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Soil State Factor Regulation of Free...

Winbourne, Joy Beth.

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Soil State Factor Regulation of Free-living Nitrogen Fixation in Temperate and Tropical Forests.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Soil State Factor Regulation of Free-living Nitrogen Fixation in Temperate and Tropical Forests./
Author:	Winbourne, Joy Beth.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2015,
Description:	113 p.
Notes:	Source: Dissertation Abstracts International, Volume: 77-04(E), Section: B.
Contained By:	Dissertation Abstracts International77-04B(E).
Subject:	Ecology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3737046
ISBN:	9781339261379

Soil State Factor Regulation of Free-living Nitrogen Fixation in Temperate and Tropical Forests.
Winbourne, Joy Beth.

Soil State Factor Regulation of Free-living Nitrogen Fixation in Temperate and Tropical Forests. - Ann Arbor : ProQuest Dissertations & Theses, 2015 - 113 p.

Source: Dissertation Abstracts International, Volume: 77-04(E), Section: B.

Thesis (Ph.D.)--University of California, Davis, 2015.

This item is not available from ProQuest Dissertations & Theses.

Nitrogen (N) availability regulates a number of essential ecosystem functions including net primary productivity and nutrient recycling via decomposition. Despite the widespread capacity of bacteria able to convert the abundant atmospheric di-nitrogen (N2) into biologically available forms of N (e.g. ammonium and nitrate), N limitation remains widespread. N fixing organisms require a number of rock-derived nutrients in order to function, namely phosphorus (P), molybdenum (Mo), and iron (Fe), and the availability of these rock-derived elements is influenced by variation in soil forming state factors. The primary objective of my dissertation research is to understand the regulation of free-living N fixation across specific ecosystem state factors in temperate and tropical forests. In a temperate conifer forest, I investigated the controls on rates of free-living N fixation across a soil age gradient during litter decomposition. I observed significant declines in rates of free-living N fixation with corresponding increases in soil age and declines in soil fertility. Using a reciprocal litterbag decomposition experiment, I determined that site fertility had a stronger influence on rates of N fixation than did changes in litter substrate quality. In a tropical lowland rainforest of Belize, I investigated the influence of parent material (limestone versus volcanic bedrock) on patterns of free-living N fixation in decomposing leaf litter. Rates of free-living N fixation were three times greater during the wet season in forests growing on limestone P-rich soils compared to P-poor volcanic soils, suggesting a coupling between the N and P cycle in these systems. I directly tested for limitation by Fe, P, and Mo in forests growing on these two different parent materials using a fertilization experiment. In response to Fe additions, rates of N fixation were three times greater in limestone forests compared to volcanic forests during the wet season but this effect dissipated into the drier months. The response of N fixation to Fe additions tracks patterns of iron availability and biological demand for Fe; DTPA extractable Fe was lower in the limestone soils, and the activity of siderophores -- a proxy for biological demand -- was greater in the limestone soils when compared to volcanic soils. N fixation in the volcanic site did not respond to Fe additions; rather, rates were stimulated by additions of the trace metal Mo during the dry season. These findings reveal a new role for Fe in controlling tropical forest nutrient cycling. Lastly, we investigated the influence of soil P versus phylogeny on the foliar stoichiometry of major tree canopy species found on the two different parent materials, as well as along a topographic gradient within the limestone geology. Phylogeny had a stronger influence on foliar chemistry than soil P pools in lowland tropical forests of Belize, suggesting a possible role of species diversity on patterns of N fixation in tropical forests. These findings together provide evidence that biological N fixation can be related to, and thereby scaled with variation in ecosystem state factors.

ISBN: 9781339261379Subjects--Topical Terms:

516476
Ecology.

Soil State Factor Regulation of Free-living Nitrogen Fixation in Temperate and Tropical Forests.
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500 $a Source: Dissertation Abstracts International, Volume: 77-04(E), Section: B.
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502 $a Thesis (Ph.D.)--University of California, Davis, 2015.
506 $a This item is not available from ProQuest Dissertations & Theses.
520 $a Nitrogen (N) availability regulates a number of essential ecosystem functions including net primary productivity and nutrient recycling via decomposition. Despite the widespread capacity of bacteria able to convert the abundant atmospheric di-nitrogen (N2) into biologically available forms of N (e.g. ammonium and nitrate), N limitation remains widespread. N fixing organisms require a number of rock-derived nutrients in order to function, namely phosphorus (P), molybdenum (Mo), and iron (Fe), and the availability of these rock-derived elements is influenced by variation in soil forming state factors. The primary objective of my dissertation research is to understand the regulation of free-living N fixation across specific ecosystem state factors in temperate and tropical forests. In a temperate conifer forest, I investigated the controls on rates of free-living N fixation across a soil age gradient during litter decomposition. I observed significant declines in rates of free-living N fixation with corresponding increases in soil age and declines in soil fertility. Using a reciprocal litterbag decomposition experiment, I determined that site fertility had a stronger influence on rates of N fixation than did changes in litter substrate quality. In a tropical lowland rainforest of Belize, I investigated the influence of parent material (limestone versus volcanic bedrock) on patterns of free-living N fixation in decomposing leaf litter. Rates of free-living N fixation were three times greater during the wet season in forests growing on limestone P-rich soils compared to P-poor volcanic soils, suggesting a coupling between the N and P cycle in these systems. I directly tested for limitation by Fe, P, and Mo in forests growing on these two different parent materials using a fertilization experiment. In response to Fe additions, rates of N fixation were three times greater in limestone forests compared to volcanic forests during the wet season but this effect dissipated into the drier months. The response of N fixation to Fe additions tracks patterns of iron availability and biological demand for Fe; DTPA extractable Fe was lower in the limestone soils, and the activity of siderophores -- a proxy for biological demand -- was greater in the limestone soils when compared to volcanic soils. N fixation in the volcanic site did not respond to Fe additions; rather, rates were stimulated by additions of the trace metal Mo during the dry season. These findings reveal a new role for Fe in controlling tropical forest nutrient cycling. Lastly, we investigated the influence of soil P versus phylogeny on the foliar stoichiometry of major tree canopy species found on the two different parent materials, as well as along a topographic gradient within the limestone geology. Phylogeny had a stronger influence on foliar chemistry than soil P pools in lowland tropical forests of Belize, suggesting a possible role of species diversity on patterns of N fixation in tropical forests. These findings together provide evidence that biological N fixation can be related to, and thereby scaled with variation in ecosystem state factors.
590 $a School code: 0029.
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650 4 $a Biogeochemistry. $3 545717
650 4 $a Soil sciences. $3 2122699
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710 2 $a University of California, Davis. $b Ecology. $3 1678659
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