University of Innsbruck

DP ABGC Student Paper Award 2021

The DP Student Paper Award 2021 was awarded to Elia GuarientoKathiravan MeeranCharlotte Permann and Katharina Scholz. Find a summary for each of the awarded papers below.


Ant community and functional ecology over the alpine tree line ecotone

Ants are ecologically a dominant insect family, that have a significant influence in almost all terrestrial habitats. This is true also for the higher montane coniferous forest of the European Alps. In the alpine environment however, ants tend to have a reduced abundance and diversity reaching their distribution margin.

In the two studies here presented we investigate the ant community from the mountain forest over the tree line ecotone to the alpine grassland. In the first paper we focus upon the community composition, diversity and functional traits. In the second study we target directly the trophic role and position of the community and single species by means of experiments and molecular analysis.

In the first paper we recorded a higher richness directly on the ecotone, however it appeared to be determined by a higher species packing rather than an expected mixing of two communities. Further, using functional traits we detected a change in the feeding preferences of this generalist feeders from the alpine habitat to the forest were more feeding in interaction with trophobiosis occurs. In the second study we confirmed this outcome both using bait visitation and stable isotope analysis. In detail, in the forest carbohydrate baits were less visited (meaning that this resource is less limiting) and N15 scored on a lower signature.

From these results we conclude that the presence of trees, as key stone species, alter both the ant community composition and their trophic function. We argue that this happens because when trees are present, enough trophobionts occur on them to sustain the ant community with enough plant derived carbohydrates. If, on the other hand trees are missing, like in the alpine environment, the ant community turns more carnivorous. Interestingly, this trophic flexibility was also recorded intraspecifically in the two dominant species occurring over the investigated gradient, namely Formcia lemani and Formica lugubris.



Graphical abstract highlighting the main results of trophic shift and species richness over the tree line ecotone.

For his papers in the journals Ecological Entomology and Insects, DP-member Elia Guariento received the DP ABGC Student Paper Award 2021.

Guariento, E., Wanek, W. and Fiedler, K. (2021) Consistent shift in nutritional ecology of ants reveals trophic flexibility across alpine tree-line ecotones. Ecol Entomol, 46: 1082-1092.

Guariento, E, and Konrad F. (2021) Ant Diversity and Community Composition in Alpine Tree Line Ecotones. Insects 12, 3: 219

Future climate intensifies drought and recovery effects on carbon dynamics in grassland

During the mid- to late 21st century, continued consumption of fossil fuels is expected to increase atmospheric CO2 concentrations by 300 – 400 ppm above current levels, leading to global warming of 1 to 3.7˚C and an increase in the frequency and intensity of climate extremes such as drought. These global change factors can have drastic effects on ecosystems carbon (C) dynamics by altering the photosynthetic plant C uptake (GPP, i.e. gross primary productivity), soil respiration (SR) and the allocation of recently photosynthesized C to SR.

We combined a multifactor climate manipulation experiment with an in-situ isotopic pulse labeling study to assess the effects of drought and drought recovery on ecosystem C dynamics and the linkage between plant C uptake and SR. We compared drought effects under ambient versus future climate conditions (3° warming and +300 ppm of elevated CO2) We found that warming and elevated CO2 increased SR and the proportion of recently assimilated C respired in soil. At the same time, these future conditions altered the drought-and post-drought responses of ecosystem CO2 fluxes and the partitioning of recently assimilated C between plants, soil and SR. Our findings indicate that in a warmer climate under elevated CO2 drought effects on the fate of recent C in grassland will be amplified and the coupling of photosynthesis and soil respiration will be sustained. Our study highlights the necessity to consider the interactive effects between multiple global change factors for understanding and projecting grassland C cycling in a future world.


Summary of drought effects on gross primary productivity (GPP) and soil respiration (SR) and the transfer of recent C from GPP to SR under ambient (left) and future climate conditions (right). The thickness of arrows indicates proportional change in C flux due to treatment effects.

For his paper in the journal Global Change Biology, DP-member Kathiravan Meeran received the  DP ABGC Student Paper Award 2021.

Meeran, K., Ingrisch, J., Reinthaler, D., Canarini, A., Müller, L., Pötsch, E.M., Richter, A., Wanek, W. and Bahn, M. (2021), Warming and elevated CO2 intensify drought and recovery responses of grassland carbon allocation to soil respiration. Glob Change Biol, 27: 3230-3243.

