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IRISH FORESTRY
Phenology of shoot growth and date of flushing
The effect of the wrenching treatments on shoot elongation was evaluated using 10 permanent
sample trees per plot. These 10 seedlings were in the centre transplant line in each
plot. Height measurements commenced on 25 June 1999,just before the date of undercutting.
Subsequent measurements were made just before each wrenching and the scheduled
(September) wrenching date and in mid October (after all elongation had ceased).
The same sample trees were used to evaluate treatment effects on the date of flushing
in the following spring. The number of seedlings per plot that had flushed dwarf-shoot
buds was recorded during February and March 2000. The date of flushing of the longshoot
buds of the branches and leader of each plant was not determined. The long-shoot
buds usually flush in about April or May (personal observations), but the transplants were
scheduled for lifting for field planting before this time.
Morphology
In mid February 2000, 15 plants from near the centre of each plot (excluding the permanent
sample trees) were carefully lifted by hand. The soil was gently washed from the roots ofthe
seedlings to minimise root loss. The plants were stored in co-extruded polyurethane plastic
bags at 2°C until all measurements were completed (over 10 day period following lifting).
The root collar diameter (RCD), seedling height and height increment in 1999 was
recorded for each plant. After this, the shoot was excised from the root at the root collar.
The shoot and root of each plant was dried separately at 75°C for 24 h and then weighed.
The sturdiness (shoot length (cm):RCD (mm» and shoot/root ratios (shoot weight (g): root
weight (g» of each plant were calculated from these values.
Root growth potential and number of days to bud break
In a similar manner to that described for the morphology assessment, a further six plants
were carefully lifted in mid February from near the centre of each plot and placed in plastic
bags. The plants were immediately stored at 2°C at the nursery and then dispatched in early
March to University College Dublin (UCD) for testing. Six pots (replications), containing
three seedlings each, represented each treatment combination (total of 18 plants/treatment
combination). The three seedlings (one from each nursery plot) were placed in 3.5 I pots
containing a 3: 1 (vol:vol) mixture of peat-perlite. The pots were placed in a heated (17-
23°C day/15-17°C night) greenhouse at UCD. The positions of the pots were randomised.
The photoperiod was extended to 16 h using high-pressure sodium vapour lights. Relative
humidity was maintained above 50% by using time-controlled fine mist nozzles. Just after
potting, the medium was watered to field capacity and at 2-3 day intervals thereafter.
The plants were monitored at 2-5 day intervals and the dates at which the first flushing
of the lateral and terminal bud of each plant occurred were recorded. At the end of the test,
after 28 days, the plants were removed from the pots and the roots washed carefully in tap
water. The number of new white roots (> I em) per plant was recorded (Ritchie 1985).
Meteorological data and irrigation
Since undercutting/ wrenching may induce drought stress in seedlings (Duryea 1984,
Mason 1994b), rainfall data for the June to October 1999 period were obtained for a
weather station at Oakpark, Co Carlow, approximately 18 km from Ballintemple Nursery.
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