| 1. |
- Lembrechts, Jonas J., et al.
(författare)
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Global maps of soil temperature
- 2022
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 28:9, s. 3110-3144
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Tidskriftsartikel (refereegranskat)abstract
- Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0–5 and 5–15cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean=3.0±2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6±2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7±2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications.
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| 2. |
- Asplund, Johan, et al.
(författare)
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Removal of secondary compounds increases invertebrate abundance in lichens
- 2015
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Ingår i: Fungal Ecology. - : Elsevier BV. - 1754-5048 .- 1878-0083. ; 18, s. 18-25
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Tidskriftsartikel (refereegranskat)abstract
- We investigated how lichen carbon-based secondary compounds (CBSCs) affect abundance of invertebrates in five lichen species growing on the forest floor (Cladonia rangiferina, Cladonia stellaris) or on tree trunks (Evernia prunastri, Hypogymnia physodes, Pseudevemia furfuracea). To do this, CBSCs were removed by rinsing lichen thalli in acetone (which has no adverse effects on the lichens) and the lichens were re-transplanted in their natural habitat. After 4 months there was higher abundance of mites, springtails and spiders in the three epiphytic lichens that had their CBSC concentrations reduced. The increase in predatory spiders following CBSC reduction suggests that the compounds have multitrophic consequences. The acetone treatment reduced the number of nematodes in four of the lichen species. Given that lichens serve as important habitats for a diverse range of invertebrates, increased knowledge of how lichen CBSCs may regulate their abundance helps us to better understand the role that lichens and their defence compounds play in structuring forest food webs. (C) 2015 Elsevier Ltd and The British Mycological Society. All rights reserved.
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| 3. |
- Asplund, Johan, et al.
(författare)
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Secondary compounds can reduce the soil micro-arthropod effect on lichen decomposition
- 2013
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 66, s. 10-16
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Tidskriftsartikel (refereegranskat)abstract
- Phenolic compounds have been shown in several studies to have important 'carryover effects' on litter decomposition, microbial nutrient immobilization and nutrient availability. These effects arise in part because of the adverse effect they have on the feeding activities of litter-feeding invertebrates such as micro-arthropods that drive decomposition processes. However, the interactive effects of phenolic compounds and soil micro-arthropods on litter decomposition are poorly understood. Phenolic compounds can easily be removed by acetone rinsing from living lichens, allowing us to specifically test the role that phenolic compounds (and their removal) have in controlling the effects of micro-arthropods on the decomposition of their litter. We performed a litter-bag experiment aimed at exploring how lichen litter mass loss and nutrient release during decomposition was affected by phenolics (by using acetone rinsed and non-rinsed lichen material) and micro-arthropod activity (by using different mesh sizes to allow or exclude entry by micro-arthropods) for each of six contrasting lichen species (Cladonia rangiferina, Cladonia stellaris, Evernia prunastri, Hypogymnia physodes, Pseudevernia furfuracea and Usnea dasypoga). Both the removal of phenolic compounds and the presence of micro-arthropods accelerated mass and nutrient release overall, but not for either of the two Cladonia species. Removal of phenolics also had an overall positive effect on the effects of arthropods on the loss of P, but not mass and N, from the decomposing lichens. Further, for U. dasypoga, but not the other species, natural levels of phenolic compounds deterred micro-arthropods from accelerating mass loss, and the removal of these compounds enabled micro-arthropods to enhance its decomposition. Our findings that lichen phenolic compounds can sometimes interact with micro-arthropods to influence lichen litter mass loss and nutrient release during decomposition assists our understanding of how lichens and their consumers may impact on organic matter dynamics, biochemical nutrient cycling and other related ecosystem processes. (c) 2013 Elsevier Ltd. All rights reserved.
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| 4. |
- Bokhorst, Stef, et al.