 Induction of conjugation and zygospore cell wall characteristics in the alpine Spirogyra mirabilis (Zygnematophyceae, Charophyta): Advantage under climate change scenarios?

Zygnematophyceae, a class of streptophytic green algae, are the closest relatives to all land plants. A variety of adaptation strategies to terrestrial habitats are known. However, while most conducted studies concern their resistance in a vegetative state, less is known about their special way of sexual reproduction (conjugation) and its role in withstanding unfavorable environmental conditions. To better understand their evolutionary success and the role of sexual reproduction in the aspect of climate change, we studied the process of conjugation and the resulting features of the zygospores. For our study we took field samples of Spirogyra mirabilis from the Austrian alps, as such mountain regions are especially affected by global change. Our study showed that the zygospore wall was composed of three different layers, giving a complex inner structure. The outer and inner layer both consisted of polysaccharides, which exhibited a further internal structure. In contrast, complex aromatic compounds were detected in the massive middle layer. We furthermore were able to detect arabinogalactan proteins and xyloglucans integrated into the zygospore wall. The massive and complex structure of the zygospore wall, amongst others containing highly resistant aromatic compounds, most likely helps these algae to endure abiotic stresses, like freezing events or desiccation. Overall, our data support the idea that sexual reproduction in Zygnematophyceae, might have played an important role in the process of terrestrialization and most likely will play a crucial role in the adaptation to the environmental conditions accompanying global change.



 Sampling Site (Kühtai/ Tyrol) with zygnematophycean algal mat and zygospore with cell wall characteristics. A Spirogyra mirabilis zygospore, B Raman image showing aromatic compounds, C transmission electron micrograph showing multilayered wall structure, D toluidine-blue stained semithin section showing acidic carbohydrates, E fluorescence micrograph showing arabinogalactan proteins. Scale bars: A, B 5 µm, C 1 nm, D, E 2.5 µm.



For her paper in the journal Plants (Basel), DP-member Charlotte Permann received the DP ABGC Student Paper Award 2021.


Permann, C., Herburger, K., Felhofer, M., Gierlinger, N., Lewis, L. A., & Holzinger, A. 2021. Induction of Conjugation and Zygospore Cell Wall Characteristics in the Alpine Spirogyra mirabilis (Zygnematophyceae, Charophyta): Advantage under Climate Change Scenarios?. Plants (Basel, Switzerland)10(8), 1740.


 Atmospheric CO2 Exchange of a Small Mountain Lake

Lakes and rivers are considered to be substantial sources of carbon dioxide (CO2). Yet, continuous measurements of lake-atmosphere CO2 exchange are sparse. To better understand the magnitude, temporal variability, and driving factors of CO2 fluxes of a small mountain lake, a team of ecologists of the University of Innsbruck and WasserCluster Lunz monitored the CO2 exchange at the air-water interface of Lake Lunz for an entire year.

To capture CO2 fluxes at the air-water interface, several methods with differing temporal and spatial resolution exist. In this study, the scientists compared the results of CO2 fluxes measured with two different methods – the Eddy Covariance (EC) and the Boundary Layer Model (BLM) approach. In addition, the local wind regime and its influence on the CO2 exchange and on the respective measurement method was analyzed. Overall, the measured CO2 fluxes were low with highest emissions in fall during lake turnover. Furthermore, the results demonstrated that the existence of a local land-lake wind regime directly influenced the CO2 exchange at the air-water interface by determining the atmospheric CO2 concentration. During night, the air was typically draining down the slopes of the surrounding land towards the lake which was accompanied by a substantial increase in atmospheric CO2. During the day, strong westerly winds persisted above the lake and atmospheric CO2 was typically lower.  Because the gas transfer at the air-water interface is largely determined by the concentration difference at the interface, this resulted in a diel pattern in CO2 fluxes with higher CO2 emissions throughout the day and lower emissions or CO2 uptake during the night.

EC data were biased towards higher fluxes, because with the EC approach an upwind signal is captured and the instruments were set up on the east shore of the lake, therefore measuring lake fluxes only during westerly winds. 



For her paper in the journal Journal of Geophysical Research: Biogeosciences, DP-member Katharina Scholz received the DP ABGC Student Paper Award 2021.


Scholz, K., Ejarque, E., Hammerle, A., Kainz, M., Schelker, J., & Wohlfahrt, G. 2021. Atmospheric CO2 exchange of a small mountain lake: Limitations of eddy covariance and boundary layer modeling methods in complex terrain. Journal of Geophysical Research: Biogeosciences, 126, e2021JG006286.


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