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Soil respiration at a Colorado subal...

Denton, Laura Elaine Scott.

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Soil respiration at a Colorado subalpine forest.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Soil respiration at a Colorado subalpine forest./
Author:	Denton, Laura Elaine Scott.
Description:	134 p.
Notes:	Source: Dissertation Abstracts International, Volume: 66-02, Section: B, page: 0671.
Contained By:	Dissertation Abstracts International66-02B.
Subject:	Biology, Ecology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3165811
ISBN:	9780542008832

Soil respiration at a Colorado subalpine forest.
Denton, Laura Elaine Scott.

Soil respiration at a Colorado subalpine forest. - 134 p.

Source: Dissertation Abstracts International, Volume: 66-02, Section: B, page: 0671.

Thesis (Ph.D.)--University of Colorado at Boulder, 2005.

Our ability to describe the global carbon budget is dependent on a strong understanding of the mechanisms that control soil respiration. Soil is one of the planet's largest carbon reserves, and soil respiration is one of the largest CO2 fluxes. Furthermore, it is ecosystems' annual respiration, not carbon accumulation, that plays the strongest role in determining whether an ecosystem is a sink or source of carbon to the atmosphere in a given year. This thesis examines soil respiration at the Niwot Ridge Ameriflux site at the C.U. Mountain Research Station. In the first study I measured soil respiration rates and related them to root biomass, microbial biomass, soil carbon, soil moisture, soil temperature, ammonium concentration, and organic horizon thickness. I found that organic layer thickness and microbial biomass predict spatial variation in soil respiration rate. Soil temperature and day of the year can be used to construct seasonal models of soil respiration rate, and soil moisture is most useful in accounting for differences in total annual respiration. In drought years soil respiration rates were depressed at mid-summer. The second study looks at soil respiration in plots where trees have been girdled and the perimeters trenched, which eliminates fresh photosynthate to the rhizosphere. In girdled plots, the surface respiratory efflux should be exclusively from the soil heterotrophs. Girdling reduced respiration rates by 31--44%. In a drought summer, girdled plots' respiration was depressed much more than control plots' respiration, suggesting the heterotrophs are more sensitive to drought than the rhizosphere. This study yielded several other novel observations including an ephemeral springtime carbon flush to the soil by the trees of the control plots and high levels of soil sucrose in the winter. I hypothesize that winter sucrose is due to root damage during a period of soil disruption due to the mechanical effects of freezing. The third study used an empirical relationship between soil respiration rate and a constructed index of "tree-influence" to create two-dimensional GIS maps of soil respiration rates. This modeling exercise demonstrated the efficacy of using stem maps as proxies for a difficult to measure soil process and revealed an east-west respiration rate gradient related to tree density.

ISBN: 9780542008832Subjects--Topical Terms:

1017726
Biology, Ecology.

Soil respiration at a Colorado subalpine forest.
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245 1 0 $a Soil respiration at a Colorado subalpine forest.
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500 $a Source: Dissertation Abstracts International, Volume: 66-02, Section: B, page: 0671.
500 $a Director: Russell K. Monson.
502 $a Thesis (Ph.D.)--University of Colorado at Boulder, 2005.
520 $a Our ability to describe the global carbon budget is dependent on a strong understanding of the mechanisms that control soil respiration. Soil is one of the planet's largest carbon reserves, and soil respiration is one of the largest CO2 fluxes. Furthermore, it is ecosystems' annual respiration, not carbon accumulation, that plays the strongest role in determining whether an ecosystem is a sink or source of carbon to the atmosphere in a given year. This thesis examines soil respiration at the Niwot Ridge Ameriflux site at the C.U. Mountain Research Station. In the first study I measured soil respiration rates and related them to root biomass, microbial biomass, soil carbon, soil moisture, soil temperature, ammonium concentration, and organic horizon thickness. I found that organic layer thickness and microbial biomass predict spatial variation in soil respiration rate. Soil temperature and day of the year can be used to construct seasonal models of soil respiration rate, and soil moisture is most useful in accounting for differences in total annual respiration. In drought years soil respiration rates were depressed at mid-summer. The second study looks at soil respiration in plots where trees have been girdled and the perimeters trenched, which eliminates fresh photosynthate to the rhizosphere. In girdled plots, the surface respiratory efflux should be exclusively from the soil heterotrophs. Girdling reduced respiration rates by 31--44%. In a drought summer, girdled plots' respiration was depressed much more than control plots' respiration, suggesting the heterotrophs are more sensitive to drought than the rhizosphere. This study yielded several other novel observations including an ephemeral springtime carbon flush to the soil by the trees of the control plots and high levels of soil sucrose in the winter. I hypothesize that winter sucrose is due to root damage during a period of soil disruption due to the mechanical effects of freezing. The third study used an empirical relationship between soil respiration rate and a constructed index of "tree-influence" to create two-dimensional GIS maps of soil respiration rates. This modeling exercise demonstrated the efficacy of using stem maps as proxies for a difficult to measure soil process and revealed an east-west respiration rate gradient related to tree density.
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