This is a cache of https://www.uibk.ac.at/projects/claimes/news/index.html.en. It is a snapshot of the page at 2024-11-21T08:06:40.042+0100.
News – University of Innsbruck

News


New publication within project CLAIMES

Schirpke U., Ebner M., Fontana V., Enigl K., Ohndorf M., Pritsch H., Kurmayer R. (2023). Climate response of alpine lakes and impacts on ecosystem services, Landscape Online 98: 1109, doi:10.3097/LO.2023.1109  . https://landscape-online.org/index.php/lo/article/view/LO.2023.1109

Global warming and human influence are factors that can strongly affect the ecological integrity of small alpine lakes. In the interdisciplinary project CLAIMES  (CLimate response of AlpIne lakes: resistance variability and Management consequences for Ecosystem Services) limnological data and surface temperature modeling as well as potential impacts on associated ecosystem services were investigated at 15 lakes in the Niedere Tauern (Austria) and South Tyrol (Italy). Prioritized ecosystem services were quantified using several indicators, and potential future impacts were assessed based on several possible worst-case scenarios.
Our results show that global warming will reduce the duration of ice cover, affecting ecosystem functions and consequently trophic status. The results also show that the provision of ecosystem services by lakes is largely influenced by local socio-ecological characteristics. The predicted decline in ecosystem services in the future calls for better integration of ecosystem services of alpine lakes into decision and policy making at different levels of governance.

online since 07.07.2023


New publication within project CLAIMES

Pritsch H., Schirpke U., Jersabek C.D., Kurmayer R. (2023). Plankton community composition in mountain lakes and consequences for ecosystem services, Ecological Indicators 154: 110532, https://doi.org/10.1016/j.ecolind.2023.110532

Pritsch et al-2023

 

Mountain lakes provide a variety of ecosystem services (ES) including water, habitat, recreation, and aesthetic values. Due to various influences, these lakes are coming under increasing pressure. The development of appropriate indicators to monitor changes in ES will help in planning targeted conservation measures. Limnological data are used as a basis for conservation issues. In this study, in addition to widely used standard parameters, genetic analysis of phytoplankton by metabarcoding based on 16S/18S rDNA high-throughput sequencing (HTS) was used. The results of the study indicate that degradation of ecological conditions in mountain lakes could negatively affect the future provision of ES. Therefore, it is increasingly important to protect pristine lakes, and data on plankton community composition can provide useful guidance for deciding which lakes should be prioritized for protection through appropriate measures.

online since 23.06.2023

 


CLAIMES PhD successfully defended

MEbnerEinladung defensio MEbner-2022

Manuel Ebner defended his PhD with the title "Assessing ecosystem services of mountain lakes:
An integrative approach to link socio-cultural perspectives, multi-metric indicators, and global change pressure" within the project CLAIMES at the Department of Ecology of the University of Innsbruck with distinction.

Congratulations from the team!

online since December 19th, 2022 


"Österreichs Fischerei" informs about the project CLAIMES

 OEF

In the current issue of the journal Österreichs Fischerei , 75. Jhg. Heft 2/3, Februar/März, reports on the project CLAIMES. The article with the title "Studie zum Einfluss des Klimawandels auf Alpine Seen und deren Ökosystemleistungen" gives insights in the goal and research background as well as the results.

read the article (in German)

online since 21.02.2022

Alpine lakes during climate change - "wissenswert"

 Alpenseen

The December issue of the journal "wissenswert" of the Leopold-Franzens-Universität Innsbruck, offers a link to the video  "Alpenseen im Klimawandel". In this reseach video (in German) the project leader Rainer Kurmayer and the PhD student Hanna Pritsch from Research Department for Limnology, Mondsee, inform about the impact of climate change on alpine lakes in Niedere Tauern (Austria) and Southern Tyrol (Italy) which is investigated in the project CLAIMES.

 online since, 10.01.2022

 


New publications within project CLAIMES

Ebner, M., Fontana, V., Schirpke, U., Tappeiner, U., (2022). Stakeholder perspectives on ecosystem services of mountain lakes in the European Alps. Ecosystem Services 53: 101386, https://doi.org/10.1016/j.ecoser.2021.101386

This study identifies the most important ecosystem services (ES) of mountain lakes and investigates how stakeholders perceive the importance of these ES and their contribution to human well-being. The results of the mixed-methods approach, based on sociocultural valuation methods, were obtained by interviewing different stakeholders from the government, business, research and public sectors in South Tyrol (Italy) in the Central European Alps. The results show that ES preserving habitats and aesthetic values were given the highest importance, followed by surface water, outdoor recreation, and representation and entertainment. The results obtained are discussed in terms of their implications for research and practice and represent a first step towards an integrative assessment of mountain lakes.

