PhD Theses at SCIENCE – University of Copenhagen

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Impacts of Climate Change Induced Vegetation Responses on BVOC Emissions from Subarctic Heath Ecosystems

Publication: ResearchPh.D. thesis

Hanna Maritta Valolahti

The role of biogenic volatile organic compounds (BVOCs) affecting Earths’ climate system is one
of the greatest uncertainties when modelling the global climate change. BVOCs presence in the
atmosphere can have both positive and negative climate feedback mechanisms when they involve
atmospheric chemistry and physics.
Vegetation is the main source of BVOCs. Their production is directly linked to temperature and the
foliar biomass. On global scale, vegetation in subarctic and arctic regions has been modeled to have
only minor contribution to annual total BVOC emissions. In these regions cold temperature has
been regulating annual plant biomass production, but ongoing global warming is more pronounced
in these regions than what the global average is. This may increase the importance of subarctic and
arctic vegetation as a source of BVOC emissions in near future.
This thesis aims to increase the understanding of the controls of BVOC emissions from subarctic
ecosystems under climate change by studying the responses to long-term manipulations from leaf
level to small ecosystem scale. Leaf-level studies showed different anatomical responses for
warming and shading manipulations between studied species, but no significant effects on BVOC
emissions on plant individual level were found. The lack of changes in BVOC emissions after longterm
exposure could be at least partially explained by long term-acclimation, which is supported by
the observed anatomy responses. Whereas warming was not found to alter the BVOC emissions on
plant individual level, emissions from ecosystem level was found to increase significantly.
Anatomical acclimations and decrease in BVOC emissions on plant individual level have probably
been compensated for by rapidly increasing foliar biomass on ecosystem level and have lead to
increases in total BVOC emissions from subarctic ecosystems.
Ecosystem level emissions showed two-fold increase in monoterpene emissions and over five-fold
increase in sesquiterpene emissions after a decade of warming. These increases were probably
driven by the changes in vegetation composition. Increased autumnal leaf litter amount simulated
by litter addition experiment was found to increase the plant biomass production, probably due to
increased soil nutrient availability. The observed increase in BVOC emissions from litter addition
treatment was therefore partially explained by increasing plant biomass and partially by increasing
amount of BVOCs released from the decomposing litter.
According to the results presented in this thesis, I suggest the pronounced increase of BVOC
emissions found after long-term exposure to climate manipulations is mainly carried indirectly via
vegetation changes. Climate manipulations used in this study increased the ecosystem-scale BVOC
emissions, supporting the prediction of increasing importance of subarctic regions for global BVOC
emissions in near future.
Original languageDanish
PublisherDepartment of Biology, Faculty of Science, University of Copenhagen
Number of pages145
StatePublished - 2015

ID: 150342640