Topographic variation of soil nitrogen dynamics at Walker Branch Watershed, Tennessee
- ORNL
- University of Wisconsin
Understanding the spatial and temporal variability of soil nitrogen (N) transformations is central to quantifying the N dynamics and productivity of ecosystems. The objectives of this work were to examine spatial and temporal variation of soil N dynamics and to identify factors correlated with topographic variation in soil N dynamics in a forest watershed. Net N mineralization and net nitrification potential were measured by aerobic laboratory incubations of surface (0-7 cm) mineral soils. Principal components analysis was used to describe sampling sites across the watershed based on 13 site characterization variables. A topographic index used in hydrologic modeling, In ({alpha}/tan {beta}), was calculated for each site as the natural logarithm of the ratio of the upslope drainage area per unit contour length ({alpha}) to the local slope angle (tan {beta}). Soils from valley floors had greater total N concentrations, lower carbon-to-nitrogen (C:N) ratios, greater potential net nitrification, and greater microbial activity (as indicated by short-term urease assays) than soils from ridges. Mean net nitrification potential was 0.59 {micro}g N g{sup -1} d{sup -1} in surface soils from valley floors and was < 0.01 on ridges and slopes. The first principal component was related to the N and C properties of soils, leaf litter, and leaf fall at a site. The second principal component was related to forest stand composition. The topographic index was significantly correlated with important variables related to soil N dynamics. Once calibration data are derived, this index may be useful as a first approximation to total soil N concentrations and soil C:N ratios in forest watersheds because In ({alpha}/tan {beta}) can be calculated from geographic information systems that contain topographic data.
- Research Organization:
- Oak Ridge National Laboratory (ORNL); Oak Ridge National Environmental Research Park
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 989635
- Journal Information:
- Forest Science, Journal Name: Forest Science Journal Issue: 3 Vol. 40; ISSN FOSCAD; ISSN 0015-749X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Variation in foliar [sup 15]N abundance and the availability of soil nitrogen on Walker Branch Watershed
Relationships between soil nitrogen dynamics and natural 15N-abundance in plant foliage from the Great Smoky Mountains National Park
Related Subjects
59 BASIC BIOLOGICAL SCIENCES
99 GENERAL AND MISCELLANEOUS
APPROXIMATIONS
CALIBRATION
DRAINAGE
ECOSYSTEMS
FORESTS
GEOGRAPHIC INFORMATION SYSTEMS
MINERALIZATION
NITRIFICATION
NITROGEN
PRODUCTIVITY
SAMPLING
SIMULATION
SITE CHARACTERIZATION
SOILS
TENNESSEE
TRANSFORMATIONS
UREASE
WATERSHEDS