『Summary
Sediment tracing technology relies on the use of natural biogeochemical
tracers to identify sediment sources in a watershed. This improves
sediment tracer technology by presenting a method to model the
spatial distribution of biogeochemical tracers. The nitrogen stable
isotope of surface soils is modeled across the landscape and was
chosen due to (i) its ability to reflect land management changes
across the landscape, (ii) the lack of understanding regarding
its distribution at the watershed scale, and (iii) its recent
successful use within sediment tracer technologies and anticipated
future use. Potential linkages between watershed variables that
vary across the landscape and nitrogen stable isotopes are postulated
based on assessment of the watershed variables in a geographical
information system, field assessment, and review of biogeochemical
processes. Thereafter field data collection and analyses of nitrogen
stable isotope using an isotope ratio mass spectrometer are performed
followed by statistical analyses and modeling of the tracer across
the landscape. The nitrogen stable isotope is statistically dependent
upon land management practices, geomorphologic landform and soil
depth in the agricultural soils, which is a result of plant harvest
as a nitrogen sink, fertilization and mineralization rates. Short-range
variability of soil moisture and surface heterogeneity due to
cobbles and gravel, woody debris and litter control nitrogen isotopic
b\variability in the forest and only a small portion of the total
data variance is dependent upon the watershed variables. The spatially
distributed model of nitrogen stable isotope of surface soils
is presented and is expected to provide further pin-pointing of
sediment sources using natural tracer technology.
Keywords: Surface erosion; Sediment tracing; Stable nitrogen isotope;
Biogeochemical processes; spatially distributed model; GIS』
Introduction
Assessment of the distribution of watershed variables
Review of the processes and variables controlling δ15N
Field data collection and biogeochemical analyses of δ15N
Statistical analysis of δ15N dependence upon watershed
variables
Explanation of δ15N variability and dependence upon
watershed variables
Modeling of the spatial distribution of δ15N
Conclusions
References