Seppo Ruotsalainen

Effects of temperature on the site productivity of Pinus sylvestris and lodgepole pine in Finland and Sweden

The influence of temperature regime on forest production in the northern boreal forest was studied by analysing the variation in site index for 20 provenance tests of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) in Finland and Sweden with respect to temperature. The site indices were regressed with several different temperature variables, which were obtained from interpolated monthly averages over 30 years from permanent meteorological stations nearby. There were strong correlations between all tested temperature variables and site index (r = 0.80–0.94). Site fertility influenced site index to some extent but the slope of the test sites did not. An increase in temperature sum from 600 to 1200 degree days (corresponding to an increase of the mean temperature in July from 13 to 15°C) was associated with an increase in site index of Scots pine (Pinus sylvestris L.) from 12.2 to 21.6 m (77%). Such an increase in site index can be assumed to correspond to an increase of 6.5 m3 ha−1 wood (183%)...

Increased forest production through forest tree breeding

Forest tree breeding started in the middle of the twentieth century and since then the use of improved forest regeneration material has become an essential part of forestry in many countries. This review describes methods and achievements of tree breeding programmes, which aim at increasing the quantities and improving qualities of wood-based raw materials through selection, field testing and controlled crossings. Most improved materials currently deployed are seed crops from first-generation phenotypic or tested seed orchards, which offer 10–25% gains in yield depending on the selection intensity of parent trees. Methods of vegetative propagation are developed intensively so that it could be applied to a larger range of species, because it offers high genetic gain and uniformity of the material. Genomic tools are also developed to enhance the efficacy of selection. Applications of genetic engineering are currently limited to research purposes. Forest tree breeding will be an integral part of bioeconomy in securing the production of good quality raw materials in large quantities and will have a significant economic impact on the profitability of forestry in the long term.

Temperature and soil fertility as regulators of tree line Scots pine growth and survival – implications for the acclimation capacity of northern populations

The acclimation capacity of leading edge tree populations is crucially important in a warming climate. Theoretical considerations suggest that adaptation through genetic change is needed, but this may be a slow process. Both positive and catastrophic outcomes have been predicted, while empirical studies have lagged behind theory development. Here we present results of a 30-year study of 55,000 Scots pine (Pinus sylvestris) trees, planted in 15 common gardens in three consecutive years near and beyond the present Scots pine tree line. Our results show that, contrary to earlier predictions, even long-distance transfers to the North can be successful when soil fertility is high. This suggests that present northern populations have a very high acclimation capacity. We also found that while temperature largely controls Scots pine growth, soil nutrient availability plays an important role-in concert with interpopulation genetic variation-in Scots pine survival and fitness in tree line conditions. These results suggest that rapid range expansions and substantial growth enhancements of Scots pine are possible in fertile sites as seed production and soil nutrient mineralization are both known to increase under a warming climate. Finally, as the ontogenetic pattern of tree mortality was highly site specific and unpredictable, our results emphasize the need for long-term field trials when searching for the factors that control fitness of trees in the variable edaphic and climatic conditions of the far North.

Annual growth rhythm of Larix sibirica and Larix gmelinii provenances in a field trial in southern Finland

Abstract The aim of this study was to analyse how the growth onset and shoot elongation of seedlings differ in field conditions in Finland for 20 Russian larch provenances and five comparison entries, and if they could be explained by the geographic and climatic conditions of the provenance origins. In this work, the Dahurian larch (Larix gmelinii Rupr.) provenances had the earliest growth onset and the northern Siberian larches (Larix sibirica Ledeb.) slightly earlier bud burst. The temperature sum and latitude of the provenances explained the differences in shoot elongation. The time needed for shoot elongation and the temperature sum needed to obtain 50% of total shoot elongation were quite equal in the years 2008 and 2009 (larger difference with the 90% level). The growth cessation was affected by photoperiod regardless of provenance. However, it was affected in the southern provenances also by declining temperatures in autumn. The final height was in 2009 largest in southern Dahurian larches. Despite our findings, the use of seed sources of domesticated Raivola origin is the safest choice for regeneration in Finland. We should still study more in detail the performance of other provenances and their adaptation capacity and suitability to Finnish forestry.

Bud set and autumn coloration of Larix sibirica and Larix gmelinii provenances in a field trial in southern Finland

The main aim of this study was to analyse the differences in the bud set, autumn coloration and needle shedding of seedlings in 20 Russian larch provenances and five comparison entries in field conditions in southern Finland over two growing seasons. Furthermore, it was studied if the differences could be explained by the geographic and climatic conditions of the provenance origins. We found that the provenances from cold northern climates developed both their terminal buds first and formed autumn colour as well as shed their needles much earlier than southern provenances. The timing of the bud set occurred earlier in 2008 compared to 2009, which was probably caused by lower than average temperatures in July and August of 2008. Thus, in addition to photoperiod, temperature also seemed to affect the bud set. The southern Dahurian larch provenances were able to utilise the length of the growing season the most effectively. The climatic adaptation, growth and properties of the provenances should be, however, studied over a longer time period. Therefore, currently used Raivola origin is still the safest choice for larch forestry in Finland.