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Under the global warming, the research on ecological effects caused by extreme climate events has received widespread attention. Based on a total of 913 literatures collected by the China National Knowledge Infrastructure (CNKI) and the Web of Science Core Collection database from 2000 to 2020, CiteSpace software was applied to visualize and analyze the current research status, progresses and trends of ecological effects caused by extreme climate events. The results showed that the number of publications in this field experienced three phases: slow growth, steady growth, and rapid growth. The number of publications in China was seriously insufficient and relatively scattered compared with that in foreign countries over the same period. The institutions and authors with the highest publications were the Chinese Academy of Sciences and Beierkuhnlein Carl, respectively. Keywords with high frequency of appearance included "climate change", "drought", "response", "temperature", and "extreme climate". Current research on the ecological effects of extreme climate events mainly tends to focus on the impacts of extreme drought, extreme precipitation and extreme temperature on terrestrial ecosystems. The carbon cycle, resistance and stability, sensitivity and dynamic evolution of ecosystems under extreme climate have been research hotspots in recent years. In the future, it is necessary to standardize the terminology related to extreme climate events and to carry out long-term ecological effects research on discrete and compound extreme climate eventsusing new techniques methods. [ABSTRACT FROM AUTHOR]

[Objective] This study was aimed to understand the spatiotemporal changes in extreme climate and its influence on vegetation. [Methods] Based on daily meteorological data (1960—2020) from 115 weather stations in the Qinling-Daba mountains (QBMs) and surrounding areas and satellite-derived normalized difference vegetation index (NDVI), the spatiotemporal variation characteristics of the NDVI in the QBMs and its response to 19 extreme climate indices were analyzed. Geographic detector was used to identify the contribution rate of extreme climate indices and their influence on the NDVI. [Results] (1) The NDVI significantly increased in the majority of the QBMs (80.34%) and decreased in only a few regions (1.09%) from 2000 to 2020. The interannual change rate in the study area was approximately 0.03/10 a. (2) Noticeable warming was observed in the QBMs from 1960 to 2020, with the temperature increasing more at night than during the day, and regions with a larger change in extreme temperature events were mostly found in the Western Qinling Mountains (WQMs). During the study period, extreme precipitation events showed weak changes, extreme precipitation intensity increased in the southwestern QBMs, while in the eastern QBMs, extreme precipitation intensity decreased but extreme precipitation frequency increased. (3) Extreme precipitation events were the main factor affecting NDVI in the west Qinling region, while extreme temperature events were the main factor affecting NDVI in the Qinling and Daba mountain regions; the impact of extreme climate events on NDVI was not independent, and the interaction between extreme climate indices enhances the impact of a single factor on NDVI in a double-factor or nonlinear way. [Conclusion] The spatiotemporal changes in extreme climate and its influence on vegetation were clarified, which could establish scientific evidence for the protection and restoration of vegetation in the QBMs in response to global climate change.

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[Objective] The aims of this study are to clarify the high incidence areas and time periods of extreme climate events within a continuous spatiotemporal range in the Chinese region, enhance understanding of the occurrence patterns of extreme climate events in China, and provide an important scientific basis for human society to mitigate and adapt to climate change. [Methods] We analyzed the spatiotemporal distribution characteristics of different types of extreme climate events in China from 1981 to 2015, using both the 1.5 times standard deviation and the continuous spatiotemporal extreme event analysis method based on the temperature and precipitation data of CRUNCEP. [Results] There were 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 which occurred in the subtropical tropical monsoon climate region from 2001 to 2015. Extreme high temperature events occurred frequently in 1991—2000（42%） and 2001—2015（43%）. There were 21% of extreme low temperature events which 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（34%）, and concentrated in 2001—2015（23%）. [Conclusion] That single-factor extreme climate events and composite extreme climate events have strong differences in the four major climate zones in China. In the future, it is necessary to strengthen the analysis of the spatiotemporal distribution characteristics of extreme climate events on short time scales such as day and month in regions of China. [ABSTRACT FROM AUTHOR]

Taking "One Belt and One Road" region as the research area, based on monthly historical climate data from 1990 to 2018 and annual vegetation phenology data from 1981 to 2016, trend analysis and statistical analysis are used to study spatiotemporal variation of extreme climate events and vegetation phenology, and select cultivated land in Southeast Europe, Inner Mongolia grassland in China, cultivated land in the Indian mainland, and cultivated land in northern Thailand as typical agricultural regions, and analyze the influence of typical extreme climate events on the growing season. The results showed that, (1) the extreme climate events in "One Belt and One Road" region are mainly extreme warm and cool events, and generally show an increasing trend. The increasing trend of extreme high temperature events is obvious, while extreme low temperature events show a decreasing trend. (2) Start of Season (SOS), End of Season (EOS) and the Length of Season (LOS) are generally layered with latitude, altitude and precipitation also significantly affect the growing season. Under the influence of global warming, SOS in most areas of "One Belt and One Road" region has a trend of advancement, while EOS has a trend of delay, which leads to a general extension of LOS. (3) When an extreme high temperature event occurs, SOS generally early, while EOS generally postponed. Extreme low temperature events will cause the delay of SOS and the advance of EOS. In addition, the more severe the extreme climate events, the greater the impact on vegetation phenology. [ABSTRACT FROM AUTHOR]

Vegetation net primary production (NPP) is an essential index for determining the quality of terrestrial ecosystems and their potential carbon storage ability. The impacts of extreme climate events on vegetation NPP are different under different altitude gradients. However, the research on the impact of extreme climate events on the spatial variation in vegetation NPP and the coupling effects under different altitude conditions remain insufficient. Using the MOD17A3HGF remote sensing data set and RClimDex 1.9 software, the vegetation NPP and 10 extreme climate indices in the Songhua River Basin from 2001 to 2020 were calculated, respectively. The spatial and temporal evolution characteristics of vegetation NPP and its response mechanism to extreme climate events in the Songhua River Basin under different altitude gradients were analyzed by means of trend analysis, correlation analysis, regression analysis, GeoDetector, and relative importance analysis. The results showed that:① the vegetation NPP (calculated by C) in the Songhua River Basin increased significantly at the rate of 4.13 g·(m 2 ·a) -1 from 2001 to 2020 ( P < 0.01), and the rates of 3.65, 4.04, 4.70, 5.09, and 4.57 g·(m 2 ·a) -1 at the altitude gradients of 29-255, 255-440, 440-658, 658-935, and 935-2 589 m, respectively ( P < 0.01). ② The spatial distribution pattern of vegetation NPP presented "high around and low in the middle," and the fluctuation of vegetation NPP in high altitude areas was more obvious than that in low altitude areas; for example, the average value of vegetation NPP at an altitude gradient from 29 to 255 m had a lower value, whereas the other altitude gradients had higher mean values than the mean value of the basin. ③ The extreme precipitation events in the Songhua River Basin were the main influencing factors of vegetation NPP, i.e., the vegetation NPP in low-altitude areas was mainly affected by extreme precipitation events, whereas the values in high-altitude areas were affected by both extreme precipitation events and extreme temperature events. The results of this research can provide a scientific basis for improving the carbon cycle model of the terrestrial ecosystem in the Songhua River Basin, quantifying the ability of carbon storage of vegetation and formulating policies to deal with climate change.