Preprint #96-33
Design and Estimation for Investigating the Dynamics
of Natural Resources
by
S.M. Nusser, F.J. Breidt, W.A. Fuller
Abstract
Federal agencies, policy makers, and scientists have long been interested
in monitoring natural resources and environmental conditions on a national
and regional scale. One of the main objectives of these studies is to
estimate temporal changes in the extent and condition of natural resources.
In its simplest form, temporal change can be defined as the difference
between population parameter values at two time points for a given
population. A more complex investigation of change in an ecological
system involves studying the underlying dynamics that produce an observed
net change. We discuss the general problem of sample design and
statistical estimation to support investigations of the dynamics of
change in ecological systems. We focus in particular on large-scale
natural resource monitoring surveys through the example provided by
the National Resources Inventory (NRI), a panel survey conducted by the
USDA Natural Resources Conservation Service (formerly the Soil Conservation
Service) in cooperation with the Iowa State University Statistical
Laboratory. Sample design, data collection and statistical methods for
constructing an accessible database are outlined with emphasis on features
that support investigations concerned with temporal dynamics. An example
from the 1992 NRI is presented to illustrate methods for investigating
temporal changes in land use in relation to observed changes in erosion
rates over time. Finally, we discuss how statistical methods developed
for the NRI program can be applied more broadly to environmental
monitoring studies.
Copies of preprints are available from the author upon request. Use
the preprint number (located at the top of the page) and
make the request directly to the author, Iowa State
University,
Department of Statistics, Snedecor Hall, Ames, IA 50011-1210.