REWM 3500Rangeland Plant EcophysiologyNovember 30, 2009

Human impact on the global nitrogen cycle – how will rangelands respond?

Natural vs Anthropogenic Nitrogen Fixation

Consequences of altered N biogeochemistry1) Where is this nitrogen going?2) Effects on plant populations and communities3) Effects on biodiversity4) 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 cycleAtmospheric deposition of reactive N

From Galloway 2005

Sinks Canyon, Fremont County, WyomingAnnual inorganic nitrogen deposition 1984-2007

http://nadp.sws.uiuc.edu

From Galloway 2005

Human impacts on the global N cycle

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 fixationabiotically fixed N2

biologically fixed N2

anthropogenic N fixationHaber processmineralizationnitrificationdenitrificationnitrous oxide (N2O)