Abstract

The objective was to study the influence of felling time on the vegetative production of alders and to quantify the potential for sprouting and suckering by naturally regenerating alders for utilisation of the biomass for biofuel production. Twenty-five naturally regenerated 15-year-old common alders (Alnus glutinosa (L.) Gaertn.) were cut each month from March to November 1993, and twenty 8-year-old grey alders (Alnus incana (L.) Moench) each month from March to December 1998, leaving 20 cm high stumps in each case. The common alders were located in southern Sweden (Lat. 57˚ 58’ N. Long. 12˚ 26’ E.) on abandoned farmland, while the grey alders were located in central Sweden on abandoned farmland (Lat. 60˚ 15’ N. Long. 16˚ 01’ E.). The common alder stumps were examined in September of the year after cutting and again 2, 5 and 11 years after cutting. The grey alder stumps were examined in September 1, 2 and 6 years after felling. The numbers of living stumps and sprouts produced by each stump of both species, and the numbers of suckers produced by the grey alder stumps, were recorded. When the sprouts of the grey and common alders were 6 and 11 years old, respectively, their diameter at breast height was measured. The proportions of common alder stumps that were still alive after 11 years were highest for trees cut in July, August, September and October (64, 84, 56 and 68%, respectively) and lowest for trees cut in March, April and May (24, 28 and 20% respectively). The mean number (1.8 ± 0.1) of common alder sprouts varied little between months, ranging between 1.3 and 2.3 per living stump. The greatest numbers of sprouts per stump occurred for trees cut in August, September and October (2.1, 2.3 and 2.1 sprouts per stump, respectively). For grey alder the percentages of living stumps that had been cut in specific months six years after cutting ranged from 25 to 55 % (mean, 37%). The percentage, after six years, was highest (55%) for trees cut in March and May, and lowest (30%) for trees cut in July, August and October. The mean number of grey alder sprouts per living stump was 1.7±0.8 with values ranging between 1.2 and 2.0. The most sprouts were produced by stumps of trees cut in March and September, (2.0±0.4 sprouts per stump), while trees felled in July produced the least (1.2±0.2). Significant differences in sprout height were found between different cutting periods for both common and grey alders. Both species also showed significant differences in the breast height diameters of sprouts between different cutting periods. Practical recommendations are given for biomass production after cutting at various times of the year. The results in the study indicate that common alders should be cut between July and September and grey alders in March to May in order to maximise biomass production. To minimize the number of sprouts or biomass production common alders should be cut in November and grey alders in July. Cutting should take place in June, August or September if high production of grey alder suckers is required and in March or December if low production of suckers is desired. In addition to the biomass potential from alders, growing sprouts or suckers above Norway spruce (Picea abies (L.) Karst.) seedlings are an excellent way to decrease the amount of frost damage to the seedlings

Keywords

Biomass production; carbohydrate content; common alder; cutting periods; grey alder; sprouting; suckering

Published in

Rapport (Institutionen för energi och teknik, SLU)
2009, number: 008
Publisher: Sveriges lantbruksuniversitet, Institutionen för energi och teknik

SLU Authors

• Johansson, Tord

  • Department of Energy and Technology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Forest Science
Renewable Bioenergy Research


Permanent link to this page (URI)

https://res.slu.se/id/publ/25898