Spatial variation of soil net nitrogen mineralization and nitrification in an old-growth beech-oak forest on Mt. Hakusan
2019
Iimura, Y. (Gifu University (Japan). River Basin Research Center) | Suchewaboripont, V. | Hirota, M. | Yoshitake, S. | Ohtsuka, T.
The objectives of the present study were to characterize the spatial patterns of net nitrogen mineralization and nitrification by focusing on the gap/canopy mosaic structure in an old-growth beech-oak forest on Mt. Hakusan, Japan. We observed high spatial variations in soil net nitrogen mineralization (2.7-94.7kg-N /ha /period) and nitrification rates (0.1-31.1kg-N /ha /period) with averages of 24.6kg-N /ha /period and 4.9kg-N /ha /period, respectively during a field incubation period of 135 days. In addition, the nitrification ratio for nitrogen mineralization exhibited high spatial variation that ranged from 0.9% to 91.5% and averaged 24.3%. The net nitrogen mineralization, nitrification rates, and canopy openness parameters showed a significant positive correlation with inorganic nitrogen content (NO3-N and NH4-N), soil bulk density, and nitrogen input to the soil. In contrast, these parameters displayed a significant negative correlation with the C : N ratio of the soil. Furthermore, the canopy openness exhibited a significant positive correlation with net nitrogen mineralization and nitrification rates. These results suggest that structural heterogeneity, which is the gap/canopy mosaic structure, influenced the soil net nitrogen mineralization and nitrification rates in the old-growth forest on Mt. Hakusan.
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