Open Access

Schirpke, U., Scolozzi, R., Kiessling, A., Tappeiner, U. (2021). Recreational ecosystem services of mountain lakes in the European Alps: Preferences, visitor groups and management implications. Journal of Outdoor Recreation and Tourism 35: 100421. https://doi.org/10.1016/j.jort.2021.100421

In this publication, people's preferences were identified with a focus on recreational activities, accessibility and tourist facilities. 526 responses from an online survey were analyzed using cluster analysis and show that respondents primarily use the mountain lakes studied for passive recreation such as nature observation and relaxation. Hiking and walking trails along the lakeshore as well as direct access to the lake are particularly appreciated. The study resulted in the classification of respondents into the two visitor groups of (1) nature-oriented visitors and (2) recreation-oriented visitors. Although conflicts may arise between these two groups of visitors, the presence of lakes with different levels of accessibility may mitigate such conflicts. The results provide valuable insights for developing targeted management strategies based on the preferences of the different visitor groups.

Open Access

Schirpke, U., Tasser, E., Ebner, M., Tappeiner, U. (2021). What can geotagged photographs tell us on cultural ecosystem services of lakes? Ecosystem Services 51, 101354. https://doi.org/10.1016/j.ecoser.2021.10135

In this study, photos uploaded to the photo-sharing platform Flickr were used to analyze the ecosystem services (ES) of 2,807 lakes in the European Alps. The spatial distribution of photo-user-days, the importance of lakes for providing ES, and the most important ES were identified through text analysis. This allowed the identification of 12 different ES, including aesthetic experiences and recreation. The results suggest that lakes are important for providing multiple ESs, but future research should incorporate user survey data to deepen understanding of people's perceptions and preferences.

Open access


Conclusion of field work 2021

Just in time before the cold snap, the field season of the CLAIMES 2021 project was successfully completed. Once again, the project team had the support of ambitious student helpers and interns from schools in the field and also in the laboratory, during sample processing.

CLAIMES-Freiland Rainer2 CLAIMES-Freiland Rainer3

 CLAIMES-Freiland Hanna 2 CLAIMES-Freiland Hanna 1

Wirpitschsee-CLAIMES Fischersee-CLAIMES

Impressions of the field work, photos: R. Kurmayer, H. Pritsch

 


Influence of climate change on alpine lakes - article in "Salzburgs Fischerei"

Salzburgs Fischerei Titel

"Salzburgs Fischerei" a journal of the Fishing Association Salzburg has published a comprehensive article about the project CLAIMES. In this article the reader gets insights about the background, activities and goals of the project and also an outlook on the further progress. First results of the years 2019-2020 show an average rise of the water temperature in the project lakes of appr. 1°C within the warmest month. The ice coverage in the lakes below 1900-2000m above sea level decreased by appr. 10-20 days. Comparing data from earlier investigations the researchers found an increase of the water temperature of all lakes sampled by a mean of 0,42° bis 1,35°C per decade.

articlel in "Salzburgs Fischerei" (in German)

online seit 27.09.2021


Field work campaign 2021 started successfully

Probenahme 2021

CLAIMES field work group 2021 at Klafferkessel, photo: H. Pritsch

The CLAIMES field work campaign 2021 has started in Southern Tyrol. In this region the sampled have been taken already and will be followed by sampling of seven lakes in the Niedere Tauern within the next two weeks. The project team is supported by three FFG fellows and one University student who help with field work and analyses. 

online since, 13.09.2021


New CLAIMES publication about the aesthetic value of lakes in the Alps

Tourismus Moaralmsee

photo: R. Kurmayer

 Schirpke U., Scolozzi R., Tappeiner U. (2021). “A Gem among the Rocks”—Identifying and Measuring Visual Preferences for Mountain Lakes. Water 13(9), 1151. https://www.mdpi.com/2073-4441/13/9/1151

