Some patterns in crop structure and productivity for unthinned Sitka spruce.

  • G.J. Gallagher Research Branch, Forest and Wildlife Service, Department of Lands, Dublin.
Keywords: Crop structure, unthinned sites, site productivity, Sitka spruce, Picea sitchensis, regression analysis, management tables, yield class, mortality, basal area, silviculture, crop structure patterns.


Patterns of crop structure in unthinned Sitka spruce stands are examined by multiple and polynomial regression. Productivity categories for top height are evolved on the basis of confidence belts. Wide variation in volume to 8cm top diameter amounting to 160-200m3/ha is shown within a range of top heights 7m to over 20m. Volume production per ha to 8 cm top diameter for top height is greater in young unthinned stands in Ireland than indicated in the Forest Management Tables (1971). Total stemwood volume is equivalent to timber volume plus 20m3/ha. Top height/age patterns indicate a range of Yield classes to over 24m3/ha/an. Mortality is not severe up to 14m top height. Variation in site conditions meant that volume/top height patterns could not easily be explained by the site factors, elevation, aspect and slope.
How to Cite
Gallagher, G. (1972) “Some patterns in crop structure and productivity for unthinned Sitka spruce.”, Irish Forestry. Available at: (Accessed: 4October2023).