Is forest management a significant source of monoterpenes into the boreal atmosphere?

S Haapanala,H Hakola,J Levula,J Rinne,H Hellén,M Vestenius

doi:10.5194/bg-9-1291-2012

Abstract

Abstract. Volatile organic compounds (VOCs) including terpenoids are emitted into the atmosphere from various natural sources. Damaging the plant tissue is known to strongly increase their monoterpene release. We measured the terpenoid emissions caused by timber felling, i.e. those from stumps and logging residue. The emissions from stumps were studied using enclosures and those from the whole felling area using an ecosystem-scale micrometeorological method, disjunct eddy accumulation (DEA). The compounds analyzed were isoprene, monoterpenes and sesquiterpenes. Strong emissions of monoterpenes were measured from both the stumps and from the whole felling area. The emission rate decreased rapidly within a few months after the logging. In addition to fresh logging residue, the results suggest also other strong monoterpene sources may be present in the felling area. These could include pre-existing litter, increased microbial activity and remaining undergrowth. In order to evaluate the possible importance of monoterpenes emitted annually from cut Scots pine forests in Finland, we conducted a rough upscaling calculation. The resulting monoterpene release was approximated to be on the order of 15 kilotonnes per year, which corresponds to about one tenth of the monoterpene release from intact forests in Finland.

Highlights

Biogenic volatile organic compounds (VOC) have many important effects on the atmosphere and climate
Emission rates from Scots pine (Pinus sylvestris) have been measured throughout the growing season (Tarvainen et al, 2005) and there are few measurements from Norway spruce (Picea abies) during dormant period (Hakola et al, 2003). These studies show that few biogenic VOCs are emitted during winter, and that these emission rates are low due to low temperatures (Tarvainen et al, 2005)
Since extensive forestry work is conducted during winter and spring months in boreal forests, cut stumps and logging residue can provide a source of VOCs into the atmosphere, possibly during these biologically inactive periods

Summary

Introduction

Biogenic volatile organic compounds (VOC) have many important effects on the atmosphere and climate. Emission rates from Scots pine (Pinus sylvestris) have been measured throughout the growing season (Tarvainen et al, 2005) and there are few measurements from Norway spruce (Picea abies) during dormant period (Hakola et al, 2003) These studies show that few biogenic VOCs are emitted during winter, and that these emission rates are low due to low temperatures (Tarvainen et al, 2005). Mechanical damage to trees is known to enhance VOC emissions from, e.g. coniferous trees (Juuti et al, 1990; Litvak and Monson, 1998; Loreto at al., 2000) and birch species (Hakola et al, 2001) For coniferous trees this is expected to be important as they store significant amounts of monoterpenes within their resin ducts. The spring is of great interest as the maximum aerosol particle formation events are observed at that time of year (Dal Maso et al, 2005), and is so expected to be strongly affected by VOCs in the atmosphere (Kulmala et al, 2004)

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