First Advisor

Andres Holz

Term of Graduation

January 2023

Date of Publication

1-1-2023

Document Type

Dissertation

Language

English

Subjects

Araucaria-Nothofagus forests, Fire ecology

Physical Description

1 online resource ( pages)

Abstract

Fire regime shifts due to climate and land use changes are threatening ecosystems worldwide, affecting their capacity to recover after severe wildfires. Increase of fire frequency, severity and intensity may severely affect forest ecosystems whose fire regimes have been characterized by infrequent stand-replacing fires. The temperate forests of southern South America, specifically the Andean temperate forests dominated by the conifer Araucaria araucana and the angiosperm species from Nothofagus genus, have evolved with less fire pressure, where severe wildfires may happen after decades or centuries. Recent severe and short-interval fires exacerbated by warmer and drier climate conditions have affected these forests, threatening the ecosystem’s resilience to cope with the effects of wildfires. The study of this dissertation is conducted in two study areas affected by a single fire (2015) and by short-interval fires (2002 and 2015) in the Andean region of south-central Chile. The three chapters of this dissertation elucidate the post-fire responses of understory communities of forests dominated by A. araucana and Nothofagus species, examines post-fire structure and regeneration patterns of the main tree species, and explores drivers of tree mortality and burn severity on these forests. In the first chapter, I found that burn severity drives the post-fire composition of the understory, where resprouter species are favored by the effects of severe and short-interval fires. In the second chapter, I found that severe and short-interval fires change forest structure patterns, as well as seedling establishment is importantly reduced (e.g., A. araucana) or totally absent (e.g., Nothofagus spp.) in areas affected with high burn severity and reburns, but particularly one tree species (i.e., N. alpina) can profusely resprout in reburned areas. Finally, in the third chapter I found that tree attributes distinctly affected the probability of mortality according to species trait groups, while the main driver of burn severity was the topographic settings given by the aspect, which had different effect on the single fire and reburns. The results from these chapters provide insightful information about how fire sensitive ecosystems respond to severe and short-interval wildfires, which was unknown for forests dominated by A. araucana and Nothofagus species in the western side of the Andes in south-central Chile.

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