| Terrestrial carbon sinks have significant interannual changes and are the main contributors to the change of atmospheric CO2 concentration.The regional contribution and formation mechanism of the interannual change of terrestrial carbon sinks have been the focus and frontier in the field of global change ecology.In the context of global climate change,China’s regional extreme climate events are increasing,which has an important impact on the interannual change of China’s land carbon sinks.At present,there is a lack of systematic research on the contribution of different types of extreme climate events in China to the interannual change of China’s land carbon sinks and their regional differences.This study uses the simulated data of CLM4.5 model to analyze the spatiotemporal distribution characteristics of different types of extreme climate events in China from 1981 to 2015 and their contribution to the interannual change of China’s land carbon sink,identify the climate attribution of China’s land carbon sink extreme events and its important impact areas,and provide a new understanding for predicting the impact of future climate change on the carbon sink of terrestrial ecosystems,and for China’s response to climate change Support the realization of carbon neutrality goal.The main results are as follows:(1)There are different regional patterns of extreme climate events in those years experiencing extreme annual precipitation and air temperature events for the whole country.For the years with extreme heavy annual precipitation in 1983,1998 and 2012,extreme heavy annual precipitation events mainly occurred in the middle and lower reaches of the Yangtze River,the upper reaches of the Yangtze River and Eastern Inner Mongolia,and the middle and lower reaches of the Yangtze River and Inner Mongolia,respectively.The national extreme drought event existed in 1986 and 2011.Most regions of the country were drier than that in normal years in 1986,while the extreme drought events mainly occurred in the subtropical and tropical monsoon climate region in 2011.The extreme high temperature and extreme low temperature events occurred in 1998 and 2012,respectively.The mean air temperature in most parts of the country was higher than usual in 1998.The extreme low temperature events in 2012 occurred frequently in the temperate continental climate region.During 1981-2015,46% of extreme heavy precipitation events occurred in 2001-2015.There were 13% of extreme drought events occurred in the subtropical tropical monsoon climate region from2001 to 2015.Extreme high temperature events occurred frequently in 1991-2000 and 2001-2015.There were 21% of extreme low temperature events occurred in the temperate continental climate region from 2001 to 2015.The proportion of compound extreme climate events had a decadal increasing trend.The extreme low temperature and heavy precipitation events had the highest proportion,and concentrated in 2001-2015.(2)The extreme drought event in the extreme drought year and the extreme high temperature event in the extreme high temperature year in the country led to the decrease of NEP of 127.3 TgC/yr and 14.7 TgC/yr,respectively.The extreme heavy precipitation event in the year of extreme heavy precipitation and the extreme low temperature event in the year of extreme low temperature caused the NEP to increase by 41.2 TgC/yr and 16.3 TgC/yr,respectively.For the 200 largest single-factor extreme weather events,NEP is most affected by extreme drought events.Extreme drought will cause a sharp decrease in NEP,extreme high temperature will cause a small decrease in NEP,extreme heavy precipitation events and extreme low temperature events will cause an increase in NEP to a certain extent,and the response intensity of NEP to extreme heavy precipitation events is slightly higher than that of extreme low temperature events.In general,the impact of the 200 largest composite extreme weather events on NEP is close to the sum of the two corresponding single-factor extreme weather events on NEP.(3)From 1981 to 2015,the positive end of NEP in China’s terrestrial ecosystem took place in 1988 and 1998,and the negative end of NEP took place in 2001.The subtropical-tropical monsoon climate zone and temperate continental climate zone made the largest contribution to the extreme year of NEP,of which the subtropical-tropical monsoon climate zone mainly contributed to forests and farmland,and the temperate continental climate zone mainly contributed to grassland.From 1981 to 2015,the sum of the absolute values of the inter-annual fluctuation of NEP in China’s terrestrial ecosystem was 3.1 PgC/yr,and the sum of the absolute values of the inter-annual fluctuation of carbon sink extreme values was 2.3PgC/yr,accounting for 74.2% of the total absolute values of the inter-annual fluctuation of NEP in China’s terrestrial ecosystem.The NEP extreme events can largely guide the characteristics of the inter-annual variation of NEP in China’s terrestrial ecosystem.The probabilities of different types of extreme weather events triggering NEP positive and negative extreme events are 44.3% and 56.4% respectively,among which NEP negative extreme events are often more closely related to extreme drought,while extreme heavy precipitation plays a major role in NEP positive extreme events. |
