Long-Term Fire and Vegetation Change at Cocha Cashu Biological Station, Peru

Abstract

Past human influence from the pre-Columbian and colonial periods may have played a role in shaping modern Amazonian vegetation. Here, we assessed past human activities and vegetation change from a well-studied research station in the Peruvian Amazon using charcoal and phytoliths recovered from soil cores. The moderate seasonality has contributed to its high diversity, while its remoteness has generally led to assumptions of minimal past land modification by humans. We asked: (i) Is there evidence of past human influence, including cultivation, forest opening, or plant enrichment/depletion, in the forests around Cocha Cashu Biological Station? and (ii) was there a consistent increase in palm phytolith abundances through time as has been documented in the aseasonal forests of northwestern Amazonia? Only 38 (14%) of the 279 samples analyzed contained charcoal, highlighting the rarity of past fire at Cocha Cashu. The two charcoal fragments large enough for ¹⁴C dating had ages of 570–670 and 1350–1520 calibrated years before present. No cultivar phytoliths were found. Spheroid echinate phytoliths, produced by the palm genera Attalea, and Oenocarpus, and Euterpe, were more abundant in past samples than in modern samples. There was no increase in palm phytolith abundances from the bottom to top of the core, contrasting with recent findings from northwestern Amazonia. Our results support ideas that Cocha Cashu is composed of old growth forests and suggest that gradients of past human activities exist on local and regional scales in western Amazonia.