(författare)
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Changing Arctic snow cover : A review of recent developments and assessment of future needs for observations, modelling, and impacts
- 2016
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 45:5, s. 516-537
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Forskningsöversikt (refereegranskat)abstract
- Snow is a critically important and rapidly changing feature of the Arctic. However, snow-cover and snowpack conditions change through time pose challenges for measuring and prediction of snow. Plausible scenarios of how Arctic snow cover will respond to changing Arctic climate are important for impact assessments and adaptation strategies. Although much progress has been made in understanding and predicting snow-cover changes and their multiple consequences, many uncertainties remain. In this paper, we review advances in snow monitoring and modelling, and the impact of snow changes on ecosystems and society in Arctic regions. Interdisciplinary activities are required to resolve the current limitations on measuring and modelling snow characteristics through the cold season and at different spatial scales to assure human well-being, economic stability, and improve the ability to predict manage and adapt to natural hazards in the Arctic region.
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| 5. |
- Bokhorst, Stef Frederik
(författare)
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Climatic and biotic extreme events moderate long-term responses of above- and belowground sub-Arctic heathland communities to climate change
- 2015
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 21, s. 4063-4075
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Tidskriftsartikel (refereegranskat)abstract
- Climate change impacts are not uniform across the Arctic region because interacting factors causes large variations in local ecosystem change. Extreme climatic events and population cycles of herbivores occur simultaneously against a background of gradual climate warming trends and can redirect ecosystem change along routes that are difficult to predict. Here, we present the results from sub-Arctic heath vegetation and its belowground micro-arthropod community in response to the two main drivers of vegetation damage in this region: extreme winter warming events and subsequent outbreaks of the defoliating autumnal moth caterpillar (Epirrita autumnata). Evergreen dwarf shrub biomass decreased (30%) following extreme winter warming events and again by moth caterpillar grazing. Deciduous shrubs that were previously exposed to an extreme winter warming event were not affected by the moth caterpillar grazing, while those that were not exposed to warming events (control plots) showed reduced (23%) biomass from grazing. Cryptogam cover increased irrespective of grazing or winter warming events. Micro-arthropods declined (46%) following winter warming but did not respond to changes in plant community. Extreme winter warming and caterpillar grazing suppressed the CO2 fluxes of the ecosystem. Evergreen dwarf shrubs are disadvantaged in a future sub-Arctic with more stochastic climatic and biotic events. Given that summer warming may further benefit deciduous over evergreen shrubs, event and trend climate change may both act against evergreen shrubs and the ecosystem functions they provide. This is of particular concern given that Arctic heath vegetation is typically dominated by evergreen shrubs. Other components of the vegetation showed variable responses to abiotic and biotic events, and their interaction indicates that sub-Arctic vegetation response to multiple pressures is not easy to predict from single-factor responses. Therefore, while biotic and climatic events may have clear impacts, more work is needed to understand their net effect on Arctic ecosystems.
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| 6. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Contrasting responses of springtails and mites to elevation and vegetation type in the sub-Arctic
- 2018
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Ingår i: Pedobiologia. - : Elsevier. - 0031-4056 .- 1873-1511. ; 67, s. 57-64
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is affecting the species composition and functioning of Arctic and sub-Arctic plant and soil communities. Here we studied patterns in soil microarthropod (springtails and mites) communities across a gradient of increasing elevation that spanned 450 m, across which mean temperature declined by approximately 2.5 degrees C, in sub-Arctic Sweden. Across this gradient we characterized microarthropod communities in each of two types of vegetation, i.e., heath and meadow, to determine whether their responses to declining temperature differed with vegetation type. Mite abundance declined with increasing elevation, while springtail abundance showed the opposite response. Springtail communities were dominated by larger species at higher elevation. Mite abundance was unaffected by vegetation type, while springtail abundance was 53% higher in the heath than meadow vegetation across the gradient. Springtails but not mites responded differently to elevation in heath and meadow vegetation; hemi-edaphic species dominated in the heath at higher elevation while epiedaphic species dominated in the meadow. Our results suggest that sub-Arctic mite and springtail communities will likely respond in contrasting ways to changes in vegetation and soil properties resulting from climate warming.
