The effect of slope exposition on growth dynamics of Gmelin larch in permafrost conditions of Central Siberia. II. Specifics of tree radial growth at different heights of the stems

The research was carried on in even-aged Gmelin larch trees (Larix gmelinii (Rupr.) Rupr.), growing in permafrost conditions of the north and south facing slopes (Central Siberia, 64°19′23″N, 100°13′28″E). 13 even-aged larch trees growing in the north facing slope and 5 ones growing in south facing slope were selected. Tree ring widths were measured at 1/4, 1/2, 3/4 of the stem height and at beneath apex. The sliding response functions were calculated in the common period 1974–2009. It has been revealed negative trend in the variation of the mean tree ring widths along the stems of the trees growing in the north facing slope. Indexed radial increments at higher levels in the stems (3/4 of the stem height and just beneath apex) of these trees correlated negatively with air temperature in the third decade of April as well as positively correlated with this climate factors from the 20-th of May to the middle of June. In the south-facing slope the similar correlations were not revealed. In the north facing slope, with the correlation of those measured just beneath top of a tree with precipitation in the third decade of May was especially notable. These tendencies were considered as circumstantial arguments in favor of Gmelin larch trees growing in the north facing slope experienced harsh water deficiency from 20-th of May to the middle of June. Water deficiency could reduce water potential of tree tops, which could be responsible for their drying off