Browsing by Author "Moreno, Patricio, I"

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    Fires and rates of change in the temperate rainforests of northwestern Patagonia since-18 ka
    (2023) Moreno, Patricio, I; Mendez, Cesar; Henriquez, Carla A.; Fercovic, Emilia, I; Videla, Javiera; Reyes, Omar; Villacis, Leonardo A.; Villa-Martinez, Rodrigo; Alloway, Brent, V
    We examine the temporal and spatial structure of wildfires and rates of vegetation change in the Pacific sector of northwestern Patagonia (40 degrees-44 degrees S) over the last-18,000 years. Macroscopic Charcoal Accu-mulation Rates (CHAR), a proxy of past local fires, shows a geographic variation that mirrors the modern north-to-south and low-to-high elevation increase in annual precipitation and decrease in precipitation seasonality, and the frequency of explosive volcanic events. Variability in past fires is evident at multiple timescales, with a significant multi-millennial low between-18-13.1 ka, an abrupt rise between-13.1 -12.5 ka, and heightened fire activity between-11.4-8.2 ka with significant high values between-10 -9.4 ka. A subsequent decline led to the lowest Holocene values between-6-5.4 ka, which rose and led to significant high values between-3.1 ka and the present. Andean and Western Upwind Environments share a multi-millennial structure of fire activity since-18 ka, overprinted by millennial and centennial -scale divergences. These differences underscore the role of explosive volcanism as a trigger or modulator of fire activity in the vicinity of Andean eruptive centers. We posit that fire activity in Western Upwind Environments was driven primarily by hydroclimate variations, namely changes in the intensity of the Southern Westerly Winds. Compilations of CHAR and the Rates of Change (ROC) parameter, a measure of the magnitude and rapidity of changes in the pollen records, covary during the onset of the interglacial fire regime at-13.1 ka and the last-4000 years, suggesting that fires catalyzed vegetation changes during specific intervals since the last glaciation. Highly mobile human occupations deployed along the coasts started at-6.2 ka, increased in pulses, and spread widely during the last two millennia. Covariation with CHAR and ROC since-4 ka suggests that hunter-gatherer -fishers contributed to enhanced fire activity and abrupt vegetation changes at regional scale. The ubiquitous fire maximum over the last four cen-turies relates to widespread settlement and associated large-scale land clearance conducted by Euro-pean/Chilean settlers.(c) 2022 Elsevier Ltd. All rights reserved.
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    Glacial geomorphology of the central and southern Chilotan Archipelago (42.2 degrees S-43.5 degrees S), northwestern Patagonia
    (TAYLOR & FRANCIS LTD, 2022) Soteres, Rodrigo L.; Sagredo, Esteban A.; Moreno, Patricio, I; Lowell, Thomas, V; Alloway, Brent, V
    We present a geomorphic map of the glacial landforms associated with the Golfo Corcovado ice lobe in northwestern Patagonia. Built upon prior studies, our map elaborates on the central and southern sectors of Isla Grande de Chiloe and neighboring islands. Through a combination of remote sensing techniques and exhaustive fieldwork, we identified a suite of ice-marginal, subglacial, and glaciofluvial features created by the Golfo Corcovado ice lobe during four maxima within the last glacial cycle, in none of which the ice-front reached the Pacific coast of Isla Grande de Chiloe. Our mapping builds a foundation and provides insights for future interdisciplinary research on the Late Quaternary sequence of glacial and paleoclimatic events in this key sector of northwestern Patagonia.
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    The role of climate and disturbance regimes upon temperate rainforests during the Holocene: A stratigraphic perspective from Lago Fonk (-40 degrees S), northwestern Patagonia
    (PERGAMON-ELSEVIER SCIENCE LTD, 2021) Henriquez, Carla A.; Moreno, Patricio, I; Lambert, Fabrice; Alloway, Brent, V
    Climate and disturbance regimes play key roles in shaping the structure, composition and functioning of terrestrial ecosystems. Despite this importance, very few stratigraphic studies in the temperate rainforests from northwestern Patagonia have explored this relationship in detail along a time continuum through the entire Holocene. Here we present a high-resolution fossil pollen and charcoal record from Lago Fonk (median resolution: 20 years), a small closed-basin lake in the lowlands of the Chilean Lake District (41 degrees S), where wildfires and explosive volcanism have intermittently taken place during the Holocene, along with pronounced human-induced disturbance in post-colonial time. Our results show persistence of temperate rainforest throughout the Holocene, with changes in the composition and structure of Valdivian rainforests (VRF) at millennial timescales. We detect centennial-scale alternations in dominance between the VRF tree Eucryphia/Caldcluvia and generalist trees found in VRF and North Patagonian rainforests after-6.5 cal ka BP. Intervals dominated by VRF coincide with enhanced fire occurrence signaling negative hydroclimate anomalies with a mean duration of-150 years, which alternate with positive hydroclimate anomalies lasting-312 years on average. Our results suggest that the magnitude and rapidity of vegetation changes detected at 10.2-9.9, 4.0-3.0,-1.0, and-0.7 cal ka BP were amplified by disturbance regimes, and led to the establishment and maintenance of Eucryphia/Caldcluvia-dominated forests in the Longitudinal Valley of the Chilean Lake District. On several occasions the higher incidence of fire disturbance during warm/dry climate intervals coincided with episodes of heightened explosive volcanic activity from multiple eruptive centers within the Southern Andean Volcanic Zone. (c) 2021 Elsevier Ltd. All rights reserved.