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| 7. |
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| 8. |
- Bokhorst, Stef Frederik
(författare)
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Extreme winter warming events more negatively impact small rather than large soil fauna: shift in community composition explained by traits not taxa
- 2012
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 18, s. 1152-1162
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Tidskriftsartikel (refereegranskat)abstract
- Extreme weather events can have negative impacts on species survival and community structure when surpassing lethal thresholds. Extreme winter warming events in the Arctic rapidly melt snow and expose ecosystems to unseasonably warm air (210 similar to degrees C for 214 similar to days), but returning to cold winter climate exposes the ecosystem to lower temperatures by the loss of insulating snow. Soil animals, which play an integral part in soil processes, may be very susceptible to such events depending on the intensity of soil warming and low temperatures following these events. We simulated week-long extreme winter warming events using infrared heating lamps, alone or with soil warming cables for two consecutive years in a sub-Arctic dwarf shrub heathland. Minimum temperatures were lower and freeze-thaw cycles were 211 times more frequent in treatment plots compared with control plots. Following the second event, Acari populations decreased by 39%; primarily driven by declines of Prostigmata (69%) and the Mesostigmatic nymphs (74%). A community-weighted vertical stratification shift occurred from smaller soil dwelling (eu-edaphic) Collembola species dominance to larger litter dwelling (hemi-edaphic) species dominance in the canopy-with-soil warming plots compared with controls. The most susceptible groups to these winter warming events were the smallest individuals (Prostigmata and eu-edaphic Collembola). This was not apparent from abundance data at the Collembola taxon level, indicating that life forms and species traits play a major role in community assembly following extreme events. The observed shift in soil community can cascade down to the micro-flora affecting plant productivity and mineralization rates. Short-term extreme weather events have the potential to shift community composition through trait composition with potentially large consequences for ecosystem development.
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| 9. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Impact of understory mosses and dwarf shrubs on soil micro-arthropods in a boreal forest chronosequence
- 2014
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 379, s. 121-133
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Tidskriftsartikel (refereegranskat)abstract
- Plant species and functional groups are known to drive the community of belowground invertebrates but whether their effects are consistent across environmental gradients is less well understood. We aimed to determine if plant effects on belowground communities are consistent across a successional gradient in boreal forests of northern Sweden.We performed two plant removal experiments across ten stands that form a 364-year post-fire boreal forest chronosequence. Through the removal of plant functional groups (mosses or dwarf shrubs) and of individual species of dwarf shrubs, we aimed to determine if the effects of functional groups and species on the soil micro-arthropod community composition varied across this chronosequence.Removal of mosses had a strong negative impact on the abundance and diversity of Collembola and Acari and this effect was consistent across the chronosequence. Only specific Oribatid families declined following dwarf-shrub species removals, with some of these responses being limited to old forest stands.Our results show that the impacts of plants on micro-arthropods is consistent across sites that vary considerably in their stage of post-fire ecosystem development, despite these stages differing greatly in plant productivity, fertility, humus accumulation and moss development. In addition, mosses are a much stronger driver of the micro-arthropod community than vascular plants.
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| 10. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Lichen physiological traits and growth forms affect communities of associated invertebrates
- 2015
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 96, s. 2394-2407
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Tidskriftsartikel (refereegranskat)abstract
- While there has been much interest in the relationships between traits of primary producers and composition of associated invertebrate consumer communities, our knowledge is largely based on studies from vascular plants, while other types of functionally important producers, such as lichens, have rarely been considered. To address how physiological traits of lichens drive community composition of invertebrates, we collected thalli from 27 lichen species from southern Norway and quantified the communities of associated springtails, mites, and nematodes. For each lichen species, we measured key physiological thallus traits and determined whether invertebrate communities were correlated with these traits. We also explored whether invertebrate communities differed among lichen groups, categorized according to nitrogen-fixing ability, growth form, and substratum. Lichen traits explained up to 39% of the variation in abundances of major invertebrate groups. For many invertebrate groups, abundance was positively correlated with lichen N and P concentrations, N: P ratio, and the percentage of water content on saturation (WC), but had few relationships with concentrations of carbon-based secondary compounds. Diversity and taxonomic richness of invertebrate groups were sometimes also correlated with lichen N and N: P ratios. Nitrogen-fixing lichens showed higher abundance and diversity of some invertebrate groups than did non-N-fixing lichens. However, this emerged in part because most N-fixing lichens have a foliose growth form that benefits invertebrates, through improving the microclimate, independently of N concentration. Furthermore, invertebrate communities associated with terricolous lichens were determined more by their close proximity to the soil invertebrate pool than by lichen traits. Overall, our results reveal that differences between lichen species have a large impact on the invertebrate communities that live among the thalli. Different invertebrate groups show contrasting responses to traits that are indicative of thallus quality (nutrient concentrations), and thallus growth form is often an important determinant of the invertebrate community. Given the large diversity of lichen traits and growth forms that occur in many ecosystems, lichen-invertebrate communities may be an important contributor to overall community diversity in boreal forests.
