Influence of interspecific plant interactions on the stress response of grassland species in a future climate

Date: 19 April 2017

Venue: UAntwerpen, Campus Drie Eiken, Promotiezaal Q0.02 - Universiteitsplein 1 - 2610 Antwerpen-Wilrijk (route: UAntwerpen, Campus Drie Eiken)

Time: 4:00 PM

Organization / co-organization: Department of Biology

PhD candidate: Helena Van De Velde

Principal investigator: Ivan Nijs & Dries Bonte

Short description: Public defence of the PhD thesis of Mrs. Helena Van De Velde - Faculty of Science - Department of Biology



Abstract

Wherever they grow, plants are continuously exposed to stress factors of varying nature. Due to the current climate change, these stress factors will in the near future occur under greatly modified atmospheric conditions, with higher CO2 concentrations and higher average air temperatures. This raises the question whether plants will exhibit the same stress response under these conditions. The uncertainty regarding stress responses is even greater in natural, multi-species communities than in single species. In multi-species communities, a future climate can modify the direction and the intensity of species interactions (such as plant-plant interactions). As a result, the direct effects of a future climate on the species-specific stress response might be strengthened or (partly) cancelled out. The purpose of this thesis was to investigate the direct and indirect (via altered plant-plant interactions) effects of a future climate on the stress responses of grassland species. We focused on the abiotic stressor drought and the biotic stressor herbivory.

In a first part, we demonstrated that warming aggravated the drought impact of Lolium perenne and elevated CO2 only partly alleviated the stress impact caused by warming and drought. Contrary to what was found with L. perenne, a future climate did not alter the drought response of Plantago lanceolata. Furthermore, we showed that plant-plant interactions did not have an impact on the drought response of L. perenne and P. lanceolata in a future climate. Remarkably, combined warming and drought, with or without elevated CO2 induced higher senescence and mortality of L. perenne long after the drought ended, while no such lagged effects were apparent in the current climate. P. lanceolata also exhibited post-drought lagged effects on senescence and mortality, but only under combined warming and elevated CO2.

In a second part, we showed that a future climate altered the leaf quality and enhanced both the systemic and induced defence system of P. lanceolata against aphids. Notwithstanding these effects of a future climate on the host plant, the host plant did not have an impact on aphid performance. However, under laboratory conditions experimental warming affected aphid performance directly in non-linear manner. Aphids performed best at moderate warming, where they grew faster, had a shorter generation time and grew larger. Nevertheless, a future climate with warming and elevated CO2 did not have direct effects on aphid performance under semi-natural conditions.

Next to these responses of plants and aphids to a future climate, we demonstrated that plant-plant interaction can mediate these species responses. Plant-plant interactions affected aphid performance through an interaction with temperature and influenced the effect of combined warming and elevated CO2 on leaf quality and the defence system of P. lanceolata. We found that interspecific plant competition neutralized the effect of elevated CO2 on the defence molecules of P. lanceolata.



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