3 Lithomorphic soils – rendzina

Lithomorphic soils have a well-developed topsoil but no subsoil and are very shallow (<30cm) soils over rock, rubble or unaltered sediment. One reason they are so shallow is that they are at a very early stage of formation. Another, is because some parent materials weather only very slowly. On rocks like limestone and chalk, it is because no matter how quickly they weather, there is very little residue after solution weathering. The various subtypes may reflect this. Rankers are non-calcareous, and may be quite acid, sometimes with peaty surface layers, formed over hard, slow weathering rock types. Sand rankers are formed over very recently accumulating sands and represent a development on from the Terrestrial Raw Soils . One special type of Lithomorphic soils – Rendzina are calcareous, usually with a normal topsoil, formed over limestone (or chalk) and are very common on Anglesey. The Carboniferous limestone on Anglesey is frequently very pure and leaves very little residue after dissolving, perfect parent material for rendzina formation. However, when looking for these soils, beware of glacial till over eroded limestone surfaces!
Location: Mariandrws, just north of Beaumaris, Anglesey – located in a small disused quarry on a sharp bend in the unclassified road from Llanddona to Mariandrws at SH595812. Follow the public footpath, noting the soil on top of the quarry face on the left for about 50 yards

Humic rendzina (Marian Series), parent material Carboniferous limestone; vegetation, plants of limestone grassland; land use rough grazing.

Profile

0-18 Ah very dark greyish-brown, almost black, highly organic sandy loam. Well- developed crumb structure, very abundant fine roots, earthworms present, sharp, irregular boundary to

18+ R hard, white Carboniferous limestone, slightly fractured.

Lithomorphic soils – Rendzina – can be found on most limestone outcrops from Lligwy to Penmon