Plasticity, Intraspecific Variability and Local Adaptation to Climatic Extreme Events of Ecotypes/Provenances of Key Plant Species

Climate change, and especially an increase of magnitude and frequency of climatic extreme events such as drought periods or heatwaves, will alter growing conditions for plants in the future. Persistent ecosystems, with long-living organisms, such as forest or permanent grassland will be particularly impacted by this development. The velocity of these changes is likely to occur at a pace, which species may not be able to keep track with by natural dispersal or genetic adaptation. Agriculture, forestry and ecosystem management must develop counteracting practices to secure the persistence and functioning of these ecosystems and thus their provision of goods and services. Therefore it is important to develop a better understanding how species and ecosystems may respond to future climatic stressors. Impact assessments, e.g. via climatic envelope modelling are prone to misinterpretations of the adaptive capacity of species, as they do not incorporate the intraspecific genetic and phenotypic differences that exist within the populations accross the distribution range of a species. Yet, intraspecific variation may exhibit potential tools for the development of climate change adaptation strategies. Here, I focus on key ecosystems in Central Europe. In particular the selective use of plant provenances or ecotypes may help to make ecosystems climate-resilient without a potentially more problematic introduction of exotic species. Especially provenances from warmer, drought-prone regions, with a current climate similar to the projected one for Central Europe recently came into focus as potential substitutes for local provenances, as they might have developed local adaptations to climate conditions at their location of origin. Insights about the response of these provenances to changing averages and extreme event regimes are crucial for a reasonable use of within-species diversity in climate change adaptation. First, the concept of assisted colonization or migration of species or ecotypes and the role it can play as an adaptation strategy in agriculture, forestry or nature conservation is introduced (Manuscript1). It is suggested that a focus should be laid on keystone species that ensure ecosystem persistence and functioning as they govern the habitat structure and microclimate of a site. The assisted colonization of pre-adapted ecotypes of keystone species from climates similar to future projections for the target site is proposed. Furthermore, provenances of selected grassland and forest key-species were exposed to drought and warming in two experiments in Bayreuth and Landau, and their ecological responses were analysed. Results suggest that local adaptations to climatic stressors exist. However, the magnitude and direction of responses strongly depend on species and climatic variables. For grassland species, e.g. differences in drought sensitivity could be demonstrated in some cases (Manuscript 4). Fagus sylvatica exhibited differences between the provenances in response to drought conditions, as well (Manuscript 3). It seems that marginal provenances, from the dry margins of the distribution range, show less increment reduction due to the drought treatment. Yet, under more favourable conditions of water supply these provenances did not yield the same high increment rates than more central provenances, indicating a trade-off between stability under stress and yield under non-stress conditions. A pine species that is generally considered to be rather drought-resistant, Pinus nigra, which is a potential substitute for climate-threatened conifers on dry sites in Central Europe, did not show any differences in response to drought and warming (Manuscript 2), maybe due to a weak selective pressure as a result of high drought-resistance across the whole distribution range. The impacts of drought on increment became not visible before the second year after the treatment, stressing the need for more long-time experiments in climate impact research. Even in a generally warmer environment, cold extremes in winter or spring are expected still to prevail in the future. Therefore, the provenances of the selected species were tested for their cold-hardiness and late frost resistance (Manuscripts 5-7). Growth of the grassland species and F. sylvatica were negatively impacted by a late frost event and differences in late-frost sensitivity between provenances or ecotypes were identified. The (sub-) mediterranean species P. nigra showed differences between provenances in their winter cold hardiness. Correlations between performance under cold stress and winter conditions or late frost proneness of the places of origin could be established for almost all species. However, preceding climate experience, such as the warming or drought treatment of the plants altered their reaction to cold extremes compared to the control treatment, indicating the complexity of the interactive impacts of climate factors on ecosystem and plant performance. The uncertainty of climate projections and the multitude of changing climatic stressors, though, make the prospect of an easy and rapid success in the search for single “best-adapted” provenances very questionable. In economics the portfolio effect shows that a diversification of investments decreases the risk of a total loss of profits. Hence, in a modelling procedure based on the increment data from the above mentioned experiment it was tested if a “portfolio investment” in several provenances in one stand decreases the risk of yield losses (Manuscript 8). Results indicate that the higher the number of provenances the higher the chance for a “best-performer” to be included in the set. So the likelihood of higher yields, under different climatic conditions increases, yet the risk of low yields stays stable. Generally, it seems that the selective use of plant species and ecotypes in climate change adaptation can be a feasible tool to maintain ecosystem functionality and productivity. However, the uncertain projections, the multitude of climatic stressors and their interplay with other environmental factors and the potential impacts of assisted colonization of ecotypes on the genetic diversity within species and populations require further research.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Bayreuth

Year

2013

Author dc:creator

• Thiel, Daniel

Contributors dc:contributor

• Beierkuhnlein, Carl

Repository record source_url

https://epub.uni-bayreuth.de/id/eprint/75/

OAI identifier oai:identifier

oai:epub.uni-bayreuth.de:75