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Ecology and ecophysiology of alpine treelines

See also our dedicated treeline website: www.alpine-treelines.net

2019-2022: Alpine-treeline spatial pattern as an indicator for climate-change responses: community-supported pattern-based modelling

Maaike Bader, Thorsten Wiegand (UFZ Leipzig), Lukas Flinspach (PhD student). Funded by the German Research Foundation (DFG).

2018-2019: sTreelines synthesis workshops in Leipzig (Germany)

PIs: Maaike Bader, Bradley Case (Auckland University of Technology)

See https://www.idiv.de/en/streelines.html for the project summaries on the iDiv website.

2018-2022: Ecosystem engineering at tropical treeline: How water availability and facilitation influence the establishment dynamics of tree species at Andean treelines

Lirey Ramirez (PhD student), Maaike Bader, Luis Daniel Llambí (ULA, Mérida, Venezuela). Funded by the German Academic Exchange Service (DAAD).

2017: MRI synthesis workshop on treeline spatial patterns in Jaca (Spain)

See http://www.mountainresearchinitiative.org/index.php/news-content/global/mri-synthesis-workshop-on-treeline-spatial-patterns

2010-2016: Climatic constraints and vegetation effects on germination and seedling establishment at the alpine treeline

Maaike Bader, Gerhard Zotz (Uni Oldenburg), Hannah Loranger (PhD student). Funded by the German Research Foundation (DFG).

The potential altitudinal limit for tree growth is probably set by a lack of warmth during the growing season. However, the elevational limit for tree establishment is probably set by quite different climatic factors, such as freezing temperatures and interacting stressors such as excess solar radiation. This may explain why few alpine treelines currently reach the potential tree-growth limit, and establishment limitations also have important bearings for treeline responses to climatic changes.

While most ecophysiological treeline research currently focuses on growth limitations for adult trees, this project focused on the earliest life stages, germination and seedling performance, which represent strong demographic bottlenecks determining treeline dynamics and positions.

The goal of the project was to understand the processes that determine treeline dynamics in different tree species, distinguishing generalised and species-specific responses. We were particularly interested in the relative importance and the interactions of growing season warmth, growing season length, and frost and radiation stress for the initial establishment of trees in the alpine life zone. We also studied the role of plant-plant interactions in modifying these factors. We used germination experiments and manipulative field experiments using seeds and small seedlings of various tree species, measuring growth and performance through the seasons. Field sites were located at the Lautaret Alpine Station in the French Alps.

Publications from this project:

Bader, M.Y., H. Loranger, G. Zotz & G. Mendieta Leiva 2018. Responses of tree seedlings near alpine treeline to delayed snowmelt and reduced sky exposure. Forests 9, 12; doi: 10.3390/f9010012
Loranger, H., G. Zotz & M.Y. Bader 2017. Competitor or facilitator? The ambiguous role of grassland vegetation tree seedling emergence, survival and carbon relations at the alpine treeline. Oikos 10.1111/oik.04377
Loranger, H., G. Zotz & M.Y. Bader 2016. Early establishment of trees at the alpine treeline: idiosyncratic species responses to temperature-moisture interactions. AoB Plants 8: plw053; 10.1093/aobpla/plw053 
Bader, M.Y., H. Loranger & G. Zotz. 2014. A cool experimental approach to explain elevational treelines, but can it explain them? American Journal of Botany 101: 1403-1408.

Hannah Loranger

Hannah Loranger

Seedling performance and seed germination experiment in the French Alps. Installation in progress and experiment in place: open-top chambers for day warming, roofs for shading and/or night warming, plots with and without alpine vegetation. In the background: Peak and glacier of La Meije (2013; photos by Hannah Loranger)

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