Abstract. Satellite observations reveal that China has been leading
the global greening trend in the past 2 decades. We assessed the impact of
land cover change as well as climate variability on total biogenic volatile organic compound (BVOC) emission in
China from 2001–2016. We found the greening trend in China is leading a
national-scale increase in BVOC emission. The BVOC emission level in 2016
could be 11.7 % higher than that in 2001 because of higher tree cover
fraction and vegetation biomass. On the regional scale, the BVOC
emission level from 2013–2016 could be 8.6 %–19.3 %
higher than that from 2001–2004 in hotspots including (1) northeastern
China, (2) Beijing and its surrounding areas, (3) the Qin Mountains, (4) Yunnan Province, (5) Guangxi–Guangdong provinces, and (6) Hainan island because
of the land cover change without considering the impact of climate
variability. The comparison among different scenarios showed that vegetation
changes resulting from land cover management are the main driver of BVOC
emission change in China. Climate variability contributed significantly to
interannual variations but not much to the changing trend during the study
period. In the standard scenario, which considers both land cover change and
climate variability, a statistically significant increasing trend can still be
found in regions including Beijing and its surroundings, Yunnan
Province, and Hainan island, and BVOC emission total amount in these regions
from 2013–2016 is 11.0 %–17.2 % higher that from 2001–2004. We
compared the long-term HCHO vertical columns (VC) from the satellite-based
Ozone Monitoring Instrument (OMI) with the estimation of isoprene emission
in summer. The results showed statistically significant positive correlation
coefficients over the regions with high vegetation cover fractions. In
addition, the isoprene emission and HCHO VC both showed statistically
significant increasing trends in the south of China where these two
variables have high positive correlation coefficients. This result may
support our estimation of the variability and trends of BVOC emission in
this region; however, the comparison still has large uncertainties since the
chemical and physical processes, including transportation, diffusion and
chemical reactions, were not considered. Our results suggest that the
continued increase in BVOC will enhance the importance of considering BVOC
when making policies for controlling ozone pollution in China along with
ongoing efforts to increase the forest cover fraction.
Comparison of land-cover change and climate variability impacts on runoff using hydrological modelling and sensitivity-based approaches