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| 11. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Micro-arthropod community responses to ecosystem retrogression in boreal forest
- 2017
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 110, s. 79-86
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Tidskriftsartikel (refereegranskat)abstract
- Explaining the variation in communities of soil organisms across plant communities or ecosystems remains a major challenge for ecologists. Several studies have explored how soil communities are affected along ecosystem successional gradients but most of these are based on relatively short term chronosequences. To address the impact of ecosystem age on micro-arthropod communities, we utilized a 5000 year old post-fire chronosequence, which consists of thirty lake islands differing greatly in time since fire in the boreal forested zone of northern Sweden. The Acari community did not change along this chronosequence, indicating that Acari rapidly(<60 yr) reach equilibrium after forest fire and that they are relatively unresponsive to subsequent long term changes in plant community composition and soil quality. The Collembola community composition, however, showed greater responsiveness to the chronosequence and this was best explained through their functional traits. Notably, the youngest (most recently burned) islands, which had the highest ecosystem productivity and fungal mass turnover, were dominated by soil-dwelling (eu-edaphic) Collembola species that are best positioned to take advantage of resource input to the soil. Although plant community characteristics did not emerge as powerful drivers of the Collembola community, we found that Collembola community composition was related to the quality (N and P) of the soil substrate, which reflects a long term legacy of the plant community. Collembola life history characteristics proved to be important for understanding how abundances of different taxa varied relative to one another across the gradients of plant diversity and substrate quality gradients that occur across long-term chronosequences. The causal connection between vertical stratification of Collembola and substrate quality is at present unclear but is likely to be related to their feeding preferences and microhabitat conditions. Because the soil-dwelling Collembola showed a strong decline in abundance with ecosystem retrogression while surface-dwelling Collembola did not these two life history groups may operate as functionally distinct groups within the soil food web across these long-term chronosequences. 2017 Elsevier Ltd. All rights reserved.
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| 12. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Microclimate within litter bags of different mesh size: Implications for the 'arthropod effect' on litter decomposition
- 2013
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 58, s. 147-152
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Tidskriftsartikel (refereegranskat)abstract
- In conclusion, different mesh sizes can be used to reliably quantify the role of soil animals in litter mass loss from litter bags. The greater litter mass loss from litter bags with coarser mesh sizes is however caused by the soil animals both promoting litter decomposition and greater litter fragmentation (with the undecomposed fragments then being lost from the bags). Additional approaches are needed to determine the relative importance of these two effects of soil animals on litter mass loss from litter bags. (C) 2012 Elsevier Ltd. All rights reserved.
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| 13. |
- Bokhorst, Stef Frederik
(författare)
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Rapid photosynthetic recovery of a snow-covered feather moss and Peltigera lichen during sub-Arctic midwinter warming
- 2013
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Ingår i: Plant Ecology and Diversity. - : Informa UK Limited. - 1755-0874 .- 1755-1668. ; 6, s. 383-392
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Tidskriftsartikel (refereegranskat)abstract
- Conclusions: The moss, and to a lesser extent the lichen, may contribute to subnivean midwinter ecosystem respiration, and both are opportunistic, and can take advantage of warmer winter phases for photosynthesis and growth. This ought to be taken into account in vegetation change projections of cryptogam-rich ecosystems.
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| 14. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Reduction in snow depth negatively affects decomposers but impact on decomposition rates is substrate dependent
- 2013
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 62, s. 157-164
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Tidskriftsartikel (refereegranskat)abstract
- Decomposition of organic matter in high latitude biomes makes a significant contribution to global fluxes of nutrients and carbon and is expected to accelerate due to climate change. The majority of studies have focused on decomposition during the growing season, but winter climate is expected to change dramatically. Furthermore, knowledge of the drivers of organic matter decomposition, such as litter chemical composition, has primarily been tested across the growing season so it is unknown whether these drivers are also important during the winter. Given that the depth of snow cover insulates the sub-nivean climate from the much colder air, it is an important control on winter decomposition and is expected to be influenced by climate change, we experimentally manipulated snow cover to simulate impacts of different winter precipitation scenarios on soil processes. Our results show that despite snow reduction negatively affecting decomposer abundance (by 99%) and bulk soil respiration (by 47%), litter decomposition rates showed little to no response. Furthermore, variation in winter decomposition rates among litter types was unrelated to nutrient status, indicating that our current understanding of drivers of litter decomposition may not hold during winter months. Despite very large reductions in decomposer fauna due to snow removal, litter decomposition rates were not consistently responsive, indicative of decoupled responses of soil organisms and soil processes to winter climate change. (c) 2013 Elsevier Ltd. All rights reserved.
