Profiles

Marianne Stoessel, PhD student

Marianne Stoessel

Doktorand

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Works at Department of Physical Geography
Telephone 08-16 48 87
Email marianne.stoessel@natgeo.su.se
Visiting address Svante Arrhenius väg 8
Room V412
Postal address Inst för naturgeografi 106 91 Stockholm

About me

Member of the Bolin centre, in the research areas 7 (landscape processes and climate) and 8 (biodiversity and climate).

I am PhD student in the Biogeography and Geomatics unit, and I am studying the interacting effects of land-use and global warming on northern grasslands, under the supervision of Regina Lindborg.

My profile:

I am a passionate ecologist and I like to study nature through different perspectives, if possible different disciplines. Originally, I studied behavioural ecology and ecophysiology. I have been introduced to the world of bio-logging in Strasbourg (2012, with Yan Ropert-Coudert).

I also developed other skills in animal monitoring such as camera trapping surveys, bird ringing and animal tracking through different projects, jobs and traineeships.

Then I did the Master programme in landscape ecology at Stockholm University (2016). There I have been studying community ecology in winter (with Bodil Elmhagen and the Arctic fox research project).

I also worked with Helle Skånes as a research assistant, working on mapping processes and biotope classification in urban land (2017).

Teaching

Since 2016, I have been assisting teaching in courses mainly for Master students in landscape mapping and analysis, where I held labs about connectivity analysis, biotope mapping, coloured infrared orthophoto interpretation for vegetation mapping, landscape interpretation in the field and initiating the students to the use of R for spatial analysis and geo-computation.

I also assist the students for their individual projects at the end of the course. 

I have helped organising seminars (on topics such as e.g. landscape mapping and semantics).

Research

My PhD project:

Grasslands in northern Fennoscandia are under increasing pressure because of climate change. Grazing has an extensive effect on vegetation and can help to keep the landscape open. Yet, grazing activities are also getting increasingly disturbed by concurrent human activities at northern latitudes. For my PhD project, I aim at highlighting hotspots under multiple stressors and studying how much grazing activities are affected by other human activities. In fine, my objective is to study how these stressors affect the quality and the extent of the grazing land.

Publications

A selection from Stockholm University publication database
  • 2018. Marianne Stoessel (et al.). Ecography

    Global warming is predicted to change ecosystem functioning and structure in Arctic ecosystems by strengthening top‐down species interactions, i.e. predation pressure on small herbivores and interference between predators. Yet, previous research is biased towards the summer season. Due to greater abiotic constraints, Arctic ecosystem characteristics might be more pronounced in winter. Here we test the hypothesis that top‐down species interactions prevail over bottom‐up effects in Scandinavian mountain tundra (Northern Sweden) where effects of climate warming have been observed and top‐down interactions are expected to strengthen. But we test this ‘a priori’ hypothesis in winter and throughout the 3–4 yr rodent cycle, which imposes additional pulsed resource constraints. We used snowtracking data recorded in 12 winters (2004–2015) to analyse the spatial patterns of a tundra predator guild (arctic fox Vulpes lagopus, red fox Vulpes vulpes, wolverine Gulo gulo) and small prey (ptarmigan, Lagopus spp). The a priori top‐down hypothesis was then tested through structural equation modelling, for each phase of the rodent cycle. There was weak support for this hypothesis, with top‐down effects only discerned on arctic fox (weakly, by wolverine) and ptarmigan (by arctic fox) at intermediate and high rodent availability respectively. Overall, bottom‐up constraints appeared more influential on the winter community structure. Cold specialist predators (arctic fox and wolverine) showed variable landscape associations, while the boreal predator (red fox) appeared strongly dependent on productive habitats and ptarmigan abundance. Thus, we suggest that the unpredictability of food resources determines the winter ecology of the cold specialist predators, while the boreal predator relies on resource‐rich habitats. The constraints imposed by winters and temporary resource lows should therefore counteract productivity‐driven ecosystem change and have a stabilising effect on community structure. Hence, the interplay between summer and winter conditions should determine the rate of Arctic ecosystem change in the context of global warming.

  • 2019. Rasmus Erlandsson (et al.). Remote Sensing in Ecology and Conservation

    Studies of ecological processes should focus on a relevant spatial scale, as crude spatial resolution will fail to detect small scale variation which is of potentially critical importance. Remote sensing methods based on multispectral satellite images are used to assess primary productivity and aerial photos to map vegetation structure. Both methods are based on the principle that photosynthetically active vegetation has a characteristic spectral signature. Yet they are applied differently due to technical differences. Satellite images are suitable for calculations of vegetation indices, for example Normalized Difference Vegetation Index (NDVI). Colour infrared aerial photography was developed for visual interpretation and never regarded for calculation of indices since the spectrum recorded and post processing differ from satellite images. With digital cameras and improved techniques for generating colour infrared orthophotos, the implications of these differences are uncertain and should be explored. We tested if plant productivity can be assessed using colour infrared aerial orthophotos (0.5 m resolution) by applying the standard NDVI equation. With 112 vegetation samples as ground truth, we evaluated an index that we denote rel‐NDVIortho in two areas of the Fennoscandian mountain tundra. We compared the results with conventional SPOT5 satellite‐based NDVI (10 m resolution). rel‐NDVIortho was related to plant productivity (Northern area: P = <0.001, R2 = 0.73; Southern area: P = <0.001, R2 = 0.39), performed similar to SPOT5 satellite NDVI (Northern area: P = <0.001, R2 = 0.76; Southern area: P = <0.001, R2 = 0.40) and the two methods were highly correlated (cor = 0.95 and cor = 0.84). Despite different plant composition, the results were consistent between areas. Our results suggest that vegetation indices based on colour infrared aerial orthophotos can be a valuable tool in the remote sensing toolbox, offering a high‐spatial resolution proxy for plant productivity with less signal degradation due to atmospheric interference and clouds, compared to satellite images. Further research should aim to investigate if the method is applicable to other ecosystems.

Show all publications by Marianne Stoessel at Stockholm University

Last updated: July 15, 2019

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