Spruce bark beetles ( Ips typographus ) cause up to 700 times higher bark BVOC emission rates compared to healthy Norway spruce ( Picea abies )

[摘要] Biogenic volatile organic compound (BVOC) emissions from trees subjected tobiotic stress are higher compared to healthy trees, and they may also have adifferent compound composition. This in turn affects atmospheric chemistryand can lead to either positive or negative feedback to the climate.Climate change favors the abundance of the European spruce bark beetle( Ips typographus ) which attacks the bark of Norway spruce ( Picea abies ) trees, causing induced BVOCemissions from the trees as a response to the insect stress. Here, resultsare reported from a study analyzing the difference in emission rates betweenhealthy and bark-beetle-infested Norway spruce trees, changes in emissionrates over time since the infestation started, and differences in emissionrates from bark-beetle-drilled entry and exit holes. Bark chamber measurements on both healthy and infested trees were performedduring the summer of 2019 at Hyltemossa and Norunda research stations inSweden. The measurements showed that induced BVOC emissions following thebark beetle infestation were dominated by entry hole emissions in the earlygrowing season and exit hole emissions in the later season. The resultsshowed a significant difference in emission rates between healthy andinfested trees during both seasons. The seasonal average standardized BVOCemission rate of healthy trees was 32  ±  52  µ g m −2  h −1 (mean  ±  standard deviation), while the average standardized BVOC emission rates of infested trees were 6700  ±  6900 and 2000  ±  1300  µ g m −2  h −1 during the early and late season respectively. BVOC emissionrates were highest at the start of the infestation and decreasedexponentially with time, showing induced emission rates for up to 1 yearafter which the emission rates were similar to those from healthy bark.Constitutive needle emission rates from healthy trees were found to be 11 times higher than bark emissions from healthy trees. However, when Norway spruce trees were infested, the bark emission rates were instead 6 to 20 times higher than the needle emissions, causing substantial increases in the total tree BVOC emission rate. This could lead to high impacts onatmospheric processes, specifically the formation of secondary organicaerosols, which have a higher yield from some monoterpene compounds, whichincreased from infested trees.

[学科分类] 大气科学