Above-ground grazing affects floristic composition and modifies soil trophic interactions

• Published in: Soil biology & biochemistry 2002-10, Vol.34 (10), p.1507-1512
• Main Authors: Neilson, Roy, Robinson, David, Marriott, Carol A., Scrimgeour, Charlie M., Hamilton, David, Wishart, Jane, Boag, Brian, Handley, Linda L.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Ecosystem function; Fundamental and applied biological sciences. Psychology; Grazing; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil ecosystems; Soil science; Stable isotopes; Trophic interactions; Zoology (interactions between soil fauna and agricultural or forest soils)
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/S0038-0717(02)00122-0

There are few data on the functional inter-relationships between above- and below-ground components of soil ecosystems. Here, we report changes in below-ground soil invertebrate trophic relationships (manifested as alterations in stable isotope natural abundances, δ 13C and δ 15N) that arose in association with the removal of sheep grazing and from the resulting changes in above-ground floristic composition. Consequent to grazing removal, Lolium perenne L. (perennial rye-grass) was replaced as the dominant plant species in ungrazed treatments by Ranunculus repens L. (creeping buttercup), a species with more 13C-enriched foliage. Consequently, all invertebrate functional groups studied, but not whole soil, were more 13C-enriched in ungrazed treatments. Earthworms (detritivore) from grazed treatments were significantly 15N-enriched compared with earthworms from ungrazed treatments. In contrast, slug (herbivore) δ 15N exhibited no treatment effect. Reasons for this are unclear but may be related to the effects of above-ground grazing on the composition of below-ground microbial/microfaunal communities. Omnivores/carnivores (beetles and spiders), were more 15N-enriched than primary producers in the grazed than in the ungrazed treatments (6 vs. 4‰) suggesting a longer below-ground foodchain in the grazed plots. The cessation of fertilizer application had no comparable effects on below-ground trophic relationships.