BVOC emissions from English oak (<i>Quercus robur</i>) and European beech (<i>Fagus sylvatica</i>) along a latitudinal gradient

Abstract

Abstract. English oak (Quercus robur) and European beech (Fagus sylvatica) are amongst the most common tree species growing in Europe, influencing the annual biogenic volatile organic compound (BVOC) budget in this region. Studies have shown great variability in the emissions from these tree species, originating from both genetic variability and differences in climatic conditions between study sites. In this study, we examine the emission patterns for English oak and European beech in genetically identical individuals and the potential variation within and between sites. Leaf scale BVOC emissions, net assimilation rates and stomatal conductance were measured at the International Phenological Garden sites of Ljubljana (Slovenia), Grafrath (Germany) and Taastrup (Denmark). Sampling was conducted during three campaigns between May and July 2014. Our results show that English oak mainly emitted isoprene whilst European beech released monoterpenes. The relative contribution of the most emitted compounds from the two species remained stable across latitudes. The contribution of isoprene for English oak from Grafrath and Taastrup ranged between 92 and 97 % of the total BVOC emissions, whilst sabinene and limonene for European beech ranged from 30.5 to 40.5 and 9 to 15 % respectively for all three sites. The relative contribution of isoprene for English oak at Ljubljana was lower (78 %) in comparison to the other sites, most likely caused by frost damage in early spring. The variability in total leaf-level emission rates from the same site was small, whereas there were greater differences between sites. These differences were probably caused by short-term weather events and plant stress. A difference in age did not seem to affect the emission patterns for the selected trees. This study highlights the significance of within-genotypic variation of BVOC emission capacities for English oak and European beech, the influence of climatic variables such as temperature and light on emission intensities and the potential stability in relative compound contribution across a latitudinal gradient.

Final author response

“…The dif-ference was larger for the stomatal conductance (G S ): oak 1 showed a significant difference with increasing light (P < 0.05) in comparison to oak 2, which showed higher internal variation (P > 0.2). In regards to their photosynthetic and stomatal conductance ranges, they are comparable with studies performed on oak leaves grown in either shaded or semi-shaded conditions (Morecroft and Roberts, 1999;Valladares et al, 2002). For beech, A n increased from darkness to the PAR level of 500 µmol m −2 s −1 (P < 0.001) but did not show a response to further increase in light (P > 0.6).…”

Variability of BVOC Emissions from Commercially Used Willow (Salix spp.) Varieties

“…The sample cartridges were filled in a 2-bed configuration with Tenax TA (porous organic polymer) and Carbograph 1TD (graphitized carbon black) adsorbents. Similar set-ups had been used in other studies before [26,[29][30][31].…”

“…Samples were collected at seven light levels (0, 150, 300, 450, 600, 1000 and 1500 µmol m 2 s −1 ) in order to generate a light response curve for the BVOC emissions. Measurements started 1 h after enclosing the leaf by the chamber to prevent stress-induced BVOC emissions from affecting the samples [29], and the air from the chamber was sampled for 20 min at 200 mL min −1 (total sample volume of 4 L). After switching the light conditions for the next step, 30 min was allowed to pass to allow for the leaf to adapt to the new light conditions before BVOC sampling was continued at the new light level.…”

The Uncertain Role of Biogenic VOC for Boundary-Layer Ozone Concentration: Example Investigation of Emissions from Two Forest Types with a Box Model

“…In this context, a major aspect of uncertainty is the emission of individual sesquiterpenes and thus mean reactivity, which are affected by different tree species, tree injuries, sesquiterpene specification and the local variation of needle/leaf temperatures [44]. In our case, the mean reactivity of sesquiterpenes with ozone was assumed to be k(sqt, O 3 ) = 4 × 10 −16 cm 3 molec −1 s −1 based on individual sesquiterpene emission contributions for different species [54][55][56] and the corresponding reaction rate coefficients [33]. Please note that our calculations provide an average response for a mean forest tree type mixture.…”