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Crop Structure and Productivity for Unthinned Sitka Spruce 51(1) The possib~lity of equivalent yield classes but shorter rotationsthan indicated in the Forest Management Tables(1971).(II) The possibility of a temporary reduction in productivity duepossibly to stand conditons, with greater final production.(6) Total stemwood production is equivalent to V plus approxi-8mately 20m. 3 /ha. This comes from small sized trees and tops.(7) Mortality is not high up to 16m. top height (some 5%). Thereis tentative evidence that it increases fairly rapidly from then on.(8) Altitude, Aspect and Slope did not correlate well with eithervolume or height.MISCELLANEOUS OBSERVATIONS(1) The data suggested a slight inverse correlation betweenhigh volume ratios and top height and also between altitude andtop height. Considerable leader breakage was observed during thesurvey so that there may be some link between exposure, leaderbreakage, and high production for top height(2) When the survey was undertaken, plots were grouped accordingto four arbitrary regions.(I) East(II) Northwest(III) Midlands(IV) Southwest.The percentage of stands with high volumes for top height weregreater in the order (I) to (IV).Overall differences between crop structure in unthinned standsand that shown by the tables of Hamilton and Christie for thinnedstands appear to exist. These might well influence the futuremanagement of the species here and investigations on potentialincrement at rotation age are warranted. There is a need to studystands at varying stocking levels, especially those approachingculmination of increment.ACKNOWLEDGEMENTSAcknowledgements are due to Mr. W. Luddy, Mr. A. Buckleyand the late Mr. S. Dennehy who carried out field work; and toMr. A. O'Leary and Mr. D. O'Brien for assistance in computationand analysis.