Improving efficiency in broad-scale vegetation
inventories:
Examples from the Nevada photo-based inventory
pilot
Gretchen Moisen[1], Tracey Frescino1, Val Nelson1, Kevin Megown[2], Mark Finco2, Paul Patterson1
The U.S. Forest Service Forest Inventory and Analysis
Program (FIA) conducts and continuously updates a comprehensive inventory of
the forests throughout the U.S. The complex nature of this type of broad-scale,
strategic-level inventory demands constant evolution and evaluation of methods
to get the best information possible while continuously increasing efficiency.
The state of Nevada poses some interesting challenges for FIA: it is not yet
funded for annual inventory; it has the most incomplete and outdated periodic
data in the Interior West; it is comprised of predominantly non-forested
federal lands; and the small proportion of forest land is dominated by woodland
tree species. Consequently, it offers a good test bed for alternative
methodologies to improve precision in estimates of forest parameters, reduce
field data collection costs, address the potential of strategic-level inventory
on lands not traditional sampled by FIA such as rangelands and riparian areas.
In 2004, the ÒNevada Photo-based Inventory PilotÓ (NPIP) was launched involving
the acquisition and processing of large-scale real time GPS-controlled aerial
photography (LSAP) throughout the State of Nevada over two field seasons. The
over-arching goals of this pilot are to exceeding information requirements, step-up
inventory timeline, and reduce inventory costs. In this paper, we describe the
photo-interpretation process, outline the estimation strategies, and report
initial results for White Pine county. On both forest and nonforest lands, we
illustrate level of details that can be obtained from LSAP, repeatability
between photo-interpreters, and consistency with field calls. For forested
lands, we compare photo- and field-based estimates of area by forest type and
percent cover by species, and present a cost-analysis for use of LSAP in an
annual inventory system.