Micromorphological assessment of the effect of liming on faunal excrement in an upland grassland soil

Abstract

We investigated the impacts of liming on faunal activity over a 2 year period as expressed in excrement in an upland grassland soil. Undisturbed samples for micromorphological analysis were collected in June 1999 and June 2001 from limed and control plots at a research farm in south-eastern Scotland. Thin sections prepared from these samples were analysed using point counting methods with data collated on a horizon basis. Attention focussed on features indicative of faunal activity, viz. excremental pedofeatures and void space. In both limed and control samples, there was a very close association between types of excremental pedofeatures and soil horizons. Excrement from earthworms was mainly found in the LF and H horizons, whilst excrement from enchytraeids was concentrated in the uppermost organo-mineral horizon (Ah). Undifferentiated or fused excrement was the most common, especially in a lower H horizon which also contained phytolith fragments. Over the 2 year period, there was a decline of undifferentiated excrement, and an increase in excrement of earthworm origin in the control plots. Overall it proved difficult to separate the influence of liming from background changes in faunal activity as occurred in the control plots. Despite the heavy application of lime to this upland soil, the effect on earthworm activity was limited to the uppermost organic horizon.