The effects of lichen cover upon the rate of solutional weathering of limestone

• We compare calcium loss from lichen-colonised and lichen-free limestone surfaces.
• Microcatchment surfaces were exposed to natural rainfall for 12 months.
• Calcium loss is greater from lichen-free surfaces than the lichen-colonised ones.
• The rate of calcium loss is 1.001 g m− 2 a− 1 from lichen-covered limestone surfaces.
• The rate of calcium loss is 1.228 g m− 2 a− 1 from lichen-free limestone surfaces.

The contribution of lichens to the biomodification of limestone surfaces is an area of conflict within bioweathering studies, with some researchers suggesting a protective effect induced by lichen coverage and others a deteriorative effect induced by the same organisms. Data are reported demonstrating the potential role of endolithic lichen, in particular of Bagliettoa baldensis, in the active protection of Carboniferous limestone surfaces from rainfall-induced solutional weathering. During a 12-month microcatchment exposure period in the west of Northern Ireland, average dissolutional losses of calcium are greater from a lichen-free limestone surface compared with a predominantly endolithic lichen-covered surface by just under 1.25 times. During colder winter months, the lichen-free surface experiences calcium loss almost 1.5 times greater than the lichen-covered surface. Using extrapolation to upscale from the micro-catchment sample scale, for the year of sample exposure, the rate of calcium loss is 1.001 g m− 2 a− 1 from lichen-covered limestone surfaces and 1.228 g m− 2 a− 1 from lichen-free bare limestone surfaces. This research has implications for our understanding of karst environments, the contribution of lichens to karren development and the conservation of lichen-colonised dimension stone within a cultural setting.