Drought effects on volatile organic compound emissions from Scots pine stems.

Area of Science:

• Forest Ecology
• Atmospheric Chemistry
• Plant Physiology

Background:

• Tree stems are sources of volatile organic compounds (VOCs) crucial for defense and atmospheric processes.
• Understanding the drivers and scale of stem VOC emissions across ecosystems is limited.
• Extreme drought impacts are increasingly significant in forest ecosystems.

Purpose of the Study:

• To investigate the effects of drought on VOC emissions from mature Scots pine stems.
• To compare VOC emission rates and dynamics between drought-stressed and irrigated trees.
• To identify environmental drivers of stem VOC emissions in a drought-prone forest.

Main Methods:

• Utilized custom-made stem chambers for VOC measurement.
• Employed online Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) and adsorbent sampling.
• Compared emission rates from naturally dry Scots pine with long-term irrigated trees during a hot-dry summer.

Main Results:

• Scots pine stems were identified as significant sources of monoterpenes, likely from resin.
• Daily VOC emission dynamics correlated with temperature.
• Monoterpene and acetaldehyde emissions decreased nonlinearly with increasing drought severity.
• Late-summer emission peaks of monoterpenes, acetaldehyde, and acetone were observed, possibly due to stressors.

Conclusions:

• Stem VOC emissions, particularly monoterpenes, are significant in Scots pine ecosystems.
• Drought stress can reduce stem VOC emissions, but other factors may cause emission bursts.
• Further research in diverse environments is needed to fully understand the ecosystem VOC budget contribution from tree stems.