The aim of this study was to evaluate the preferences of visitors with regard to the visual properties of mountain lakes with the help of an online questionnaire. First qualitative and later also quantitative characteristics were queried and analyzed. In particular, the preference for visual water properties was very homogeneous across sociocultural groups and confirmed earlier study data. The results obtained in this way were linked with spatial and limnological data in order to quantify the aesthetic values ​​for four selected study lakes from the project CLAIMES in the European Alps. In addition, the conclusions related to the increasing demand for nature-related experiences and the implications for decision-making were discussed.

online since 22.04.2021


CLAIMES will be represented in the digital "Lange Nacht der Forschung 2020"

LNF digital Video CLAIMESLNF digital

The project  CLAIMES will be represented with a video at the digital Lange Nacht der Forschung 2020. In the province of Tyrol, the region of Innsbruck and the institution University of Innsbruck the video "Am Antholzer See - Was forschen Limnologen?" informs about the research work within the project and delivers an insight into the sampling and field work for later analyses at  Antholzer Sees in Southern Tyrol. PI Rainer Kurmayer and PhD student Hanna Pritsch explain details about the project details in short interviews.

The video will be online from October 9th to December 30th, 2020 at the Lange Nacht der Forschung webpage.

online since October 13, 2020


The sampling campaign 2020 is finished

Probenahme CLAIMES Sept2020 Probenahme CLAIMES Sept2020-3

Videoaufnahmen LNF2020 Probenahme CLAIMES Sept2020-1

photos: CLAIMES

From September 2020 onwards the CLAIMES Team was working in the field with support of students and two training fellows. After sampling the Lower Tauern Region (Austria) and the lakes in Southern Tyrol (Italy) they did a second sampling tour in the Lower Tauern Region. For WP1 (short-term changes) sampling has been nearly completed and the relevant data have been acquired. In addition LST models have been created and applied on a monthly basis for a time series 1880 – 2010. With the beginning of October the sampling campaign had to be closed because of the harsh weather conditions. During the field work in Southern Tyrol a video "Am Antholzer See - Was forschen Limnologen?" was produced for the "digitale Lange Nacht der Forschung 2020". It is online for watching between October 9th 2020 and December 30th 2020 at the Website of the Lange Nacht der Forschung.

online since October 13, 2020


CLAIMES project at GMS Forum 2020

GMS-2020-Ebner

On 06.10.2020, Manuel Ebner presented at the Global Mountain Sustainability Forum 2020 (Sexten/Italy, online) the recent work of the CLAIMES project regarding the participatory identification and socio-cultural valuation of mountain lakes’ ecosystem services.


PROJECT MEETING 2020 with stakeholders

CLAIMES-Meeting1CLAIMES-Meeting3

CLAIMES Meeting in Radstadt 2020, photos: V. Fontana

On August 4th 2020, we finally held our second focus group meeting which was postponed several times due to the current Corona-crisis. This time, we met in Radstadt in Salzburg. H. Pritsch presented first limnological results and M. Ebner and V. Fontana moderated the evening event. Ten participants representing interest groups such as nature conservation, research, tourism, administration, and landowners discussed on goods, services and contributions to human well-being provided by mountain lakes. Further, potential conflicts of use, involved actors, and future visions for maintaining a stable ecosystem service supply and sustainable development of mountain lakes were addressed alike the first meeting in South Tyrol.

online August 24, 2020


Job offer Limnological Field Work at Mountain Lakes

To support the limnological field work on mountain lakes within the CLAIMES project, we are looking for sportive people who love the mountains and have basic knowledge in biology or geology.

Period: September 2020, interested persons should have time over the entire period

Working area: 25 different mountain lakes (1500 - 2400 m a. s. l.) in the “Niedere Tauern” and South Tyrol

Your job: Hiking with equipment to the lakes and sampling of water and sediment samples as well as recovery of sediment traps

Employment: Working contract as student assistant

The CLAIMES project is funded by the Austrian Academy of Sciences and deals with the effects of climate change on the ecology of mountain lakes and their ecosystem services. Further information on the project is available at: https://www.uibk.ac.at/projects/claimes/project/

You are fit? You like hiking and you are interested in limnological field work? Contact me by mail or phone:

Email: hanna.pritsch@uibk.ac.at
phone: +43 512 507-50263

Packen -Aufstieg-Langsee-2019sAntholzer See-2019sTiefenbachsee-2019s

online April 29, 2020 


First Focus Group Meeting at EURAC Research

On January 9th 2020 M. Ebner and V. Fontana organized and moderated the first focus group meeting at Eurac Research in Bolzano (South Tyrol). 14 participants representing interest groups such as nature conservation, research, tourism, administration, and communalities discussed on goods and services provided by mountain lakes. Further, potential conflicts of use, involved actors, and future visions for maintaining a stable ecosystem service supply were addressed.

