Browsing by Author "Nanavati, William"

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A Holocene history of monkey puzzle tree (pehuén) in northernmost Patagonia
(Wiley, 2020-12) Nanavati, William; Whitlock, Cathy; Outes, Valeria; Villarosa, Gustavo
Aim Although it is established that climate and fire have greatly influenced the long-term ecosystem dynamics of Patagonia south of 40°S, the environmental history from northernmost Patagonia (37–40°S), where endemic and endangered monkey puzzle tree (Araucaria araucana) occurs, is poorly known. Here we ask: (a) What is the Holocene vegetation and fire history at the north-eastern extent of A. araucana forest? (b) How have climate and humans influenced the past distribution of A. araucana? Location Northernmost Patagonia, Argentina and Chile (37–40°S). Taxa Araucaria araucana, Nothofagus, Poaceae. Methods Sedimentary pollen and charcoal from Laguna Portezuelo (37.9°S, 71.0°W; 1,730 m; 11,100 BP) were evaluated using statistical methods and compared with other palaeoecological, independent palaeoclimate, and historical records to assess how changes in climate and land use influenced local-to-regional environmental history. Results An open forest-steppe landscape persisted at L. Portezuelo throughout the Holocene with generally low-to-moderate fire activity. Increased Nothofagus pollen after ~6,590 BP suggests increases in shrubland and moisture in association with cooler conditions and greater seasonality and ENSO activity. Araucaria pollen appeared at L. Portezuelo at ~6,380 BP, but was low in abundance until ~370 BP, when it rose with charcoal levels. This increase in Araucaria and fire coincided with a regional influx of Mapuche American Indians. Nothofagus deforestation and Pinus silviculture marked Euro-American settlement beginning in the 19–20th century. Main conclusions (a) Rapid postglacial warming and drying limited the distribution of Araucaria in the central valley of Chile. In the middle and late Holocene, decreased temperatures and greater seasonality and ENSO activity increased precipitation variability allowing Araucaria expansion at its north-eastern limit. (b) Greater abundance of Araucaria and heightened fire activity at L. Portezuelo after 370 BP coincided with increased Mapuche-Pehuenche American Indian land use, suggesting that Araucaria may have been managed in a human-altered landscape.
Testing soil fertility of Prehispanic terraces at Viejo Sangayaico in the upper Ica catchment of south-central highland Peru
(Elsevier, 2016-07) Nanavati, William; French, Charles; Lane, Kevin; Huaman Oros, Oliver; Beresford-Jones, David
This study presents a pilot geoarchaeological investigation of terraced agricultural systems near San Francisco de Sangayaico, in the upper Ica catchment of the Southern Peruvian Andes. It aims to assess the evidence for soil fertility associated with agricultural strategies practised throughout the Prehispanic, Spanish colonial and modern occupations in this region. A series of twenty-two test pits were hand excavated through two terraced field systems, and sampled to examine the changes in soil physical and chemical characteristics down-profile and downslope. This study provides the first geoarchaeological analyses of the agrarian soil system surrounding Viejo Sangayaico in the upper Ica catchment. Results demonstrate that the soil system was much modified prior to the creation of the terrace systems, probably about 900 years ago. This system was characterised by a weakly acidic to slightly calcareous pH, a consistent but low electrical conductivity, reasonable-but-variable phosphorus content, and a loamy soil texture with a component of weathered volcanic tonalite parent material. The shallow terrace soil build-up on the slopes investigated indicates that slope modification was as minimal as possible. Moreover, the relatively low frequencies of organic material and phosphorus suggest that the terraces were not heavily fertilised in the past, making the stability and management of the nutrient-rich topsoil vital. The results of these excavations and soil fertility analyses are situated within the context of the wider Andean ethno-historic and the archaeological record to address questions regarding how the terraces were built and maintained over time. Agricultural terraces undoubtedly mitigated the effects of slope erosion associated with cultivation. But, the terrace soil features observed at Sangayaico do not appear to be the same as those documented in other geoarchaeological studies of Andean terrace systems. These contrasts may be accounted for by a combination of differing geological substrate and hydrological conditions, as well as variable trajectories in past soil development, erosion factors, manuring/field management practises and crop selection.