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Universidade de Coimbra (2020)

Assessing alpine shrub response to climate change

Rudley, Danielle Lacerda

Titre : Assessing alpine shrub response to climate change

Avaliação da resposta dos arbustos alpinos às mudanças climáticas

Auteur : Rudley, Danielle Lacerda

Université de soutenance : Universidade de Coimbra

Grade : Mestrado em Ecologia apresentada à Faculdade de Ciências e Tecnologia 2020

Résumé
Serra da Estrela is an exceptional place to study the effect of global warming on ecosystems since it is in the transition zone between the Mediterranean and temperate climates. Serra da Estrela is also the highest mountain range and only alpine region in continental Portugal, thus, having a huge interest for conservation. However, thus far, there is little research on the response of Estrela alpine ecosystems to global warming. We used dendrochronological and quantitative wood anatomy techniques to analyze the response to climate of the two main alpine shrub species of Serra de Estrela, Juniperus communis subsp. alpina and Cytisus oromediterraneus. Our main hypotheses were 1) Shrub growth has increased for both species in the last 5 years following the current warming trend ; 2) SRW will be positively influenced by increases in temperature in spring and autumn, i.e., at the beginning and end of the growing season ; and 3) wood anatomy is more affected by precipitation in C. oromediterraneus than in J. communis.Shrub ring width displayed a positive trend from 2015-2019, coinciding with an increasing trend in global temperatures. Generalized Additive Models indicated spring and autumn temperatures influenced J. communis SRW, and spring and autumn precipitation most influenced C. oromediterraneus SRW. Thus, a longer growth period due to warming has a direct effect only for J. communis subsp. alpina. In addition, J. communis hydraulic conductivity was influenced by early spring and autumn precipitation, while spring and summer temperature did so for C. oromediterraneus.These results indicate that warming can promote the growth of the two dominant alpine shrub species in the high plateau of Serra da Estrela Natural Park, but may eventually lead to changes in plant performance and distribution shifts in the longer term due to species-specific differences in the response to climatic variables.

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