Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen Ø, Denmark.
Center for Permafrost (CENPERM), University of Copenhagen, Copenhagen K, Denmark.
Glob Chang Biol. 2021 Jun;27(12):2928-2944. doi: 10.1111/gcb.15596. Epub 2021 Apr 4.
Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long-term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem-level net BVOC fluxes were measured in the experimental plots using proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS). The warming treatment increased monoterpene and isoprene emissions by ≈50%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by ~50%-75%) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interact and influence BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not only a response to changes in temperature and light intensity, as the circadian clock also affects emission rates.
传统上，生物源挥发性有机化合物（BVOC）排放通常被认为是从生态系统到大气的单向通量，但最近的研究清楚地表明了双向交换的潜力。在这里，我们旨在调查在亚北极地区的长期野外实验中，变暖和添加落叶如何影响 BVOC 的双向交换（通量）。我们还评估了与一天中的时间有关的净 BVOC 通量变化以及不同植物物候阶段的影响。该研究是在瑞典北部阿比斯库的一个冻原荒地中进行的一个全面因子实验，其中包括开顶室变暖处理和年度落叶添加处理。经过 18 年的处理，使用质子转移反应飞行时间质谱（PTR-ToF-MS）在实验小区中测量生态系统水平的净 BVOC 通量。变暖处理使单萜烯和异戊二烯的排放增加了约 50%。由于昼夜变化，温度升高既可以增加 BVOC 的排放，又可以同时增加生态系统的吸收。对于任何给定的处理，单萜烯、异戊二烯和丙酮的排放也随着昼夜变化引起的环境空气温度升高而增加。乙醛、甲醇和倍半萜烯的排放减少可能是由于沉积通量。对于落叶添加，仅观察到对异戊二烯和单萜烯通量的间接显著影响（减少约 50%-75%）。落叶添加可能会改变土壤水分条件，导致植物物种组成和生物量的变化，这可能随后导致 BVOC 排放成分的变化。物候阶段对甲醇、异戊二烯和单萜烯通量有显著影响。我们认为，物候阶段对 BVOC 净排放的影响不同，但环境空气温度和光合有效辐射（PAR）也会相互作用，并以不同的方式影响 BVOC 净排放。我们的结果还表明，BVOC 通量不仅是对温度和光强度变化的响应，因为昼夜节律时钟也会影响排放速率。
