title: Trends in plant carbon concentration and plant demand for N throughout this century.
abstract: Atmospheric CO2concentration has increased by 25% over the preindustrial level. A parallel increase in C concentration and decreases in N concentration and δ13C of plants grown throughout this century have been observed in plant specimens stored in herbaria. We tested our previous results in a study of 12 more species collected in the western Mediterranean throughout this century (1920-1930, 1945-1955, and 1985-1990) and tree rings of Quercus pubescens from the same area. These changes were accompanied by apparent increases in condensed tannin concentration. A decreasing trend in δ15N both in herbarium material and tree rings was also found, indicating that ecosystems might cope with higher plant N demand by decreasing N losses and increasing N fixation and mineralization. These results may contribute to a better understanding of the effects of global change on carbon and nitrogen cycling.
authors.affiliation: Centre de Recerca Ecològica i Aplicacions Forestals, Facultat de Ciències, Universitat Autònoma, 08193 Bellaterra, Barcelona, Spain, , , , , , ES.
authors.forename: J
authors.initials: J
authors.lastname: Peñuelas
authors.affiliation: Centre de Recerca Ecològica i Aplicacions Forestals, Facultat de Ciències, Universitat Autònoma, 08193 Bellaterra, Barcelona, Spain, , , , , , ES.
authors.forename: Marc
authors.initials: M
authors.lastname: Estiarte
keywords: Herbarium specimens; Key words Atmospheric CO2 concentration; Nitrogen; δ13C; δ15N