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| 15. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Responses of communities of soil organisms and plants to soil aging at two contrasting long-term chronosequences
- 2017
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 106, s. 69-79
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Tidskriftsartikel (refereegranskat)abstract
- Soil fertility and vegetation are major drivers of soil communities. Soil community responses to vegetation development and associated changes in soil fertility have been mostly reported for chronosequences that span time scales from decades to centuries. Here we evaluated soil communities for two contrasting chronosequences, the Franz Josef chronosequence in southern New Zealand caused by glacial retreat and spanning 120,000 years, and the Cooloola chronosequence in eastern Australia caused by aeolian movement of sand that spans 700,000 years. Both chronosequences feature later-phase retrogressive stages characterized by reduced nutrient availability and plant stature. We hypothesized that soil communities would mirror the patterns of vegetation across these long-term chronosequences with organism biomasses, abundances and diversity increasing throughout early stages of the succession and declining at retrogression stages. The hypothesis was not consistently supported. Bacterial and fungal biomass increased across the youngest chronosequence stages but remained unchanged across the later stages, while fungal-to-bacterial ratios increased throughout. Microbial biomass was related to soil nitrogen concentrations across both chronosequences. Invertebrate abundance and richness increased during the early stages of ecosystem development in both chronosequences, but different groups peaked at different stages at each chronosequence, and not all invertebrate groups declined during the retrogressive stages. Invertebrate groups had no consistent correlations with biotic or abiotic ecosystem properties across either chronosequence. Our study demorBtrates that soil organisms track changes in plant biomass and richness and soil fertility during the initial stages of both chronosequences, but with increasing age of the chronosequences, these relationships weaken and other factors drive the soil community. Possible explanations for the different patterns in soil communities at the two chronosequences include that they differ strongly in soil organic matter, nutrient concentrations and abundances of soil organisms (all of which are much higher at Franz Josef than Cooloola), overlaid with different macroclimate and geology, so that different factors are likely to restrict the presence of particular organisms across both chronosequences. As such, while soil fertility and vegetation are widely recognized as important drivers of the soil community, the manner in which these factors directly and indirectly shape the soil community can vary greatly across organism groups, among chronosequences, and over the time scales that ecosystems develop. (C) 2016 Elsevier Ltd. All rights reserved.
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| 16. |
- Bokhorst, Stef Frederik
(författare)
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Shifts in soil microorganisms in response to warming are consistent across a range of Antarctic environments
- 2012
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Ingår i: ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 6, s. 692-702
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Tidskriftsartikel (refereegranskat)abstract
- Because of severe abiotic limitations, Antarctic soils represent simplified systems, where microorganisms are the principal drivers of nutrient cycling. This relative simplicity makes these ecosystems particularly vulnerable to perturbations, like global warming, and the Antarctic Peninsula is among the most rapidly warming regions on the planet. However, the consequences of the ongoing warming of Antarctica on microorganisms and the processes they mediate are unknown. Here, using 16S rRNA gene pyrosequencing and qPCR, we report highly consistent responses in microbial communities across disparate sub-Antarctic and Antarctic environments in response to 3 years of experimental field warming (+0.5 to 2 degrees C). Specifically, we found significant increases in the abundance of fungi and bacteria and in the Alphaproteobacteria-to-Acidobacteria ratio, which could result in an increase in soil respiration. Furthermore, shifts toward generalist bacterial communities following warming weakened the linkage between the bacterial taxonomic and functional richness. GeoChip microarray analyses also revealed significant warming effects on functional communities, specifically in the N-cycling microorganisms. Our results demonstrate that soil microorganisms across a range of sub-Antarctic and Antarctic environments can respond consistently and rapidly to increasing temperatures. The ISME Journal (2012) 6, 692-702; doi: 10.1038/ismej.2011.124; published online 22 September 2011
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| 17. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Snow fungi as a food source form micro-arthropods
- 2014
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Ingår i: European Journal of Soil Biology. - : Elsevier BV. - 1164-5563 .- 1778-3615. ; 60, s. 77-80
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Tidskriftsartikel (refereegranskat)abstract
