3a: Extreme ecosystems and unusual events

3a:       Extreme ecosystems and unusual events

Conveners:     Stef Bokhorst (Vrije Universiteit Amsterdam)

                       Runa Magnusson (Wageningen University)

                       Maarten Loonen (University of Groningen)

1. Vegetation type shapes microarthropod communities in Antarctic ecosystems

Ingeborg Klarenberg, Rong Liu, Peter Convey, Hans Cornelissen and Stef Bokhorst, Amsterdam Institute for Life and Environment, systems ecology, Vrije Universiteit Amsterdam

Mosses and lichens are important hosts for microarthropods such as mites and springtails, especially in the polar regions. However, to what extent mosses and lichens differ in their microarthropod communities is poorly quantified. We examined microarthropod abundance, species richness and diversity, and community composition across four major Antarctic vegetation types: lichens, mosses, green algae, grass. We found that microarthropod community composition significantly differed between major vegetation groups. Green algae supported the highest densities of microarthropods, while lichens hosted the lowest, though mosses supported greater abundances than lichens. This pattern was consistent for springtails; however mites were more numerous in lichens than mosses. These findings highlight how vegetation types influence terrestrial biodiversity in Antarctica. Understanding these roles is important, as changes in Antarctic vegetation composition could alter microarthropod communities and impact Antarctic terrestrial food webs.

2. Come rain, come shine: peatland ecosystem functioning under shifting climatic conditions

Janna Barel, Egle Köster, Eeva-stiina Tuittila and Vincent Jassey, Ecology & Biodiversity group, Dept. of Biology, Utrecht University, Utrecht, The Netherlands

Global change threatens the functioning of peatlands, for example, by wide-spread drying and shifting rainfall patterns. Since local hydrology is determining many biogeochemical processes in peatlands it is important to understand how peatland ecosystem functioning is impacted by changing conditions. A recent greenhouse experiment pointed out that increasingly intense, but less frequent rainfall events destabilise water table dynamic, with cascading effects on peatland C fluxes. A related field study indicates that long-term drying effects modulate the responses of peatland vegetation to short-term variation in weather conditions. This presentation discusses the implications of these findings for peatland ecosystem functioning. 

3. Arabidopsis lyrata and its response to extreme weather events

Maarten Posthuma, Mark de Jong, Robin Lexmond, Niels Wagemaker, Heidrun Huber, Eelke Jongejans, Philippine Vergeer, Plant Ecology and Nature Conservation Wageningen University

Under climate change, species inhabiting northern mountainous areas are predicted to decline. Here we investigate the relation between life history traits, population growth rates and environmental change by comparing the life history traits of eight Norwegian Arabidopsis lyrata populations in the period 2005-2007 to 2022-2024. We find that extreme, and local weather events such as flooding, and drought are the main drivers in changes in life history resulting in changes in population growth rates and in turn population size. Next to this, we show that there are differences between populations in their ability to cope with these stressors, and shed light on the genetic and epigenetic mechanisms that underly differences in adaptability. This emphasizes the need of including these mechanisms in models predicted the response of species to climate change.

4. Plant diversity maintains soil detritivore activity under drought

Shengnan Wang, Kathryn Barry, George Kowalchuk, Nico Eisenhauer, Xiaobin Pan, Merel Soons, Yann Hautier, Ecology and Biodiversity Group, Department of Biology, Utrecht University

Extreme droughts and plant diversity loss due to climate change threaten terrestrial ecosystems by disrupting soil organic matter decomposition. Soil detritivores are key to this process, but the combined effects of plant diversity and extreme drought on their feeding activity across soil depths remain unexplored. We subjected plant communities with different species richness levels to historical precipitation and an extreme drought event, and quantified their combined impacts on soil detritivore feeding activity across soil depths. Plant diversity increased feeding activity in both historical and drought conditions, with higher activity during drought. Under historical precipitation, the average feeding activity decreased with soil depth, and the positive impact of plant diversity on feeding activity weakened. In contrast, during drought, the average feeding activity remained stable, and the positive effect of plant diversity on feeding activity increased. This suggests that vertical shifts sustain the impact of plant diversity on detritivore activity during drought.

5. Drying ponds in the Arctic; Extreme conditions in already extreme environments

Maaike Everts, Rijksuniversiteit Groningen

The Arctic is known for its extreme environmental conditions; low temperatures, limited light, little precipitation, and the coverage of snow and ice in winter. In addition, the Arctic region is currently dramatically affected by climate change, where both air temperature and precipitation continue to increase more rapidly than in any other region of the world. The regional effects of global warming are already visible on the island of Spitsbergen, where several freshwater ponds have dried out in years with a warm summer season, due to evaporation and deepening of the active layer of the permafrost. In the period 2018 to 2024, we have annually sampled shallow freshwater ponds. This analysis focuses on ponds that were dry in one or more years in our time series. We can obtain a better understanding of the impact of extremely warm summers and consequently drought, on these shallow, fishless water bodies by assessing the zooplankton communities before and after the dry year. The number of zooplankton for each sample did not change significantly when the years before and after the drought were compared. This finding suggests that zooplankton can survive extreme environmental conditions such as drought through the production of for example resting eggs (ephippia). The study shows the resilience of organisms living in these Arctic ponds, and their ability to adapt to extreme events.