SOIL QUALITY INDICATORS AND VEGETATION RESPONSES FOLLOWING ECOLOGICAL RESTORATION THINNING OF PONDEROSA PINE ON THREE SOIL PARENT MATERIAL TYPES UNDER GRAZING AND NON-GRAZING IN NORTHERN ARIZONA

Author

Christopher MacDonaldFollow

Date of Award

Summer 2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy - Forestry

Department

Forestry

First Advisor

Kenneth Farrish

Second Advisor

Brian Oswald

Third Advisor

Matthew McBroon

Fourth Advisor

Mindy Faulkner

Abstract

This research was performed in a northern Arizona ponderosa pine (Pinus ponderosa P. & C., Lawson) forest. The objectives were to a) increase understanding of long-term vegetation responses to ecological restoration treatments on three soils types, with and without grazing, b) evaluate the responses soil physical, chemical, and biological properties to restoration treatments, with and without grazing, c) determine the utility of measured soil quality indicators to informing risks to sustainable soils management in southwestern ponderosa pine forests.

There were no significant differences in soil bulk density by soil type, treatment type, or grazing treatment. No significant differences in saturated infiltration capacity were observed among treatment types under either grazed or non-grazed conditions. Saturated infiltration capacity was affected by soil type under non-grazed conditions. Grazing resulted in lower soil aggregate stability in comparison to non-grazing. Soil slaking was affected by grazing and forest treatment type. Grazing on basalt-derived soils was less negative to soil slaking potential than limestone-derived soils (p = 0.008). There were no significant differences in soil organic matter, organic carbon, nitrogen, calcium , or potassium (Mg ha^-1) in the upper 10 cm of soil based on soil type, forest treatment type, or grazing treatment. There were significant differences in soil magnesium content (Mg ha^-1) by soil type. Basalt-derived soils had significantly lower soil phosphorus (P) levels than benmoreite-derived soils. Limestone-derived soils had significantly lower soil S than basalt- and benmoreite-derived soils.

Vegetative cover and species richness were affected by forest treatment type, soil parent material type, grazing treatment, and measurement year, depending on life form, longevity, and nativity. As observed by Abella et al. (2015), responses were hierarchically controlled, with soil parent material type often moderating vegetative responses. Limestone-derived soils had the greatest overall total plant cover and benmoreite-derived soils often had the lowest. Grazing affected vegetative cover, depending on measurement year, but rarely affected species richness.

This study highlights the importance of considering both inherent and dynamic soil properties when planning ecological restoration treatments since soil parent material type strongly influences vegetative responses of cover and richness, particularly in relation to livestock and wildlife forage production and sustaining healthy native plant communities following forest restoration treatments.

Repository Citation

MacDonald, Christopher, "SOIL QUALITY INDICATORS AND VEGETATION RESPONSES FOLLOWING ECOLOGICAL RESTORATION THINNING OF PONDEROSA PINE ON THREE SOIL PARENT MATERIAL TYPES UNDER GRAZING AND NON-GRAZING IN NORTHERN ARIZONA" (2022). Electronic Theses and Dissertations. 460.
https://scholarworks.sfasu.edu/etds/460

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