Nutrient concentrations in Pinus sylvestris growing on an ombrotrophic pine bog, and the effects of PK and NPK fertilization

Abstract

Nutrient concentrations in different tree compartments and the effects of PK(MgB) and NPK(MgB) fertilization were studied in a Scots pine (Pinus sylvestris L.) stand growing on a low‐shrub pine bog in eastern Finland.

The nutrient concentrations in all tree compartments were lower than those for plant material in general, although they did not differ very much from the values obtained from Scots pine in previous studies. The nutrient composition of the current needles were closest to those considered optimum for the development of higher plants. The highest macronutrient concentrations were found in the foliage. Zinc, Cu and B concentrations were also high in the living branches, stembark and small and fine roots. Iron concentrations were highest in the small and fine roots and dead branches. Stemwood had the lowest nutrient concentrations.

The rapidly soluble ammonium nitrate and potassium chloride fertilizers increased the foliar and stemwood N and K concentrations within the three year study period. Nitrogen concentrations also increased in the small and fine roots, and those of K in the living branches. The fertilization effect was greater in the young needles than in the old ones, indicating a delay in nutrient uptake, or retranslocation from the old needles to the youngest ones. Slowly soluble raw phosphate fertilizer clearly increased the small and fine root phosphorous concentrations only. The effect of sodium borate was rapid in the above‐ground compartments, where the B concentrations increased in the foliage and living branches. The B concentrations increased more in the older than in the younger needles, which was explained by poor translocation of the fertilizer B in the foliage.

Magnesium sulphate fertilization did not change the Mg concentration in any of the studied tree compartments. The decrease in foliar Fe and Mn concentrations after fertilization could be due to the “dilution effect”; of the main nutrient fertilization, inhibited uptake by other fertilizer cations or soil reactions. The foliar N, P, K and B concentrations and N/K and N/P ratios were below the optimum values before fertilization. The foliar N and P concentrations and N/P and N/K ratios remained below the optimum values despite the changes caused by fertilization. The K and B concentrations reached optimum values in the current needles.

Key words:

• Scots pine
• tree compartment
• element content
• peatland
• nutrient application.