Investigating the Effects of Permafrost Thaw on Fungal Communities from Subarctic Soil

• Main Author: Hernandez, Serena N.
• Other Authors: Mackelprang, Rachel, Bermudes, David, Guerra Amorim, Carlos
• Format: Master Thesis
• Language: unknown
• Published: California State University, Northridge 2024
• Subjects: Dissertations; Academic > CSUN > Biology; Transplant; Active Layer; microbiology; in situ; permafrost; ITS2 sequencing; fungi; Holocene; Pleistocene; permafrost thaw; Kya; Subarctic
• Online Access: https://hdl.handle.net/20.500.12680/rb68xk876

Permafrost, perennially frozen ground at Earth's polar regions, underlies a large portion of Earth's surface and is thawing due to climate change. As global temperatures increase, millennia-old carbon that was previously trapped by frozen temperatures becomes available for microbial metabolism. These microorganisms metabolize carbon and release CO2 and CH4 into the atmosphere, creating a positive feedback loop that increases the release of greenhouse gases into the atmosphere. In temperate soils, fungi play a critical role in carbon cycling as decomposers. However, little is known about them in thawing permafrost because nearly all research has focused on bacteria and archaea. Given their importance in other soils, fungi are likely key contributors to carbon turnover during permafrost thaw, making them a crucial unknown in the climate change equation. To identify fungal response to permafrost thaw, the Mackelprang lab simulated thaw by transplanting Holocene (~5 kya) and Pleistocene (~40 kya) permafrost samples into the active layer (soil which overlies permafrost and experiences annual freeze-thaw cycles) and retrieved samples at two-week and two-month time points. Here we show that fungal communities respond to thaw after short thaw durations, and that fungal taxa from the active layer are significantly different than taxa from permafrost. Observing changes in fungal community structure and their response to warming can tip the balance between soils being a carbon source versus carbon sink. Understanding these effects may be important to predicting the ultimate consequences of permafrost thaw to climate change.