We explored relationships between plant productivity and annual fluxes
of nitrogen (N-2) and nitrous oxide (N2O) in a tallgrass prairie land
scape in central Kansas. Our objective was to develop predictive relat
ionships between these variables that could be used in conjunction wit
h remote sensing information on plant productivity to produce large-ar
ea estimates of N gas fluxes. Our hypothesis was that there are inhere
nt relationships between plant productivity and N gas fluxes in tallgr
ass prairie because both are controlled by water and N availability. T
he research was carried out as part of a multi-investigator project, t
he First ISLSCP Field Experiment (FIFE, ISLSCP = International Satelli
te Land Surface Climatology Program), directed toward the use of remot
e sensing to characterize land-atmosphere interactions. Fluxes of N-2
(denitrification) and N2O were measured using soil core techniques. Es
timates of annual flux were produced by temporal extrapolation of meas
ured rates. Annual aboveground net primary productivity (ANPP) was est
imated from measurements of the maximum standing crop of plant biomass
. There were strong relationships between ANPP and N gas fluxes, and b
etween a satellite remote sensing-based index of plant productivity (n
ormalized difference vegetation index, NDVI) and gas fluxes. We used t
hese relationships to convert images of NDVI into images of N gas flux
es for one 83 ha watershed and for the entire 15 by 15 km FIFE site. T
hese images were used to compute mean landscape gas fluxes (0.62 g N m
(-2) y(-1) for N-2, 0.66 g N m(-2) y(-1) for N2O) and total N gas prod
uction for the two areas. Our flux and production values are useful fo
r comparison with values produced by simulation models and site-specif
ic studies, and for assessing the significance of N gas production to
ecosystem and landscape scale processes related to nutrient cycling, w
ater quality and atmospheric chemistry.