Seasonal variations in terpene emission factors of dominant species in four ecosystems in NE Spain

Joan Llusia,Josep Peñuelas,Alex Guenther,Francesca Rapparini

doi:10.1016/j.atmosenv.2013.01.005

Abstract

We studied the daily patterns in the rates of foliar terpene emissions by four typical species from the Mediterranean region in two days of early spring and two days of summer in 4 localities of increasing biomass cover in Northern Spain. The species studied were Thymelaea tinctoria (in Monegros), Quercus coccifera (in Garraf), Quercus ilex (in Prades) and Fagus sylvatica (in Montseny). Of the total 43 VOCs detected, 23 were monoterpenes, 5 sesquiterpenes and 15 were not terpenes. Sesquiterpenes were the main terpenes emitted from T. tinctoria. Total VOC emission rates were on average about 15 times higher in summer than in early spring. The maximum rates of emission were recorded around midday. Emissions nearly stopped in the dark. No significant differences were found for nocturnal total terpene emission rates between places and seasons. The seasonal variations in the rate of terpene emissions and in their chemical composition can be explained mainly by dramatic changes in emission factors (emission capacity) associated in some cases, such as for beech trees, with very different foliar ontogenical characteristics between spring and summer. The results show that temperature and light-standardised emission rates were on average about 15 times higher in summer than in early spring, which, corroborating other works, calls to attention when applying the same emission factor in modelling throughout the different seasons of the year.

Highlights

Many studies have shown the importance of environmental conditions, both abiotic and biotic, for the production and emission rates of VOCs (Langenheim, 1994; Takabayashi et al, 1994; Peñuelas and Llusia, 2001; Paris et al, 2010)
The dominant vegetation there is composed by T. tinctoria, Genista sp., Rosmarinus officinalis, Thymus vulgaris, Helichrysum sp. and Pinus halepensis
Differences in seasonal emission rates are very significant in all species

Summary

Introduction

Many studies have shown the importance of environmental conditions, both abiotic and biotic, for the production and emission rates of VOCs (Langenheim, 1994; Takabayashi et al, 1994; Peñuelas and Llusia, 2001; Paris et al, 2010). The campaigns of MONTES aimed to measure the emissions of VOCs in four different terrestrial ecosystems with increasing. The results of the measurements at the leaf level for the dominant species of each of the studied sites are here presented with the aim of providing emission factors useful for upscaling to landscape emission rates and discerning the potential need of using different emission factors for the different seasons of the year. The study aimed to provide knowledge on seasonal and daily emission patterns including the assessment of the role of immediate temperature and PFD response relative to changes in emission factor due to phenology and ontogeny. For Prades, a holm oak forest, the dominant species, Quercus ilex, was analysed and for Montseny beech forest, the dominant species, Fagus sylvatica, was analysed

Methods

Results

Conclusion