Ny viktning av överlevnad och tillväxt för maximal långsiktig arealproduktion vid tallförflyttning i norra Sverige

Old Scots Pine ( L.) experiments were revisited in order to improve the accuracy of long-term production forecasts in breeding programs based on early evaluations of field trials. Using data from five mainly north Swedish provenance trials (in the “Stefansson provenance series”) we estimated the within-site relation between survival and mean tree height at 18 years, and the total yield at 51 – 52 years (VT) as VT = cin0.42h1.42, where ci=a site-specific constant (i = 1, …, 5), n = number surviving trees-ha-1, and h = their mean height. The form s0.42h1.42 (s = survival) should be generally useful for comparative yield prognoses for different Scots pine stocks within the same site.

The field trials are situated mainly at about 63 – 66o N on sites up to 500 m in elevation. They are composed of open pollinated seeds collected from Scots pine in natural stands about 59 – 68o N. The general applicability of the expression may be diminished by, among other things, the fact that only about half as many seedlings than were planted in the trials are usually planted per unit area in commercial forestry nowadays. That offers fewer selection opportunities at thinning and may cause more remaining open patches, due to mortality, in the final forest.

In addition, our results elucidate once again the well-known benefit of a southward transfer of Scots pine to improve hardiness at harsh regeneration sites. The transfer distance for the highest production per unit area is shorter than that for maximizing the product of early survival and mean height (sh).

(Presented at the 2004 IUFRO Joint Conference of Division 2, “Forest Genetics and Tree Breeding in the Age of Genomics: Progress and Future”, November 1 – 5, 2004, Charleston, South Carolina)