全球变化知识资源中心

Multi-proxy analysis of a sediment core recovered from Lago Ditkebi in Chirripo National Park, Costa Rica, was undertaken to develop a multi-decadal to sub-centennial-scale reconstruction of Holocene hydroclimate and environmental change for the region. Analyses of sub-fossil chironomid assemblages, macroscopic charcoal, and bulk sediment geochemistry suggest that the glacial highlands in Chirripo National Park experienced notable hydroclimate variability, periodical burning by wildfires and climate-related vegetation change during the last similar to 8100 years. A single chironomid taxon, Procladius, most commonly associated with cold glacial lakes in Costa Rica, dominates the Holocene sub-fossil chironomid assemblage in Lago Ditkebi. Inferred from the proxy records, the interval between similar to 8100 and 5270 cal yr BP at the glacial highlands was relatively cold and dry with low effective moisture and limited fire activity. Cool and dry conditions were also observed between similar to 2820 cal yr BP and present but co-occurred with more frequent, low-severity fires. The highest fire frequency occurred between similar to 3300 and 1600 cal yr BP. The shifts in the chironomid assemblage and the low delta C-13 values detected between similar to 5270 and 2820 cal yr BP suggest a warm and wet climate and a decrease in abundance of Muhlenbergia, a C-4 grass during that time. Concurrent maxima in C/N, charcoal accumulation and the abundance of thermophilous chironomid taxon, Polypedilurn N type, at similar to 5200 cal yr BP are indicative of an abrupt climate change event that was characterized by rapid warming, quickly increased effective moisture and intense wildfires in the glacial highlands of Costa Rica.