Scots Pine Stems as Dynamic Sources of Monoterpene and Methanol Emissions

Abstract

The volatile organic compound (VOC) fluxes of living plant compartments other than foliage are poorly known. In this paper we describe for the first time the methanol and monoterpene fluxes from living Scots pine stems in situ, over 4 years at the SMEAR II station in southern Finland. The VOC fluxes from stems were measured online with an automated chamber measurement system. Both methanol and monoterpene emissions showed strong diurnal and seasonal cycles. Methanol emission rates were highest in midsummer , and coincided with the most intensive period of stem radial growth. Methanol emission rates correlated moderately with the xylem sap flow rate and foliage transpiration rate, which suggests that many simultaneous and overlapping processes are related to methanol transport and production in trees. Monoterpene emissions from stems were highest on the hottest summer days, but also substantial in winter during times when the temperature was above zero • C for several days. Overall, the emissions from stems constitute about 2% of the whole stand monoterpene emissions under normal, non-stressed conditions. This can be used in stand monoterpene emission models as the rough estimate of woody compartment contribution.

Drought effects on volatile organic compound emissions from Scots pine stems

“…They also emitted methanol, acetone and acetaldehyde. The stem emission rates of these compounds followed temperature at a daily scale, corresponding to earlier findings (Rissanen et al, 2016; Staudt et al, 2019; Vanhatalo et al, 2020). Over the measurement period from June to August, emission rates generally decreased with decreasing SWP with the exception of late‐summer emission peaks of dry control trees.…”

“…In comparison, α‐ and β‐pinene emission rates ranged between −2 and 99 ng m −2 s −1 from maritime pine stems in France, in a temperature range of 15 to 34°C (Staudt et al, 2019). In moist and cool boreal conditions, the summertime monoterpene emission rates of the lower stem were generally smaller, 0—25 ng m −2 s −1 (Vanhatalo et al, 2020).…”

Heatwave frequency and seedling death alter stress-specific emissions of volatile organic compounds in Aleppo pine

“…Monoterpene emissions are known to respond strongly to temperature increase by release from specific storage pools depending on diffusion parameters and volatility (Kleist et al 2012 ; Peñuelas and Llusià 1999 ; Staudt et al 2017 ), including leaves and stems (Vanhatalo et al 2020 ). On the other hand, MT emissions of pines have been shown to originate to more than 50% directly from photosynthetic products under stressed conditions (Ghirardo et al 2010 ; Taipale et al 2011 ).…”

Fourier transform infrared spectroscopy and interference of volatile organic compounds on measurements of methane (CH4) fluxes at tree stems – a general phenomenon for plant systems?

“…Flux data were checked for normal distribution (Shapiro-Wilk test) and equality of variances in the different subpopulations. Given the typical mixing ratio of 20 ppbv monoterpenes at the end of stem chamber closure in coniferous Scots pine trees (example from Kohl et al, 2019), which are known to be substantial sources of monoterpenes (Vanhatalo et al, 2020), we are skeptical that this provides clear evidence for significant VOC interference on CH 4 measurements in such a systemeven when only a limited library is used.…”