Paula Jylhä

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...

Biomass production and carbon sequestration of dense downy birch stands on cutaway peatlands

ABSTRACT The establishment of biomass plantations with short-rotation forestry principles is one of the after-use options for cutaway peatlands. We studied biomass production and carbon sequestration in the above- and below-ground biomass of 25 naturally afforested, 10–30 years old downy birch (Betula pubescens Ehrh.) stands located in peat cutaway areas in Finland. Self-thinning reduced the stand density from 122,000 trees ha−1 (stand age of 10 years) to 10,000 trees ha−1 (25–30 years), while the leafless above-ground biomass increased from 17 Mg ha−1 up to 79–116 Mg ha−1. The total leafless biomass (including stumps and roots) varied from 46 to 151 Mg ha−1. The mean annual increment (MAI) of the above-ground biomass increased up to the stand age of 15 years, after which the MAI was on the average 3.2 Mg ha−1a−1. With below-ground biomass, the MAI of the stands older than 15 years was 4.7 Mg ha−1. The organic matter accumulated in the O-layer on the top of the residual peat increased linearly with the stand age, reaching 29.3 Mg ha−1 in the oldest stand. The O-layer contributed significantly to the C sink, and the afforestation with downy birch converted most of sites into C sinks.