Using ALLADYNS (Argentinean Lake region Landscape DYNamics Simulator) to unravel climate vegetation-human influences on fire regimes in northern Patagonia

KITZBERGER, T.; TIRIBELLI, F.; GOWDA, J.H.; MERMOZ, M.; MORALES, J.M.

Bozeman, Montana

Taller; PIRE Workshop: Understanding climate-human-fire interactions at different temporal and spatial scales; 2017

Montana State University

Fire frequency, intensity, and size reflect complex climate?vegetation?human interactions and their evolution through time. Forest/steppe boundaries are among the most dynamic ecosystems on Earth and are highly vulnerable to changes in climate and land use. The north Patagonian forest-steppe ecotone has witnessed during Holocene important changes in human occupation, vegetation and climate impacting on fire regimes. We used a landscape simulation model parameterized for the northern Patagonian landscape (ALLADYNS) to compare pollen/charcoal records extending throughout the Holocene with simulated changes in vegetation and fire run under contrasting scenarios of past climate, ignitions and fire-vegetation feedbacks. We compared three paleorecords: L. El Trébol, L. Padre Laguna and Huala Hue. With landscape simulations performed over southern Nahuel Huapi National Park. Polygons of local pollen/charcoal influence (?pseudocores?) were constructed around each core location based on statistics of wind direction frequency. On each of the pseudocores we recorded annual % area of forest, shrubland, and number of burned pixels. Simulations were run 3000 years with initial conditions present landscapes and 500 years spin up. A scenario mimicking modern ignition regimes was derived from NHNP fire records. Based on tree ring evidence a pre European ignition scenario was set to be 1.6 times higher than modern ignition frequency. Modern climate variability used the modern Bariloche station precipitation record. High/ variability scenarios were set by changing standard deviations of the precipitation distribution by +/- 50% and wetter/dryer scenarios by changing the mean precipitation by +/- 50%. Preliminary results indicate how that charcoal deposition rates are compatible with pre European ignition frequencies rather than modern frequencies. Peaks of high fire activity correlated with increased shrubland dominance in the landscape can be generated without changes climate or ignition regimes. These results underscore the importance of intrinsic vegetation-fire feedbacks that can modulate fire regimes and vegetation dynamics.