Long-term Impacts of Management Intensification on Soil Carbon Dynamics in Subtropical Grasslands

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Material Information

Title:
Long-term Impacts of Management Intensification on Soil Carbon Dynamics in Subtropical Grasslands
Physical Description:
1 online resource (138 p.)
Language:
english
Creator:
Adewopo, Julius B
Publisher:
University of Florida
Place of Publication:
Gainesville, Fla.
Publication Date:

Thesis/Dissertation Information

Degree:
Doctorate ( Ph.D.)
Degree Grantor:
University of Florida
Degree Disciplines:
Soil and Water Science
Committee Chair:
SILVEIRA,MARIA LUCIA
Committee Co-Chair:
GERBER,STEFAN
Committee Members:
SOLLENBERGER,LYNN E
MARTIN,TIMOTHY A

Subjects

Subjects / Keywords:
bahiagrass -- carbon -- d13c -- dndc -- dynamics -- ecosystem -- fractions -- grasslands -- intensification -- long -- management -- modeling -- native -- process -- rangelands -- silvopasture -- slashpine -- soil -- subtropical -- term
Soil and Water Science -- Dissertations, Academic -- UF
Genre:
Soil and Water Science thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract:
Proper management of grassland ecosystems for improved pasture productivity can enhance their potential to sequester atmospheric CO2 in the soil. However, soil C dynamics in subtropical grassland ecosystems is poorly understood, and knowledge about the long-term impacts of grassland management intensification on soil C within this environmental condition is lacking. This study was conducted to assess long-term (greater than 22 years) effect of grassland management intensification on ecosystem and soil C dynamics (including stocks, particle-size fractions, and losses), based on a gradient of management intensities ranging from native rangeland (lowest), silvopasture (intermediate), to sown pasture (highest). The replicated (n equal to 2) experimental sites (6 ha) were located at University of Floridas Rangeland Cattle Research and Education Center, Ona, Florida (27.13N, 82.8W) and were characterized by homogeneous topography, same predominant soil series and climatic conditions. The silvopasture and sown pastures were established by clearing native rangeland fields ~35 years ago, and were managed to mimic moderate and optimal management intensity (including N fertilization levels and grazing practices), commonly practiced by grassland managers within the region. The impacts of grassland intensification on soil and ecosystem C stocks (above- and below-ground biomass), soil C fractions, 13C natural isotopic abundance, and in-situ soil respiration fluxes were determined. The process-based denitrification decomposition (DNDC) model was tested for predicting soil C dynamics in this biome. Management intensification increased soil C stocks (0 to 30 cm depth) from 41 Mg ha-1 in the native rangeland to 62 and 69 Mg ha-1 in sown pasture and silvopasture, respectively. Silvopastoral ecosystem favored C sequestration in more stable mineral-associated C pool (41.8 Mg ha-1; 200% increase) compared to the native rangeland (20 Mg ha-1). Although the mixed C3-C4 composition of silvopasture limited full elucidation of C sources, the loss of relic stable C fraction (decreased from 13.2 to 10.6 Mg ha-1) and the gains in recent (C4 derived) C (increased from 6.7 to 17.5 Mg ha-1) in sown pasture suggests that C inputs from the sown grass species (Bahiagrass Paspalum notatum Flugge) contributed to stable C sequestration. Increasing management intensity from native rangeland to sown pasture elevated soil respiration during the summer but not during the winter. Mean summer heterotrophic respiration increased from 0.34 g CO2 m-2 hr-1 to 0.46 g CO2 m-2 hr-1, and temperature sensitivity (Q10) increased from 1.48 to 2.29, respectively, suggesting a potential for management-induced positive temperature feedback on CO2. DNDC model performed reliably in simulating observed soil respiration and soil C stocks (coefficient of determination, R2 greater than 0.79; ratio of performance to deviation, RPD greater than 1.91, modeling efficiency, EF greater than 0.71). However, further recalibration may be needed to improve its performance to predict soil respiration components and abiotic control factors. This study shows that grassland management intensification can enhance soil C sequestration and the use of strategic management practices such as integration of trees can improve soil C stability and reduce potential soil C loss under similar subtropical conditions. These findings are important to inform and support management decisions and policies that can foster long-term productivity and sustainability of subtropical grassland biomes.
General Note:
In the series University of Florida Digital Collections.
General Note:
Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility:
by Julius B Adewopo.
Thesis:
Thesis (Ph.D.)--University of Florida, 2014.
Local:
Adviser: SILVEIRA,MARIA LUCIA.
Local:
Co-adviser: GERBER,STEFAN.
Electronic Access:
RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2015-05-31

Record Information

Source Institution:
UFRGP
Rights Management:
Applicable rights reserved.
Classification:
lcc - LD1780 2014
System ID:
UFE0046691:00001