FIELD VISIT TO MOUNT
CALLAN, COUNTY CLARE
by Pro Silva Ireland and Pro Silva Europe
by Marie-Christine Flechard and Huw Denman
Pro Silva Ireland visited Mount Callan on the 10th August 2002 courtesy
of the owners Robert and Jane Tottenham. Ten people attended the meeting
including Thomas Hartung, president of Pro Silva Europe and Huw Denman,
Director of SelectFor Ltd, a company offering advice on continuous cover
Mount Callan is a 400-hectare plantation of mainly Sitka spruce established
progressively over the last 40 years. Elevation is from 50 metres to 300
metres with rainfall being 2000mm???
Being close to the sea, high rainfall and occult deposition results in
a very humid mild climate ideally suited to growth of Sitka spruce and
very high Yield Classes are encountered. Soils vary from podzolic brown
earth on the better sites to deep peat.
A short walk from Mount Callan house we encountered an area of 13-year-old
natural regeneration next to an area of plantation 1st thinning. The plantation
area had been planted with a mixture of Sitka, improved Sitka and western
red cedar. Thinnings at Mount Callan are carried out in year 12 with 2
rows in every 12 being removed. Within the matrix, an additional systematic
thinning is carried out removing every 6th row in herring-bone fashion
and at right angles to the extraction rack. No selection is carried out
at this stage. The improved Sitka were clearly out performing the unimproved
and some were removed in thinnings. However the uniform planting pattern
and thinning regime meant that generally the improved trees were retained
during the 1st thinning. Second thinnings are a repeat of the 1st thinning
pattern in year 15. The natural regeneration had not yet been thinned
and discussion was based on whether it should be left to self thin or
not. Huw Denman said that the self thinning would not be practical as
it would take too long and intervention would be necessary as the regeneration
was dense, the over storey having been completely removed (It would be
cheaper to respace at an early age). Thomas Hartung added that self selection
would occur in an irregular stand as the overstorey could be used to exercise
control over the regeneration.
The 2nd site was 40 year old Sitka, which had been thinned several times.
The crop was relatively uniform due to the uniformity of previous thinnings
but was beginning to develop irregularity through regeneration of beech,
alder and other species.
Site 3 - windblow
Our next stop was an area which had blown down and had been replanted
following site preparation with a mixture of 3 different provenances of
Sitka, western red cedar and Japanese larch. There was great differentiation
in height between the provenances and species and this was a good example
of planning diversity into a planted crop at the establishment phase.
There was evident natural regeneration of birch, sycamore, oak, ash, rowan,
Sitka spruce and ash. Despite the excellent establishment by planting,
maybe there was a lost opportunity here: natural establishment of seedlings
following windblow can give an idea of the species more suitable for the
site conditions and those should be encouraged. Windblow can be a good
method of identifying areas not wholly adapted to the planted species
and an opportunity to diversify the woodland through natural regeneration
of other species or by enrichment planting if the seed trees are not present.
Site 4 - creating irregularity and diversity?
We next visited 40 year old Sitka which had recently been Target Diameter
felled, reducing the stocking density and creating gaps. Natural regeneration
of Sitka was seen where there was enough light (less than 30m2/ha) and
the owner had planted common alder, red alder, Cryptomeria Japonica and
western red cedar in the gaps. The discussion centred on whether gaps
should be created to initiate irregularity. The Pro Silva approach would
be not to compromise the growing stock by artificially felling gaps but
to fell individual trees when their value increment starts to decline.
However, it was felt by some that in conditions where there is high Yield
Class and high windthrow risk, value increment may be declining before
the irregular structure becomes present due to many sawmills now dictating
smaller maximum diameters.
