BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//132.216.98.100//NONSGML kigkonsult.se iCalcreator 2.20.4//
BEGIN:VEVENT
UID:20251105T161016EST-8967NNMlVg@132.216.98.100
DTSTAMP:20251105T211016Z
DESCRIPTION:pre-defense will be at 13:45 (room MS2-022)  Abstract:   Denitr
 ification is responsible for much of the gaseous nitrogen (N) loss from te
 rrestrial ecosystems\, particularly in riparian buffers where periodic flo
 oding results in anoxic conditions that favor the activity of bacterial de
 nitrifiers. Earthworms affect denitrification in controlled laboratory and
  field studies\, indicating that earthworm-denitrifier interactions occur 
 across temporal and spatial scales. However\, the effects of earthworm on 
 denitrification need to be evaluated at spatio-temporal scales that can be
  extrapolated to the ecosystem scale. The general objective of this thesis
  was to determine how earthworm-denitrifying bacteria interactions affect 
 N dynamics at a physiological level (within the earthworm body) to the ind
 ividual level (earthworm drilosphere)\, then finally determine whether the
 se small-scale effects can be detected at the ecosystem scale (in riparian
  buffers). In the microcosm study (physiological level)\, earthworms were 
 fed with organic substrates with different C:N ratio\, but earthworm maint
 ained a constant C:N ratio of 3.37 to 5.25 in their muscular tissue\, rega
 rdless of the food N content.  Adult L. terrstris had a significantly grea
 ter denitrification rate with the N-rich soybean mixture than with peat mo
 ss\, but there was more variability in denitrification from A. tuberculata
 . These results suggest that earthworms are a source of gaseous N loss\, s
 uch that ecosystems with abundant L. terrestris population and N-rich orga
 nic substrates would have greater  N2O and dinitrogen (N2) fluxes due to e
 arthworms. In a 69 day mesocosm study (drilosphere level)\, earthworm pres
 ence increased the cumulative N2O emissions by 50% in the dry soil treatme
 nt\, but earthworms decreased cumulative N2O emissions by 34% in the wet s
 oil treatment and reduced N2O emissions significantly by 82% in the treatm
 ent of rewetting-drying cycles (WD). Denitrification enzyme activity (DEA)
  increased significantly when earthworms were present and the abundance of
  16S rRNA\, nirS\, and nosZ genes was affected significantly by the earthw
 orm × soil moisture interaction. These results suggested that the decrease
  in cumulative N2O emissions from soil at wet soil and the WD treatment by
  earthworms was due to their stimulation of N2O consuming bacteria and a g
 eneral alteration of the denitrifying bacterial community composition. Mor
 eover\, the results implied that earthworms would decrease the N2O emissio
 ns from saturated soils. In the ecological scale\, earthworm demographics 
 were investigated in temporary flooded riparian region (TR) and non-floode
 d riparian region (NR) in Quebec\, Canada\, from spring to autumn\, 2012. 
 The TR had more earthworm diversity (9 species) and larger population and 
 biomass than NR (6 species). Earthworm population and biomass were largest
  in spring and autumn but declined in summer. Earthworm presence significa
 ntly decreased the DEA by 1.5 times in TR and 1.2 times in NR. Path analys
 is indicated that soil moisture was the most important factor influencing 
 the DEA\, and earthworms affected the DEA directly\, probably due to earth
 worm bioturbation that disrupted the living habitats of denitrifiers\, as 
 well as indirectly by reducing the soil NO3- concentration. In conclusion\
 , my results indicate that the effects measured at the small scale (within
  the earthworm body) cannot be extrapolated directly from the lab to the f
 ield because the indirect earthworm effects would overwhelm the soil N dyn
 amics and N2O production. Nevertheless\, the mesocosm scale work is more r
 elevant to the earthworm influence on N2O in field. The studies from the m
 esocosm scale and the field scale suggest that the N2O output from riparia
 n soils is the result of the moisture-earthworm-microbial interaction: soi
 l moisture act as a crucial control on the final product of denitrificatio
 n (N2O or N2) and earthworms reduced the soil denitrifier activity in the 
 saturated soils. Moreover\, earthworms influence the gaseous N losses from
  natural riparian buffers through both direct and indirect effects on deni
 trifiers and substrates required for the denitrification reaction.   
DTSTART:20131115T190000Z
DTEND:20131115T190000Z
LOCATION:MS2-022\, Macdonald-Stewart Building\, CA\, QC\, St Anne de Bellev
 ue\, H9X 3V9\, 21111 Lakeshore Road
SUMMARY:Ph.D. Thesis Defense: Ms. Chen Chen: Earthworm interactions with de
 nitrifying bacteria in riparian buffers:  Signficance for nitrogen dynamic
 s from the physiological to ecological scales 
URL:/nrs/channels/event/phd-thesis-defense-ms-chen-che
 n-earthworm-interactions-denitrifying-bacteria-riparian
END:VEVENT
END:VCALENDAR