Jyrki Hytönen

High nitrogen deposition causes changes in amino acid concentrations and protein spectra in needles of the scots pine (Pinus sylvestris).

Growth of the Scots pine (Pinus sylvestris) suffered considerably in forests close to fur farms in western Finland, with the occurrence of winter time dieback in the youngest shoots and leading to a bush-like, flat crown canopy. One reason for this growth disturbance may be a serious imbalance in nitrogen metabolism caused by the extra N supply, emitted as NH3 from the dung of the animals. Total N and NH4+ concentrations in the needles and soluble nitrogen concentration in the soil increased considerably in the vicinity of the fur farms. The extra N in the needles was bound in the first place in arginine, the concentration of which increased 10(2)-10(3) fold compared with control trees, and to a lesser extent in glutamine and other amino acids. Alterations in the quantitative and qualitative protein patterns of the needles were obtained. The extra N increased the concentration of total soluble proteins, although it inhibited the formation of certain polypeptides (particularly in the areas of 30, 38, 50 and 65-90 kDa) which were possibly essential for the normal wintering processes. One reason for the winter time dieback in the high N area could thus be found in the altered protein profiles.

Effects of weed control on the early growth of Betula pendula seedlings established on an agricultural field

Various herbicides (glyphosate, sethoxydim, pendimethalin, chlorthiamid, dichlobenil, ter‐buthylazine) as well as particle board mulch and a cover crop (clover, Trifolium repens) were compared during the first two post‐planting years as weed control means in a silver birch (Betula pendula) plantation established on agricultural soil in southern Finland. Chlorthiamid, dichlobenil and terbuthylazine exhibited good weed control for two years and also increased the height growth of the seedlings by 40–50 cm and much greater relative increase in leaf area and volume as compared to untreated control plots. Weed control had a significant effect on the foliar nutrient concentrations of birch, particularly that of N. As the amount of weed vegetation increased, foliar N, P (second year), K, Cu and B decreased and, respectively, foliar P (first year), Ca and Mg increased. Vegetation control also had a great indirect influence on the state of health of the seedlings. Incidences of vole damage and bark necrosis diseas...