International audience | Compost spreading in Mediterranean shrublands has no strong short-term effect on Q. coccifera monoterpene emissions at leaf level. a b s t r a c t Monoterpene emissions of Quercus coccifera L. were repeatedly measured during the two years following the spreading of a sewage sludge compost at rates of 50 Mg ha À1 and 100 Mg ha À1 , in a twelve-year-old post-fire Mediterranean shrubland. We also monitored the patterns of change in soil and leaf nutrient content, plant water potential, chlorophyll fluorescence, and plant growth. Compost spreading resulted in weak changes in leaf nutrient content and plant water status, and therefore no significant effect on monoterpene emissions at leaf scale, except during one summer sampling, probably related to advanced leaf maturity with the highest compost rate. However, compost increased plant growth, particularly the leaf biomass. The results suggest that compost spreading in Mediterranean shrublands has no strong short-term effect on Q. coccifera monoterpene emissions at leaf level, but may indirectly increase volatile organic compound fluxes at the stand scale, which may contribute to regional ozone pollution.

Monoterpene emissions of Quercus coccifera L. were repeatedly measured during the two years following the spreading of a sewage sludge compost at rates of 50Mgha⁻¹ and 100Mgha⁻¹, in a twelve-year-old post-fire Mediterranean shrubland. We also monitored the patterns of change in soil and leaf nutrient content, plant water potential, chlorophyll fluorescence, and plant growth. Compost spreading resulted in weak changes in leaf nutrient content and plant water status, and therefore no significant effect on monoterpene emissions at leaf scale, except during one summer sampling, probably related to advanced leaf maturity with the highest compost rate. However, compost increased plant growth, particularly the leaf biomass. The results suggest that compost spreading in Mediterranean shrublands has no strong short-term effect on Q. coccifera monoterpene emissions at leaf level, but may indirectly increase volatile organic compound fluxes at the stand scale, which may contribute to regional ozone pollution.

Plants can respond physiologically to damaging ultraviolet-B radiation by altering leaf chemistry, especially UV absorbing phenolic compounds. However, the effects on terpene emissions have received little attention. We conducted two field trials in plots with supplemented UV-B radiation and assessed the influence of feeding by pine weevils, Hylobius abietis L., on volatile emissions from 3-year old Norway spruce trees (Picea abies L. Karst.). We collected emissions from branch tips distal to the feeding weevils, and from whole branches including the damage sites. Weevil feeding clearly induced the emission of monoterpenes and sesquiterpenes, particularly linalool and (E)-β-farnesene, from branch tips, and the sums of monoterpenes and sesquiterpenes emitted by whole branches were substantially increased. We discovered little effect of UV-B radiation up to 30% above the ambient level on volatile emissions from branch tips distal to damage sites, but there was a possible effect on bark emissions from damage sites. Chronic exposure to enhanced UV-B radiation has little effect on volatile emissions of Norway spruce.

Une estimation des emissions biogeniques annuelles de composes organiques volatils (COV) non methaniques dues a la couverture forestiere en France a ete realisee. Trente-deux especes d'arbres representant 98 % de la foret francaise ont ete retenues pour l'estimation. Celle-ci a porte sur un reseau constitue de 93 mailles (departements) de 75 km x 75 km de dimensions moyennes. On a affecte des taux d'emission et des densites de biomasse foliaire specifiques a chacune des 32 especes. Les variables micrometeorologiques (temperatures, intensites lumineuses) ont ete collectees pour l'ensemble des departements francais. Un effort a ete fait pour utiliser, dans les algorithmes de calcul de "Guenther" des facteurs emissifs specifiques aux especes poussant en France ou bien dans les pays limitrophes de celle-ci. Sur les cinq annees (1994-1998) de l'etude, on a calcule la moyenne annuelle des emissions d'isoprene, de monoterpenes et autres composes organiques volatils (ACOV) a l'echelle des departements et de la France. Sur le plan national, l'isoprene dont l'emission estimee est de 457 kt/an represente environ 49 % de l'emission totale, alors que les monoterpenes avec 350 kt/an, et les ACOV avec 129 kt/an representent respectivement 37 % et 14 % du total. L'emission biogenique annuelle de COV en France represente sensiblement la moitie de la source anthropique. Cependant, dans certaines regions (mediterraneennes), les emissions naturelles peuvent largement depasser durant certaines periodes les emissions anthropiques. Notons que l'ensemble de ces resultats demeure empreint d'une grande incertitude, puisque les estimations effectuees sont proposees avec des facteurs correctifs qui peuvent atteindre des valeurs comprises entre 4 et 7

Emission characteristics of biogenic volatile organic compounds (BVOCs) (such as isoprene and monoterpenes) emitted from major species of street trees and urban forests by variations in temperature and photosynthetically active radiation (PAR) were investigated. The isoprene and monoterpene emission rates from Prunus sargentii, Ginkgo biloba, Zelkova serrata and Taxus cuspidata were meager. In contrast, the isoprene and monoterpene emission rates from Metasequoia glyptostroboides were very high. In particular, the emission of α-pinene from Metasequoia glyptostroboides was over 10,000 times higher than that from Ginkgo biloba. The patterns of isoprene emissions from the four tree species except for Metasequoia glyptostroboides concerning temperature and PAR were difficult to determine because the emission rate is very low. However, monoterpene emissions from all five tree species were clearly affected by temperature and PAR. These results showed that the characteristics of isoprene and monoterpene emissions differed depending on the tree species. Regarding monoterpene composition, α-pinene (81.3%) accounts for the majority of total monoterpenes from Metasequoia glyptostroboides. This could be a critical consideration when planting trees in an urban forest because BVOC emissions (e.g., α-pinene) have been well known to affect ground-level ozone formation rate via photochemical reaction with NOX. Since Metasequoia glyptostroboides showed relatively high BVOC emissions, the use of this type of tree in an urban forest with relatively high nitrogen oxide emissions should be carefully considered.