Abstract
Scots pine (Pinus sylvestris L.) provenances cover broad ecological amplitudes. In a greenhouse study, we investigated the impact of drought stress and rewetting on gas exchange for three provenances (Italy: Emilia Romagna; Spain: Alto Ebro; Germany: East-German lowlands) of 2-year old Scots pine seedlings. CO2, water vapour and isoprenoid exchange of stressed and control trees were quantified with a four-chamber dynamic-enclosure system in the controlled environment of a climate chamber. The three provenances showed distinct isoprenoid emission patterns and were classified into a non-Δ3-carene, with either high α-/β-pinene or β-myrcene fraction, and a Δ3-carene dominated type. Isoprenoid emission rates, net-photosynthesis and transpiration were reduced during summer drought stress and significantly recovered after rewetting. A seasonal increase of isoprenoid emission rates towards autumn was observed for all control groups. Compared with the German provenance, the Spanish and Italian provenances revealed higher isoprenoid emission rates and more plastic responses to drought stress and seasonal development, which points to a local adaptation to climate. As a result of drought, net carbon uptake and transpiration of trees was reduced, but recovered after rewetting. We conclude from our study that Scots pine isoprenoid emission is more variable than expected and sensitive to drought periods, likely impacting regional air chemistry. Thus, a provenance-specific emission assessment accounting for reduced emission during prolonged (summer) drought is recommend for setting up biogenic volatile organic compound emission inventories used in air quality models.
Highlights
Biogenic volatile organic compounds (BVOCs) are emitted into the atmosphere by many biomes
We investigated the impact of drought stress and rewetting on gas exchange for three provenances (Italy: Emilia Romagna; Spain: Alto Ebro; Germany: EastGerman lowlands) of 2-year old Scots pine seedlings
This study showed that Scots pine provenances consisted of different chemotypes, classified in four groups at the end of the growing season as Δ3-carene emitters (GER: 10 out of 12 trees; ITA: 2 out of 12 trees) and non-Δ3-carene emitters which are either β-myrcene dominated (GER: 1; ESP: 4; ITA: 6) or are separated by their α-/β-pinene emission ratios (GER: 1; ESP: 8; ITA: 4)
Summary
Biogenic volatile organic compounds (BVOCs) are emitted into the atmosphere by many biomes. Monoterpenes are emitted into the atmosphere by different processes, such as diffusion through the cell wall and stomata (Niinemets et al 2004) or damage of wood and leaf structures with resin- containing structures with MT pools, e.g., by insects (Klepzig et al 1995, Achotegui-Castells et al 2013), wind (Haase et al 2011) and other mechanical influences (Schade et al 2011). The emitted amount of MTs is limited by the current storage in pools and the actual synthesis capacity (Niinemets et al 2004, Ghirardo et al 2010). Both source types are driven by light and temperature (Shao et al 2001, Dindorf et al.2006). The recovery to normal emission levels after different stress events can vary
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