BVOC dynamics between a Pinus sylvestris stand and the atmosphere in response to drought
Biogenic volatile organic compounds (BVOC) play a central role for atmospheric chemistry because they provide the fuel to form tropospheric ozone and secondary aerosols. Their importance for atmospheric chemistry stems from their high reactivity with respect to OH and their global emission magnitude. The effect of drought on the dynamics of BVOC emissions is highly uncertain, because various factors can alter their production (and emission) strengths. This makes it difficult to project future changes of BVOC emission paths with respect to climate change.
Research questions and hypothesis
The research project aims at quantifying the exchange of key BVOCs emitted by a Pinus sylvestris stand in response to water limitation and drought. A particular emphasis is to understand the dynamics of BVOC emissions under water limited conditions, and to what extent the dynamics differ compared to variations of GPP, transpiration rates and other physiological parameters. Further we are interested to what extent drought can modulate the diversity of BVOC emissions (e.g. magnify emissions of LOX or shikimate VOCs) of Pinus sylvestris, and whether chemical tracers can be detected in the air that hint at early signs of ecosystem scale stress such as drought or heat stress.
Approach and methods
Ecosystem scale BVOC and ozone flux measurements will be combined with branch enclosure measurements on site allowing specific process level experiments (e.g. establishing light and temperature response parameterizations during drought and after soil moisture recharge events). The planned experiments will be combined with the canopy version of the MEGAN modelling framework (Guenther et al., 2006), allowing to distinguish the well established short term dynamics of BVOC emissions from drought induced modulation. The modelling framework will help rationalizing likely paths for BVOC emission changes from Pinus sylvestris under drier conditions in the future.
Thomas Karl, Ilse Kranner, Walter Oberhuber, Stefan Mayr, Georg Wohlfahrt
Alex Guenther, University of California