Plant neighbor has stronger influence on pinyon pine ectomycorrhizal fungi than soil history of fire

Trimber, Gillian Margaret (2023) Plant neighbor has stronger influence on pinyon pine ectomycorrhizal fungi than soil history of fire. Masters thesis, Northern Arizona University.

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Abstract

Mycorrhizal fungi have the ability to improve plant responses to stressors such as heat and drought and may play a critical role in seedling establishment in semi-arid landscapes. Wildfire and the introduction of novel species have been shown to change mycorrhizal fungal communities, including in the long-term. As wildfire frequency and severity increases across the Southwest due to climate change, the recovery of pinyon pine (Pinus edulis) and juniper (Juniperus osteosperma) woodland ecosystems and their fungal communities following disturbance is becoming increasingly uncertain. We sought to understand the interactions between soil history of wildfire, introduced grasses, and pinyon pine mycorrhizae using a plant neighbor greenhouse experiment. Pinyon seedlings were grown in soils collected at Mesa Verde National Park from areas that burned in a stand-replacing fire in 2002 or in soils from adjacent intact woodlands. Each pinyon was grown in the same pot as an invasive grass (cheatgrass, Bromus tectorum), a native grass (western wheatgrass, Pascopyrum smithii) or another pinyon seedling. We measured mycorrhizal abundance and fungal community composition, as well as metrics of plant performance, including biomass and plant water stress. Our results show that even twenty years after fire, ectomycorrhizal community composition differs from that of intact pinyon-juniper woodlands, and that fire history and plant neighbor interact to affect fungal abundance. Importantly, the presence of either invasive or native grasses had a stronger negative effect on pinyon mycorrhizae than burning, resulting in an average 38% drop in colonization and an altered community. Seedling water stress, however, was controlled by soil fire history, despite controlling for other environmental conditions. This work has the potential to inform post-fire management strategies and suggests that interactions among plant species, long-term effects of fire on soil, and mycorrhizal fungi may help determine the trajectory of recovery in western ecosystems following disturbance.

Item Type:	Thesis (Masters)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	cheatgrass; fire; invasive species; mycorrhizae; pinyon pine; plant-soil interactions; Mesa Verde National Park
Subjects:	Q Science > QK Botany
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > Biological Sciences
Date Deposited:	20 Oct 2025 21:36
Last Modified:	20 Oct 2025 21:36
URI:	https://openknowledge.nau.edu/id/eprint/6225

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