Multi-Proxy Studies of Holocene Environmental Change in the Páramos of Central and South America

Páramos are montane tropical grasslands found from Central America to the northern Andes. This dissertation contributes to conversations about ancient human-environment interactions in neotropical páramos through a multi-proxy approach to paleolimnology, the study of environmental records in lake sediments. Specifically, this work develops and interprets records of macroscopic charcoal, non-pollen palynomorphs (NPPs), bulk stable isotopes, and ancient sedimentary DNA from Costa Rica and Ecuador to investigate environmental changes in páramos since the Late Pleistocene.

Laguna Culebrillas (2.4232 °S, 78.8603 °W; 3900 m a.s.l.) is a glacial lake on the Eastern Cordillera of the Ecuadorian Andes. Two studies were conducted on sediments from Laguna Culebrillas to investigate human-landscape interactions in the surrounding páramo. In the first, records for macroscopic charcoal, bulk stable isotopes, and pollen were developed for the late glacial and Holocene. Results suggest that humans have burned the páramo since at least the middle Holocene (ca. 6200 cal yr BP), and likely long before then.

The second study from Laguna Culebrillas explored plants and livestock between ca. 1770 and 4420 cal yr BP through ancient sedimentary DNA. The results establish the presence of authentic plant sedaDNA in the core. This research also suggests that camelid livestock may have been kept in the páramo in the past, but more work is needed to confirm this interpretation.

Lago de las Morrenas 1 (LM1; 9.4925 ºN, 83.4848 ºW; 3480 m a.s.l.) is a glacial lake in a cirque on the north slope of Cerro Chirripó in the Cordillera de Talamanca of Costa Rica. Exploratory research on NPPs was conducted on the LM1 sediments, with a focus on how fungal spore assemblages changed through time. To investigate how NPPs have responded to changes in the environment, NPP data were compared with existing records of microscopic charcoal, pollen, and geochemistry using a multivariate statistical approach. The results show that Arthrinium conidiospores are indicative of grassland ecosystems and that herbivore activity intensified in the páramo at ca. 7930 cal yr BP.