Nazaries, Loïc (2011) Impact of land-use changes on the methanotrophic community structure. PhD thesis, University of Warwick.

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Abstract

Methane (CH4) is one of the most potent greenhouse gases and its increasing concentration in
the Earth’s atmosphere is linked to today’s global warming. The types of land and land-use
have an impact on net CH4 fluxes, e.g. wetlands are generally net CH4 emitters while upland
forest soils are a sink for CH4. This project aimed to elucidate the effect of afforestation and
reforestation on net CH4 fluxes and to determine the control of the CH4-oxidising bacteria
(methanotrophs) on net CH4 flux rate. This was investigated using a combination of
molecular (T-RFLP, cloning/sequencing, microarray) and activity-specific (PLFA-SIP)
approaches. Several sites were selected to analyse soil methanotrophs under shrubs
regenerating after a fire compared to a native mature forest (in New Zealand), and under bog,
grass, heath, pine and birch vegetation (in Scotland). Furthermore, a simple bottom-up
approach was applied to seasonal measurements of local net CH4 fluxes in Scotland. These
were upscaled to annual values in order to estimate the contribution to the national CH4
budget for each habitat investigated. The effect on CH4 mitigation of the conversion of
different types of non-forested habitat to forests was then estimated.
Afforestation/reforestation was always found to induce net CH4 oxidation at rates much faster
than previously estimated. This preliminary analysis suggests that heathland conversion to
birch forest was beneficial in term of CH4 sinks but it also induced large and permanent
losses of soil C. However, bog afforestation with pine trees can potentially neutralise the
national CH4 emissions from non-forested areas, while preserving soil C stocks. This project
also revealed that changes in net CH4 flux due to land-use changes were closely related to
shifts in the structure of the methanotrophic community. The relative abundance of members
of the USCα cluster (high-affinity methanotrophs) was a strong predictor of net CH4 fluxes.
Finally, the sole presence of trees suggested a niche-specific adaptation of the methanotrophs,
which may have been correlated to some of the soil characteristics.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QR Microbiology S Agriculture > SD Forestry
Library of Congress Subject Headings (LCSH):	Methane, Afforestation, Reforestation, Methanotrophs, Greenhouse gas mitigation
Official Date:	March 2011
Dates:	Date Event March 2011 Submitted
Institution:	University of Warwick
Theses Department:	School of Life Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Singh, Brajesh
Sponsors:	Macaulay Development Trust
Extent:	xix, 262 leaves : ill., charts
Language:	eng

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