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Ozawa, M.; Shibata, Hideaki; Satoh, Fuyuki; Sasa, Kaichiro

doi:10.1023/a:1013877316949

Cited by 10 publications

(1 citation statement)

References 7 publications

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“…This variation was explained by an increase of nitrification rate with decreasing precipitation: when plants uptake nitrate as the sole source of N, high nitrification causes the ammonium-to-nitrate reaction to go further towards completion, which would decrease the isotope fractionation factor from ammonium to nitrate. Thus Δδ 15 N becomes small and nitrate becomes less deficient in 15 N. For an example of the third cause of Δδ 15 N variation, Fujiyoshi et al (2017) (Ozawa et al 2001;Fukuzawa et al 2006;Nagasaka et al 2015), whereas N loss due to leaching is negligible in taiga forests in northern Mongolia (Shugalei and Vedrova 2004). We hypothesize that a difference in soil N availability in the two regions influenced by climate leads to a difference in Δδ 15 N, because a difference in soil N availability is expected to link with a difference in the processes which causes Δδ 15 N variation from the previous studies above.…”

Section: Introductionmentioning

confidence: 99%

Influence of soil N availability on the difference between tree foliage and soil δ15N from comparison of Mongolia and northern Japan

Fujiyoshi

Sugimoto

Yamashita

et al. 2019

Ecological Indicators

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Nitrogen isotope ratios (δ 15 N) in plants and soil are widely known as indicators of the N cycle in terrestrial ecosystem. Recent studies have proposed that the difference between plant and soil δ 15 N (Δδ 15 N) is a better indicator of the N cycle than plant δ 15 N or soil δ 15 N alone. However, the processes of the N cycle indicated by Δδ 15 N are not well understood. The present study compared Δδ 15 N variations between different ecosystems of northern Mongolia and northern Japan (Hokkaido) to associate the Δδ 15 N characteristics with soil N availability. Needles of Siberian larch (Larix sibirica Ledeb.) in Mongolia, Todo-fir (Abies sachalinensis (F.Schmidt) Mast.) in Hokkaido, and mineral soils from both regions were acquired for determination of Δδ 15 N values. Δδ 15 N showed similar large variations (8‰) in the two regions with no significant correlations to climate factors. On the other hand, the relationship between Δδ 15 N and soil δ 15 N was opposite between the two regions with a positive correlation in Mongolia (rs = 0.504) and a negative correlation in Hokkaido(rs = -0.600). Moreover, total inorganic N (total amount of NH4 + and NO3 -) contents were up to 20 times higher in Hokkaido than in Mongolia. Δδ 15 N showed significant correlation with the fraction of NO3relative to total inorganic N in the 0-10 cm soil layer in Hokkaido. These results indicate that Δδ 15 N variation in Hokkaido can be explained by progression of nitrification in soil, which is different in Mongolia where Δδ 15 N variation is explained by microbial N immobilization. Our findings suggest that soil N availability affects Δδ 15 N indicator owing to changes in the N cycle process, which are reflected in the relationships of foliage δ 15 N or soil δ 15 N with Δδ 15 N.

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Section: Introductionmentioning

confidence: 99%

Influence of soil N availability on the difference between tree foliage and soil δ15N from comparison of Mongolia and northern Japan

Fujiyoshi

Sugimoto

Yamashita

et al. 2019

Ecological Indicators

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Relationship of topography to surface water chemistry with particular focus on nitrogen and organic carbon solutes within a forested watershed in Hokkaido, Japan

Ogawa

Shibata

Suzuki

et al. 2006

Hydrological Processes

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Abstract:We studied the relationships between streamwater chemistry and the topography of subcatchments in the Dorokawa watershed in Hokkaido Island, northern Japan, to examine the use of topography as a predictor of streamwater chemistry in a watershed with relatively moderate terrain compared with other regions of Japan. Topographic characteristics of the Dorokawa watershed and its subcatchments were expressed as topographic index (TI) . Distinctive spatial patterns were observed for dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and NO 3 concentrations of streamwater across the watershed. Statistical analyses indicated significant linear relationships between the average TI values of subcatchments and DOC, DON, and NO 3 concentrations. Furthermore, the proportion of DOC in streamwaters in the wet season increased with TI values relative to other nitrogen species, whereas NO 3 concentrations decreased with TI. The gradients of soil wetness and the presence of wetlands explained many of the observed spatial and temporal patterns of DOC, DON, and NO 3 concentrations in the surface waters of the Dorokawa watershed. Our results suggest that the TI is especially useful for predicting the spatial distribution of DOC, DON and NO 3 in the surface waters of Hokkaido, where topographical relief is moderate and wetlands more common than in other regions of Japan.

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Dissolved organic carbon and nitrate concentrations in streams: a useful index indicating carbon and nitrogen availability in catchments

Konohira

Yoshioka

Forest Ecosystems and Environments

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Untitled

Cited by 10 publications

References 7 publications

Influence of soil N availability on the difference between tree foliage and soil δ15N from comparison of Mongolia and northern Japan

Influence of soil N availability on the difference between tree foliage and soil δ15N from comparison of Mongolia and northern Japan

Relationship of topography to surface water chemistry with particular focus on nitrogen and organic carbon solutes within a forested watershed in Hokkaido, Japan

Dissolved organic carbon and nitrate concentrations in streams: a useful index indicating carbon and nitrogen availability in catchments

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