Fire, Forest, Ice, and Fungi: Exploring The Mesh Of Relationships Driving Seedling Regeneration In The Siberian Arctic

Date of Award

2020

Degree Name

M.S. in Biology

Department

Department of Biology

Advisor/Chair

Advisor: Ryan W. McEwan

Abstract

Arctic warming may influence the global climate system by altering of ecological processes that preserve vast quantities of carbon stored in permafrost. Thirty-two percent of global forest carbon stock is stored in boreal forests, and a majority of this carbon is found in Russian forests. Boreal forests of the Siberian Arctic are dominated by monospecific stands of Larix cajanderii that grow on permafrost and may sequester up to 35% of the carbon stored in Russian boreal forests. Due to the spatial extent of its range, the single-species nature of this forest, and permafrost underlying these forests, Larix cajanderii is a crucial component of the Siberian Arctic carbon sink and may be a key regulator of global climate. This boreal tree species is symbiotic with ectomycorrhizal fungi, which are critical to their growth. Post fire recruitment density of L. cajanderii varies widely, and may be impacted by surrounding vegetation and fungal communities. In this study, I investigate factors affecting ectomycorrhizal fungal (EMF) colonization of roots of L. cajanderii in plots representing a gradient of seedling density after fire in northeast Siberia. In nine burn scars among upland or lowland landscape positions, I measured soil characteristics, seedling metrics, and surrounding EMF inoculum sources to examine the influence these factors have on EMF colonization of tree seedling roots. To determine the effect of EMF colonization on larch seedlings, I quantified percentage of fine root length colonized by EMF for 110 harvested recruits across density treatments. Seedling density treatments of none, moderate and high were observed and a control treatment located in the adjacent unburned stand. EMF were present on nearly all samples collected for analysis. I found that there is a positive relationship between EMF colonization and fresh seasonal growth of recruited seedlings. Together these results demonstrate that EMF may be essential to seedling success. Site topography influenced EMF colonization rates, and an inverse relationship between soil organic layer (SOL) depth and EMF colonization appeared. From the environmental variables sampled, no trend emerged associating certain habitat characteristics with seedling density, and there was no detectable variation in colonization rates across density treatments. A Principle Components Analysis revealed little difference in SOL depth, thaw depth, canopy openness, moisture, or temperature between density treatments, but between upland and lowland sites a higher degree of separation appeared in regards to these abiotic factors. Surprisingly, proximity and species of nearby EMF host plants influenced the colonization on seedling root systems and may indicate post-fire sources of inoculum for L. cajanderii seedlings. This study showed that EMF have increased colonization in shallow SOL depths and in upland habitats. Climate warming affects ecosystem characteristics, potentially influencing post-fire EMF inoculum potential. Understanding the ectomycorrhizal fungal colonization on L. cajanderii roots in post-fire habitats will provide insight into the potential resilience of Larix forests. Ultimately, this knowledge of the intricacies of vegetation responses to the increasing local disturbance and regional temperature increase may help identify the vulnerability of the ecosystem in the face of climate change.

Keywords

Biology, Climate Change, Forestry, Forestry, Arctic, Ectomycorrhizal fungi, Forest Regeneration

Rights Statement

Copyright © 2020, author

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