Author/Authors :
Neilson، نويسنده , , R. and Hamilton، نويسنده , , D. and Wishart، نويسنده , , J. and Marriott، نويسنده , , C.A. and Boag، نويسنده , , B. and Handley، نويسنده , , L.L. and Scrimgeour، نويسنده , , C.M. and McNicol، نويسنده , , J.W and Robinson، نويسنده , , D.، نويسنده ,
Abstract :
In an exploratory study of below-ground trophic relations, natural abundances of the stable isotope pairs 13C/12C and 15N/14N (δ13C and δ15N) were measured on samples of plant shoots, whole soil and soil invertebrates taken in 1994 from two contrasting treatments of a pre-existing experiment: (1) continued grazing by sheep, with N:P:K fertiliser additions from 1990 onward; and (2) no added fertiliser, but sheep grazing removed entirely. Stepwise trophic increases were documented better by seasonal averages of δ13C and δ15N and by seasonal trends, composed of data collected on several occasions, than by instantaneous values. Seasonal changes in plant monocot vs dicot differences for shoot δ13C and δ15N were detected from patterns over several individual sampling dates; instantaneous samples were neither statistically significant nor qualitatively interpretable. Significant isotopic differences between treatments were evident in invertebrates only as seasonal averages or trends. Seasonal variations of δ13C and δ15N in earthworms and slugs may reflect previously unsuspected invertebrate behaviour. Whole soil δ13C was static through time and across treatments. Whole soil δ15N changed seasonally, an effect consistent with 15N/14N fractionation, e.g. during denitrification.
