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The Influence of Antecedent Soil Moisture Conditions and Nutrient Management on Soil Nitrous Oxide Emissions.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	The Influence of Antecedent Soil Moisture Conditions and Nutrient Management on Soil Nitrous Oxide Emissions./
作者:	Barrat, Harry A.
面頁冊數:	1 online resource (138 pages)
附註:	Source: Dissertations Abstracts International, Volume: 84-04, Section: B.
Contained By:	Dissertations Abstracts International84-04B.
標題:	Floods. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29343234click for full text (PQDT)
ISBN:	9798352601587

The Influence of Antecedent Soil Moisture Conditions and Nutrient Management on Soil Nitrous Oxide Emissions.
Barrat, Harry A.

The Influence of Antecedent Soil Moisture Conditions and Nutrient Management on Soil Nitrous Oxide Emissions. - 1 online resource (138 pages)

Source: Dissertations Abstracts International, Volume: 84-04, Section: B.

Thesis (Ph.D.)--Bangor University (United Kingdom), 2022.

Includes bibliographical references

Nitrous oxide (N2O) is a powerful greenhouse gas and ozone depleter, and it is produced in large quantities when a dry soil is rewetted in a phenomenon known as a hot moment. Therefore understanding this phenomena is important for tackling agriculture's impact on climate change. A literature review and meta-analysis of N2O hot moments was conducted in Chapter 2, revealing that the amount of water added to the soil and how saturated the soil gets during rewetting are the most important controlling factors. For example, rewetting from 50 to 90% water filled pore space (WFPS), would produce more N2O emissions, than rewetting the same soil from 50% to 70%. However, it was clear that the current literature suffered from the lack of a standardised approach, as it was difficult to draw conclusions from experiments with different designs that had different rewetting strategies, controlled temperatures and soil core sizes. Moreover, drought length (i.e. the amount of time the soil stays dry before it was rewetted) had not been adequately investigatedIt was still an open question as to how and why the soil's microbial communities were responding in this manner to soil drought and rewetting, and so Chapter 3 was a lab experiment that aimed to investigate two of the key hypotheses suggested by the current literature. Firstly that drought and the resulting osmotic stress created a selection pressure which favoured the soil microbes that could rapidly denitrify upon rewetting. Secondly, that more carbon (C) and nitrogen (N) would become available from lysed microbes that could not survive the osmotic change. Neither of these were confirmed, as changes in the soil C and N and functional gene abundance could not explain differences in the sizes of the induced hot moments.Chapter 4 repeated this experiment, with the same aims, and an additional measurement of messenger RNA abundance of key N cycling genes. While functional gene and transcript abundance failed to provide an explanation, ammonium (NH4+) in the driest treatment increased and then reduced in correlation with the largest hot moment. It was concluded that while the soil C and N pools can be enhanced by necromass, this is not the cause of the hot moment. This chapter also included a second experiment to investigate the effect of drought length, which was observed to have an inverted U shaped response, with the least amount of N2O being released when the drought phase was 24 days. Overall, it was concluded that there are two stages of microbial quiescence that explain N2O hot moments and its response to changing antecedent conditions. The first stage is a state of semi-quiescence as the soil's microbial communities prepare for the moisture conditions to change, during this stage they can rapidly respond to the changing WFPS by catabolising intercellular osmotic compounds, and the lower the WFPS the more of the soil microbial community are in this state, and therefore the greater the response once the soil is rewetted. However, once the drought becomes too extreme they enter a second stage of quiescence to survive the harsher conditions, which no longer allows a rapid response, explaining the quadratic effect of drought length.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798352601587Subjects--Topical Terms:

549458
Floods.
Index Terms--Genre/Form:

542853
Electronic books.

The Influence of Antecedent Soil Moisture Conditions and Nutrient Management on Soil Nitrous Oxide Emissions.
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500 $a Source: Dissertations Abstracts International, Volume: 84-04, Section: B.
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502 $a Thesis (Ph.D.)--Bangor University (United Kingdom), 2022.
504 $a Includes bibliographical references
520 $a Nitrous oxide (N2O) is a powerful greenhouse gas and ozone depleter, and it is produced in large quantities when a dry soil is rewetted in a phenomenon known as a hot moment. Therefore understanding this phenomena is important for tackling agriculture's impact on climate change. A literature review and meta-analysis of N2O hot moments was conducted in Chapter 2, revealing that the amount of water added to the soil and how saturated the soil gets during rewetting are the most important controlling factors. For example, rewetting from 50 to 90% water filled pore space (WFPS), would produce more N2O emissions, than rewetting the same soil from 50% to 70%. However, it was clear that the current literature suffered from the lack of a standardised approach, as it was difficult to draw conclusions from experiments with different designs that had different rewetting strategies, controlled temperatures and soil core sizes. Moreover, drought length (i.e. the amount of time the soil stays dry before it was rewetted) had not been adequately investigatedIt was still an open question as to how and why the soil's microbial communities were responding in this manner to soil drought and rewetting, and so Chapter 3 was a lab experiment that aimed to investigate two of the key hypotheses suggested by the current literature. Firstly that drought and the resulting osmotic stress created a selection pressure which favoured the soil microbes that could rapidly denitrify upon rewetting. Secondly, that more carbon (C) and nitrogen (N) would become available from lysed microbes that could not survive the osmotic change. Neither of these were confirmed, as changes in the soil C and N and functional gene abundance could not explain differences in the sizes of the induced hot moments.Chapter 4 repeated this experiment, with the same aims, and an additional measurement of messenger RNA abundance of key N cycling genes. While functional gene and transcript abundance failed to provide an explanation, ammonium (NH4+) in the driest treatment increased and then reduced in correlation with the largest hot moment. It was concluded that while the soil C and N pools can be enhanced by necromass, this is not the cause of the hot moment. This chapter also included a second experiment to investigate the effect of drought length, which was observed to have an inverted U shaped response, with the least amount of N2O being released when the drought phase was 24 days. Overall, it was concluded that there are two stages of microbial quiescence that explain N2O hot moments and its response to changing antecedent conditions. The first stage is a state of semi-quiescence as the soil's microbial communities prepare for the moisture conditions to change, during this stage they can rapidly respond to the changing WFPS by catabolising intercellular osmotic compounds, and the lower the WFPS the more of the soil microbial community are in this state, and therefore the greater the response once the soil is rewetted. However, once the drought becomes too extreme they enter a second stage of quiescence to survive the harsher conditions, which no longer allows a rapid response, explaining the quadratic effect of drought length.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2023
538 $a Mode of access: World Wide Web
650 4 $a Floods. $3 549458
650 4 $a Emissions. $3 3559499
650 4 $a Greenhouse effect. $3 3562309
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710 2 $a Bangor University (United Kingdom). $3 3546296
773 0 $t Dissertations Abstracts International $g 84-04B.
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29343234 $z click for full text (PQDT)