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 forestry.
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 shoe-less!
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.