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Nitrogen mineralization in riparian soils along a river continuum within a multi-landuse basin
Citation:
Evans, D. M., S. H. Schoenholtz, P. J. WIGINGTON JR, AND S. M. Griffith. Nitrogen mineralization in riparian soils along a river continuum within a multi-landuse basin. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL. Soil Science Society of America, Madison, WI, 75:719-728, (2011).
Impact/Purpose:
Nitrogen dynamics in riparian systems are often addressed within one landuse type and are rarely studied on watershed scales involving multiple land uses.
Description:
Nitrogen dynamics in riparian systems are often addressed within one landuse type and are rarely studied on watershed scales involving multiple land uses. This study tested for both temporal trends and watershed-wide spatial patterns in N mineralization and identified site factors related to N mineralization. We measured net N mineralization at monthly intervals for one year at 32 riparian sites over the 124 km length of the Calapooia River, a mixed land-use basin, in western Oregon. Net N mineralization had seasonal trends with relatively low mean net mineralization rates in the fall and winter (29.8 and 30.1 kg N ha-1 yr-1, respectively) and relatively high mean rates in the spring and summer (122.1 and 99.7 kg N ha-1 yr-1, respectively) when conditions for microbial activity and decomposition were likely enhanced. Annual net N mineralization 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 identified total soil nitrogen, calcium and total tree basal area as significant positive predictors of N mineralization per kg of soil. Annual net N mineralization per ha 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. Regression analysis revealed hardwood basal area and coverage of grass as significant positive predictors of N mineralization per ha. Location along the river explained 22% of the variability of N mineralization per ha, indicating that riparian areas may function differently along the length of the river.