The establishment of stem nutrient distribution zones of European larch and tamarack using principal component analysis

Some parts of the xylem can act as a nutrient reserve (or source) to satisfy the plant needs during spring flush or when uptake is insufficient. The distribution patterns have been used to delimit different distribution zones of nutrients in the stem but establishing the limits of the zones can be subjective when a single element is used. In this study, we provide a new methodology for analyzing stem nutrients, taking into consideration the common underlying of nutrients in the different distribution zones. The distribution of P, K, Ca, Mg, Mn and Zn was evaluated on an annual basis, using disks from 8 trees, sampled every 20 cm along the stem, in two 18-year-old plantations of European larch Larix decidua (Mill.)] and tamarack {Larix laricina K. Koch (Du Roi)]}. Using principal component analysis, more than 90% of the total variance was explained by the first three components. Based on these components, three groups of nutrients were identified: P and K (mobile), Ca and Mn (immobile), and Mg and Zn (intermediately mobile). Five distribution zones were delimited using factorial scores: bark, apical region, external xylem, transition xylem, and internal xylem. The apical and external xylem zones were characterized by mobile nutrients while the internal zone of the xylem was characterized by immobile and intermediately mobile nutrients. As well as establishing common zones of each nutrient, principal component analysis enabled us to characterize zones based on a group of nutrients. If the different distribution zones are considered, the estimation of the internal reserve contribution to plant's nutritional status and the evaluation of the changes in the distribution patterns of elements following natural or artificial perturbations could be improved. Discriminant functions are provided to classify new observations in the different distribution zones.