15N fractionation between vegetation, soil, faeces and wool is not influenced by stocking rate

Abstract

Understanding stable isotope fractionation in trophic networks is important for the interpretation of stable isotope composition of ecosystem components. This work explores the influence of grazing pressure on the nitrogen isotope composition (δ N of wool (from a yearly shearing) reflects vegetation at the whole-year grazing grounds-scale while faeces reflect that of the area grazed within a few days. Stocking rate had no effect on δ 15

Comparison of isotopic variability in proteinaceous tissues of a domesticated herbivore: a baseline for zooarchaeological investigation

“…The δ 15 N keratin values (6.1 − 8.6‰) were higher than those for sheep wool from mainland Europe or east Asia, but lay within the very wide range of values from Turkey (2.8 − 10.1‰) . Again, the geographical pattern of greater enrichment in 15 N in sheep protein samples from the UK than in those from mainland Europe matched that previously reported .…”

Sheep Wool δ13C Reveals No Effect of Grazing on the C3/C4 Ratio of Vegetation in the Inner Mongolia–Mongolia Border Region Grasslands

“…The relatively high 13Δ4 is mainly caused by C. squarrosa, which dominates the C4 community and which has a high leakiness affecting 13Δ [26]. A bias due to the selection of sheep or differences in the digestibility of C3 and C4 components was unlikely over the entire range of grazing intensities, as was confirmed by the results from a controlled grazing experiment [14], [27]. Also, a change in species composition within the C3 and C4 communities and a change in species discrimination as a response to varied grazing intensities caused 13Δ3 and 13Δ4 to deviate by not more than 0.2‰ [12] while the difference between both endmembers is about 10‰.…”

Isotopic composition of soil, vegetation or cattle hair no suitable indicator of nitrogen balances in permanent pasture

“…The animals' N excretion was calculated as a percentage of their N intake (determined as explained below). It was expected that 90% of the N intake was excreted again (Whitehead 1995).…”

“…In all these cases, the influences of the management are integrated in the stable isotope composition of the samples, which are stable over time (with some seasonal variation) if the management is stable (e.g. Neilson et al 1998;Schnyder et al 2010;Wittmer et al 2010).…”