Projekttreffen 2020-1Foto Projekttreffen 2020-2

online February 7, 2020


CLAIMES Project Meeting

R. Kurmayer, U. Schirpke, V. Fontana, C. Matulla, M. Ohndorf, K. Enigl, M. Ebner, H. Pritsch and S. Vorhauser met on 12.11.2019 in Innsbruck for a general CLAIMES project meeting. The current project status and the plans in the individual work packages were discussed. The latest news from the three work packages (WP) were presented.

In WP 1 the lake samplings for this season were completed on 11.10.2019. Samples will be analyzed beginning next year. Data on water chemistry and physicochemical parameters are compared to the historical data from 1998/99. A report on the project and the samplings is in progress and will be completed by end of the year and sent by email to the owners and tenants as well as to the water protection agencies and the responsible communities of the sampled lakes. The climatologists gave an overview of the potentially available data. In particular, it is planned to create a high temporal resolution (monthly to daily if required) of the temperature of the individual lakes.

An intense literature research was carried out by WP 2 on the topic of ecosystem services related to alpine lakes. For next steps regarding the search and selection of indicators for the ES, the results of the expert round table and the stakeholder workshops in South Tyrol are awaited. Furthermore, the results from the SIL-workshop given in October at the SIL-Austria Conference in Mondsee were discussed.

In WP 3 a first overview of the potential actors and stakeholders in the South Tyrolean project region was given. A sub-group (approx. 8-12 persons) from more than 40 actors will be invited for an introductory focus group meeting to identify the primary/most important ES of alpine lakes. The members of the focus group are from various areas of interest and different institutions. They have a direct contextual reference and are key persons/institutions with high centrality and radius of impact. The pairwise-questionnaires of the ES weighting for South Tyrol will be carried out in the 1st quarter 2020. Further projects are the implementation of a (participatory) stakeholder and network analysis to describe the relationships between actors and their characteristics.

The next CLAIMES-Meeting will take place in April/May 2020.

online November 12, 2019


Publication within CLAIMES:

Ma T., Jiang Y., Elbehery A.H., Blank S., Kurmayer R., Deng, L. (2019). Resilience of planktonic bacterial community structure in response to short-term weather deterioration during the growing season in an alpine lake. Hydrobiologia, 1-14, https://link.springer.com/article/10.1007/s10750-019-04118-8
The disturbing effect of a short-term cooling period during summer on planktonic bacterial community structure of an alpine lake was investigated using 16S rDNA pyrosequencing. Proteobacteria, Actinobacteria, and Bacteroidetes constituted the most abundant phyla. During the sampling period (from July to August 2010), a sudden cooling period with high precipitation occurred, as indicated by a decrease in conductivity, calcium, and dissolved organic carbon concentration resulting from increased runoff. The relative abundance of Actinobacteria, Betaproteobacteria, and Cyanobacteria decreased during this short-term cooling period. Instead, a rapid shift from Betaproteobacteria to Gammaproteobacteria occurred, which was mainly caused by an increase of Acinetobacter rhizosphaerae. Soon after the short-term cooling period, warmer weather conditions got re-established and Betaproteobacteria recovered and became again dominant. Non-metric multi-dimensional scaling analysis and Venn diagrams revealed a planktonic bacterial community composition with high similarity at the beginning and the end of the growing season. Air temperature and precipitation were significantly correlated with the observed variation in operational taxonomic unit (OTU) relative abundance. It is concluded that, in response to the short-term cooling period, a distinct planktonic bacterial OTU community developed. It rapidly diminished, however, as summer conditions became re-established, implying the recovery of the original bacterial community structure.
 

