Forest plant dynamics along a latitudinal gradient in the face of climate change

• Main Author: De Frenne, Pieter
• Other Authors: Verheyen, Kris, Hermy, Martin, Graae, Bente J
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Ghent University. Faculty of Bioscience Engineering 2011
• Subjects: Earth and Environmental Sciences; Northern Sweden
• Online Access: https://biblio.ugent.be/publication/1210172; http://hdl.handle.net/1854/LU-1210172; https://biblio.ugent.be/publication/1210172/file/4335534

Climate change is considered to be one of the major threats to biological diversity. The global average earth surface temperature has increased by 0.8°C between 1956 and 2005 and is predicted to increase by an additional 1.8-4°C by the end of this century. Biodiversity of temperate forests is mainly a function of the herbaceous understorey community. Many forest understorey plants, however, are probably not able to track the shifting climate due to their limited colonisation capacity. The acclimation potential to climate change within their occupied habitats will likely determine their short- and long-term persistence. Yet, it remains largely unclear to what extent forest understorey plants will be able to respond to climate change. In this thesis we contributed to fill this knowledge gap by quantifying the response of growth and reproduction of a set of herbaceous forest understorey plants to temperature variation along a latitudinal gradient from northern France to northern Sweden and to experimentally elevated temperatures. We mainly focused on the spring flowering geophytic forb Anemone nemorosa and the early summer flowering grass Milium effusum due to their slow colonisation, distribution range, reproductive traits, phenology and growth form. The plant height of A. nemorosa and M. effusum showed an increase in natural populations along a latitudinal gradient. Hence, plants grew taller in the north. This phenomenon could be attributed to northward increasing light availability due to increasing canopy openness and photoperiod in the growing season. Furthermore, by sampling A. nemorosa seeds in natural populations along the gradient, we were able to demonstrate a decline in the seed nitrogen concentration with increasing latitude. This can be caused by (i) the lower soil nitrogen (N) availability as a consequence of lower N depositions towards the north or (ii) a greater investment in clonal reproduction in northern populations. Since the degree of seed provisioning co-determines seedling survival, changes ...