems is largely lacking. The application of OTCs in forests might become important in the future since the effects of climate warming on growth, reproduction, and future distribution of understorey forest herbs have rarely been investigated. Therefore, polycarbonate OTCs covered with (OTCs+GF) and without permeable polypropylene GardenFleece (OTCs−GF) were installed in a temperate deciduous forest to create an experimental warming gradient. Short-term responses in phenology, growth, and reproduction of a model understorey forest herb (Anemone nemorosa L.) to OTC installation were determined. In a second growing season, an in-depth study of multiple abiotic conditions inside OTCs−GF was performed. Both OTCs+GF and OTCs−GF raised air and soil temperature in a realistic manner (ca. +0.4°C to +1.15°C), but OTCs−GF only in the leafless period (up to +1.5°C monthly average soil temperature). The early flowering forest herb A. nemorosa also showed a clear phenotypic response to OTC installation. Based on these facts and the large ecological drawbacks associated with OTCs+GF (mostly in connection with a higher relative air humidity and a lower light quantity) and very modest abiotic changes in OTCs−GF, we encourage the use of OTCs−GF in deciduous forest ecosystems for evaluating climate-warming effects on early flowering understorey forest herbs. There is also a potential to use this warming method on later flowering species, but this needs further research.
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| 8. |
- Eriksson, Britas Klemens, et al.
(författare)
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Cascading predator control interacts with productivity to determine the trophic level of biomass accumulation in a benthic food web
- 2012
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Ingår i: Ecological research. - : Wiley. - 0912-3814 .- 1440-1703. ; 27:1, s. 203-210
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Tidskriftsartikel (refereegranskat)abstract
- Large-scale exploitation of higher trophic levels by humans, together with global-scale nutrient enrichment, highlights the need to explore interactions between predator loss and resource availability. The hypothesis of exploitation ecosystems suggests that top-down and bottom-up control alternate between trophic levels, resulting in a positive relationship between primary production and the abundance of every second trophic level. Specifically, in food webs with three effective trophic levels, primary producers and predators should increase with primary production, while in food webs with two trophic levels, only herbivores should increase. We provided short-term experimental support for these model predictions in a natural benthic community with three effective trophic levels, where the number of algal recruits, but not the biomass of gastropod grazers, increased with algal production. In contrast, when the food web was reduced to two trophic levels by removing larger predators, the number of algal recruits was unchanged while gastropod grazer biomass increased with algal production. Predator removal only affected the consumer-controlled early life-stages of algae, indicating that both the number of trophic levels and the life-stage development of the producer trophic level determine the propagation of trophic cascades in benthic systems. Our results support the hypothesis that predators interact with resource availability to determine food-web structure.
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| 9. |
- Håkanson, Lars, et al.
(författare)
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A dynamic mass balance model for phosphorus fluxes and concentrations in coastal areas
- 2007
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Ingår i: Ecological research. - : Wiley. - 0912-3814 .- 1440-1703. ; 22:2, s. 296-320
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a general, process-based mass balance model (CoastMab) for total phosphorus (TP) in defined coastal areas (at the ecosystem scale). The model is based on ordinary differential equations and calculates inflow, outflow and internal fluxes on a monthly basis. It consists of four compartments: surface water, deep water, erosion/transportation areas for fine sediments and accumulation areas for fine sediments. The separation between surface water and deep water is not done based on water temperature, but on sedimentological criteria instead (from the theoretical wave base). There are algorithms for all major internal TP fluxes (sedimentation, resuspension, diffusion, mixing and burial). Validations were performed using data from 21 different Baltic coastal areas. The results show that the model predicts monthly TP in water and chlorophyll a very well (generally within the uncertainty bands of the empirical data). The model has also been put through sensitivity tests, which show that the most important factor regulating the predictions of the model is generally the TP concentration in the sea beyond the coast. The model is simple to apply, since all driving variables may be accessed from maps or monitoring programs. The driving variables include coastal area, section area (between the defined coastal area and the adjacent sea), mean and maximum depths, latitude (used to predict water temperatures, stratification and mixing), salinity and TP concentration in the sea. Many of the model structures are general and could be used for areas other than those included in this study, e.g., for open coasts, estuaries or tidal coasts, as well as for other substances than phosphorus.
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| 10. |
- Håkanson, Lars, et al.
(författare)
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Modeling the foodweb in coastal areas : a case study of Ringkobing Fjord, Denmark
- 2008
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Ingår i: Ecological research. - : Wiley. - 0912-3814 .- 1440-1703. ; 23:2, s. 421-444
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Tidskriftsartikel (refereegranskat)abstract
- This work utilizes the CoastWeb model, a foodweb model for coastal areas that also includes a mass-balance model (CoastMab) for phosphorus and many abiotic/biotic interactions, to study the development in Ringkobing Fjord, Denmark, from 1985 to 2004. This shallow coastal lagoon has an area of 300 km(2) and a mean depth of 1.9 m. The water exchange between the lagoon and the North Sea is regulated by a sluice. In 1996 there was a major regime shift in this lagoon with drastic reductions in chlorophyll-a concentrations, significant increases in water clarity (Secchi depth) and major changes in the number and biomass of clams as well as in macrophyte cover. Regime shifts is a "hot" topic in aquatic ecology and in this work the CoastWeb model is used as a tool to understand and quantify the causes behind this regime shift. The CoastWeb model is general and can also be used for other coastal areas. The basic model calculates monthly production values and changes in biomasses of ten functional groups of organisms (phytoplankton, bacterioplankton, herbivorous, and predatory zooplankton, benthic algae, macrophytes, jellyfish, zoobenthos and prey and predatory fish) and in Ringkobing Fjord, also for clams (Mya arenaria). In spite of its complexity, the model is relatively simple to use, since all driving variables may be readily accessed from maps or monitoring programs. The model includes much abiotic/biotic feedback and it can also be used to address other causes for regime shifts other than the changes in salinity and nutrient inflow, which have caused the changes in Ringkobing Fjord. The model has previously been tested for more than 20 smaller coastal areas and was shown to predict variations in foodweb characteristics very well. The focus of this paper is on temporal variations within one well-studied coastal area. The paper compares modeled values to empirical data for Ringkobing Fjord and discusses fundamental ecosystem features such as regime shifts and compensatory effects in a way that is not practically feasible without the use of quantitative models.
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