THE ESTABLISHMENT OF STEM NUTRIENT DISTRIBUTION ZONES OF EUROPEAN LARCH AND TAMARACK USING PRINCIPAL COMPONENT ANALYSIS

Some parts of the xylem can acts as a nutrient reserve (or source) to satisfy the plant needs during spring flush or when uptake is insuffic ient. The distribution patterns have been used to delimit different di stribution 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, taki ng into consideration the common underlying of nutrients in the differ ent distribution zones. The distribution of P, K, Ca, Mg, Mn and Zn wa s evaluated on an annual basis, using disks from 8 trees, sampled ever y 20 cm along the stem, in two 18-year-old plantations of European lar ch [Larix decidua (Mill.)] and tamarack {Larix laricina [K. Koch (Du R oi)]}. Using principal component analysis, more than 90% of the total variance was explained by the first three components. Based on these c omponents, three groups of nutrients were identified: P and K (mobile) , Ca and Mn (immobile), and Mg and Zn (intermediately mobile). Five di stribution zones were delimited using factorial scores: bark, apical r egion, external xylem, transition xylem, and internal xylem. The apica l and external xylem zones were characterized by mobile nutrients whil e the internal zone of the xylem was characterized by immobile and int ermediately 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 zo nes are considered, the estimation of the internal reserve contributio n to plant's nutritional status and the evaluation of the changes in t he distribution patterns of elements following natural or artificial p erturbations could be improved. Discriminant functions are provided to classify new observations in the different distribution zones.