© 1995 by Institute of Chartered Foresters
Survival rates and performance of multi-trunked trees in even-aged stands of Sitka spruce in western Scotland
Institute of Terrestrial Ecology, Banchory Research Station Hill of Brathens, Banchory, Kincardineshire, AB31 4BY, Scotland
Survival and performance of all trees in 26 stands of Sitka spruce (Picea sitchensis (Bong.) Carr) were monitored for periods of 4–15 years in Glenbranter Forest, Argyll. Initial stand ages ranged between 8 and 35 years, and in the younger stands many trees were multi-trunked.
Some multi-trunked trees became single-trunked and a smaller number died. The trees becoming single-trunked were distributed fairly evenly among classes and quartiles based on initial girth; the trees dying belonged chiefly to the lowest quartiles.
Declines in the incidence of multi-trunking occurred mostly in stands aged between 18 and 45 years. Declines were caused principally by trees becoming single-trunked, mortality being no greater in multi-trunked trees than in single-trunked trees.
Multi-trunked trees grew more slowly than single-trunked trees, judged from the girth increment of the bigger or biggest trunk. Growth was most reduced in the top-quartile girth classes, but in the lowest quartiles multi-trunked trees tended to have slightly greater increment than single-trunked trees.
Nearness to top-quartile trees reduced girth increment in both single and multi-trunked trees.
Individual multi-trunked trees showed a widening in the ratio of the girths of their first- and second-ranked trunks during the study period. But the trees becoming single-trunked were usually more disparate in trunk girth than the trees remaining multi-trunked. So the mean girth ratios calculated for all multi-trunked trees in stands of three ages changed little during the study period, widening only slightly in the younger stands and narrowing in the older stands.
Received 5 January 1994.
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