Contents in brief
The following is the editor's own interpretation of the articles in issue no. 2, 2007.
Genetic improvement produces increasingly better tree material, but its current genetic gain can seldom be utilized immediately in the forest. Biological and economical constraints force the seed orchard owner to mass-propagate “yesterday's improved trees”. However, it should be possible to optimize the seed orchards to obtain as much gain as possible for a certain amount of money. Yousry El-Kassaby and his colleagues present such a model, applied on Scots pine in Sweden. They found that seed orchards should have a faster turnover and a shorter lifespan than today.
Noble fir is an attractive species for greenery production. Ulrik Bräuner Nielsen found that the quality and quantity of the usable branches varied a lot among provenances and families. By selecting the better families, it should be possible to increase the net income from greenery production by 600–900 euros per hectare.
Can trees be “vaccinated” against diseases? Gunilla Swedjemark and her colleagues showed that Norway spruce that was infected with root rot became resistant to new root rot infections for at least 78 weeks. They also showed that this induced resistance was systemic, which means that the resistance was induced in the whole plant, not only the point of infection.
Tapani Repo and his colleagues asked what happens with a spruce if the frost does not thaw in time. By isolating the ground, they were able to delay the soil thawing until July, compared with May for the control trees. The delay caused later budburst and some reduced functions of the photosynthesis apparatus. Surprisingly, radial increment of the wood was faster in the delayed-frost treatment.
Chemical treatment is often necessary to protect seedlings against pine weevil damage. The protection need to be effective for at least a whole season in the field, and preferably for two seasons; otherwise, reapplication in the field may be necessary. Heli Viiri and colleagues tested the persistence of deltamethrin. They showed that the protection was unaffected by freeze storage, and that dipping the seedlings was much more efficient than spraying them with the chemical.
The increasing demand for bioenergy is likely to increase the removal of nutrients from the forest. Besides, high nitrogen deposition may cause an imbalance in the nutrients available to the trees. Vitality fertilization with other elements, such as phosphorus and potassium, could thus compensate for the deficiencies. Pei Wang and colleagues tested vitality fertilization together with wood ash and logging residue application. They found no effect on tree growth, but could detect some changes in the nutrient content of needles and roots.
Patrick Insinna and his colleagues undertook the tremendous job of reconstructing the growth history of over 100-year-old pines of two species. With the “needle trace method” they were able to describe the lifetime development of the tree crown. They found that ponderosa pine produced twice as much needle dry mass as Scots pine, which explains the higher yield of ponderosa pine.
Supplementary planting is seldom successful, at least according to a long-term study by Urban Nilsson and Pelle Gemmel. Seedlings that were planted in gaps in already established regenerations grew more slowly, and the original seedlings surrounding the gap utilized the gap themselves. However, the supplementary planted seedlings may help to improve the quality of the surrounding trees.
Sinikka Jauhiainen and her colleagues used aerial photographs to describe peatland vegetation in Finland over a 50-year period. The digitized photographs were effective for reconstructing the changes over long periods and larger areas. It was, for example, easy to separate drained and undrained mires. However, the photographs were not detailed enough to identify vegetation at a small-scale level.