Isoprenoid emission response to changing light conditions of English oak, European beech and Norway spruce

Abstract

Abstract. Light is an important environmental factor controlling biogenic volatile organic compound (BVOC) emissions, but in natural conditions its impact is hard to separate from other influential factors such as temperature. We studied the light response of foliar BVOC emissions, photosynthesis and stomatal conductance on three common European tree species, namely English oak (Quercus robur), European beech (Fagus sylvatica) and two provenances of Norway spruce (Picea abies) in Taastrup, Denmark. Leaf scale measurements were performed on the lowest positioned branches of the tree in July 2015. Light intensity was increased in four steps (0, 500, 1000 and 1500 µmol m −2 s −1 ), whilst other chamber conditions such as temperature, humidity and CO 2 levels were fixed.Whereas the emission rate differed between individuals of the same species, the relative contributions of compounds to the total isoprenoid emission remained similar. Whilst some compounds were species specific, the compounds α-pinene, camphene, 3-carene, limonene and eucalyptol were emitted by all of the measured tree species. Some compounds, like isoprene and sabinene, showed an increasing emission response with increasing light intensity, whereas other compounds, like camphene, had no significant emission response to light for most of the measured trees. English oak and European beech showed high light-dependent emission fractions from isoprene and sabinene, but other emitted compounds were light independent. For the two provenances of Norway spruce, the compounds α-pinene, 3-carene and eucalyptol showed high light-dependent fractions for many of the measured trees. This study highlights differences between compound emissions in their response to a change in light and a possible light independence for certain compounds, which might be valid for a wider range of tree species. This information could be of importance when improving emission models and to further emphasize the discussion regarding light or temperature dependencies for individual compounds across species.

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

“…As expected [31,34,[39][40][41], isoprene increased with increasing PAR levels. Studies have also shown that the emission rates of isoprene have a hyperbolic relationship with PAR [34,40,42,43].…”

“…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].…”

Leaf-Scale Study of Biogenic Volatile Organic Compound Emissions from Willow (Salix spp.) Short Rotation Coppices Covering Two Growing Seasons

“…Besides the branch chamber, a portable photosynthesis system (LI-6400XT, LI-COR, NE, USA) was used in 2016 to provide photosynthesis information in parallel with BVOC measurements from individual Salix leaves [42,46,50,52]. The leaf chamber has a capacity to measure leaves with an area up to 6 cm 2 (2 × 3 cm 2 ) and the measurements were done on the middle part of the leaves to obtain the maximum area of the leaves.…”

“…Air from the dynamic chamber was pulled through an adsorbent cartridge for 20 min per sample at a flow rate of 200 mL min −1 using a flow-controlled pump (Pocket Pump, SKC Ltd., Dorset, UK), leading to a total sample volume of 4 L. In the case of the leaf chamber, the photosynthesis system had been modified with a trace-gas tube connection after the outlet of the leaf chamber [42,46,50,52]. This way, BVOC samples could be taken in parallel to the on-going photosynthesis measurements.…”

“…During the campaigns, BVOC samples were taken during day time (8:00-18:00). In the case of the leaf chamber, measurements started one hour after the leaf was inserted to avoid potential stress-induced BVOCs from physical handling [42,52]. When a new light level was set, 30 min passed before the BVOC sampling started so the leaf had time to adapt to the new condition [52].…”