Grassland and Heath
The Irish climate promotes vigorous growth of grasses. Rainfall is evenly spread, so we rarely suffer drought and our temperatures are not too extreme. Grasses are one of the most successful groups of plants in the plant kingdom. Grass seeds and growth patterns differ from other plants. Most plants have their growing point at the top, whereas grasses have a growing point at the base of the stem, if the tips are removed, the plant will survive and continue to grow. Constant grazing encourages growth.
After the Ice Age, grasslands were the first landscape feature, they were quickly invaded by scrub and eventually forest. The early farmers and settlers cleared the woodlands, reinstating the earlier grasslands for their stock.
The peaty soil of the Wicklow uplands is dark and acidic resulting in poor diversity in grass species. The high rainfall washes most minerals and nutrients away decreasing the diversity even more. Only hardy grasses will survive in this environment such as Mat Grass which tends to dominate. On lower mountain slopes, there are areas of wet grassland where you will find Purple Moor-grass and rushes such as Soft Rush and Compact Rush. Along the river valleys, you will see Deer Grass and different rushes such as Black Bog Rush and Bulbous Rush.
Any grassland where heathers and bilberry exceed 25% is considered heath. Heath vegetation is the dominant habitat on the open hillside in the Park. Heath is commonly formed over upland, peaty soils and often grows in association with upland grassland. Heath can be described as being wet or dry depending on the depth of peat and drainage.
Dry heath is dominated by heathers such as Ling and Bell Heather. Other common plants are Mat Grass and Bent Grasses. Wet heath would have grasses such as Purple Moor-grass, sedges such as Star Sedge and heathers such as Cross-leaved Heath . Heath can sometimes be confused with blanket bog. There are a couple of distinctions which can help to identify these two habitats from each other. Generally, if the peat is deeper than 0.5m, it is blanket bog. More usefully, the near absence of sphagnum mosses which are an essential component of blanket bog, a high cover of acid tolerant grasses and a relatively dry surface would all indicate that the area is heath.
Moor burning is a major agricultural practice carried out by the sheep farmers in the Wicklow uplands. Burning kills off the old heather shoots and encourages the growth of younger shoots. Traditional management of heather areas involves burning of heather every ten years to kill off old shoots. However, if burning is too frequent it will destroy the ecosystem, as the heather will not return and bracken or coarse grasses will take over. In some areas of the Park, the frequency of burning is too high and has led to damage in the uplands. Burning of growing vegetation is illegal between March 1st and August 31st each year.
The increase in recreational use of the mountains has created eroded scars across the heaths and grasslands of the mountains. Erosion will start to occur when vegetation is damaged by trampling and the fragile peaty soils are exposed to the elements. With the help of the water, gullies start to form and the peaty soils are washed away exposing the underlying mineral soils and rock . Severe gullies have formed in many over-used areas in the Park, for example descending from Derrybawn into Glendalough and on the path up to the top of Djouce Mountain. In recent years, Park staff have been involved in building boardwalks (traditionally known as tochars), in some areas in the hope of encouraging regeneration of the vegetation. More recently, the emphasis is moving away from the use of boardwalk and using local materials instead. Other voluntary organisations such as Mountain Meitheal have done extensive pathworks in areas of the National Park such as Glensoulan valley.