Fire regimes in north-eastern Cambodian monsoonal forests, with a 9300-year sediment charcoal record
To provide insights concerning changes in fire regime in north-eastern Cambodia over the course of the Holocene, and discuss implications of these long-term data for fire management in the present day. Location
Southern Ratanakiri Province, north-eastern Cambodia. The lake sites sampled here are embedded in a mosaic of mostly open, strongly deciduous dipterocarp forest, with patches of riparian, semi-evergreen and evergreen forests. Methods
Background information on the environmental and cultural setting comes from informal and semi-structured interviews of local villagers to determine present-day burning patterns and customs. Primary data come from analysis of changes in charcoal concentration within sediments from small, closed basin lakes. Charcoal data are compared with changes in pollen and sediment physical characteristics, and to present-day local customs, to infer or speculate on changes in human use of fire. Results
Interviews with local people reveal two general types of human-induced fires, one type for swidden cultivation in denser forests, the other type for clearance of ground layer vegetation in more open forests. A 9300-year sediment record of microscopic charcoal deposition shows strongest fire activity ending by 8000 years ago, and the remainder of the early Holocene reflecting a strong summer monsoon and low fire activity. Beginning c. 5500 years ago, forest disturbance and fire activity increased. A subtle change in the record at c. 3500 years ago and more marked change at c. 2500 years ago suggest that fire frequency, and maybe human control over fire, became more important during that period and continuing up to the present. Main conclusions
With this type of empirical data from only one site, it is impossible to make accurate conclusions about long-term human impacts from burning. However, this record does show that present-day charcoal input from fire activity is among the lowest for the last 9300 years. Considered together with other changes in the record and with present-day customs, there is a suggestion that anthropogenic fire is an adaptation to the monsoonal environment, and may be conservative of forest cover in open forest formations. This long-term perspective on the role of indigenous land-use customs in landscape evolution should be considered in forest management and biological conservation, as it differs significantly from the traditional rationale for policies of fire suppression in tropical forests.