An understated player of Climate Change - increased air humidity - impact on volatile signaling compound emission at northern forests

Global climate simulations predict increased atmospheric humidity (AH) for northern latitudes. Water vapor, as an effective
greenhousegas, can magnify the rise in temperature even more. There is large uncertainty of the impact of elevated AH on
the production of biogenic volatile compounds (BVCs) by plants, which in turn, might contribute considerably to changes in
atmospheric chemistry. The aim of this project is to clarify the impact of increased AH and diffuse irradiation to carbon
assimilation, allocation and consequently BVC emissions from northern forests. This study will combine a unique free-air
manipulation experiment of increased AH in a temperate forest with analysis of long-term data of plant responses to natural
variation in AH. A broad selection of environmental and plant parameters (incl. BVCs, growth, photosynthesis, leaf pigment
and nitrogen content, tree hydraulics) will be measured during the period of shoot development in spring, to clarify the impact
of seasonality and physiological constraints on the emission of BVCs. Increased AH appears to influence photosynthesis,
transpiration and foliage nutrient supply in trees and previous research by the applicant has revealed that changes in light
use efficiency (LUE), nitrogen and carbon allocation into pigments result from differences in irradiance and temperature, but
BVC emissions are not well predicted by current carbon-allocation and climate models. This project hypothesizes that control
and humidified trees vary in LUE due to differences in sink-source limited growth and resultant differences in allocation of
carbon to synthesis of pigments or to BVCs. As an outcome of this project, the feedback mechanisms between carbon
production, allocation and BVC emissions will be analyzed and the link between air humidity and BVC production will be
proposed as an important agent of climate change. The project will substantially elaborate the professional competence and
perspectives of the applicant.