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Nature in Wales


Vol. 3, no. 2 Summer 1957

Poa Pratensis subspecies Subaerulea, in north Glamorgan and south Brecon

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Royal Agricultural College, Cirencester
THESE notes are an account of the distribution and field characters
of Poa pratensis L. subspecies subcaerulea (Sm.) (Tutin) in the hill
country of north Glamorgan and south Brecon. Before dealing with
the details it is worth recounting the taxonomic opinions of the
species, for Poa pratensis is classified by some (Akerberg 1942,
Gustaffson 1947, and Tutin 1952) into at least four subspecies or
form-complexes, whilst Hubbard (1954) in his classical account of
the British grasses considers that the three subspecies present in
this country are sufficiently distinct to merit separate specific rank.
Thus subspecies subcaerulea is sometimes referred to as Poa subcaerulea
(Sm.), and yet again is often listed as subspecies irrigata (Lindm.)
Lindberg f. However, although there is debate about the rank of
the taxon, its characteristics are well appreciated and have been
described by Hubbard (1954). It is frequently found in moist soils
at varying elevations, and in such diverse habitats as coastal sand-
dunes and mountain grasslands, and abroad it has been studied by
Love (1952) and Akerberg (1942), though Melderis (1955) com-
ments that no work has been done on the populations in this country.
Thus the present collections are an attempt to gather some in-
formation as a preliminary to more detailed transplant studies.
Hyde and Wade (1934) have already recorded the subspecies in
Monmouth, Glamorgan, Brecon and Anglesey.
During collection in these hill areas subcaerulea has been found
in a considerable variety of habitats, and these are listed below
(1) Permanent grasslands It has been found in both
enclosed and unenclosed grasslands where Agrostis tenuis is dominant
and Festuca ovina and F. rubra are present. In these pastures the
plants are poorly tillered and most noticeable when the panicles
have emerged.
Subcaerulea is very common on road verge grazings along open
mountain roads where sheep grazing may be intensified in narrow
strips, and where Nardus stricta and Molinia caerulea become dominant
further away from the roads.
(2) Sheep shelters Where localised shelter or camping
is taken by sheep, as under walls, banks, or stunted hawthorn, then
heavy trampling and faeces concentration results in localised
modification of the flora. On these small areas bare ground is
obvious and subcaerulea is frequently found, often in well developed
mats, together with such species as Agrostis tenuis, Poa annua and
Stellaria media. These local modifications are often much isolated
amongst large acreages of Nardus grazings.
(3) Pathways In the area of study it is often possible to find
subcaerulea on sheep and cattle paths. When found, the plants tend
to be much more heavily tillered than in the adjoining grassland.
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