Spatio-temporal dynamics of burnt areas in federal Protected Areas in the south-east of European Russia

The paper is aimed to detect burnt sites in Protected Areas (PAs) in the arid zone of Russia: Astrakhansky State Nature Reserve, Bogdinsko-Baskunchaksky State Nature Reserve, Chernye Zemli State Nature Reserve, Melketinsky Sanctuary, Sarpinsky Sanctuary, Kharbinsky Sanctuary, and Stepnoy Sanctuary. The study covers the period of 2001–2019. Regular landscape wildfires are a significant factor of the vegetation cover dynamics. Therefore they should be considered during performing the landscape and environmental research. This study is based on visual expert interpretation of colour-synthesised spectrozonal satellite data of Landsat and Sentinel 2 using shortwave and near infrared bands as well as the analysis of informational products for detecting active wildfire foci and burnt sites. This allowed us to reveal that summer and autumn wildfire events prevail in the Bogdinsko-Baskunchaksky State Nature Reserve, Chernye Zemli State Nature Reserve, Mekletinsky Sanctuary, Sarpinsky Sanctuary, Kharbinsky Sanctuary, and Stepnoy Sanctuary. In the intrazonal landscapes of the River Volga delta of the Astrakhansky State Nature Reserve, over 80% of wildfires occur in March and April. A total of 10 169 wildfire events have been identified over the entire research period in the studied PAs and in the 12-km surroundings. In the Chernye Zemli State Nature Reserve, there were no sites left untouched by a wildfire. In 2006 and 2015, the area of burnt sites in the Chernye Zemli State Nature Reserve exceeded 1100 km2. Across all of the studied PAs, the largest total burned-out sites were registered in 2002 and 2006, when more than 2500 km2 were burnt, as well as in 2007, 2011 and 2015, with burnt areas over 1500 km2. In the Astrakhansky State Nature Reserve, an annual average of 17 wildfire events were registered. In addition, the Astrakhansky State Nature Reserve was characterised by the maximum frequency of wildfire events: up to 18–19 wildfire events at the same sites within an area of about 4 km2. Astrakhansky State Nature Reserve, Chernye Zemli State Nature Reserve and Stepnoy Sanctuary were characterised by a decrease in wildfire rate with distancing from the boundaries of these PAs. In all steppe PAs, a decrease in wildfire incidence was observed in 2011–2019 as compared to 2000–2010, including by 2.7 times in the Bogdinsko-Baskunchaksky State Nature Reserve and by 30% in the Chernye Zemli State Nature Reserve. Only the Astrakhansky State Nature Reserve demonstrated the absence of considerable changes in the number and area of wildfires during the study period. Mineralised strips along the borders of the Bogdinsko-Baskunchaksky State Nature Reserve up to 20 m wide restrain the advance of wildfire into this PA. So, the area of the Bogdinsko-Baskunchaksky State Nature Reserve is three times less flammable than the area of the Baskunchak Natural Park, which does not have mineralised strips and surrounds the Bogdinsko-Baskunchaksky State Nature Reserve. Along the borders of the Chernye Zemli State Nature Reserve, the width of mineralised strips does not exceed 4–5 m, which is not sufficient to prevent the advance of wildfires. So, up to 90% of wildfires from a 5-km radius and all wildfires from the buffer zone of the Chernye Zemli State Nature Reserve penetrate into the core zone of this PA. The map data obtained as a result of this study can be used to research pyrogenic changes in ecosystems as well as to determine the most flammable areas for optimisation of preventive measures.