Fire frequency, nutrient concentrations and distributions, and δ¹³C of soil organic matter and plants in a southeastern Arizona grassland

Persistent Link:
http://hdl.handle.net/10150/282517
Title:
Fire frequency, nutrient concentrations and distributions, and δ¹³C of soil organic matter and plants in a southeastern Arizona grassland
Author:
Biggs, Thomas Howard, 1949-
Issue Date:
1997
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Over the past century, woody plants and shrubs have increased in abundance at the expense of grasslands in many semiarid regions. The availability and concentrations of nutrients influence the relative success of plants, but the effects of fire frequency on soil nutrients is unknown for semiarid grasslands. On the gunnery ranges of Fort Huachuca in southeastern Arizona, study sites were established to examine the effects of fire frequency on soil biogeochemistry, plant biochemistry, and δ¹³C values in soil organic matter (SOM). The sites were on homogeneous granitic alluvium where wildfire frequency history is known from 1973 to present and no cattle grazing has occurred in recent decades. Subplots represent fire frequencies of no burns, 3 fires per decade, and 5 fires per decade. The "no burn" plot has abundant C3 Prosopis velentina (mesquite) trees, whereas the burned plots are open C4-dominated grasslands with scattered mesquite trees. Prosopis trees have altered SOM pools by the concentration of plant nutrients and the addition of isotopically light shrub litter. Frequent fires have altered the basic geochemistry and nutrient availabilities of the soil, and the changes appear to be significant enough to affect plant growth. Soil pH increases with burning frequency, and TOC, total nitrogen, and plant-available phosphorus show significant increases on the infrequently burned plot. Burning is advantageous for preservation or restoration of grasslands, as total living grass biomass is greater on the two burned plots. Root biomass 11 is significantly lower on the "frequently burned" plot. Concentrations of the key nutrients nitrogen and phosphorus are reduced in plants on the burned sites compared to plants on the unburned site. Fires help re-distribute nutrients but evidence of nutrient concentrations and δ¹³C values are retained in SOM for many decades. Estimates of bulk carbon turnover rates range from 112 to 504 years. Evidence for modern C3 shrub expansion is found in the shift of SOM δ¹³C values from values characteristic of C4 grasses to C3 shrubs in surface soil layers. δ¹³CSOM values indicate that the Holocene and Late Pleistocene were dominated by C4 grasslands, and the pre-Late Pleistocene vegetation was a C4-grass savanna with abundant C3 plants.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, Ecology.; Biogeochemistry.; Paleoecology.; Agriculture, Soil Science.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Geosciences
Degree Grantor:
University of Arizona
Advisor:
Quade, Jay

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleFire frequency, nutrient concentrations and distributions, and δ¹³C of soil organic matter and plants in a southeastern Arizona grasslanden_US
dc.creatorBiggs, Thomas Howard, 1949-en_US
dc.contributor.authorBiggs, Thomas Howard, 1949-en_US
dc.date.issued1997en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractOver the past century, woody plants and shrubs have increased in abundance at the expense of grasslands in many semiarid regions. The availability and concentrations of nutrients influence the relative success of plants, but the effects of fire frequency on soil nutrients is unknown for semiarid grasslands. On the gunnery ranges of Fort Huachuca in southeastern Arizona, study sites were established to examine the effects of fire frequency on soil biogeochemistry, plant biochemistry, and δ¹³C values in soil organic matter (SOM). The sites were on homogeneous granitic alluvium where wildfire frequency history is known from 1973 to present and no cattle grazing has occurred in recent decades. Subplots represent fire frequencies of no burns, 3 fires per decade, and 5 fires per decade. The "no burn" plot has abundant C3 Prosopis velentina (mesquite) trees, whereas the burned plots are open C4-dominated grasslands with scattered mesquite trees. Prosopis trees have altered SOM pools by the concentration of plant nutrients and the addition of isotopically light shrub litter. Frequent fires have altered the basic geochemistry and nutrient availabilities of the soil, and the changes appear to be significant enough to affect plant growth. Soil pH increases with burning frequency, and TOC, total nitrogen, and plant-available phosphorus show significant increases on the infrequently burned plot. Burning is advantageous for preservation or restoration of grasslands, as total living grass biomass is greater on the two burned plots. Root biomass 11 is significantly lower on the "frequently burned" plot. Concentrations of the key nutrients nitrogen and phosphorus are reduced in plants on the burned sites compared to plants on the unburned site. Fires help re-distribute nutrients but evidence of nutrient concentrations and δ¹³C values are retained in SOM for many decades. Estimates of bulk carbon turnover rates range from 112 to 504 years. Evidence for modern C3 shrub expansion is found in the shift of SOM δ¹³C values from values characteristic of C4 grasses to C3 shrubs in surface soil layers. δ¹³CSOM values indicate that the Holocene and Late Pleistocene were dominated by C4 grasslands, and the pre-Late Pleistocene vegetation was a C4-grass savanna with abundant C3 plants.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, Ecology.en_US
dc.subjectBiogeochemistry.en_US
dc.subjectPaleoecology.en_US
dc.subjectAgriculture, Soil Science.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorQuade, Jayen_US
dc.identifier.proquest9814408en_US
dc.identifier.bibrecord.b37742528en_US
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