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Alternative models exist for the movement of large urban populations following the 15th-century CE abandonment of Angkor, Cambodia. One model emphasizes an urban diaspora following the implosion of state control in the capital related, in part, to hydroclimatic variability. An alternative model suggests a more complex picture and a gradual rather than catastrophic demographic movement. No decisive empirical data exist to distinguish between these two competing models. Here we show that the intensity of land use within the economic and administrative core of the city began to decline more than one century before the Ayutthayan invasion that conventionally marks the end of the Angkor Period. Using paleobotanical and stratigraphic data derived from radiometrically dated sediment cores extracted from the 12th-century walled city of Angkor Thom, we show that indicia for burning, forest disturbance, and soil erosion all decline as early as the first decades of the 14th century CE, and that the moat of Angkor Thom was no longer being maintained by the end of the 14th century. These data indicate a protracted decline in occupation within the economic and administrative core of the city, rather than an abrupt demographic collapse, suggesting the focus of power began to shift to urban centers outside of the capital during the 14th century.

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Throughout the Angkor period (9th to 15th centuries CE), the Khmer kingdom maintained a series of interconnected cities and smaller settlements across its territory on mainland Southeast Asia. One such city was Koh Ker, which for a brief period in the 10th century CE even served as a royal capital. The complexity of the political landscape meant the Khmer kings and the elite were particularly mobile through the Angkor period, and rupture in royal houses was common. However, while the historical record chronicles the 10th century migration of the royal seat from Koh Ker back to Angkor, the fate of Koh Ker’s domestic population has remained unknown. In this article, we reconstruct the settlement history of Koh Ker, using palaeoecological and geoarchaeological techniques, and show that human activity and land use persisted in the city for several centuries beyond the city’s abandonment by the royal court. These results highlight the utility of multi-proxy environmental reconstructions of Khmer urban settlements for re-evaluating prevailing assumptions regarding the use and occupation of Angkor-period cities.

Aim: To assess the relative roles of long-term (millennial-scale) climatic change, fire and volcanic disturbance on the dynamics of Araucaria-Nothofagus forests of southcentral Chile. Through this analysis, we provide insight into how these iconic ecosystems may respond to future ash-fall events under anticipated changes to climate and burning regimes. Location: Lago Cilantro is a small lake located in south-central Chile (38°51′36.72 S, 71°17′14.52 W, 1,400 m asl), proximal to several active volcanos within the Southern Volcanic Zone of the Andes Mountain range. Taxon: Araucaria araucana (Araucariaceae); Nothofagus spp. (Nothofagaceae). Methods: We developed a continuous 8,700-year long pollen and charcoal record from Lago Cilantro. We compared these results with proxies of regional climatic change and used a combination of principal component analysis and superposed epoch analysis to test the relationship between tephra deposition and pollen composition. Results: We detect a shift in dominance from Araucaria araucana to Nothofagus species between ~8.7 and ~5.5 ka (ka = 1,000 years before present-1950 CE), in concert with increasing regional precipitation and decreasing local-scale fire activity. A reversal in this trend occurred after ~4 ka, contemporaneous with a reduction in regional precipitation. Centennial-scale increases in Araucaria araucana from ~0.2 to 0.9 ka, ~5.2 to 4.2 ka and ~8.6 to 7 ka are associated with reductions in fire return intervals. We found 24 tephra layers in this record; tephra >2 cm thickness are associated with short-term (<100 year) compositional shifts in the pollen spectra, while a single large (255 cm) tephra at ~3 ka is associated with a substantial reduction in Nothofagus and no change in Araucaria. Main Conclusions: Climate change drove millennial-scale shifts in Araucaria-Nothofagus forests and fire regimes near Lago Cilantro. A shortening of the fire return interval is associated with an increase in the importance of Araucaria, supporting the notion that recurrent fires are required to allow this tree species to compete with