- Snow fungi are often visibly abundant on tundra and forest understory vegetation immediately after snow melt in Nordic regions. Fungal hyphae are a common food source for many terrestrial arthropods and snow fungi could therefore be a potentially important component of an as of yet unexplored winter food web. We compared the abundance of soil arthropods (Acari and Collembola) from paired patches with and without dense infections of snow fungi in the forest understory of a northern Swedish boreal forest after snow melt. Although we did not find increased abundance of these animals when snow fungi were present, Collembola and Acari were sustained on a diet of snow fungi for six months. The isotope signature of the snow fungi clearly differed from humus and other fungal types from literature values obtained from similar boreal forests, suggesting that these fungi may occupy a novel N niche during winter in northern boreal forests. Our study shows for the first time that snow fungi are a potential food source for micro-arthropods during winter and spring. Potentially, snow fungi may represent the basis of an unexplored sub-nivean winter food web but further work is required to assess their importance for community development and winter litter decomposition. (C) 2013 Elsevier Masson SAS. All rights reserved.
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| 18. |
- Bokhorst, Stef Frederik
(författare)
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The spatial structure of Antarctic biodiversity
- 2014
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Ingår i: Ecological Monographs. - : Wiley. - 0012-9615 .- 1557-7015. ; 84, s. 203-244
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Forskningsöversikt (refereegranskat)abstract
- Patterns of environmental spatial structure lie at the heart of the most fundamental and familiar patterns of diversity on Earth. Antarctica contains some of the strongest environmental gradients on the planet and therefore provides an ideal study ground to test hypotheses on the relevance of environmental variability for biodiversity. To answer the pivotal question, "How does spatial variation in physical and biological environmental properties across the Antarctic drive biodiversity?" we have synthesized current knowledge on environmental variability across terrestrial, freshwater, and marine Antarctic biomes and related this to the observed biotic patterns. The most important physical driver of Antarctic terrestrial communities is the availability of liquid water, itself driven by solar irradiance intensity. Patterns of biota distribution are further strongly influenced by the historical development of any given location or region, and by geographical barriers. In freshwater ecosystems, free water is also crucial, with further important influences from salinity, nutrient availability, oxygenation, and characteristics of ice cover and extent. In the marine biome there does not appear to be one major driving force, with the exception of the oceanographic boundary of the Polar Front. At smaller spatial scales, ice cover, ice scour, and salinity gradients are clearly important determinants of diversity at habitat and community level. Stochastic and extreme events remain an important driving force in all environments, particularly in the context of local extinction and colonization or recolonization, as well as that of temporal environmental variability. Our synthesis demonstrates that the Antarctic continent and surrounding oceans provide an ideal study ground to develop new biogeographical models, including life history and physiological traits, and to address questions regarding biological responses to environmental variability and change.
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| 19. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Variable temperature effects of Open Top Chambers at polar and alpine sites explained by irradiance and snow depth
- 2013
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 19:1, s. 64-74
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Forskningsöversikt (refereegranskat)abstract
- Environmental manipulation studies are integral to determining biological consequences of climate warming. Open Top Chambers (OTCs) have been widely used to assess summer warming effects on terrestrial biota, with their effects during other seasons normally being given less attention even though chambers are often deployed year-round. In addition, their effects on temperature extremes and freeze-thaw events are poorly documented. To provide robust documentation of the microclimatic influences of OTCs throughout the year, we analysed temperature data from 20 studies distributed across polar and alpine regions. The effects of OTCs on mean temperature showed a large range (-0.9 to 2.1 degrees C) throughout the year, but did not differ significantly between studies. Increases in mean monthly and diurnal temperature were strongly related (R-2 = 0.70) with irradiance, indicating that PAR can be used to predict the mean warming effect of OTCs. Deeper snow trapped in OTCs also induced higher temperatures at soil/vegetation level. OTC-induced changes in the frequency of freeze-thaw events included an increase in autumn and decreases in spring and summer. Frequency of high-temperature events in OTCs increased in spring, summer and autumn compared with non-manipulated control plots. Frequency of low-temperature events was reduced by deeper snow accumulation and higher mean temperatures. The strong interactions identified between aspects of ambient environmental conditions and effects of OTCs suggest that a detailed knowledge of snow depth, temperature and irradiance levels enables us to predict how OTCs will modify the microclimate at a particular site and season. Such predictive power allows a better mechanistic understanding of observed biotic response to experimental warming studies and for more informed design of future experiments. However, a need remains to quantify OTC effects on water availability and wind speed (affecting, for example, drying rates and water stress) in combination with microclimate measurements at organism level.