Publication within CLAIMES:

Jiang Y., Huang H., Ma T., Ru J., Blank S., Kurmayer R., Deng, L. (2019). Temperature Response of Planktonic Microbiota in Remote Alpine Lakes. Frontiers in Microbiology 10: 1714. https://www.frontiersin.org/articles/10.3389/fmicb.2019.01714/full

Alpine lakes are considered pristine freshwater ecosystems and sensitive to direct and indirect changes in water temperature as induced by climate change. The bacterial plankton constitutes a key component in the water column and bacterial metabolic activity has direct consequences for water quality. In order to understand bacterial response to global temperature rise in five alpine lakes located in the Austrian Alps (1700–2188 m a.S.L.) water temperature was compared within a decadal period. Depth-integrated samples were characterized in community composition by 16S rDNA deep-amplicon sequencing early [56 ± 16 (SD) days after ice break up] and later (88 ± 16 days) in the growing season. Within the 10 years period, temperature rise was observed through reduced ice cover duration and increased average water temperature. During the early growing season, the average water temperature recorded between circulation in spring until sampling date (WAS), and the day of autumn circulation, as well as chemical composition including dissolved organic carbon influenced bacterial community composition. In contrast, only nutrients (such as nitrate) were found influential later in the growing season. Metabolic theory of ecology (MTE) was applied to explain the dependence of taxonomic richness on WAS in mathematical terms. The calculated activation energy exceeded the frequently reported prediction emphasizing the role of WAS during early growing season. Accordingly, the relative abundance of predicted metabolism related genes increased with WAS. Thus, the dominant influence of temperature after ice break up could be explained by overall climate change effects, such as a more intense warming in spring and an overall higher amplitude of temperature variation.


SIL-Austria Conference in Mondsee 28.-30.10.2019

SIL-Austria 

On 29.10.2019 R. Kurmayer, U. Schirpke, M. Ebner and H. Pritsch held a workshop with the topic ‘Which indicators can be used for the representation of ecosystem services in lakes? From methodological aspects to ecological basis concepts.’ at the SIL-Austria Conference in Mondsee.

In the workshop, we aimed for indicators, which can be used to measure specific ecosystem services that are related to alpine lakes. Ecosystem services were divided into three groups: cultural, providing and regulating ecosystem services. For each selected ecosystem service at least one indicator was found. Depending on the ES indicators can be standard measurements in limnology, different hydrological parameters as well as the analysis of different media elements.

CLAIMES presentations at the SIL-Austria conference:

Kurmayer R., Matulla C., Fontana V., Schirpke U., Ohndorf M. (2019). CLAIMES - Climate response of alpine lakes: resistance variability and management consequences for ecosystem services. Talk given at the SIL-Austria Conference, Mondsee, October 28-30, 2019.


Presentation of CLAIMES at the Researchers´ Night 2019
at EURAC Research Bozen, Southern Tyrol

LNF-2019-EURAC

On 27.09.2019 the Researchers´ Night took place in Bolzano, Southern Tyrol. More than 10,000 visitors commuted between 13 locations to gain insights into the world of science. The CLAIMES project was also represented with a booth at the EURAC Research site. In a playful and interactive way, children, young people and adults were able to understand what ecosystem services are and which services are provided by lakes. Furthermore, the visitors were encouraged to think about possible changes in lakes due to climate change.


Field work ended

field workPacken für Langsee, H. Pritsch, 2019

We have installed sediment traps and temperature recorders in a total of 25 lakes. These will be taken out by us in September 2020, thus ensuring that we include August as the warmest month of the year in the temperature records.

online October 11, 2019 


International Mountain Conference (IMC) in Innsbruck 08.-12.09.2019

IMC19

CLAIMES at the IMC in Innsbruck, where R. Kurmayer chaired a workshop with the topic Lakes in Mountain regions as integrative landscape elements: ecosystem services (ES) and threats.

In the workshop it was talked about different subtopics. In the following the results of the workshop regarding the topic of alpine lakes limnology and ecosystem services which are relevant for the CLAIMES project are summarized.

1) Evaluating Ecosystem services (ES) (of lakes), comparing different tools to evaluate ecosystem services

It was noted that the evaluation of ES has its limits. For example is it still common to put a monetary value on an ecosystem. Though it is often ignored that some ecosystem services cannot be translated into monetary value. Another limit is that biodiversity as such is not directly reflected in the ES concept but rather indirectly through ecological functioning or nature conservation. Besides that the results of ES evaluation are potentially biased by the respective participants deciding on relevant ES. Nevertheless, it was found that ecosystem services assessment is a concept with limits, but is currently the best available method. As long as the weaknesses are known, the method can be refined to achieve effective results.

