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The upper Mae Nam (River) Mun Valley of northeast Thailand has been occupied at least since the Bronze Age, but is notable for the rapid expansion of intense town-based Iron Age settlement. The area presently forms the seasonally-arid core of mainland southeast Asia, and is presently dominated by increasingly saline soils, low-productivity rice cultivation and regrowth semi-arid scrub. However, the archaeological evidence for this region indicates a highly-productive natural environment within the last two millennia. Pollen sequences from the infill of Iron Age features provide the first palynological evidence for this part of northeast Thailand, detailing Late Holocene vegetational change. The area around the sites was initially dominated by forest, which then underwent two phases of the replacement by mosaics of grassland, probable rice cultivation, arboriculture and scrub, prior to a subsequent phase of forest and woodland regeneration. Spatial patterning of the study area’s palaeovegetation appears to have been complex. While a general progress of landscape change is evident, local compositional differences are also clear. Although the region’s archaeological and, especially, geomorphological evidence suggests significant climatic change during this period, the pollen record, as in studies further north in the region for the same period, appears to have been dominated by human influences. Of note are the effects of intensified human settlement and thus increased land and natural resource use. At present this Late Holocene pollen sequence yields no evidence for a direct relationship with climatic change. (C) 2001 Elsevier Science B.V. All rights reserved.