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| 20. |
- Callaghan, Terry V., et al.
(författare)
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Ecosystem change and stability over multiple decades in the Swedish subarctic : complex processes and multiple drivers
- 2013
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 368:1624
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Tidskriftsartikel (refereegranskat)abstract
- The subarctic environment of northernmost Sweden has changed over the past century, particularly elements of climate and cryosphere. This paper presents a unique geo-referenced record of environmental and ecosystem observations from the area since 1913. Abiotic changes have been substantial. Vegetation changes include not only increases in growth and range extension but also counterintuitive decreases, and stability: all three possible responses. Changes in species composition within the major plant communities have ranged between almost no changes to almost a 50 per cent increase in the number of species. Changes in plant species abundance also vary with particularly large increases in trees and shrubs (up to 600%). There has been an increase in abundance of aspen and large changes in other plant communities responding to wetland area increases resulting from permafrost thaw. Populations of herbivores have responded to varying management practices and climate regimes, particularly changing snow conditions. While it is difficult to generalize and scale-up the site-specific changes in ecosystems, this very site-specificity, combined with projections of change, is of immediate relevance to local stakeholders who need to adapt to new opportunities and to respond to challenges. Furthermore, the relatively small area and its unique datasets are a microcosm of the complexity of Arctic landscapes in transition that remains to be documented.
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| 21. |
- Maaroufi, Nadia, et al.
(författare)
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Nutrient optimization of tree growth alters structure and function of boreal soil food webs
- 2018
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Ingår i: Forest Ecology and Management. - Amsterdam : Elsevier. - 0378-1127 .- 1872-7042. ; 428, s. 46-56
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Tidskriftsartikel (refereegranskat)abstract
- Nutrient optimization has been proposed as a way to increase boreal forest production, and involves chronic additions of liquid fertilizer with amounts of micro- and macro-nutrients adjusted annually to match tree nutritional requirements. We used a short-term (maintained since 2007) and a long-term (maintained since 1987) fertilization experiment in northern Sweden, in order to understand nutrient optimization effects on soil microbiota and mesofauna, and to explore the relationships between plant litter and microbial elemental stoichiometry. Soil microbes, soil fauna, and aboveground litter were collected from the control plots, and short- and long-term nutrient optimization plots. Correlation analyses revealed no relationships between microbial biomass and litter nutrient ratios. Litter C:N, C:P and N:P ratios declined in response to both optimization treatments; while only microbial C:P ratios declined in response to long-term nutrient optimization. Further, we found that both short- and long-term optimization treatments decreased total microbial, fungal, and bacterial PLFA biomass and shifted the microbial community structure towards a lower fungi:bacterial ratio. In contrast, abundances of most fungal- and bacterial-feeding soil biota were little affected by the nutrient optimization treatments. However, abundance of hemi-edaphic Collembola declined in response to the long-term nutrient optimization treatment. The relative abundances (%) of fungal-feeding and plant-feeding nematodes, respectively, declined and increased in response to both short-term and long-term treatments; bacterial-feeding nematodes increased relative to fungal feeders. Overall, our results demonstrate that long-term nutrient optimization aiming to increase forest production decreases litter C:N, C:P and N:P ratios, microbial C:P ratios and fungal biomass, whereas higher trophic levels are less affected. © 2018 Elsevier B.V.
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| 22. |
- Potapov, Anton M., et al.
