Jan‐Erik Nilsson

Mechanizsed microsite preparation and direct seeding of Pinus sylvestris in boreal forests — a way to create desired spacing at low cost

The main objective of this study was to examine the cost, flexibility, and appropriate scale of mechanized microsite preparation (MP), in combination with mechanical direct seeding of Pinus sylvestris L. with orchard seed. This technique was tested at four boreal forest sites in Northern Sweden. Orchard and stand seeds were sown with and without MP. The use of orchard seed increased seedling establishment by 41% and the use of MP increased seedling establishment by 47%, respectively, after two years. The best substrates for sowing when using MP were OAh-, E- and BC-horizon, in ranked order. The use of orchard seed compared to stand seed increased mean seedling height by 25% after four years. These trials suggest that to obtain a density of 5,000 stems ha-1 four years after seeding, 61,000 viable stand seeds or 41,000 orchard seeds ha-1 should be sown if MP is not used. If MP is used, seeding rate could be reduced by about 32%. By using MP, and by further improving scarification technique so that all scarified area is thin OAh-horizon, we predict that only 32,000 stand seeds or 22,000 orchard seeds ha-1, i.e., half the dosage, should be needed. Under these optimal conditions, it would be necessary to sow about six and four germinable stand and orchard seeds, respectively, to ensure one seedling after four years. Furthermore, regeneration cost would be less than a third that of planting.

Cortical monoterpene variation in natural populations of Pinus sylvestris in Sweden

Cortical oleoresins were obtained from 10 natural populations of Pinus sylvestris L. from different geographical localities. Gas chromatography was used to determine quantities of individual monoterpenes. Considerable variation was found in monoterpene composition among different populations. High proportions of limonene occurred in greater percentages in trees of northern origins, while high sabinene was frequently found in southern trees. Mean proportions of limonene and sabinene in the populations were clinal with latitude. For some monoterpenes, variation coefficients as a measure of variability within populations appeared to be clinal with latitude. 85.4% of the variance in monoterpene composition was found within populations and 14.6 between populations. Discriminant analysis differentiates populations from different geographical localities into different groups. The differences in monoterpene patterns between adjacent populations were statistically nonsignificant. It is recommended that monoterpene...

Cold acclimation of Pinus sylvestris and Pinus contorta provenances as measured by freezing tolerance of detached needles

Differences in cold acclimation were evaluated for detached needles of six Pinus contorta Dougl. and six Pinus sylvestris (L.) provenances originating from latitudes 55° to 68° N in western Canada and northern Sweden. The needles were collected in a Swedish field trial and freeze tested at various temperatures in the range of ‐ 6°C to ‐ 29°C on four occasions from August to October. Temperatures causing 50% discolored (dead) needle tissue were considered a measure of the level of cold acclimation. Provenance variation in needle injury was evident during the whole test period. Variation within species may largely be explained by the latitude of provenance origin, the more northern, the better the frost tolerance. The cold acclimation of lodgepole pine was comparable to that of Scots pine of approximately eight to five latitudes more northern origin from August to October.

Cold Hardiness of Scots Pine ( Pinus sylvestris L.)

The natural range of Scots pine (Pinus sylvestris L.) is the widest among the pine species (Mirov 1967). It is found at latitudes from 70°N in northern Scandinavia to about 40°N in the south, in Turkey and Spain, and at longitudes from 10°W in the west, with a small population in Scotland (6°W) to 150°E in the east in Russia (Figure 1). At the eastern end of its range the northern distribution limit shifts south, reaching about 65°N at the Ural mountains. Scots pine typically grows at low altitudes, even close to sea level in western Europe, but the altitude of the growing site increases in more southerly locations. In north-eastern Europe and on the west-Siberian Lowlands the northern limit occasionally follows the southern limit of the permafrost zone (Sokolov et al. 1977). At the southern limit of its distribution in the Caucasus mountains in Turkey Scots pine grows at elevations above 800 m, even as high as 2500 m (Rubner 1960; Sarvas 1964; Boratynski 1991).

