Eryri today can be said to be mainly grassland,
this is as a result of the removal of the natural woodland for
timber, fuel, and charcoal and most important of all, agricultural
land - be it pasture or agrarian cultivation. The clearance of
the natural forest began over 4,000 years go in Neolithic times.
In the uplands this clearance developed the areas of heath we
see today as well as precipitating the formation of blanket peat-land.
In Eryri the climatic climax vegetation would have been broad-leaved
woodland, mainly of sessile oak, with birch forests on the higher
ground. The tree line of this forest would have been around 500m
on most slopes; the bracken seen on the hills today give a rough
clue as to the presence of the woodland. Very little of this 'natural'
woodland remains, one of the few upland woods that remain is Coed-y-Rhygen,
near Trasfynydd; while Coed Padarn on the hillside around the
Vivian Quarry in Llanberis is a good example of a sessile oak
At various points in Eryri, a clue as
to the variety of plant species possible can be found in the areas
fenced off to stop sheep from preventing re-growth by grazing;
one of the islands on Llyn Idwal - moated by the lake waters and
safe from the sheep also sports luxurious growth.
Sheep are therefore the most important
factor affecting plant regeneration; apparently in the Middle
Ages the pressure of 0.15 sheep per hectare was enough to retain/maintain
large areas of grassland. Today, with around 3 sheep per hectare
the pressure is obviously greater and species regeneration is
affected. In woodland open to grazing one may find mature trees
and shrub growth but few, if any, forest seedlings managing to
overcome grazing pressure to replenish the forest trees.
A number of grasses can be
found in the hill-slopes of Eryri. Mat-grass is usually the main
species found on the very poor acid soils of the upper slopes;
it is an aggressive plant apt to overgrown other areas of grassland
if they are overgrazed. Sheep will only eat the mat-grass if nothing
else is available.
In wetter areas one finds purple moor-grass
in large swathes, while on the lower slopes Sheep's Fescue is
dominant. In some areas the teaching of plant nutrients down slope
(catena) allows meadow grasses and bents to grow. Sheep are drawn
to these as they offer improved grazing, their droppings increase
soil fertility and in these areas white clover can be found, helping
to produce reasonable pasture.
In some areas such as Cefn Du, Migneint and the Rhinogau large areas
of heather can be found along with bilberry and in some areas crowberry.
In most wet hollows Cotton Grass, soft rushes and a variety of sphagnum
mosses are to be found. These plants tend to develop peat; peat
is a result of wetness and acidity halting the processes of decay
- new growth taking place atop the remains of other plants. The
accommodation of peat varies a great deal according to the conditions;
in some areas the rate of accumulation may be as small as 30 mm
per hundred years. Many of the areas of peat have been drained and
ploughed to create improved pasture.
Plant growth on rocky or even scree slopes is particularly harsh
on plants; here some deep-rooted plants such as the Western Gorse
and Parsley Fern may survive in this highly mobile environment.
Another harsh environment is the rocky tops of the mountains here
one may find such species as Wood-hair Moss, Viviparous Fescue and