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(ii) to analyse the behaviour of local provenances and also for one of the most valuable provenance after IUFRO standard (5-Moldovița);
(iii) to evaluate how populations originating from different branches of the Romanian Carpathians respond at the four local environmental conditions;
(iv) to evaluate any correlations between analysed traits and the geographical position (latitude, longitude, altitude and ecophysiological latitude) of the seed stands origin.
Also, the experimental data will be useful for the conservation of genetic resources in this important Norway spruce area.
Materials and Methods
Materijali i metode
Four field trials (Table 1) were established using seedlings obtained from bulked seed harvested from 10 seed trees belonging to each of the 33 seed stands presented in Figure 1, referred to as populations (indicating the origin of seed sources). Two trials (Brețcu and Gurghiu) were installed inside the natural range and other two (Avrig and Câmpina) outside it. Both trials established in the natural range belong to the ecological optimum for Norway spruce in Romanian Carpathians (Feurdean et al. 2011). After Stănescu et al. (1997), the average annual temperature and the amount of precipitation in the two tests outside of the natural range (Table 1) are suboptimal, mainly in Câmpina trial.
In all trials, the experimental design was an incomplete balanced square grid, with three repetitions and 49 seedlings per plot planted at a spacing interval of 2 by 2 m; every population was composed of progenies obtained from bulked seed harvested from 10 trees from every seed stand (Enescu & Ioniță 2002). The experimental design was of the 6 Ś 6 type (Șofletea et al. 2012). To realize the 6 x 6 experimental design, in each replication three populations (the ones with the code numbers 1, 2 and 3) were repeated.
Following the methodology developed by IUFRO (Lines 1967) regarding data collection in such field trials, evaluations of 10 trees were made in each unitary plot, being assessed 30 trees per population and 1080 trees per trial, respectively.
Thirty years after planting, tree height was measured using a Vertex III instrument, with tree volume determined via the volume regression equation method (Giurgiu et al. 2004). In each trial, nine trees from each population (three in each repetition, belonging to the mean diameter category) were selected in order to extract increment cores using a Pressler borer. The following traits were evaluated: RI (annual radial increments), width of earlywood and latewood and their average values in population and in trial, LP (proportion of latewood in the total width of annual ring) and CWD (conventional wood density; method presented in Șofletea et al. 2012).
Measurement of RI and earlywood/latewood values was carried out using a Rinntech LINTAB 5 tree-ring measurement station (RINNTECH, Heidelberg, Germany,