Serreze et al, 2000 Climatic Change

1
Serreze et al, 2000 Climatic Change
2
Arctic tundra C/N model
Shaver et al, 1992 Bioscience
3
Denitrification

• Microbial-mediated, anaerobic N reduction from
  NO3- to N2O and N2
• Major means of N removal from soil to atmosphere
• Once thought unimportant in arctic ecosystems,
  but with effects of climate change could be a
  significant N loss pathway

4
How does this N loss pathway contribute to
the amount of missing N? Do
denitrification rates differ between site and
with experimental fertilization?
5
(No Transcript)
6
Denitrification Assays

• Two measurements using acetylene block
• Denitrification enzyme activity (DEA) - NO3-,
  Dextrose
• Unamended denitrification rates - DI

Make systems anoxic Add acetylene (C2H2)
Incubate at room temperature on a shaker table
in the dark Collect air samples at 30, 60 and
90 minute time points N2O analysis on GC
7
(No Transcript)
8
(No Transcript)
9

10
An Upper Bound Estimate
Assume - A denitrification rate of 0.1 µg Ng
soil-1h-1 in fertilized plots Unamended CT,
Moist Acidic Tundra - Bulk density 0.06 g/cm3,
depth of denitrification activity 10cm - 100
day growing season ? This represents a
loss of 1.44 g Nm-2y-1 The annual vegetation N
uptake requirement is lt1 g
Nm-2y-1 ? Denitrification may have
considerable effects on N availability in
these systems.