Resident vegetation modifies climate-driven elevational shift of a mountain sedge
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ORIGINAL ARTICLE
Resident vegetation modifies climate‑driven elevational shift of a mountain sedge Harald Crepaz1 · Georg Niedrist1 · Johannes Wessely2 · Mattia Rossi3 · Stefan Dullinger2 Received: 12 June 2020 / Accepted: 20 October 2020 © The Author(s) 2020
Abstract Mountain plant species are changing their ranges in response to global warming. However, these shifts vary tremendously in rate, extent and direction. The reasons for this variation are yet poorly understood. A process potentially important for mountain plant re-distribution is a competition between colonizing species and the resident vegetation. Here, we focus on the impact of this process using the recent elevational shift of the sedge Carex humilis in the northern Italian Alps as a model system. We repeated and extended historical sampling (conducted in 1976) of the species in the study region. We used the historical distribution data and historical climatic maps to parameterize a species distribution model (SDM) and projected the potential distribution of the species under current conditions. We compared the historical and the current re-survey for the species in terms of the cover of important potential competitor species as well as in terms of the productivity of the resident vegetation indicated by the Normalized Difference Vegetation Index (NDVI). We found that Carex humilis has shifted its leading range margin upward rapidly (51.2 m per decade) but left many sites that have become climatically suitable since 1976 according to the SDM uncolonized. These suitable but uncolonized sites show significantly higher coverage of all dwarf shrub species and higher NDVI than the sites occupied by the sedge. These results suggest that resistance of the resident vegetation against colonization of migrating species can indeed play an important role in controlling the re-distribution of mountain plants under climate change. Keywords Alpine vegetation · Competition · Climate change · Range dynamics · Remapping · NDVI
Introduction In temperate and boreal mountain ecosystems, organisms are shifting their ranges to higher elevations (Gottfried et al. 2012; Pauli et al. 2012) and these shifts have been accelerating with accelerating rates of climate warming (Steinbauer et al. 2018). However, the extent and direction of elevational range shifts vary among individual species and populations (e.g. Lenoir et al. 2010; Chen et al. 2011). The reasons for this variation are not well understood so far. Traits related, for example, to plant architecture (Guittar et al. 2016), seed
* Harald Crepaz [email protected] 1
Eurac Research, Institute for Alpine Environment, Bozen, Italy
2
Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
3
Eurac Research, Institute for Earth Observation, Bozen, Italy
morphology (e.g. Vittoz et al. 2009; Matteodo et al. 2013) or variability in leaf traits (Henn et al. 2018) were found to correlate with species’ responses to a warming climate, but differences in traits usually e
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