(författare)
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Global fine-resolution data on springtail abundance and community structure
- 2024
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Ingår i: Scientific Data. - : Nature Publishing Group. - 2052-4463. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Springtails (Collembola) inhabit soils from the Arctic to the Antarctic and comprise an estimated ~32% of all terrestrial arthropods on Earth. Here, we present a global, spatially-explicit database on springtail communities that includes 249,912 occurrences from 44,999 samples and 2,990 sites. These data are mainly raw sample-level records at the species level collected predominantly from private archives of the authors that were quality-controlled and taxonomically-standardised. Despite covering all continents, most of the sample-level data come from the European continent (82.5% of all samples) and represent four habitats: woodlands (57.4%), grasslands (14.0%), agrosystems (13.7%) and scrublands (9.0%). We included sampling by soil layers, and across seasons and years, representing temporal and spatial within-site variation in springtail communities. We also provided data use and sharing guidelines and R code to facilitate the use of the database by other researchers. This data paper describes a static version of the database at the publication date, but the database will be further expanded to include underrepresented regions and linked with trait data.
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| 23. |
- Potapov, Anton M., et al.
(författare)
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Globally invariant metabolism but density-diversity mismatch in springtails
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Soil life supports the functioning and biodiversity of terrestrial ecosystems. Springtails (Collembola) are among the most abundant soil arthropods regulating soil fertility and flow of energy through above- and belowground food webs. However, the global distribution of springtail diversity and density, and how these relate to energy fluxes remains unknown. Here, using a global dataset representing 2470 sites, we estimate the total soil springtail biomass at 27.5 megatons carbon, which is threefold higher than wild terrestrial vertebrates, and record peak densities up to 2 million individuals per square meter in the tundra. Despite a 20-fold biomass difference between the tundra and the tropics, springtail energy use (community metabolism) remains similar across the latitudinal gradient, owing to the changes in temperature with latitude. Neither springtail density nor community metabolism is predicted by local species richness, which is high in the tropics, but comparably high in some temperate forests and even tundra. Changes in springtail activity may emerge from latitudinal gradients in temperature, predation and resource limitation in soil communities. Contrasting relationships of biomass, diversity and activity of springtail communities with temperature suggest that climate warming will alter fundamental soil biodiversity metrics in different directions, potentially restructuring terrestrial food webs and affecting soil functioning.
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| 24. |
- Virkkala, Anna Maria, et al.
(författare)
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Statistical upscaling of ecosystem CO2 fluxes across the terrestrial tundra and boreal domain : Regional patterns and uncertainties
- 2021
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 27:17, s. 4040-4059
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Tidskriftsartikel (refereegranskat)abstract
- The regional variability in tundra and boreal carbon dioxide (CO2) fluxes can be high, complicating efforts to quantify sink-source patterns across the entire region. Statistical models are increasingly used to predict (i.e., upscale) CO2 fluxes across large spatial domains, but the reliability of different modeling techniques, each with different specifications and assumptions, has not been assessed in detail. Here, we compile eddy covariance and chamber measurements of annual and growing season CO2 fluxes of gross primary productivity (GPP), ecosystem respiration (ER), and net ecosystem exchange (NEE) during 1990–2015 from 148 terrestrial high-latitude (i.e., tundra and boreal) sites to analyze the spatial patterns and drivers of CO2 fluxes and test the accuracy and uncertainty of different statistical models. CO2 fluxes were upscaled at relatively high spatial resolution (1 km2) across the high-latitude region using five commonly used statistical models and their ensemble, that is, the median of all five models, using climatic, vegetation, and soil predictors. We found the performance of machine learning and ensemble predictions to outperform traditional regression methods. We also found the predictive performance of NEE-focused models to be low, relative to models predicting GPP and ER. Our data compilation and ensemble predictions showed that CO2 sink strength was larger in the boreal biome (observed and predicted average annual NEE −46 and −29 g C m−2 yr−1, respectively) compared to tundra (average annual NEE +10 and −2 g C m−2 yr−1). This pattern was associated with large spatial variability, reflecting local heterogeneity in soil organic carbon stocks, climate, and vegetation productivity. The terrestrial ecosystem CO2 budget, estimated using the annual NEE ensemble prediction, suggests the high-latitude region was on average an annual CO2 sink during 1990–2015, although uncertainty remains high.
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