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Zeps M.,Latvian State Forest Institute Silava | Sisenis L.,Latvia University of Agriculture | Luguza S.,Latvia University of Agriculture | Purins M.,Latvia University of Agriculture | And 2 more authors.
Agronomy Research | Year: 2015

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. © 2015, Eesti Pollumajandusulikool. All rights reserved. Source


Smilga J.,Forest Competence Center | Zeps M.,Latvian State Forest Institute Silava | Sisenis L.,Latvia University of Agriculture | Kalnins J.,Latvian State Forest Institute Silava | And 2 more authors.
Agronomy Research | Year: 2015

Hybrid aspen (Populus tremuloides × P. tremula) has fast growth in climatic conditions of Northern Europe and relatively high wood quality. Therefore, breeding of it has been carried out in a number of Baltic Sea Region countries. Breeding requires notable financial investment; therefore, the aim of our study was to estimate the profitability of hybrid aspen breeding in Latvia and the factors affecting it. Financial analysis was based on the differential approach, that is, only the costs and benefits that differ between two compared alternatives – planting of hybrid aspen and natural regeneration of silver birch or common aspen – were compared. Differential gain in this case included additional monetary value of the above-ground parts of trees in planted hybrid aspen stands (values obtained from trials in Latvia); differential costs were the costs of tree breeding, plants, planting, cleaning and protection against browsing damages (repeated use of browser repellents or fencing). Profitability of hybrid aspen breeding was significantly affected by the size of the area planted annually, soil fertility (site index) and length of rotation period. The differential gain from investments in tree breeding and establishment and management of plantations (r = 3%), assuming that selected clones would be used for 15 years and 500 ha are planted annually, in comparison to natural regeneration of common aspen and to silver birch, was 662 EUR ha-1 and 1136 EUR ha-1, respectively. In contrast, if only 50 ha are planted annually, the respective figures were 588 and 756 EUR ha-1. If fencing was used for protection of the hybrid aspen plantation against browsing, the differential gain was positive only on the most fertile soils (site index Ia). © 2015, Eesti Pollumajandusulikool. All rights reserved. Source


Neimane U.,Latvian State Forest Institute Silava | Zadina M.,Latvian State Forest Institute Silava | Sisenis L.,Latvia University of Agriculture | Dzerina B.,Latvian State Forest Institute Silava | Pobiarzens A.,Forest Competence Center
Agronomy Research | Year: 2015

The Norway spruce is widely spread in Eastern Europe and it is managed mainly for the production of sawlogs, though its logging residues are now increasingly used for the production of wood chips for bioenergy. The growth of the Norway spruce is and will be affected by climatic changes; one of the possible effects might be an increase in the frequency of trees with lammas shoots. Therefore, the aim of this study was to assess the influence of lammas shoots on the length of height increment of young Norway spruce in Latvia. Tree height and height increment was repeatedly measured and the presence of lammas shoots, bud flushing grades and frost injuries were assessed in two young (8–13 years) open-pollinated progeny tests in the central part of Latvia (56°46´N, 24°48´E). The mean portion of trees with lammas shoots in one experiment was 6% at the end of 8th growing season. In another experiment, it was 8.7%, 26.9% and 8.1% at the end of 10th, 11th and 13th growing seasons, respectively; 32.3% of trees had lammas shoots at least in one of three seasons. Faster growing and earlier flushing trees had a significantly higher frequency of lammas shoots. Lammas shoots increased the length of annual height increment by 10 to 14 cm, resulting in a 14–20% taller tree height at the age of 13 years. The reduction of height increment as a result of frost damages for very early flushing trees was less pronounced for trees with lammas shoots than without them. © 2015, Eesti Pollumajandusulikool. All rights reserved. Source


Neimane U.,Latvian State Forest Institute Silava | Katrevics J.,Latvian State Forest Institute Silava | Sisenis L.,Latvia University of Agriculture | Purins M.,Latvian State Forest Institute Silava | And 2 more authors.
Agronomy Research | Year: 2016

Norway spruce (Picea abies (L.) Karst.) is a tree species with the highest economic importance in northern Europe. Therefore, it is important to improve knowledge of the potential effects of climatic changes on the growth of this tree species. An essential part of the information is the tree’s intra-annual growth cycle. There are comprehensive studies describing the formation of radial increments of coniferous trees; however, information on height growth in hemiboreal forests is scarce. The aim of our study was to characterize the intra-annual height growth of Norway spruce in Latvia. The data was collected from two Norway spruce trials located in in former arable and forest land in the central part of Latvia, including 89 and 68 open-pollinated families (respectively) of plus-trees. Weekly height increment measurements of 20 trees per family were carried out during the 9th growing season. Growth intensity culminated in 10 ± 0.2 mm day-1, following similar trend, but resulting consistently in significantly different values between the trials; the higher growth intensity was observed in higher trees and families, which also showed higher frequency of lammas shoots, boosting their height superiority even further. Significant family effect on all coefficients of shoot elongation curves, described by Gompertz model, was found. Both tree height and height increment at family mean level was strongly correlated with the asymptote parameter (rfam = 0.93, P<0.01) and the growth rate parameter (rfam = -0.70, P<0.01). © 2016, Eesti Pollumajandusulikool. All rights reserved. Source


Jansons A.,Latvian State Forest Institute Silava | Neimane U.,Latvian State Forest Institute Silava | Dzerina B.,Latvian State Forest Institute Silava | Adamovics A.,Latvian State Forest Institute Silava
Agronomy Research | Year: 2016

Scots pine is a commercially important tree species in northern Europe. Climate changes in combination with genetics cause differences in the tree growth rhythm, including the formation of lammas shoots. The aim of the study was to assess the relation between the occurrence of lammas shoots and the height of young Scots pines and its implications in tree breeding. Tree height was repeatedly measured, and the presence of lammas shoots was assessed at the end of the 4th through 8th growing seasons in two open-pollinated progeny trials (Daugmale and Norupe, both including the same 61 families) in the central part of Latvia. The proportion of trees with lammas shoots (max. 23%) decreased over the observation years. In both trials, at the age of 7 years, trees that had formed lammas shoot during at least one of the observed years were significantly (P < 0.001) higher than trees with no lammas shoots: 226 ± 3.5 cm vs 213 ± 3.3 cm in Norupe and 146 ± 3.9 cm vs 121 ± 1.9 cm in Daugmale, respectively. When only dominant trees (1,000 ha-1) were considered, the height superiority of trees with lammas shoots remained in Daugmale (trial with highest proportion of trees with lammas shoots), but not in Norupe. The earliest formed lammas shoots (assessed in the 4th growing season) had the strongest effect on the tree height. A correlation between the mean height and the proportion of trees with lammas shoots in the particular family was not found (P > 0.05). © 2016, Eesti Pollumajandusulikool. All rights reserved. Source

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