Regional to Global Biogenic Isoprene Emission Responses to Changes in Vegetation From 2000 to 2015

Abstract

Isoprene, a dominant biogenic volatile organic compound that is mainly emitted by trees, has a significant impact on the atmospheric chemistry. Regional to global changes in biogenic isoprene emission associated with vegetation variations between 2000 and 2015 were estimated using the MEGAN model with satellite land cover data for inputs in this study. The satellite data estimates of land cover changes were compared to results from previous investigators that have either conducted regional studies or have used lower resolution land cover data. The analysis indicates that tree coverage increases of >5% occurred in 13% of locations including in central China and Europe. In contrast, a decrease of >5% was observed in about 5% of locations, especially in tropical regions. The trends in global tree coverage from 2000 to 2015 resulted in a global isoprene emission decrease of only 1.5%, but there were significant regional variations. Obvious decreases in tree coverage in some tropical areas (e.g., Amazon Basin, Western Africa, Southeast Asia) resulted in a ~10% reduction of regional isoprene emission due to agricultural expansion. Distinct increments of isoprene emission (5–10%) were mainly found in Northeast China and India and were associated with afforestation efforts. Deforestation and afforestation associated with managed plantations does not only affect the total forest coverage but also impacts average isoprene emission capacity, which can result in accelerated isoprene emission variations. Consequently, isoprene variation assessments are needed that not only account for changes in vegetation fractions but also consider the changes in plant species compositions of forests and other landscapes.

Substantial ozone enhancement over the North China Plain from increased biogenic emissions due to heat waves and land cover in summer 2017

“…Based on ozone observations from 2013 to 2017, the North China Plain (NCP, an area about 400 000 km 2 in size, with Beijing located on its northeast edge; 35-42 • N, 112-119 • E), is identified as the area with the most severe ozone pollution in China compared to other regions such as the Yangtze River Delta and Pearl River Delta, possibly linked to the stimulation effect from enhanced hydroperoxy radicals (HO 2 ) due to a reduction in aerosol sink resulting from the decrease in PM 2.5 during this period (Li et al, 2019). Chen et al (2019) investigated the impact of meteorological factors such as temperature, wind speed and solar radiation on ozone pollution from 2006 to 2016 and noted that the severe ozone events in June 2017 around Beijing stand out and suggested a possible connection with the abnormal meteorological conditions. These studies motivated a need for a better understanding of the high-ozone problem over the NCP.…”

Impact of Short‐Term Climate Variability on Volatile Organic Compounds Emissions Assessed Using OMI Satellite Formaldehyde Observations

“…This effect possibly explains also the trend overestimation (by 0.4% per year) over the Southeastern United States. The trend underestimations over Southeast Europe (0.4% vs. 0.9% per year) and Western Russia (1% vs. 1.9% per year) likely reflect underestimated biogenic emissions (also suggested by the low bias of modeled columns over these regions, Figure ) and the impact of afforestation in Europe and Western Russia (Chen et al, ). The discrepancy over less productive and drier ecosystems such as Mexico and the Midwestern United States for both the trend (Figure ) and the correlation (Figure ) could be related to the neglect of soil moisture stress effect on the emission in the model.…”

“…Elsewhere, the modeled trends are comparatively smaller and in agreement with the observed trends when accounting for their respective uncertainties (Table ). The overestimations (by 0.4–0.7% per year) found over Amazonia and Borneo are possibly due to the combined effects of deforestation and increasing CO 2 on the emissions (Chen et al, ). The CO 2 effect alone is expected to cause a flux decline between −0.2 and −0.5% per year (section 2.3).…”

“…Their emissions are strongly dependent on visible radiation fluxes and especially temperature: for example, a 5 ∘ C warming is estimated to approximately double the emission rate of isoprene (Guenther et al, 2006). Therefore, these emissions are expected to increase in response of climate change, although this effect might be offset by anthropogenic land use change (Chen et al, 2018) and by the inhibition of isoprene emissions due to increasing CO 2 concentrations (Arneth et al, 2007;Possell & Hewitt, 2011). 10.1029/2018GL078676 2006,2012), as shown by its ability to reproduce the diurnal cycle and day-to-day variability of observed fluxes (Müller et al, 2008;Sindelarova et al, 2014). Longer-term variations are more complex: the emission capacity of plants is affected by phenological changes, by biotic and abiotic stresses, and by the plant adaptation to past environmental conditions (Demarcke et al, 2010;Monson et al, 1994).…”

Decadal Shifts in Wind Patterns Reduced Continental Outflow and Suppressed Ozone Trend in the 2010s in the Lower Troposphere Over Japan

“…They estimated the total emissions of BVOCs in China at 16.8 Tg in the mid‐2000s, which is an increase of 11.4% relative to the late 1980s, due to the combined effect of meteorology and land cover. A significant increase in the emissions of isoprene (>10%), the dominant BVOCs emitted in present‐climate state (Guenther et al, ), was found in central China during 2000–2015 with a large increase in tree coverage (~13%) because of extensive afforestation efforts (Chen et al, ). These results suggest that emissions of NMVOCs from China did not decrease after 2008.…”