Aspects of the ecology of bracken removal from upland pasture
A study of the floristic structure of the bracken community
indicated a continuum from high frond densities with a species-poor
sward, growing on an organic and acidic soil, to lower frond densities
with a relatively species-rich sward on a more mineralised, less acid
soil. An analysis of the biomass structure of the community showed
that an increase in frond density, litter deposition and long shoot
rhizome length, together with a decrease in soil pH, were correlated
with a decrease in turf biomass.
Excluding livestock appeared to be associated with a
decrease in bracken frond mortality but also significantly fewer
frond buds and unemerged fronds were found below ground. This suggests
that frond damage caused by livestock stimulates the production of
frond buds and, paradoxically, may lead to higher frond densities.
Asulam reduced frond production, in the year after spraying,
by approximately 80 per cent. However, the rates of recovery were
very variable such that full recovery or no recovery were observed
after three years. The percentage recovery was most rapid in areas
with the highest frond densities prior to treatment and may be due
to proportionally more rhizome remaining alive after spraying.
No significant effect of bracken control was seen on the
productivity of the underlying native sward. Furthermore the
application of lime and phosphate and the restriction of grazing
failed to significantly increase sward cover. The application of
agricultural seed mixtures indicated that those containing Agrostis
tenuis appeared to have the most potential for rapid sward development,
with the removal of bracken litter and restriction of grazing being
A model was constructed to suggest two appropriate management
strategies for long-term bracken control after spraying. For sparse
turf, reseeding and the application of lime and phosphate are necessary
but for reasonably well-developed turf no further management is required.