Grasslands of the World.pdf - Disasters and Conflicts - UNEP

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Plate 10.9
Poa bulbosa.
Grasslands of the world
and eventual height of flowering culms are poorly correlated. Lolium perenne
and Festuca rubra are obvious contrasts. Also, it is not entirely clear what the
confounding effects in a sward are of growth stage, palatability and residual
leaf area of any given species in competition with others. Whether plants with
“lower cauline-leaved rather than upper cauline-leaved foliage” are necessarily
more competitive under grazing, is therefore doubtful. Competitiveness of
a genotype is also poorly related with potential herbage yield in pure stands
(Boonman and van Wijk, 1973). See also the sections on Haymaking and on
Sown forage, below.
Poa bulbosa (Plate 10.9) heads early in spring and is thereafter not eaten.
Artemisia austriaca forms a rosette. As grazing intensity increases, Polygonum
spp. and other annuals (Cruciferae, Compositae) remain and take over. The
factors responsible are not necessarily the actual grazing itself but associated
phenomena, such as compaction due to treading. The effects of grazing on soil
compaction and soil moisture retention are recurrent themes. Hoof impact is
the cause of disappearance of moss and lichen from grassland . Positive effects
of scattered dung and urine are only evident when the pasture is sufficiently
moist and stocked by at least 0.5 Livestock Unit (LU) per ha. In the steppe, the