Abstract
AimsBiogenic volatile organic compound (BVOC) research has been mostly focused on foliar emissions. In this experiment, the main focus was on rhizosphere BVOC emissions of Scots pine seedlings under changing growth conditions.MethodsSoil-growing Scots pines were exposed to increased air (0.5°C) and soil (4.0°C) temperature and N addition (30 kg N ha− 1 yr− 1) for three growing seasons in a field experiment. In addition to these factors, seedlings were exposed to bark herbivory by large pine weevils in two last seasons. Gas-chromatography and mass-spectrometry was used for analyzing the BVOC samples collected from pine rhizosphere.ResultsAlmost 98 % of BVOCs were non-oxygenated monoterpenes (nMTs), 1 % oxygenated monoterpenes (oMTs), 0.5 % sesquiterpenes (SQTs), and 1 % other BVOCs. In both years, there was an interaction of warming, N addition and bark herbivory on rhizosphere BVOC emissions. In 2015, warming and N addition in single exposures decreased oMT emissions, while herbivory in single exposure increased oMT emissions. In 2016, the three-way interaction showed that the effects of warming, N addition and herbivory on BVOCs were mainly detected in single exposures. In 2016, warming decreased nMT, oMT, SQT and other BVOC emissions; N addition decreased oMT and SQT emissions; and herbivory decreased SQT and other BVOC emissions.ConclusionsWarming and N addition in single exposures decreased the rhizosphere BVOC emissions. The effect of bark herbivory on BVOC emissions varied between the years from increase to decrease. It seems that under altered growth conditions Scots pine seedlings may reduce carbon investment to rhizosphere BVOCs.
Highlights
Boreal forests are the largest terrestrial biome in the world (Taggart and Cross 2009)
Monoterpenes α-pinene and limonene are known chemical signals for large pine weevil (Hylobius abietis) (Nordlander et al 1986; Norlander 1990, 1991; Nordenhem and Norlander 1994), while some monoterpenes (e.g. α-pinene and β-pinene) in rhizosphere have been reported to have inhibitory effect on soil microbes (Maurer et al 2008; Adamczyk et al 2015; Lin et al 2007) have shown that most of the Scots pine rhizosphere Biogenic volatile organic compound (BVOC) remained within a 20 cm radius in the soil around the trunk, and Mäki et al (2019) have shown that the BVOCs are concentrated in the top organic- and mineral layer of the soil
We studied the interactive effects of increasing air and soil temperature (0.5°C and 4°C respectively), moderate N addition to soil of 30 kg N ha− 1 yr− 1 and bark herbivory by large pine weevil (Hylobius abietis) on the rhizosphere BVOC emissions of young Scots pines, which were grown in forest soil in a three-year-long field experiment
Summary
Boreal forests are the largest terrestrial biome in the world (Taggart and Cross 2009). Rhizosphere BVOCs can act as communication signals between rhizobacteria and mycorrhizal fungi and neighboring plants (Hiltpold and Turlings 2008; Ditengou et al 2015; Šimpraga et al 2019), control root architecture by promoting lateral root formation (Ditengou et al 2015) and act as chemical cues for herbivores (Delroy et al 2016). Monoterpenes and sesquiterpenes readily react with free radicles like OH−, get adsorbed on surfaces or dissolve in soil water, most of the monoterpenes and sesquiterpenes may not diffuse too far from the source into the soil or from soil to the atmosphere (Lin et al 2007; Hiltpold and Turlings 2008; Šimpraga et al 2019)
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