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It has been widely reported that isoprene emissions from Arctic ecosystems show a strong temperature response, and that Arctic warming is increasing ecosystem isoprene emissions. We conducted leaf-chamber experiments on two major groups of Arctic isoprene emitters—sedges and willows—near Toolik Field Station, Alaska, USA. We identify sedges (Carex spp. and Eriophorum spp.) as key contributors to this high temperature sensitivity. Sedges exhibit a markedly stronger temperature response than other isoprene emitters and than predicted by widely used isoprene emission models. In addition, we find that the hourly temperature response curve of Salix spp., the dominant isoprene-emitting shrub in the Arctic, is similar to that of temperate plants. In contrast, willow isoprene emission capacity or emission factor shows a more substantial-than-expected response to the previous day’s mean ambient temperature.
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Heat waves may trigger unexpected surge in aerosol and ozone precursor emissions from sedges in urban landscapes
Biogenic isoprene emissions from herbaceous plants are generally lower than those from trees. However, our study finds widespread isoprene emission in herbaceous sedge plants, with a stronger temperature response surpassing current tree-derived models. We measured and compared isoprene emissions from sedges grown in different climatic zones, all showing an exponential temperature response with a Q10 range of 7.2 to 12, significantly higher than the Q10 of about 3 for other common isoprene emitters. The distinct temperature sensitivity of sedges makes them a hidden isoprene source, significant during heat waves but not easily detected in mild weather. For instance, isoprene emissions fromCarex praegraciliscan increase by 320% with a peak emission of over 100 nmol m−2s−1compared to preheat wave emissions. During heat waves, the peak isoprene emissions fromC. praegraciliscan match those fromLophostemon confertus, a commonly used street tree species which is considered the dominant urban isoprene source due to higher biomass and emission capacities. This surge in isoprene from globally distributed sedges, including those in urban landscapes, could contribute to peak ozone and aerosol pollutants during heat waves.
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- PAR ID:
- 10570130
- Publisher / Repository:
- National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 121
- Issue:
- 45
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract It has been widely reported that isoprene emissions from the Arctic ecosystem have a strong temperature response. Here we identify sedges (Carexspp. andEriophorumspp.) as key contributors to this high sensitivity using plant chamber experiments. We observe that sedges exhibit a markedly stronger temperature response compared to that of other isoprene emitters and predictions by the widely accepted isoprene emission model, the Model of Emissions of Gases and Aerosols from Nature (MEGAN). MEGAN is able to reproduce eddy-covariance flux observations at three high-latitude sites by integrating our findings. Furthermore, the omission of the strong temperature responses of Arctic isoprene emitters causes a 20% underestimation of isoprene emissions for the high-latitude regions of the Northern Hemisphere during 2000-2009 in the Community Land Model with the MEGAN scheme. We also find that the existing model had underestimated the long-term trend of isoprene emissions from 1960 to 2009 by 55% for the high-latitude regions.more » « less
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Abstract Warming climate in the Arctic is leading to an increase in isoprene emission from ecosystems. We assessed the influence of temperature on isoprene emission from Arctic willows with laboratory and field measurements. Our findings indicate that the hourly temperature response curve ofSalixspp., the dominant isoprene emitting shrub in the Arctic, aligns with that of temperate plants. In contrast, the isoprene capacity of willows exhibited a more substantial than expected response to the mean ambient temperature of the previous day, which is much stronger than the daily temperature response predicted by the current version of the Model of Emissions of Gases and Aerosols from Nature (MEGAN). With a modified algorithm from this study, MEGAN predicts 66% higher isoprene emissions for Arctic willows during an Arctic heatwave. However, despite these findings, we are still unable to fully explain the high temperature sensitivity of isoprene emissions from high latitude ecosystems.more » « less
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Abstract. Isoprene emissions are a key component in biosphere–atmosphere interactions, and the most significant global source is the Amazonrainforest. However, intra- and interannual variations in biological and environmental factors that regulate isoprene emission from Amazonia arenot well understood and, thereby, are poorly represented in models. Here, with datasets covering several years of measurements at the Amazon Tall TowerObservatory (ATTO) in central Amazonia, Brazil, we (1) quantified canopy profiles of isoprene mixing ratios across seasons of normal and anomalousyears and related them to the main drivers of isoprene emission – solar radiation, temperature, and leaf phenology; (2) evaluated the effect ofleaf age on the magnitude of the isoprene emission factor (Es) from different tree species and scaled up to canopy with intra- andinterannual leaf age distribution derived by a phenocam; and (3) adapted the leaf age algorithm from the Model of Emissions of Gasesand Aerosols from Nature (MEGAN) with observed changes in Esacross leaf ages. Our results showed that the variability in isoprene mixing ratios was higher between seasons (max during the dry-to-wettransition seasons) than between years, with values from the extreme 2015 El Niño year not significantly higher than in normal years. Inaddition, model runs considering in situ observations of canopy Es and the modification on the leaf age algorithm with leaf-levelobservations of Es presented considerable improvements in the simulated isoprene flux. This shows that MEGAN estimates of isopreneemission can be improved when biological processes are mechanistically incorporated into the model.more » « less
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Hybrid-poplar tree plantations provide a source for biofuel and biomass, but they also increase forest isoprene emissions. The consequences of increased isoprene emissions include higher rates of tropospheric ozone production, increases in the lifetime of methane, and increases in atmospheric aerosol production, all of which affect the global energy budget and/or lead to the degradation of air quality. Using RNA interference (RNAi) to suppress isoprene emission, we show that this trait, which is thought to be required for the tolerance of abiotic stress, is not required for high rates of photosynthesis and woody biomass production in the agroforest plantation environment, even in areas with high levels of climatic stress. Biomass production over 4 y in plantations in Arizona and Oregon was similar among genetic lines that emitted or did not emit significant amounts of isoprene. Lines that had substantially reduced isoprene emission rates also showed decreases in flavonol pigments, which reduce oxidative damage during extremes of abiotic stress, a pattern that would be expected to amplify metabolic dysfunction in the absence of isoprene production in stress-prone climate regimes. However, compensatory increases in the expression of other proteomic components, especially those associated with the production of protective compounds, such as carotenoids and terpenoids, and the fact that most biomass is produced prior to the hottest and driest part of the growing season explain the observed pattern of high biomass production with low isoprene emission. Our results show that it is possible to reduce the deleterious influences of isoprene on the atmosphere, while sustaining woody biomass production in temperate agroforest plantations.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1073/pnas.2412817121
