William Nanavati

Portland State University

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Cathy Whitlock

Montana State University

Virginia Iglesias

University of Colorado Boulder

María Eugenia de Porras

Centro Científico Tecnológico - Mendoza

Oliver Huaman Oros

Ministry of Culture

Eric C. Grimm

Illinois State Museum

Benjamin Poulter

Goddard Space Flight Center

Kevin Lane

University of Cambridge

Jed O. Kaplan

University of Calgary

Adolfo Gil

Consejo Nacional de Investigaciones Científicas y Técnicas

Ayodele Gilbert Ogunkoya

Montana State University

Cooperative Institutions

Consejo Nacional de Investigaciones Científicas y Técnicas

Montana State University

Montana Institute on Ecosystems

University of Cambridge

Centro Científico Tecnológico - Mendoza

National University of Mar del Plata

National University of Comahue

University of Colorado Boulder

Graves Gilbert Clinic

University of Wisconsin–Madison

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A Holocene history of monkey puzzle tree (pehuén) in northernmost Patagonia

Journal of Biogeography (2020)

William Nanavati Cathy Whitlock Valeria Outes Gustavo Villarosa

Abstract 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.

Araucaria

Nothofagus

Podocarpus

Fire regime

Shrubland

10.1111/jbi.14041

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Citations (9)

Humans, fire, and ecology in the southern Missouri Ozarks, USA

The Holocene (2019)

William Nanavati Eric C. Grimm

A multiproxy study from Sweeton Pond, Ozark County, Missouri, USA, provides a high-resolution 1900-year-long history of vegetation and fire in the southern Missouri Ozarks, where the modern vegetation is oak-hickory ( Quercus-Carya) forest. Pollen and charcoal data are compared with dendroecological data to assess how climate and fire shaped local vegetation history. Land use, particularly by the Osage tribe of Native Americans, is assessed from historical and archaeological records. Three cultural periods are superimposed on the paleoenvironmental history: (1) The Pre-Osage period, ending ~1500 CE, was characterized by open oak-hickory forest and frequent low-severity fires, suggesting interannual climate variability as a driver of vegetation and fire occurrence. At ~1360 CE, mesic tree species began to expand, while fire frequency remained low. (2) The Osage period (~1500–1820 CE) was characterized by the continued expansion of mesic, fire-sensitive species, especially elm ( Ulmus), in conjunction with cool, effectively wet conditions in the southern Missouri Ozarks. Despite climate conditions less favorable for fire, Osage expansion in the region was accompanied by increased fire and fire-dependent shortleaf pine ( Pinus echinata). The expansion of both fire-sensitive and fire-dependent taxa coincident with Osage occupation suggests that anthropogenic fire and land use was local in nature and increased landscape heterogeneity prior to Euro-American settlement. (3) The Euro-American period (since ~1820 CE) was characterized by increased disturbance pollen types (e.g. Ambrosia-type) at the expense of shortleaf pine pollen, resulting from increased settlement size and extensive agricultural and logging activities. During this period, forest clearance led to fuel fragmentation, reducing fire activity; after 1920 CE, fire was actively suppressed.

Fire regime

Fire ecology

10.1177/0959683619875807

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Citations (9)

Disentangling the last 1,000 years of human–environment interactions along the eastern side of the southern Andes (34–52°S lat.)

Proceedings of the National Academy of Sciences (2022)

William Nanavati Cathy Whitlock María Eugenia de Porras Adolfo Gil Diego Navarro

Significance Understanding how people have shaped landscapes requires detailed information on past changes in climate, vegetation, fire, and land use. The environmental and human history of four sites along the eastern Andes of southern South America (34–52°S) shows the changing influence of people and climate on landscape development over the last millennia. Initially, burning by hunter-gatherers and climate variability shaped forest, shrubland, and grassland mosaics. Widespread alteration of fire regimes and vegetation ∼400 y ago is attributed to increased Native American pastoralism prior to extensive Euro-American settlement. Late-19th century ranching and logging led to broadscale changes in fire activity and vegetation across the region. These high-resolution, landscape-scale reconstructions reveal complex human–environment interactions that are often overlooked in regional-to-global syntheses.

Shrubland

Pastoralism

Fire regime

10.1073/pnas.2119813119

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Citations (13)

Drivers of recent forest cover change in southern South America are linked to climate and CO2

Landscape Ecology (2021)

Ayodele Gilbert Ogunkoya Jed O. Kaplan Cathy Whitlock William Nanavati David W. Roberts

Land Cover

10.1007/s10980-021-01330-7

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Citations (2)

Testing soil fertility of Prehispanic terraces at Viejo Sangayaico in the upper Ica catchment of south-central highland Peru

CATENA (2016)

William Nanavati Charles French Kevin Lane Oliver Huaman Oros David Beresford‐Jones

Terrace (agriculture)

Topsoil

Soil texture

Colluvium

10.1016/j.catena.2016.03.007

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Citations (14)

ERIC AS A MENTOR: LESSONS LEARNED FROM THE PALEOECOLOGICAL RECONSTRUCTION OF SWEETON POND, OZARK COUNTY, MISSOURI

Abstracts with programs - Geological Society of America (2021)

William Nanavati Pietra Mueller

10.1130/abs/2021am-366373

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Postglacial vegetation, fire, and climate history along the eastern Andes, Argentina and Chile (lat. 41–55°S)

Quaternary Science Reviews (2019)

William Nanavati Cathy Whitlock Virginia Iglesias María Eugenia de Porras

Nothofagus

Steppe

Charcoal

Fire regime

Westerlies

10.1016/j.quascirev.2019.01.014

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Citations (33)

Interpreting modern and fossil pollen data along a steep environmental gradient in northern Patagonia

The Holocene (2016)

Virginia Iglesias Flavia Quintana William Nanavati Cathy Whitlock

Vegetation reconstructions rest on modern vegetation–pollen rain relationships and deductive reasoning. Establishing this relationship is a nontrivial task because differences among pollen assemblages are not necessarily proportional to differences in vegetation. This task is particularly challenging in Patagonia, where some tree taxa have indistinguishable pollen, and pollen grains can be transported long distances. In this study, we describe the modern pollen of 48 lake and wetland samples from northern Patagonia (40.5–44°S) to better discriminate the major vegetation zones of the region through pollen analysis. Specifically, we focus on the performance of three methodological approaches, namely, pollen indicators, classification trees, and optimal thresholds of dissimilarity. As a proof of concept, we use the modern pollen–vegetation relationships to reconstruct the vegetation history at Laguna el Trébol (41.07°S; 71.5°W). Our results revealed that (1) pollen sums exceeding 260 grains ensured replicable vegetation reconstructions, (2) modern vegetation zones could not be separated solely by visual inspection of their pollen spectra, (3) the classification tree and optimal thresholds of dissimilarity permitted discrimination of most vegetation zones, (4) detection of nonanalog communities required use of pollen indicators or optimal thresholds of dissimilarity, and (5) vegetation at L. el Trébol was likely dominated by late glacial shrubland with no modern analogs in the study area (15,000–12,180 cal. yr BP), modern shrubland (12,180–6500 cal. yr BP) and mixed forest (6500 cal. yr BP–present). This study allows a more realistic understanding of the pollen–vegetation relationship and provides new tools for interpreting past vegetation in northern Patagonia.

Shrubland

Vegetation Classification

10.1177/0959683616678467

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Citations (26)