Abstract

Sprouting and growth rate after repeated cleaning to a low stump height (0-5 cm) at different dates for cleaning of birch (Betula spp.) and sallow (Salix caprea L.) was studied. The study was focussed on the influence of number of cleanings and the date of the cleaning operation on the ability of sprouting. Two experiments with birch were laid out in Dalarna (Lat 60° 05’ N. Long. 16° 00’ E.; Lat. 60° 23’ N. Long. 15° 51’ E.) in May 2005. They were located on fresh sites on farmland and forest land and the study on sallow was located on a moist farmland site. The sallow experiment was also located in Dalarna (Lat 60° 08’ N. Long. 16° 19’ E.). The treatments were made in May to September 2005 and in middle of July 2006. The number of cleaning dates was 11. The number of stumps was 25 per treatment. In a practical study two localities were laid out on forest land (Lat. 60° 53’ N. Long 14° 52’ E.) on fresh and moist sites. The clear cut areas were covered with 2-3 meter tall birches. The birches were cut to two stump heights: 20 cm and at ground level. The experiment started in May 2005. In July 50% of the birch stumps cut to ground level (0-5 cm) were cut again. The treated sites were randomly chosen. The treated birch and sallow stumps were annually examined. The percentage birch stumps without sprouts four years after treatment was highest after cleaning in May 2005 or in June 2005 and repeated once in July 15 the same year. The number of sprouts per living stump decreased during four years for all treatments with the lowest number of sprouts per stump for the above mentioned cleaning periods. In the practical study with cleaned clumps of birch the number of sprouts on low stumps four years after repeated cleaning was lower than on stumps of normal or low height after a single cleaning. As a conclusion the dates for the first and the second cleaning to a low stump height are important for an efficient cleaning with a result of low number of living stumps, low number of sprouts per living stump and short sprouts. Further on the number of living stumps and the number of sprouts after repeated cleaning of stumps to a low stump height will be lesser than after one cleaning. The study indicates that practical recommendations for repeated cleaning might reduce the costs for cleaning by utilising mechanical cleaning tools.