Long-term variability and rainfall control of savanna fire regimes in equatorial East Africa

Fires burning the vast grasslands and savannas of Africa significantly influence the global carbon cycle. Projecting the impacts of future climate change on fire-mediated biogeochemical processes in these dry tropical ecosystems requires understanding of how various climate factors influence regional fire regimes. To examine climatevegetationfire linkages in dry savanna, we conducted macroscopic and microscopic charcoal analysis on the sediments of the past 25000years from Lake Challa, a deep crater lake in equatorial East Africa. The charcoal-inferred shifts in local and regional fire regimes were compared with previously published reconstructions of temperature, rainfall, seasonal drought severity, and vegetation dynamics to evaluate millennial-scale drivers of fire occurrence. Our charcoal data indicate that fire in the dry lowland savanna of southeastern Kenya was not fuel-limited during the Last Glacial Maximum (LGM) and Late Glacial, in contrast to many other regions throughout the world. Fire activity remained high at Lake Challa probably because the relatively high mean-annual temperature (approximate to 22 degrees C) allowed productive C4 grasses with high water-use efficiency to dominate the landscape. From the LGM through the middle Holocene, the relative importance of savanna burning in the region varied primarily in response to changes in rainfall and dry-season length, which were controlled by orbital insolation forcing of tropical monsoon dynamics. The fuel limitation that characterizes the region's fire regime today appears to have begun around 5000-6000years ago, when warmer interglacial conditions coincided with prolonged seasonal drought. Thus, insolation-driven variation in the amount and seasonality of rainfall during the past 25000 years altered the immediate controls on fire occurrence in the grass-dominated savannas of eastern equatorial Africa. These results show that climatic impacts on dry-savanna burning are heterogeneous through time, with important implications for efforts to anticipate future shifts in fire-mediated ecosystem processes

Iron Production in North Pare, Tanzania : Archaeometallurgical and Geoarchaeological Perspectives on Landscape Change

Archaeology, archaeometallurgy and geoarchaeology are combined in this research to examine the chronology and development of iron metallurgy and its environmental repercussions in North Pare, Tanzania. Pare was a prominent centre for iron production from at least the second half of the first millennium AD, and it has been assumed that this technologywith its demand for wood charcoalhad a significant and detrimental effect on local forest cover. This research sought to examine this claim by exploring the spatial, chronological and technological characteristics of iron production in Pare in conjunction with geoarchaeological evidence. Contrary to older assumptions, our results demonstrate that erosion processes were well established in North Pare before the documented intensification of smelting and smithing activity, and that iron production continued despite environmental changes. We suggest that although iron production may well have contributed to deforestation and erosion in Pare, it is unlikely to be the sole causal factor