Responses of soil microinvertebrates and their ecological functions to forest thinning and prescribed fire in Valles Caldera National Preserve, New Mexico

Gibson, Kara Skye (2022) Responses of soil microinvertebrates and their ecological functions to forest thinning and prescribed fire in Valles Caldera National Preserve, New Mexico. Doctoral thesis, Northern Arizona University.

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Abstract

Most multicellular animals in forests are nematodes, collembolans, and mites living within the soil and litter. Their abundance is staggering: millions of nematodes, and tens to hundreds of thousands of mites and collembolans, usually reside within a square meter of the forest floor. These animals consume a wide range of resources, including fungi, bacteria, plants, and other soil animals. Through their feeding activities, and via their dispersal of microbes, they are important contributors to nutrient cycling, decomposition, and other ecological processes affecting plant performance. However, these key components of soil food webs have been largely neglected in forest restoration research. This dissertation focuses on responses of nematodes, collembolans, and mites to forest restoration activities in New Mexico’s Valles Caldera National Preserve. The first study examines how total abundance of these groups varies in untreated, thinned only, and thinned/burned ponderosa pine forest management units. We report that mites appear to be more sensitive to combined thinning and fire than nematodes or collembolans, and identify easily and inexpensively measured habitat and resource indicators which may aid land managers in assessing treatment implications for soil fauna. In the second study, we subjected volcanic loamy soils in a xeric mixed conifer forest to one, three, or nine passes from a feller buncher (a common type of tree harvester) to assess how disturbance from heavy logging machinery affects soil physical properties and nematode communities, with the aim of determining thresholds for negative impacts. We found that substantial compaction occurred after a single pass, affecting soil to a depth of at least 23-27 cm. Nematode communities, however, appeared relatively resistant to disturbance: impacts on sensitive nematode taxa were apparent only after nine passes. Finally, in the third study, a field mesocosm experiment, we investigated the functional implications of faunal community shifts that occur with forest restoration treatments. Our manipulation of soil mesofauna communities indicated that mesofauna can influence decomposition indirectly by affecting the functional composition of fungal communities, but that this phenomenon may be dependent on ecological context. Together, these studies assist in evaluating how restoration treatments affect the structure and functions of soil food webs.

Item Type:	Thesis (Doctoral)
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:	collembolans; forest restoration; Gadgil effect; mesocosm; mites; nematodes; New Mexico; Valles Caldera National Preserve
Subjects:	Q Science > QL Zoology
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:	16 Nov 2022 17:35
Last Modified:	25 May 2023 08:30
URI:	https://openknowledge.nau.edu/id/eprint/5871

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