The aim of the ES concept is to take a multitude of aspects into account as well as different stakeholders. It is important to state that the ES concept is not limited to monetary techniques and should be seen as assisting a potential required decision basis. Indeed monetary techniques have been criticised because of the human centred vision producing unrealistic vales. Instead, participatory and deliberative approaches combining monetary and non-monetary techniques may be a more sustainable compromise in ES evaluation. When applying participatory approaches stakeholder selection (and participation) will be most crucial and requires a careful selection (including scientists from relevant disciplines).

2) Lake ecosystem services, translating limnological measurements to indicate ES

Usually the relevant ES will help to decide the appropriate limnological measurement and which parameters are required. It is further recommended to translate “biodiversity” to parameters that are better understood by stakeholders. Although for example the term “biodiversity” is standard among nature conservationists, it is difficult to translate on the political level. In transdisciplinary work, it is generally important to speak a language that is understandable to all. This makes it possible to exchange information between different disciplines, but also to ensure understanding between science, politics and the population.

3)  Lake climatology, merging lake surface temperature modelling with “real” temperature measurements

In general, lake surface temperature (LST) modelling can be seen as an alternative approach to temperature measurement and extrapolation. While the extrapolation of long-term series has provided important information on the prediction of lake temperature in the Alps, LST can hopefully be used to answer further questions.

An important field is the application of LST modelling to physical, chemical and biological consequences in temporal and spatial resolution. A higher temporal resolution for short-term changes might be relevant to cope with the consequences of heat waves, i.e. for the physical stability of the water column. Changes in light and nutrient availability and plankton composition can be expected because of temperature influences. Larger lakes also require a higher spatial resolution, especially if the lake morphometry leads to different basins with different amounts of water. 

Other subtopics of the workshop not directly related to the CLAIMES project were the anthropogenic impacts on lakes and their ecosystem services like nanoparticles, micro-plastics, endocrine disrupting compounds, persistent organic pollutants and new synthetic particles of which impacts on aquatic ecosystems are still unknown as well as the concept of metabarcoding. Metabarcoding is a rather recent approach taking advantage of deep-amplicon sequencing of taxonomic marker gene regions which have been amplified from aquatic environmental samples. Potential improvement by this technique include a more time and cost efficient acquisition of taxa inventories, a more rapid or even on time results provision, less dependence on microscopic and subjective species keys, and less invasive (and destructive) sampling (avoiding the sacrificing of specimen in fish). From a practical point of view metabarcoding is unlikely to replace BQE monitoring in the near future. Currently only qualitative estimates are provided, e.g. taxa inventories which could be used semi-quantitatively if protocols could be installed in a strict standardized manner. This method is used in the CLAIMES project but is not a focus.

CLAIMES presentations at IMC 2019

Fontana V., Ebner M., Kurmayer R., Schirpke U., Ohndorf M., Matulla C. (2019). CLAIMES - Climate response of alpine lakes: resistance variability and management consequences for ecosystem services. Talk given at the International Mountain Conference (IMC), University of Innsbruck, September 8-12, 2019.

Matulla C., Enigl K., Schlögl M., Kurmayer R., Schirpke U., Fontana V., Ohndorf, M.; Tordai, J.; Matulla, H.; Ressl, H.; Lehner, S.; Chimani, B. (2019). Alpine lake surface-temperatures - Reconstructions and Projections for assessing Ecosystem-Service availability. Talk given at the International Mountain Conference (IMC), University of Innsbruck, September 8-12, 2019.

U. Schirpke gave a poster presentation on the CLAIMES project and cultural ecosystem services at the IMC 2019. Please find the poster online on our ResearchGate project website.

 M. Ebner presented a poster on the CLAIMES project at the IMC 2019 as well. Please find the poster online on our ResearchGate project website.

online September 12, 2019


Fieldwork started

 Currently the first CLAIMES field sampling campaign in 2019 at the Austrian lakes takes place. Please find some impressions from Twenger Almsee.

Beprobung TWE OSC Beprobung TWE

TWE TWE1

TWE2

Nach oben scrollen