What's up down there?: Climate change effects on subarctic springtail communities and their role in carbon turnover

Cornelissen, J.H.C. [Promotor]Berg, M.P. [Copromotor

Amino acid uptake among wide-ranging moss species may contribute to their strong position in higher-latitude ecosystems.

Plants that can take up amino acids directly from the soil solution may have a competitive advantage in ecosystems where inorganic nitrogen sources are scarce. We hypothesized that diverse mosses in cold, N-stressed ecosystems share this ability. We experimentally tested 11 sub-arctic Swedish moss species of wide-ranging taxa and growth form for their ability to take up double labelled

A simple experimental setup to disentangle the effects of altered temperature and moisture regimes on soil organisms

Climate manipulation experiments in the field and laboratory incubations are common methods to study the impact of climate change on soils and their biota. However, both types of methods have drawbacks either on their mechanistic interpretation or ecological relevance. We propose an experimental set-up that combines the best of both methods and can be easily obtained by modifying widely available Tullgren soil fauna extractors. This set-up creates or alters temperature and moisture gradients within intact field soil cores, after which soil biota, their activity and vertical movements can be studied. We assessed the performance and demonstrated the applicability of this set-up through a case study on Collembola response to changes in microclimatic gradients in peat bogs. Warming created a vertical temperature gradient of 14°C in peat cores without varying soil moisture conditions, while at a given temperature regime, precipitation and drought treatments shifted natural soil moisture gradients to 'wetter' and 'drier', respectively. This allowed for disentangling interacting warming and moisture effects on soil fauna. In our case study, Collembola communities showed peat layer-specific responses to these climate treatments. Warming decreased Collembola density and altered community composition in the shallowest layer, whereas precipitation increase affected Collembola community composition in the deepest layer. We showed that climate change can have layer-specific effects on soil organisms that are 'hidden' by not taking microclimatic vertical gradients into account. This experimental set-up facilitates studying (multitrophic) organism responses to climate changes, with only a small adjustment of equipment that is often already present in soil ecology laboratories. Moreover, this set-up can be easily customized to study many more other research questions related to wide-ranging organisms and ecosystems

Reservations about preservations: storage methods affect δ13C signatures differently even in closely related soil fauna.

Studies of stable isotope signatures can reveal and quantify trophic carbon transfer between organisms. However, preservation of the samples before analysis cannot always be avoided. Some preservation agents are known to alter tissue

How extreme is a extreme climatic event to a subarctic peatland springtail community?

Extreme climate events are increasing in frequency and duration and may directly impact belowground foodwebs and the activities of component soil organisms. The soil invertebrate community, which includes keystone decomposers, might respond to these newly induced soil microclimate conditions by shifts in density, species composition, spatial patterning and/or functional traits.To test if and how short-term extreme climatic conditions alter the structure, the vertical stratification and the community weighted trait means of the springtail (Collembola) community in sub-arctic peatbogs, we experimentally subjected Sphagnum peat cores in a field setting to factorial treatments of elevated temperature and episodically increased moisture content.The large precipitation peaks did not affect the springtail community, but an average soil temperature increase of 4 °C halved its density in the shallower peat layers, mainly caused by the reduced dominance of Folsomia quadrioculata. A hypothesized net downward shift of the surface-dwelling springtail community, however, was not observed. We observed species-specific responses to warming but the overall community composition in subsequent organic layers was not significantly altered. Although the effects of an extreme warming event on density, species composition and vertical stratification pattern seemed subtle, functional trait analysis revealed directional community responses, i.e. an overall increase of soil-dwelling species due to warming, even though warming did not alter layer-specific community weighted trait means.We suggest that subtle changes in moisture conditions, due to increased evapotranspiration, have decreased typically surface-dwelling species relative to soil-dwelling species. The extent to which this directional change in the community is maintained after an extreme event, and its costs for the community's resilience to multiple sequential extreme events will consequently determine its longer-term effects on the community and on ecosystem functioning. © 2013 Elsevier Ltd

Vascular plant litter input in subarctic peat bogs changes Collembola diets and decomposition patterns.

In high-latitude ecosystems climate change induced plant community shifts toward dominance of shrubs and trees will potentially have large consequences for soil carbon dynamics. Changes in the litter layer due to an altered quantity and quality of litter input, or by its indirect effect on the microclimate, might affect the decomposer community.To be able to predict the effects of increased litter input on decomposers and consequently on soil carbon dynamics, we studied the contribution of Collembola to carbon processing in a high-latitude peat bog system. Moreover, we assessed the effects of changing litter inputs on their abundance, diversity and diet choice, using

Northern peatland Collembola communities unaffected by three summers of simulated extreme precipitation

Extreme climate events are observed and predicted to increase in frequency and duration in high-latitude ecosystems as a result of global climate change. This includes extreme precipitation events, which may directly impact on belowground food webs and ecosystem functioning by their physical impacts and by altering local soil moisture conditions.We assessed responses of the Collembola community in a northern Sphagnum fuscum-dominated ombrotrophic peatland to three years of experimentally increased occurrence of extreme precipitation events. Annual summer precipitation was doubled (an increase of 200. mm) by 16 simulated extreme rain events within the three months growing season, where on each occasion 12.5. mm of rain was added within a few minutes. Despite this high frequency and intensity of the rain events, no shifts in Collembola density, relative species abundances and community weighted means of three relevant traits (moisture preference, vertical distribution and body size) were observed. This strongly suggests that the peatland Collembola community is unaffected by the physical impacts of extreme precipitation and the short-term variability in moisture conditions. The lack of response is most likely reinforced by the fact that extreme precipitation events do not seem to alter longer-term soil moisture conditions in the peat layers inhabited by soil fauna.This study adds evidence to the observation that the biotic components of northern ombrotrophic peatlands are hardly responsive to an increase in extreme summer precipitation events. Given the importance of these ecosystems for the global C balance, these findings significantly contribute to the current knowledge of the ecological impact of future climate scenarios. © 2014 Elsevier B.V

Traits underpinning desiccation resistance explain distribution patterns of terrestrial isopods

Predicted changes in soil water availability regimes with climate and land-use change will impact the community of functionally important soil organisms, such as macro-detritivores. Identifying and quantifying the functional traits that underlie interspecific differences in desiccation resistance will enhance our ability to predict both macro-detritivore community responses to changing water regimes and the consequences of the associated species shifts for organic matter turnover. Using path analysis, we tested (1) how interspecific differences in desiccation resistance among 22 northwestern European terrestrial isopod species could be explained by three underlying traits measured under standard laboratory conditions, namely, body ventral surface area, water loss rate and fatal water loss; (2) whether these relationships were robust to contrasting experimental conditions and to the phylogenetic relatedness effects being excluded; (3) whether desiccation resistance and hypothesized underlying traits could explain species distribution patterns in relation to site water availability. Water loss rate and (secondarily) fatal water loss together explained 90 % of the interspecific variation in desiccation resistance. Our path model indicated that body surface area affects desiccation resistance only indirectly via changes in water loss rate. Our results also show that soil moisture determines isopod species distributions by filtering them according to traits underpinning desiccation resistance. These findings reveal that it is possible to use functional traits measured under standard conditions to predict soil biota responses to water availability in the field over broad spatial scales. Taken together, our results demonstrate an increasing need to generate mechanistic models to predict the effect of global changes on functionally important organisms. © 2012 Springer-Verlag Berlin Heidelberg

Globally invariant metabolism but density-diversity mismatch in springtails

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