Variability of VOC emission capacity and composition during leaf phenology of the tropical tree species Hymenaea courbaril and its relation to the carbon budget
Uwe
Kuhn, Max Planck Institute for Chemistry, Biogeochemistry Dept., Mainz, Germany, Kuhn@mpch-mainz.mpg.de
Stefanie
Rottenberger, Max Planck Institute for Chemistry, Biogeochemistry Dept., Mainz, Germany, rottenbe@mpch-mainz.mpg.de
Thomas
Biesenthal, Max Planck Institute for Chemistry, Biogeochemistry Dept., Mainz, Germany, ekkatom@attglobal.net
Annette
Wolf, Max Planck Institute for Chemistry, Biogeochemistry Dept., Mainz, Germany, wolfsolf@web.de
Guenther
Schebeske, Max Planck Institute for Chemistry, Biogeochemistry Dept., Mainz, Germany, schebi@mpch-mainz.mpg.de
Paolo
Ciccioli, Istituto di Metodologie Chimiche, Area della Ricerca del CNR di Montelibretti,, Monterotondo Scalo, Italy, paolo.ciccioli@imc.cnr.it
Juergen
Kesselmeier, Max Planck Institute for Chemistry, Biogeochemistry Dept., Mainz, Germany, jks@mpch-mainz.mpg.de
(Presenting)
Changes of VOC emission capacity and composition during leaf developmental stages of the tropical tree species Hymenaea courbaril were investigated under field conditions at a remote Amazonian rainforest site. With the course of leaf development from young to mature and to senescent leaves the basal emission capacities of isoprene varied considerably from 0.7 µgC /(g h) to 111.5 µgC / (g h). By adjusting the standard emission factors for individual days, the diel courses of instantaneous isoprene emission rates could nevertheless adequately be modelled by a current isoprene algorithm. Besides the isoprene emission variability during early leaf development, light-dependent emissions of considerable amounts of monoterpenes were observed during the period between bud break and leave maturity. The finding of this temporary change in emission may be of general interest in understanding both the ecological functions of isoprenoid production and the regulatory processes involved. We discuss the profound change in emission composition during this stage as a consequence of resource availability or as a plant’s response to higher defense demand of young emerging leaves.The results demonstrate the inadequacy of using one single standard emission factor to represent the VOC emission capacity of tropical vegetation for an entire seasonal cycle. Contrasting the seasonal variation, a strong linear correlation between the isoprene emission capacity and the gross photosynthetic activity covering all developmental stages and seasons is demonstrated. Our results confirm that leaf photosynthetic properties may confer a valuable basis to model the seasonal variation of isoprenoid emission capacity; especially in tropical regions where the environmental conditions vary less than in temperate regions.