SPATIAL VARIABILITY OF SOIL TOTAL C AND N AND THEIR STABLE ISOTOPES IN AN UPLAND SCOTTISH GRASSLAND

As preparation for a below ground food web study, the spatial variabil ity of three soil properties (total N, total C and pH) and two stable isotopes (delta(13)C and delta(15)N of whole soil) were quantified usi ng geostatistical approaches in upland pastures under contrasting mana gement regimes (grazed, fertilised and ungrazed, unfertilised) in Scot land. This is the first such study of upland, north maritime grassland s. The resulting patterns of variability suggest that to obtain statis tically independent samples in this system, a sampling distance of gre ater than or equal to 13.5 m is required. Additionally, temporal chang e (a decline of 1 parts per thousand) was observed in whole soil delta (15)N for the grazed, fertilised plot. This may have been caused by ne w inputs of symbiotically-fixed atmospheric N-2.