Formation of height increment of hybrid aspen in Latvia
¹Latvian State Forest Institute ‘Silava’, Riga Str. 111, LV2169 Salaspils, Latvia
²Latvia University of Agriculture, Forest Faculty, Akademijas Str. 11, LV3001 Jelgava, Latvia
³Forest Competence Centre, Dzerbenes Str. 27, LV1006 Riga, Latvia *Correspondence: martins.zeps@silava.lv
Abstract:
Annual increment of hybrid aspen exceeds that of other tree species (including common aspen) in Baltic States. Notable (several-fold) differences in productivity between clones have been detected and therefore tree breeding programs are established to select the best genotypes (clones) for large-scale propagation. In order to aid the selection as well as understand the potential changes in growth of hybrid aspen as a result of climatic changes, it is important to analyse the intra-annual growth dynamics. Therefore aim of our study was to assess height growth intensity of hybrid aspen and factors affecting it. Weekly measurements of height increment were carried out through the third growing season of trees in two plantations, consisting of 19 clones (10 ramets per clone), on abandoned agricultural land in western (Mazirbe, 56° 36´ N, 24° 30´ E) and central (Vecumnieki, 57° 40´ N, 22° 19´ E) part of Latvia. Mean height growth period of hybrid aspen ranged from 119 ± 8.9 days for late flushing clones to 137 ± 8.6 days for early flushing and was tightly (r = 0.69) linked to total length of height increment. Mean height growth intensity during this period for respective groups of clones ranged from 7.7 ± 3.04 mm day-1 to 11.7 ± 2.93 mm day-1. Growth intensity (and height increment) was significantly affected by genotype (clone) and in both sites tightly (r = 0.57…0.84) linked with daily mean temperature, but not with precipitation. Increasing temperature in future might boost the productivity of hybrid aspen plantations, especially with early flushing clones.
Key words:
growth period, height growth intensity, Populus tremula × P. tremuloides.