Huw Denman said that a more irregular thinning prescription at an earlier
stage would help create conditions with more spatial diversity. Gaps could
be created at an early stage with minimum loss of increment by removing
groups of poor trees and high-risk areas. In his experience, poor trees
in Sitka often occurred in groups rather than scattered throughout the
plantation and these could be removed early at no loss and replanted opportunistically
to create diversity and to provide later recruitment into the diameter
classes. Thomas Hartung added that a diverse structure should not be a
stand objective in itself, and that even though sawmills may be demanding
relatively small maximum diameter logs we should be growing some of the
trees to much larger sizes. Larger trees will yield larger quantities
of quality wood and will be cheaper to harvest and therefore in the longer
term will provide a bigger margin.
Discussion was had as to species choice and how to diversify the species
at Mount Callan. Robert Tottenham has recently planted some Cryptomeria
based on the growth of a magnificent specimen near the house and the high
prices obtained for its timber in the Far East. Morgan Roche had the opinion
that where a native species was site adapted it should be used in favour
of exotic species and therefore red alder should not be used where common
alder will grow. Huw Denman agreed in principle but stated that red alder
is a natural associate of Sitka spruce in the Pacific North West, and
that it is site adapted to poorer conditions than common alder and is
capable of much more rapid growth than common alder, and therefore can
compete better in mixture with Sitka.
Site 5 - ash regeneration
The next site visited was 28 year old Sitka with ash regeneration. The
ash seemed to be regenerating within 20 metres of the single seed tree
and seemed to be thriving despite possibly being an unsuitable site. Thomas
Hartung pointed out that the ash should be encouraged, however regeneration
should not be the deciding factor for choice of trees to fell as there
is very little financial value in seedlings. Loss of value increment should
be the main factor for selection of trees to fell.
Site 6 - draining
We walked from Site 5 to an area which had been recently deep drained.
The draining had precipitated some windblow but it was obvious that the
drains were effective in moving water from the site. A variety of opinions
were expressed as the efficacy of the drains and the impact on the site.
Generally the Pro Silva approach would be to intervene less dramatically
on the basis that a small investment would be more likely to provide a
return in the long-term. Alder had been planted on the drain sides and
were thriving. Alder is a nitrogen fixing species and the leaf litter
is soil enriching.
Site 7 - the oak glen
Site 7 was a deep ravine or glen with old coppiced oak. Robert Tottenham
had recently removed all the invasive Rhododendron from the glen and the
area now has a ground flora of Luzula sylvatica and various ferns. Pro
Silva would advocate a longer-term approach to removal of exotics. The
more adventurous members of the party clambered to the bottom of the glen
in search of rare ferns and bryophytes. It was a thrilling experience
to stand in the stream bed surrounded by humid moss covered oak trees,
perhaps reminiscent of the primeval forests of Ireland. However, it was
a struggle to return to the path at the top of the glen, one member returning
Site 8 - magnificent Sitka
Our final stop of the day was a magnificent stand of 40-year Sitka with
a YC of 32. This stand showed the possibility for Sitka in Ireland with
very tall trees of good timber quality. Natural regeneration of broadleaved
trees could be seen in the understorey and the stand was beginning to
develop an irregular structure. Under Pro Silva principles no species
are rejected on the fact they are non-native. Sitka Spruce not necessarily
always a wrong choice as its introduction can pave the way to other species.
Helping in the first place to create a forest environment before engaging
in a progressive conversion of the stand into a more mixed species and
uneven forest. Notion of the “right tree at the right place and
at the right time”
Burren and the nature reserve
After tea at Mount Callan, Robert Tottenham took us for a tour of the
Burren including Mullagh More, passing Father Ted’s house (not on
Craggy Island!) and Eagle Rock. At Eagle Rock most of the party were able
to visit the hazel and ash woodland that Robert Tottenham saved from development
and was later turned into a nature reserve.
Many thanks to Robert and Jane Tottenham for hosting the visit and also
for creating such a marvellous forest.
Marie-Christine Flechard is on contract to Coford; Huw Denman is a
Director of SelectFor Ltd and a representative of CCFG.