A vegetation and fire history of Lake Titicaca since the Last Glacial Maximum

Abstract

Fine-resolution fossil pollen and charcoal analyses reconstruct a vegetation and fire history in the area surrounding Lake Titicaca (3810 m, Peru/Bolivia) since ca. 27,500 cal yr BP (hereafter BP). Time control was based on 26 accelerator mass spectrometer (AMS) radiocarbon dates. Seventeen AMS dates and 155 pollen and charcoal samples between ca. 17,500 BP and ca. 3,100 BP allow a centennial-scale reconstruction of deglacial and early-to mid-Holocene events. Local and regional fire signals were based on the separation of two charcoal size fractions, ≥180 μm and 179-65 μm. Charcoal abundance correlated closely with the proportion of woody taxa present in the pollen spectra. Little or no pollen was detected in the sedimentary record prior to ca. 21,000 BP. Very cold climatic conditions prevailed, with temperatures suggested to be at least 5-8°C cooler than present. Increases in pollen concentration suggest initial warming at ca. 21,000 BP with a more significant transition toward deglaciation ca. 17,700 BP. Between 17,700 BP and 13,700 BP, puna brava is progressively replaced by puna and sub-puna elements. The most significant changes between the Pleistocene and the Holocene floras were largely complete by 13,700 BP, providing an effective onset of near-modern conditions markedly earlier than in other Andean records. Fire first occurs in the catchment at ca. 17,700 BP and becomes progressively more important as fuel loads increase. No evidence is found of a rapid cooling and warming coincident with the Younger Dryas chron. A dry event between ca. 9,000 BP and 3,100 BP, with a peak between 6,000 and 4,000 BP, is inferred from changes in the composition of aquatics, and the marsh community as pollen of Cyperaceae is replaced by Poaceae, Apiaceae, Plantago and the shrub Polylepis. Human disturbance of the landscape is evident in the pollen spectra after ca. 3,100 BP with the appearance of weed species.

Late Archaic–Early Formative period microbotanical evidence for potato at Jiskairumoko in the Titicaca Basin of southern Peru

“…Furthermore, as discussed, the archaeological Solanum starch morphology is consistent with that of cultivated potato. A scenario of Late Archaic cultivation fits well with regional paleoenvironmental data, indicating broad-scale agricultural clearing by ∼2,000 cal y BC and contemporaneous valley-and site-level data pointing to camelid management, sedentarization, and the advent of socioeconomic inequality, discussed above (6,19,21).…”

“…Craig et al (20) concur with Paduano et al (21) that this pattern likely reflects agricultural clearing rather than fires resulting from high aridity and accumulated woody biomass. Together, the archaeological and paleoenvironmental data seem to reflect a dramatic transformation in regional land-use patterns, specifically, the onset of…”

“…Hawkes (55) observes that taxa adapted to cold, high environmentsincluding ancestral S. candolleanum-"have been able to extend much further than those restricted to isolated medium altitude valleys"-hence the progenitor's broad distribution throughout southern Peru/northwestern Bolivia. Botanical and paleoenvironmental data indicate that Jiskairumoko residents would likely have encountered S. candolleanum in their immediate environment, among other weedy, herbaceous plants (3,5,21,36,55,(66)(67)(68)(69). First, Hawkes (55) documents the occurrence of Solanum canasense and Solanum multidissectum (both = S. candolleanum) in the Department of Puno, Peru, where Jiskairumoko is located.…”

“…The site itself is situated upon a gravel knoll; as described by Rigsby et al (72) in their documentation of the Ilave Valley's fluvial history, the knoll is a remnant of an ancient river terrace, one of five created as a result of rising and falling lake levels associated with regional paleaoclimatic shifts. The terrace upon which Jiskairumoko sits (T5) was created circa 18,000 cal y BP; a nearby lower terrace (T2) was created more recently, ∼2,300 cal y BC (21,(72)(73)(74). At the time of Jiskairumoko's occupation, T2 would have been found within the river floodplain and subject to frequent inundation and aggradation resulting from then-current high rainfall and lake levels.…”

A continuous record of fire covering the last 10,500 calendar years from southern Sweden — The role of climate and human activities

“…Long et al, 1998;Carcaillet and Richard, 2000;Millspaugh et al, 2000;Paduano et al, 2003;Marlon et al, 2006;Whitlock et al, 2007) and Australia (e.g. Black and Mooney, 2006).…”