Spatial variations in larch needle and soil δ¹⁵N at a forest–grassland boundary in northern Mongolia

Abstract

The spatial patterns of plant and soil δN and associated processes in the N cycle were investigated at a forest-grassland boundary in northern Mongolia. Needles of Larix sibirica Ledeb. and soils collected from two study areas were analysed to calculate the differences in δN between needle and soil (ΔδN). ΔδN showed a clear variation, ranging from -8 ‰ in the forest to -2 ‰ in the grassland boundary, and corresponded to the accumulation of organic layer. In the forest, the separation of available N produced in the soil with N-depleted N uptake by larch andN-enriched N immobilization by microorganisms was proposed to cause large ΔδN, whereas in the grassland boundary, small ΔδN was explained by the transport of the most available N into larch. The divergence of available N between larch and microorganisms in the soil, and the accumulation of diverged N in the organic layer control the variation in ΔδN.

Life histories and niche dynamics in late Quaternary proboscideans from Midwestern North America: evidence from stable isotope analyses

“…In N limited environments such as tundra, terrestrial plants may receive relatively more N from inorganic sources. Boreal forests like those of the late Glacial Midwest, however, exhibit relatively greater biological productivity, so plant shoots are more likely to take in volatized ammonia (low δ 15 N) from organic sources such as urea (Fujiyoshi et al 2017). These results suggest a similar scale to landscape use strategies employed by late Quaternary mammoths in the Midwest as those suggested by Hoppe (Hoppe et al 1999;Hoppe 2004) for mammoths in the Great Plains and Florida.…”

Life histories and niche dynamics in late Quaternary proboscideans from midwestern North America

“…In N-limited environments such as tundra, terrestrial plants may receive relatively more N from inorganic sources. Boreal forests like those of the Midwest during the Bølling and Allerød, however, exhibit relatively greater biological productivity, so plant shoots are more likely to take in volatized ammonia (low δ 15 N) from organic sources such as urea (Fujiyoshi et al, 2017).…”

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

“…The observation period was from June to August, 2004August, -2012 in Mongolia, whereas the sites in Hokkaido was observed from June to September, 2011-2013 (Table S1). To compare Mongolia with Hokkaido, we compiled new and published data (Fujiyoshi et al 2017) for Mongolia. Among observation areas in Mongolia, needle and soil δ N in Terelj (TR) and Mongonmorit (MM) areas have been reported in Fujiyoshi et al (2017).…”

“…(1) difference in plant N source (Averill and Finzi 2011;Brearley 2013;Brenner et al 2001;Callesen et al 2013;Hobbie et al 1999); (2) nitrification progression (Kang et al 2011;Schuur and Matson 2001); and (3) N immobilization by soil microorganisms (Callesen et al 2013;Fujiyoshi et al 2017). In one example of the first cause, Δδ 15 N ranged from -3 to 0‰ with increasing elevation in the White Mountains, USA (Averill and Finzi 2011).…”

“…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.…”