Microscopic charcoal in sediments: Quaternary fire history of the grassland and savanna regions in South Africa

Abstract

The microscopic charcoal content of several Quaternary pollen sequences is used to investigate fire history in South Africa both during the Holocene and the Late Pleistocene. Although fluctuations in charcoal composition are recorded, it is difficult to link them directly to either human-made or natural fires. Strong long-term variations in microscopic charcoal of Middle and Upper Pleistocene layers are independent of pollen indications of past temperature and moisture conditions. Holocene charcoal sequences from different areas show no correlation, so no phases of regional burning are found. Some fluctuations in charcoal probably are the result of local burning in the various regions. The arrival of Iron Age people some 2000 yr ago apparently did not coincide with widespread wild fires, as these events do not consistently appear in regional microscopic charcoal records. The only exception appears to be the Wonderkrater spring deposit. Relatively open savanna environments, which are implied by pollen analysis at some sites during this period and the generally low microscopic charcoal contents, were either caused by climate change or controlled burning by Iron Age people.

Fluctuations of vegetation and climate over the last 75 000 years in the Savanna Biome, South Africa: Tswaing Crater and Wonderkrater pollen sequences reviewed

“…In the Tswaing I core, however, large sections of the sequence had poor preservation of organic matter that caused major gaps in the pollen and microscopic charcoal sequence (Scott, 1999a, b;Scott, 2002b;Scott et al, 2008) (Fig. 2).…”

“…3). Details of the local vegetation and palynological composition (Zones W1eW10) are discussed in Scott (1982a), Scott and Thackeray (1987), Scott (2002b) and Scott et al (2003Scott et al ( , 2008Scott et al ( and 2012.…”

An Anthropogenic Escape Route from the “Gulliver Syndrome” in the West African Savanna

“…In particular, natural fires fostered the spread of C 4 grasses during the last glacial maximum (Harrison and Prentice 2003) when anthropogenic effects were minor (Scott 2002). Indeed, evidence from paleoecological studies in southern Sudanian savanna suggests that the vegetation cover never consisted of closed canopy dry forest even during the mid-Holocene period when precipitation was significantly higher.…”

Controls on fire activity over the Holocene

“…Microscopic charcoal pieces in sediments have been related to fire history for different parts of the world going back in time for thousands of years (Patterson et al, 1987;Whitlock and Millspaugh, 1996;Scott, 2002). The Global Charcoal Database (Power et al, 2010) has collected over 400 radiocarbon-dated charcoal records covering the late Quaternary.…”

“…In dry regions fire activity is typically limited by fuel availability, but fuel moisture is sufficiently low to lead to successful fire ignitions. Under moist climate conditions fuel availability is sufficiently guaranteed, but fuel moisture is often too high to allow for fires to spread (van der Werf et al, 2010). Consequently, climate change will impact fire activity differently in different climate zones and fire regimes.…”