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Element cycling in a Belgian pine forest

GIELEN, Sienke
Master in de industriŽle wetenschappen: Nucleaire Technieken


Abstract :
The concentrations of elements (Al, K, Ca, Cl, Mg, Mn) in different compartments in a Pinus Sylvestris stand are analyzed using atomic absorption spectrometry and neutron activation analysis. Together with the biomass distribution several aspects are studied i.e. element relative mass and concentration distributions, inter-compartment ratios and mass and concentration related correlations between the elements. Finally, a simple box model is developed to give approximated inter-compartment transfer rates.
The relative mass distribution results show that Ca (94 wt%) and Mn (88 wt%) are mainly present in the wooden compartments, because Ca has a structural role in wooden tissues and Mn participates in the synthesis of lignin. Conversely, Cl (34 wt%) and K (23 wt%) are more present in the needles as these elements are both involved in opening the stomata. Moreover, Cl also participates in the water splitting during the photosynthesis process. Al, toxic in high amounts, is mainly present in the roots and outer bark, where it will be blocked to avoid toxicity. Mass related correlations are found between Ca and Mg (0.90), Mn and Mg (0.98), Mn and Ca (0.89) and K and Cl (0.88). These correlations result from similarities in biological functions (K and Cl are involved in the stomata opening and pressure regulation of the cells) or by a similarity in charge causing a similarity in cell to cell transport (Ca, Mg and Mn, which have a cationic charge of +2). Concentration related correlations are found between Ca and Al (0.90), Mn and Cl (0.91), K and Cl (0.85) and K and Mn (0.84). These correlations can be explained by a similarity in channel transport behaviour (Ca and Al), a biological function similarity (Mn and Cl, involved in water splitting; K and Cl, involved in pressure regulation in the cell and opening of the stomata) or due to different functions in the same compartment (K and Mn, with K involved in opening the stomata, and Mn, involved in water splitting). The inter-compartment ratios confirm the mobility and immobility of elements and give indications of the translocation of elements: a high litter needles/old needles ratio like for immobile Ca (1.31) shows that Ca is not redistributed to other leaves before leaf fall. A high ratio is also obtained for Al (litter needles/old needles ratio of 1.46 and litter twigs/young twigs ratio of 2.44). Al appears to be translocated to compartments to avoid toxicity. The expected translocations for mobile and immobile elements based on inter-compartment ratios are confirmed via the developed box model. A high transfer factor from leaves to floor (0.14 d-1) is found for immobile Ca. Conversely Mg, a mobile element, has a high transfer rate from leaves to wood (0.43 d-1). The similarities between Mn and Mg (both divalent cations, and center of the chlorophyll molecule) can also be deduced from transfer rates that are almost the same for both elements.

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If you want to cite this thesis in your own thesis, paper, or report, use this format (APA):

GIELEN, S. (2012). Element cycling in a Belgian pine forest. Unpublished thesis, Xios, TIW.
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