Crop Structure Studies in Ireland.

Abstract

Information requirements on management techniques for fast growing exotic conifers planted in the State afforestation programme emphasised the need for crop structure research. Sample plot thinning series had been used for yield studies in Europe since the last century. More recently, statistically designed experiments have been established in many countries. Research in this field commenced at the end of the 1950's in the State Service. There are now over forty spacing and thinning experiments, the majority in Sitka spruce and coastal lodgepole pine. Some of the spacing experiments have now reached first thinning, and some thinning experiments are approaching rotation age. A data storage retrieval system has been developed to facilitate summary, analysis and comparison of plot measurement. In general results are consistent with research in countries within and outside of Europe. Cumulative volume production differences due to changes in growing space have less practical significance than those for diameter size, diameter and volume distribution. Volumes in the larger tree size categories increase considerably with increased spacing and thinning. This in turn influences profitability and quality. Economic criteria tend to favour increased growing space due to wider spacing and thinning though with the former, especially, serious consideration must be given to possible quality limitations which must be investigated further. Stand stability may be safeguarded by wider spacing, and put at risk by thinning but data are scanty. There are applications for crop structure research in extending stand management options and building models to judge them by, in terms of production, end-usc and profitability. There is room for developing broader stand management strategies related to supply and demand and for constructing new forecasts. From present results a rough guide to decision making might be drawn up and improved as additional information becomes available.