Marker trait association for autumn cold acclimation and growth rhythm in pinus sylvestris

The main objective of this study was to identify quantitative trait loci (QTLs) involved in the genetic control of growth rhythm and autumn cold acclimation in Pinus sylvestris L. Eighteen full‐sib families of P. sylvestris with parental origins between latitudes 62 and 67° N in Sweden were assessed for autumn cold acclimation (frost injury measured from artificial freeze testing) and growth rhythm during the first two growing seasons. One family north × south with 108 individuals was used for the construction of one linkage map for the male and one for the female parent using 286 markers from random amplification of polymorphic DNA. Marker trait associations (QTLs) for shoot elongation, growth cessation and cold acclimation were found on both maps. Some QTLs were verified in two additional north × south families. Proportions of the additive genetic variance explained by the markers (R 2/G) indicated that genetic factors of large effect were involved in all investigated traits. Single or multiple markers accounted for between 16 and 47% of the additive variance in annual shoot elongation, between 42 and 79% of the additive variance in growth termination, and between 7 and 31% of the additive variation in autumn cold acclimation. The study confirms that there are major QTL regions on different linkage groups controlling a large part of the variation for growth rhythm and autumn cold acclimation in P. sylvestris.

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.

Autumn freeze testing of one‐year reciprocal families of Pinus sylvestris (L.)

Reciprocal families of Scots pine, Pinus sylvestris (L.), from a Swedish seed orchard were artificially freeze tested to ‐10°C at the end of the first growth period. The degree of freezing damage was used as an indication of the cold acclimatization achieved at the time of freeze testing. Both one‐year cold acclimatization and one‐year height were mainly additively inherited. Specific combining ability, reciprocal and maternal effects were small. On the family level, freezing damage was non‐significantly correlated with field survival and field height after ten years. One‐year height was positively correlated with 10‐year field height and negatively correlated with field survival on the family level. Within families, plants from early germinated seeds cold acclimated earlier and were higher at the end of the first growth period than plants from lately germinated seeds. The results indicate that conclusions made from first‐year cold acclimatization studies can be influenced by variation in the rate of seed...

Progeny freeze testing, progeny field testing and parental phenology of Pinus sylvestris (L.) clones in northern Sweden

Artificial autumn freeze testing was used as indication on the level of cold acclimation of one year old fullsib and open‐pollinated plus‐tree progenies from three north Swedish seed orchards of Scots pine. Correlations between progeny freezing damage after initial cold acclimation in various environments were generally as high or higher than correlations between survival/condition in various ten‐year field trials. Slight freezing damage was related to good field survival and tree condition at ten years of age. A large variation in the rate of cold acclimation within geographical regions indicates that the geographical origin alone is not a reliable selection criterion in breeding for hardiness. It is suggested that a combination of artificial freeze testing in the autumn of one‐year progenies and of detached shoots from the parent clones should be used in selection and breeding for better survival in Scots pine on northern latitudes.

Genetic variation in the natural pollen cloud of pinus sylvestris: a study based on progeny testing

Seeds from open pollination of individual female stroboli on different days in June 1990 in a coastal clone archive of Pinus sylvestris (L.) in northern Sweden (latitude 63°39’ N) were used for a short‐term progeny experiment to study differences over time in the genetic composition of the background pollen. Analysis of progeny growth and cold acclimatization in artificial whole‐plant freezing tests suggested no genetic differences in the fertilizing pollen between pollination days. A clinal variation with the latitude of pollen origin was observed for reference progenies from fertilization with pollen of known geographical origin. Comparisons between open‐pollinated progenies and reference progenies indicate that the pollen cloud originated from approximately 1° latitude (based on height growth) or 1.5° latitude (based on freezing injury) north of the pollination site.

Growth and survival of spontaneous provenance hybrids of Pinus sylvestris

Survival and growth were assessed for 17 provenance hybrids and three natural populations of Pinus sylvestris (L.) planted in three field trials in central and northern Sweden. Restricted to the high mortality site the 18‐year hybrid survival percentage increased by three units per degree north latitude and one percent per 100 m higher altitude of the mother. The hybrid height was less influenced by the geographical origin than hybrid survival. For both traits the natural populations were better than or equal to hybrids with the same geographical mean origin. The variance component of the mother was mostly 2–3 times larger than the provenance component. The effect of the grandmother was nonsignificant for both traits.