I started a
further revision of the management plan in 2000. Planning guidance
now focused on "Favourable Conservation Status". I had by now
realised the shortcomings of previous objectives in respect of the
butterfly population cycle. I wanted a revised objective to take
account of the variable population size over time, but it still had
to reflect the viable status of the butterfly on the site. I now
had larval web data which spanned a full cycle of the butterfly
population from the peak in 1991-1994, through the years of very
low web numbers in 1995-1997, and then the gradual rise to the next
peak in 2000. During the previous 10-year cycle, the index
fluctuated between 4 and 236. On the basis of pragmatism, I
selected a 'mid' point representing a lower limit to be exceeded
for at least half of the cycle. Factors and management
prescriptions remained unchanged from the 1995 objective. A revised
layout was adopted.
2000 marsh
fritillary objective:
To maintain the
marsh fritillary population at Rhos Llawrcwrt in favourable
condition where:
Performance
indicators:
Attribute - Larval
web index:
Upper
limit: not required
Lower
limit: The larval web index will exceed 100 for 5 years in any
10-year period.
Factor - Status of
food-plant:
Upper limit: Not
required
Lower limit: not
less than 30
Factor - Average
sward height:
Upper limit:
25cm
Lower limit:
8cm
Status of Feature:
Favourably maintained
The percent index
for the abundance of Succisa prutensis on 53 transects
representative of marsh fritillary habitat on the western block not
required not less than 30
The average sward
height on 53 transects representative of marsh fritillary habitat
on the western block will be as follows: 25 cm
8cm
favourable
maintained
Between 2000 and
2005, the fritillary population crashed and, again, I had to
reexamine management practices (Fig. CS 4.6).
Remaining
confident that management was appropriate on the western block, 1
was now anxious to pursue the reversion of agriculturally improved
fields in the NNR that had the potential to revert to a rhos
pasture type vegetation. These fields had been used to manage the
grazing programme up to 20HX), taking stock coming off the
"unimproved rhos pasture' when required. Ongoing research into
appropriate reversion techniques was indicating that at least some
improved land had the potential to revert to rhos pasture and marsh
fritillary habitat. A programme of management was based on biomass
removal to reduce nutrient levels. The long-term aim was to revert
all improved pasture and thereby significantly extend the amount of
marsh fritillary habitat on the NNR. The winter grazing of the
improved pasture by ponies in the 1990s had created a certain
amount of poaching, leading to the spread of soft rush Juncus
effusus in some fields. This proved difficult to control and
required intensive cutting programmes followed by grazing of the
aftermath.
