A proposed vegetation classification for the oceanic wet grasslands of Scotland

Abstract

The lack of clear community definitions for the oceanic wet grasslands of Scotland has resulted in them being overlooked in some conservation schemes, which have tended to focus primarily on the vegetation of the cultivated machair and associated sand dunes. This study recognises five distinct vegetation communities that could be further segregated into ten units equivalent to subcommunities of the British National Vegetation Classification (NVC). These communities show differing ranges in respect of three soil parameters: available phosphorus, pH and organic content. The subcommunities themselves differ in their tolerances to soil moisture, soil fertility and soil reaction, as assessed by their Ellenberg indicator values. The Scottish communities were distinct when compared to communities of the Calthion alliance found in England and Wales with limited overlap. When compared to the Irish Community Classification (IVS) there was more overlap of the data, but alignment to recognised communities was poor. In a broader European context, when compared with data drawn from across twelve alliances, the Scottish communities are mainly associated with the Calthion, yet are discrete from the English and Irish communities of that alliance. They occupy a narrow, central position on the fertility gradient with a broader spread along the hydrological gradient. They are generally less fertile than their English counterparts, which are in turn more fertile than many of the continental communities in the Calthion. The greatest threat to the biodiversity of these grasslands is changing management through both abandonment and intensification, and climate change through increasing rainfall and rising sea levels.