Soil Mixing Effects on Inorganic Nitrogen Production and Consumption in Forest and Shrubland Soils

Document Type

Article

Journal/Book Title/Conference

Plant & Soil

Volume

289

Publication Date

2006

First Page

5

Last Page

15

Abstract

Soils that are physically disturbed are often reported to show net nitrification and NO−3 loss. To investigate the response of soil N cycling rates to soil mixing, we assayed gross rates of mineralization, nitrification, NH+4 consumption, and NO−3 consumption in a suite of soils from eleven woody plant communities in Oregon, New Mexico, and Utah. Results suggest that the common response of net NO−3 flux from disturbed soils is not a straightforward response of increased gross nitrification, but instead may be due to the balance of several factors. While mineralization and NH+4 assimilation were higher in mixed than intact cores, NO−3 consumption declined. Mean net nitrification was 0.12 mg N kg−1 d−1 in disturbed cores, which was significantly higher than in intact cores (−0.19 mg N kg−1 d−1). However, higher net nitrification rates in disturbed soils were due to the suppression of NO−3 consumption, rather than an increase in nitrification. Our results suggest that at least in the short term, disturbance may significantly increase NO−3 flux at the ecosystem level, and that N cycling rates measured in core studies employing mixed soils may not be representative of rates in undisturbed soils.

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