Charcoal Whirlwinds and Post-Fire Observations in Serengeti National Park Savannahs

Abstract

Whirlwinds and visible dust devils occur over semi-arid ecosystems and entrain particles from the ground surface. Fires produce abundant charcoal across savannahs and the resulting blackened surfaces create a large albedo contrast. Whirlwinds have been observed associated with active fires; yet, there are few published observations on post-fire landscapes. Spatiotemporal patterns of whirlwinds have been documented for a limited number of regions and have not been made for the ecosystems of eastern Africa. From field-based sightings in the Serengeti National Park, Tanzania, we report on whirlwinds over burned savannah patches that entrained large quantities of charcoal to produce black coloured charcoal devils that lofted charcoal into the atmosphere. Two occurrences of charcoal devils were sighted and photographed, one each in the Western Corridor (Bunda District) and Lamai (Serengeti District), Mara Region. The observations were compared with regional scale meteorological data and remote sensing satellite imagery and albedo estimates of the land cover conditions. Although direct meteorological or particulate matter measurements were not made, the observations show that both charcoal devils differed in colour, funnel shape, height, and savannah land cover types (different woody to grass fuel canopies), and thus different charcoal morphologies. Charcoal laden whirlwinds require further study and characterization to analyse the contribution to local-scale redistribution of matter and regional-to-global fluxes of terrestrially derived atmospheric particulates. Future research focusing on the spatiotemporal patterns of whirlwinds over burned patches of savannah, the formation, duration and dissipation mechanisms, and characterisation of the entrained material would contribute to our understanding of the phenomena. The redistribution of organic and clastic material would contribute to understanding of detrital fluxes to depositional environments, such as lakes, wetlands, and snow.
 Keywords: Atmospheric boundary layer; Convection; Detritus; Dust devils; Fires; Particulate matter.

Late Pleistocene montane forest fire return interval estimates from Mount Kenya

“…Indeed, single fragments of grass charcoal from burned savannas have been observed to be transported 10 km across relatively flat areas during the evening by the authors. The contribution of long‐distance transport of charcoal to background charcoal accumulation rates on mountain areas has yet to be assessed (Courtney Mustaphi et al , 2021a, 2022). Future studies should incorporate quantification of charcoal transport and deposition in tropical mountain areas, similar to approaches for pollen (Schüler, 2012; Ssemmanda et al , 2014; Schüler and Hemp, 2016) and charcoal in temperate ecosystems (Adolf et al , 2018).…”

“…Future studies should incorporate quantification of charcoal transport and deposition in tropical mountain areas, similar to approaches for pollen (Schüler, 2012; Ssemmanda et al , 2014; Schüler and Hemp, 2016) and charcoal in temperate ecosystems (Adolf et al , 2018). The fire weather and convection patterns for lofting charcoal particles into the atmosphere have not been explored and remain an emerging study area for tropical mountains and lowland source areas of charcoal (Courtney Mustaphi et al , 2022).…”

“…Analysing the potential of other palaeoenvironmental research approaches, or combined approaches, for palaeofire records and disturbance ecology has yet to be a major focus in tropical ecosystems. Use can be made of other palaeoenvironmental archives (tree rings, soils, cave, marine sediments, glacial ice) (Marlon, 2020), other sediment analyses of fire proxies such as pyrogenic chemicals (Battistel et al , 2017; Karp et al , 2020), subfossil charcoal morphologies (Courtney Mustaphi and Pisaric, 2014b; Courtney Mustaphi et al , 2022; Hubau et al , 2015) and historical ecology (Phillips, 1965; Fanstone, 2016). Dendrochronological techniques for establishing past FRIs have yet to be developed for these tropical forests and have not been used to establish estimates (Higuera et al , 2011b; Brossier et al , 2014; Barhoumi et al , 2019).…”

Charcoal morphologies and morphometrics of a Eurasian grass-dominated system for robust interpretation of past fuel and fire type

“…One possible explanation for the lower wood charcoal production may be attributed to the faster combustion rates observed in oven settings, resulting in wood being ashed at the lower end of its temperature range. Field research has provided evidence that prolonged combustion through smouldering can also transform wood into white ash (Courtney Mustaphi et al, 2022). Investigations involving chemical analyses of unburnt biomass can enhance our understanding of how plants' chemical composition influences charcoal production.…”

“…Microscopic particles may be transported considerable distances and deposited into various sedimentary environments such as peats, lakes and rivers, in contrast to larger particles that tend to be deposited nearer to the source of the fire (Scott et al, 2000;Scott, 2010). Additionally, the morphology of charcoal characterised by longer and thinner shapes, typical of grass, allows for longer-distance atmospheric transport compared to spherical or denser particles, such as those from leaves and wood (Clark and Hussey, 1996;Pisaric, 2002;Scott et al, 2000;Vachula and Richter, 2018;Courtney Mustaphi et al, 2022;Vachula and Rehn, 2023). Conversely, water favours the transport of wood charcoal (Scott et al, 2000).…”