REWM 3500
Rangeland Plant Ecophysiology
November 30, 2009
Human impact on the global nitrogen cycle – how will
rangelands respond?
Natural vs Anthropogenic Nitrogen Fixation
Consequences of altered N biogeochemistry
1) Where is this nitrogen going?
2) Effects on plant populations and communities
3) Effects on biodiversity
4) Impacts on atmospheric chemistry and global warming
Connectivity
Anthropogenic production of reactive nitrogen
Natural background rate
From Galloway 2005
Human impacts on the global N cycle
Atmospheric deposition of reactive N
From Galloway 2005
Sinks Canyon, Fremont County,
Wyoming
Annual inorganic nitrogen deposition 1984-2007
http://nadp.sws.uiuc.edu
Human impacts on the global N cycle
From Galloway 2005
Sources, feedbacks and impacts of enhanced N
fixation
From Galloway 2005
Atmospheric concentrations of nitrous oxide over
the last 10,000 years and since 1750 (inset)
Terms and concepts to know:
nitrogen fixation
abiotically fixed N2
biologically fixed N2
anthropogenic N fixation
Haber process
mineralization
nitrification
denitrification
nitrous oxide (N2O)