title: A natural experiment on plant acclimation: lifetime stomatal frequency response of an individual tree to annual atmospheric CO2 increase.
abstract: Carbon dioxide (CO2) has been increasing in atmospheric concentration since the Industrial Revolution. A decreasing number of stomata on leaves of land plants still provides the only morphological evidence that this man-made increase has already affected the biosphere. The current rate of CO2 responsiveness in individual long-lived species cannot be accurately determined from field studies or by controlled-environment experiments. However, the required long-term data sets can be obtained from continuous records of buried leaves from living trees in wetland ecosystems. Fine-resolution analysis of the lifetime leaf record of an individual birch (Betula pendula) indicates a gradual reduction of stomatal frequency as a phenotypic acclimation to CO2 increase. During the past four decades, CO2 increments of 1 part per million by volume resulted in a stomatal density decline of approximately 0.6%. It may be hypothesized that this plastic stomatal frequency response of deciduous tree species has evolved in conjunction with the overall Cenozoic reduction of atmospheric CO2 concentrations.
authors.affiliation: Laboratory of Paleobotany and Palynology, Utrecht University, Utrecht, The Netherlands.
authors.forename: F
authors.initials: F
authors.lastname: Wagner
authors.forename: R
authors.initials: R
authors.lastname: Below
authors.forename: P D
authors.initials: PD
authors.lastname: Klerk
authors.forename: D L
authors.initials: DL
authors.lastname: Dilcher
authors.forename: H
authors.initials: H
authors.lastname: Joosten
authors.forename: W M
authors.initials: WM
authors.lastname: Kürschner
authors.forename: H
authors.initials: H
authors.lastname: Visscher