Wildfire, ecosystem, and climate interactions in the Early Triassic

Area of Science:

• Paleoclimatology
• Geochemistry
• Earth System Science

Background:

• Wildfires significantly impact Earth's carbon cycling and understanding past fire dynamics is crucial for predicting future climate change.
• The Early Triassic (Smithian and Spathian epochs, ~250 million years ago) is poorly understood regarding fire activity, despite significant carbon cycle perturbations, climate shifts, and biotic events.

Purpose of the Study:

• To reconstruct Early Triassic wildfire dynamics using geochemical fire indicators.
• To investigate the environmental conditions and biomass sources associated with increased wildfire activity during this period.

Main Methods:

• Analysis of polyaromatic hydrocarbons (PAHs) in Spitsbergen shales as organic geochemical fire indicators.
• Examination of diagnostic PAH ratios to infer the origin of combustion products (biomass vs. soil erosion, petrogenic carbon, or coal).

Main Results:

• A notable increase in PAH abundance was observed in shales immediately following the Smithian-Spathian boundary.
• PAH ratios indicated that the combustion products originated primarily from unaltered biomass, not soil erosion or coal combustion linked to Siberian Traps volcanism.
• Wildfire activity increased as temperatures declined in the late Smithian, coinciding with less intense hydrological conditions and vegetation changes favoring fire.

Conclusions:

• The study provides evidence for increased wildfire activity during the Early Triassic, linked to specific climatic and vegetation shifts.
• These changing wildfire regimes likely influenced biogeochemical cycles and long-term carbon sequestration.
• Understanding past wildfire-climate-vegetation interactions offers insights into potential consequences of future climate change.