The geoarchaeology of the prehistoric ditched sites of the upper Mae Nam Mun Valley, NE Thailand, III: Late Holocene vegetation history

The upper Mae Nam (River) Mun Valley of northeast Thailand has been occupie d 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 season ally-arid core of mainland southeast Asia, and is presently dominated by in creasingly saline soils, low-productivity rice cultivation and regrowth sem i-arid scrub. However, the archaeological evidence for this region indicate s a highly-productive natural environment within the last two millennia. Po llen sequences from the infill of Iron Age features provide the first palyn ological evidence for this part of northeast Thailand, detailing Late Holoc ene 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 ge neral progress of landscape change is evident, local compositional differen ces are also clear. Although the region's archaeological and, especially, g eomorphological evidence suggests significant climatic change during this p eriod, 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 a re 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 Elsevi er Science B.V. All rights reserved.