Effects of elevated CO2and temperature on the leaf chemistry of birchBetula pendula(Roth) and the feeding behaviour of the weevilPhyllobius maculicornis

Abstract

Abstract1 The effect of elevated CO2and temperature on the foliar chemistryBetula pendulaRoth and the feeding performance of polyphagous weevilsPhyllobius maculicornisGerm. was studied. Birch seedlings were grown during one growing season in chamber‐less field conditions and in closed‐top chambers exposed to four different treatments: ambient CO2(350 p.p.m) and temperature, elevated atmospheric CO2(700 p.p.m) and ambient temperature, elevated temperature +3 °C above ambient) and ambient CO2, and a combination of elevated CO2and temperature.2 In leaves under CO2enrichment, the concentration of nitrogen and some flavonol glycosides significantly decreased, whereas the concentration of total phenolics, condensed tannins and (+)‐catechin significantly increased. The total concentration of cinnamoylquinic acids was significantly increased by CO2and decreased by temperature. The concentration of salidroside increased under elevated temperature.3 Weevil‐feeding experiments were carried out in a five‐choice arrangement, one leaf from each of the five treatments (chamber‐less field controls and four different treatments in chambers) being placed in random order in a plastic box. The weevils preferred the leaves grown under elevated CO2, which had low nitrogen, high phenolics and the highest condensed tannin concentrations. Whether the reason for this trend is due to the stimulating effect of condensed tannins and/or a change in other secondary compounds, remains unknown. The weevils did not show any obviously different response in feeding performance to temperature and the combination of elevated CO2and temperature.