Securing Biodiversity in Breckland - European Commission

Figure 19. Total deposition of nitrogen (kg N ha -1 )across the UK in 2005. Source: Centre for Ecology andHydrology, UKDeleterious change in Breckland grass-heaths consistent with nitrogen impactsBio-monitoring has been recommended as an early warning system for deleterious effects ofnitrogen deposition (Leith et al. 2005; Hall, Bealey and Wadsworth 2006). However, air pollutioneffects can be difficult to distinguish from confounding effects of changes in management. Effects ofnitrogen deposition can be exacerbated by changes in management, particularly a reduction inphysical disturbance or periods with no or light grazing.Cessation of grazing management for decades during the 20 th century allowed accumulation oforganic material on many heathland sites. Species such Yorkshire fog Holcus lanatus and Wavy-hairgrass Deschampsia flexuosa are highly competitive in nitrogen enriched environments. H. lanatus isnow often dominant on areas restored by scrub removal or bracken control.During the early 20 th century acid grass-heath vegetation (e.g. U1/H1), comprised acidiphiloussheep’s fescue - common bent grass Festuca ovina-Agrostis capillaris grass-heath, and lichen heathvegetation (e.g. Watt 1940) while wavy hair grass Deschampsia flexuosa was almost entirely absent.This is in marked contrast to the dominance of Deschampsia flexuosa across large areas of Brecklandheathland by the late 20 th century. At Lakenheath Warren, Alex Watt recorded wavy hair-grass D.flexuosa in just one patch in 1936, but stated that by 1960 it formed several colonies. By 1971 GigiCrompton noted that "The most striking change in the vegetation of Lakenheath Warren has been in100