Strong correlation between isoprene emission and gross photosynthetic capacity during leaf phenology of the tropical tree species Hymenaea courbaril with fundamental changes in volatile organic compounds emission composition during early leaf development

Abstract

Changes of the volatile organic compounds (VOC) emission capacity and composition of different developmental stages of the tropical tree species Hymenaea courbaril were investigated under field conditions at a remote Amazonian rainforest site. The basal emission capacity of isoprene changed considerably over the course of leaf development, from young to mature and to senescent leaves, ultimately spanning a wide range of observed isoprene basal emission capacities from 0.7 to 111.5 m m m m g C g ---during the course of the year. 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. 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. A strong linear correlation between the isoprene emission capacity and the gross photosynthetic capacity (GP max ) covering all developmental stages and seasons was observed. The present results provide evidence 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. In addition to induction and variability of isoprene emission during early leaf development, considerable amounts of monoterpenes were emitted in a light-dependent manner exclusively in the period between bud break and leaf maturity. The fundamental change in emission composition during this stage as a consequence of resource availability ( supply side control ) or as a plant's response to the higher defence demand of young emerging leaves ( demand-side control ) is discussed. The finding of a temporary emergence of monoterpene emission may be of general interest in understanding both the ecological functions of isoprenoid production and the regulatory processes involved.

Global data set of biogenic VOC emissions calculated by the MEGAN model over the last 30 years

“…They attribute the emission difference to higher emission rates from young mature leaves at the end of the dry season when compared to emission rates from older mature leaves present at the end of the wet season. The isoprene emission rates of different leaf developmental stages were well correlated with the leaf's gross photosynthetic capacity (Kuhn et al, 2004b). They also discuss a potential impact of long-term temperature conditions preceding both campaigns.…”

Global terrestrial isoprene emission models: sensitivity to variability in climate and vegetation

“…As HCHO is a principal atmospheric isoprene oxidation product, these patterns have been interpreted as a seasonal isoprene emission low, arising from a lag between substantial new leaf area growth (which takes place during that period of the year and continues well into the dry season; Huete et al, 2006;Myneni et al, 2007) and the delayed onset of isoprene emission in newly-developed leaves. However, in warm growth environments, the period between onset of photosynthesis and isoprene emissions in newly-emerging foliage has been found to be short (Kuhn et al, 2004;Wiberley et al, 2005), lags on the order of weeks may thus be difficult to fully reconcile with the process of leaf growth alone. Leaf isoprene emissions (normalised)…”

Concentrations and fluxes of biogenic volatile organic compounds above a Mediterranean macchia ecosystem in western Italy

“…This may be related to the temperature, which was approximately 3 • C higher during the second part of the campaign (Fares et al, 2009), and the more advanced phenological state of the plants in the flux footprint area. Isoprene emission is known to be dependent on leaf development (Wiberley et al, 2005) and monoterpene emission from deciduous broad leafed trees exhibit the same developmental behaviour (Hakola et al, 1998;Kuhn et al, 2004).…”

“…Basal emission rates calculated between 20 to 27 May showed isoprene rates of 511 µg m −2 h −1 a and monoterpene rates of 1490 µg m −2 h −1 while the period after the storm, from 28 May to 3 June had emission rates of 1010 µg m −2 h −1 for isoprene and 3290 µg m −2 h −1 for monoterpenes. This increase in the basal emission rate throughout the measurements period may reflect the physiological state of the plants as they developed over the months (Kuhn et al, 2004). Fares et al (2009) from leaf and plant emission measurements made during the second part of this study calculated an isoprene emissioin rate of 79 µg m −2 h −1 and a monoterpene emission rate of 1199 µg m −2 h −1 while Owen et al (1997) a bottom up approach for calculating an area basal emission rate is highly dependent upon the plant species selected and the estimation of coverage over the area which may explain the large difference between the isoprene emission potential of Fares et al (2009) and that calculated from our flux rate approach.…”