NATURAL REGENERATION IN GLENCREE – 6 August 2002
By Arie van der Wel
The first Field Day was held in Glencree Forest where Coillte research and UCD (part funded by Coford) are studying natural regeneration.
Robert introduced our host for the day Mr Donal O’Hare who, as an independent research forester, currently looks after the experiments which are on Coillte property. Robert also welcomed those present, especially Mr Huw Denman, UK representative of CCFG. Unfortunately Mr Thomas Harttung, Pro Silva European President, did not arrive until later in the day. We were also introduced to two European assistant research foresters, Matt Holzman from Germany and Marie Flechard from France, who are currently on contract to COFORD.
Our morning subject at Glencree Forest ( Deerpark property) was (I) the establishment and growth of a range of species under different canopy densities compared with clear fell and (2) the germination and early growth of SS (Sitka Spruce) under the same conditions.
The experiment was deer fenced and is now in its 3rd year. The SS was planted in 1957 and first thinned in the mid 70’s, with a transformation thinning carried out in April 1999. The experiment was laid down in April / May 1999. The site is considered very stable.
LONG TERM STUDY
Donal O’Hare stated that the experiment is to be reviewed at year five and expressed the shared view that it is vitally important that the trial should run for at least 30 years in order that conclusions can be drawn from it.
Three regimes are being looked at:
(I) Thin to 150 stems /ha. BA 38 sq.m /ha.
(II) Thin to 300 stems / ha BA 15 sq.m / ha.
(III) Clear fell.
(I)- Underplanting was carried out with 6 species: – Sitka Spruce; Norway Spruce; Western Hemlock; Western Red Cedar; Beech and Oak.
Survival under all 3 regimes was satisfactory, with growth vigour increasing with increasing amount of light. Increased light also favoured other (herb) ground vegetation, in particular on the clear felled plots where gorse (ulex) appeared to become very invasive. The secret, Huw Denman explained, is to get the right amount of light to the forest floor to keep the planted or naturally regenerated trees thriving.
(II)- Seeding plots of 1metre x1metre (scarified and un scarified) were laid out under the various regimes and sown with different seed densities. Germination had taken place under all treatments, but seedling vigour was best under the more open canopy (< 150 stems/Ha.). Quite a lot of random natural regeneration of SS is taking place as well – again most vigorous under a very light overhead canopy. Some other naturally sown seedlings were also observed – Holly, Rowan, Birch and Oak.
The exclusion (or careful management) of deer is all important in order for these plants / seedlings to establish and grow away.
A complication in the experiment manifested itself soon after the 1999 (heavy) thinning under regime 1 (i.e. reduced stand to 150 stems/Ha.) due to wind-snap of stems (which is on going) and those plots now look more like clear fell sites. Lesson: Opening-up of stand should start at an earlier age, before trees get too tall.
At the end of this morning’s session we drove down to Laragh where we had our lunch in the local establishment as an outdoor picnic was out of the question due to the continuous rain and rather disappointing temperature for early August.
GROUP FELLING AT BALLARD
Here Donal introduced us to a similar SS stand in which coups have been created by group felling, original coup size slightly less than tree height. No deer fence in place.
A number of seeding plots of 1mx1m were laid down in each coup, using different methods: scarifying, fencing, applying seed – or not. The coup areas were heavily infested with grass, apparently blown in from the roadside, which appears to prevent any natural regeneration. Of the plots only the scarified and seeded and fenced ones showed a reasonable number of seedlings (11.48sdl. /400cm2). The initial group felling did not cause any wind blow or breakage damage, as we saw during the morning in the heavily thinned plots.
The coup can or will be enlarged as time goes on, without putting the existing stand at too much risk.
Felling and particularly extraction can be more easily managed in the coup system than in a respaced stand, when extraction can do a lot of damage.
Again it would be better to start opening the plantation at an earlier age and lower height.
After a lively discussion Robert Tottenham thanked Donal on behalf of us all for this most interesting day and expressed our appreciation to UCD, Coford and Coillte for undertaking these experiments.
Arie van der Wel is a nurseryman and Proprietor of Cappagh Nurseries, Aughrim, Co Wicklow