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Soil phytoliths as indicators of initial human impact on San Cristóbal Island, Galápagos

Abstract:

I analyzed phytoliths from soil profiles on San Cristóbal Island in the Galápagos Islands to determine whether historical human impact and recent vegetation dynamics are visible in the phytolith record. I extracted phytoliths from soil samples taken from four test pits located at the village, an abandoned field, a forest, and an active agricultural field - all located within the former El Progreso plantation (AD 1860–1920). Changes in the ratio of tree to grass phytoliths with depth in all four samples suggest changes in vegetation composition from forest to open vegetation dominated by grasses, which reflects the removal of forest with colonization and the first permanent human occupation of the archipelago in the middle 19th century. This paper shows that the changes in vegetation brought about by colonization and land clearing for plantations are documented in the soil phytoliths record, and suggests that phytoliths can be used as an indicator of past vegetation change in future work on the historical ecology of the Galápagos archipelago.