Impact of sub-canopy removal on the stand-level volatile organic compounds exchange

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Title: Impact of sub-canopy removal on the stand-level volatile organic compounds exchange
Author: Ahi, Mohamadali
Contributor: University of Helsinki, Faculty of Agriculture and Forestry, Department of Forest Sciences
Publisher: Helsingin yliopisto
Date: 2020
Language: eng
Thesis level: master's thesis
Discipline: Metsien ekologia ja käyttö
Forest Ecology and Management
skoglig ekologi och resurshushållning
Abstract: Removal of sub-canopy trees is a type of forest management practice, mainly employed to minimize subsequent harvesting costs. Such management activities, however, are a source of disturbance in boreal forests, including those of Finland. The removal of understory trees causes mechanical damage to trees, with coniferous trees, such as Scots pine, being particularly susceptible. The resulting injuries significantly enhance emissions of biogenic volatile organic compounds (BVOCs) to the atmosphere, thereby modulating its gas composition. BVOCs are involved in plant growth, reproduction and defence, while functioning as communication media within and between plants. These plant-released compounds have high chemical reactivity with large mass emission rate from vegetation into the atmosphere; therefore, they are major determinants of atmospheric gas composition with important implications for the Earth’s atmosphere and climate. Despite the wealth of knowledge on this topic, our understanding of how forest management activities affect BVOC emissions is limited. Uncertainty remains as what the impact of sub-canopy removal is on BVOC emissions from forest trees over a long timescale. This is important since such management activities are common, with equal or potentially even larger impact on BVOC emissions both in the short- and long-run. To address this knowledge gap, I test the impacts of sub-canopy removal on the emissions of BVOCs from a Scots pine stand in a boreal forest. In so doing, I also consider the effects of temperature, soil moisture, and photosynthetically active radiation on the concentrations of these compounds above the canopy. The research sheds light on the complex and intertwined effects of the sub-canopy removal and environmental variables on the stand-level BVOC emissions. The results have implications regarding how forest management practices, and more broadly anthropogenic activities, influence forest-atmosphere interactions. Finally, the research provides promising avenues for future research.
Subject: Biogenic Volatile organic compounds (BVOCs)
Sub-canopy removal
Forest management
Forest–atmosphere interactions

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