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Abstract. Information concerning the spatial and temporal characteristics of vegetative drought is essential for decision-making and for many environmental and agricultural applications. This study presents a comprehensive spatio-temporal analysis of vegetative drought conditions that used the vegetation condition index (VCI) data product obtained from NOAA/AVHRR (National Oceanic and Atmospheric Administration/Advanced Very High Resolution Radiometer) to reveal the vegetative drought patterns across China from 1981 to 2015. Considering the characteristics of VCI as drought indicators, multiple methods were designed for these analyses, including drought frequency analysis, trend analysis, anomaly index analysis, and Mann-Kendall testing. The results show that China is a country with high vegetative drought frequency, but that most areas experienced only slight or moderate periods of drought. In addition, drought has obvious seasonal and geographical differences and occurs with greater frequencies in regions that are highly affected by monsoons such as the northern and southern regions-particularly in the spring and autumn. In contrast, vegetative drought frequencies in regions less affected by monsoons such as the Tibetan Plateau and the northwestern regions were much lower except in northern Sinkiang, eastern Inner Mongolia, and southern Tibet. During 1981-2015, the VCI had an increasing trend in most areas of China (except in the southern region, where it decreased), indicating a reduced frequency of vegetative drought throughout the country. Moreover, the trend was wavelike rather than a one-way change and could be divided into four phases: (1) a slowly increasing phase from 1981 to 1990, (2) an intensively fluctuating phase from 1991 to 2000, (3) a steadily increasing phase from 2001 to 2010, and (4) a slowly decreasing phase after 2010. Mann-Kendall analysis further suggested that upward trends of the VCI were more evident in spring and autumn than in summer and that both trends mutated in 1997. Specifically, the trend reached the 0.05 level of significance in the spring.

The identification of a new circovirus (Porcine Circovirus 3, PCV3) has raised concern because its impact on swine health is not fully known. In Fujian Province in eastern China, even its circulating status and genetic characteristics are unclear. Here, we tested 127 tissue samples from swine from Fujian Province that presented respiratory symptoms. All of the PCV3 positive samples were negative for many other pathogens involved in respiratory diseases like PCV2, PRRSV, and CSFV, suggesting that PCV3 is potentially pathogenic. From phylogenetic analysis, PCV3 strains are divided into two main clades and five sub-clades; PCV3a-1, PCV3a-2, PCV3a-3, PCV3b-1, and PCV3b-2. Our identified strains belong to genotypes PCV3a-1, PCV3a-2, PCV3a-3, and PCV3b-2, indicating a high degree of genetic diversity of PCV3 in Fujian province until 2019. Interestingly, we found the time of the most recent common ancestor (tMRCA) of PCV3 was dated to the 1950s, and PCV3 has a similar evolutionary rate as PCV2 (the main epidemic genotypes PCV2b and PCV2d). In addition, positive selection sites N56D/S and S77T/N on the capsid gene are located on the PCV3 antigen epitope, indicating that PCV3 is gradually adaptive in swine. In summary, our results provide important insights into the epidemiology of PCV3.