Nitrogen Mineralization in Riparian Soils along a River Continuum within a Multi-Land-Use Basin
- Daniel M. Evans *ab,
- Stephen H. Schoenholtzac,
- Parker J. Wigingtond and
- Stephen M. Griffithe
- a Forest Engineering, Resources and, Management Dep. Oregon State Univ. Corvallis, OR 97331
b Current Address: Dep. of Forest Resources and Environmental Conservation Virginia Tech 228 Cheatham Hall Blacksburg, VA 24061
c Current Address: Virginal Water Resources Research Center, Virginia Tech, 210 Cheatham Hall, Blacksburg, VA 24061
d USDA-EPA, National Health and Environmental Research Lab. Western Ecology Division, 200 S.W. 25th St.Corvallis, OR 97333
e USDA-ARS, 3450 S.W. Campus Way, Corvallis, OR 97331
Nitrogen dynamics in riparian systems are often addressed within one land-use type and are rarely studied on watershed scales across multiple land uses. This study tested for temporal trends and watershed-wide spatial patterns in N mineralization and identified site factors related to N mineralization. We measured net N mineralization in situ at monthly intervals for 1 yr at 32 riparian sites along the 124-km length of the Calapooia River, Oregon. We observed seasonal trends of mean net N mineralization with relatively low rates in the fall (29.8 kg N ha−1 yr−1) and winter (30.1 kg N ha−1 yr−1) and relatively high rates in the spring (122.1 kg N ha−1 yr−1) and summer (99.7 kg N ha−1 yr−1) when conditions for microbial activity and decomposition were likely enhanced. Annual net N mineralization on an area basis ranged from −13.5 to 234.0 kg N ha−1 yr−1 with a mean for all sites of 50.1 kg N ha−1 yr−1 Annual net N mineralization per kilogram of soil ranged from −16.2 to 207.1 mg N kg soil−1 yr−1, with a mean for all sites of 64.4 mg N kg soil−1 yr−1 Regression analysis revealed hardwood basal area and coverage of grass as significant positive predictors of kilograms of N mineralized per hectare. Location along the river explained 22% of the variability of N mineralization per hectare, indicating that riparian areas may function differently along the length of the river.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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