This proposal requests funding for a new Konza LTER initiative on the role of native ungulate grazers in affecting soil
belowground N transformations and the fate of added N in tallgrass prairie
ecosystems. Specifically, we request funding for (1) the purchase of 15N-labelled
compounds, (2) the production of 15N-labelled
urine and dung, (3) the construction of gas sampling chambers to measure
ammonia volatilization losses in the field, and (4) 15N
analysis of soil, plant and gas samples from a proposed field experiment.
While this research is clearly in line with the goals of the Konza Prairie
LTER program, it also represents a significant new effort to incorporate
stable isotope tracers our grazing-and-belowground-processes research,
which would not be possible within the constraints of our base LTER budget.
The relatively high costs of 15N materials
and sample analyses prohibit us from conducting such studies without funding
from additional sources. This supplemental LTER funding will allow us to
conduct an field experiment on the effects of chronic grazing by native
ungulates on the transformations and fate of added N (detailed below),
provide new data on magnitude of ammonia volatilization losses in grazed
areas (a missing component of Konza N budgets) and, of equal importance,
will provide data on the feasibility of producing and using 15N-labelled
urine and dung to follow the transformations and fate of N inputs in those
forms. This will be invaluable information as we pursue additional funds
for future grazing studies at Konza. Further, the background data on natural
abundance of 15N (d15N),
to be gathered as part of the isotope enrichment studies proposed here,
may provide additional insights into the long-term effects of grazers on
soil N transformations (using an approach developed by Doug Frank). The
ultimate goal of these, and related studies at Konza, is to determine if,
and over what spatial and temporal scales, bison regulate fundamental ecosystem
processes such as N cycling and energy flow in the tallgrass prairie landscape
('top down' regulation).