A., Jansons, J., Neimane, U., Jansons, Ā. 2016. Infl uence of spot mounding on height growth and tending of Norway spruce: case study in Latvia. -Forestry Studies | Metsanduslikud Uurimused 65, 24-33. ISSN 1406-9954. Journal homepage: http://mi.emu.ee/forestry.studies Abstract. Norway spruce is commonly regenerated by planting and disc trenching is by far the most widely used soil preparation method in Latvia; however, in specifi c site conditions other methods might be benefi cial. Therefore aim of our study was to assess infl uence of spot mounding on early growth and tending of Norway spruce in hemiboreal forests. Spot mounding was compared with disc trenching or no soil preparation in central part of Latvia (57° N 24° E) in fi ve different forest types, where two-year-old containerized Norway spruce seedlings were planted. Infl uence of soil preparation method on tending was assessed in the same region in two different sites in a single forest type on drained fertile mineral soil. Spot mounding had positive effect on the height increment of the dominant trees at the 6 th to 8 th growing season. Mean height of Norway spruce at the end of 8 th growing season on mounds signifi cantly exceeded that on unprepared soil: 179 ± 6.5 and 152 ± 6.2 cm, respectively. Similarly mean height on mounds was signifi cantly larger than on furrows: 209 ± 3.9 and 154 ± 4.0 cm, respectively. Projective vegetation cover before the tending was signifi cantly higher in spot-mounded, but after -in disc trenched sites. Networking time for brashsaw operators in spot-mounded (478 min/ha -1 ) and disc trenched (462 min/ha -1 ) sites was similar (p > 0.05). Overall, spot mounding ensured more suitable microenvironment resulting in higher productivity of planted trees and had no negative effect on quality or effi ciency of tending, therefore its wider use is recommended.

Highlights • The initial fertilization increased the productivity of Picea abies increasing stem volume by 17% at the age of 34 years. • The tree-ring width was affected for up to15 years. • The fertilization did not affect mean tree-ring density, although the latewood density was increased.

Norway spruce is a relatively fast-growing tree species that is primarily regenerated by planting, which requires significant investments. The formation of lammas shoots (i.e., second flushing in late summer) have been proven to affect the quality and productivity of Norway spruce stands. The aim of our study was to assess the proportion of trees with lammas shoots in young stands of Norway spruce and to investigate the factors affecting their formation. Data have been collected at the end of 2011 in 102 three-to seven-year-old Norway spruce plantations randomly selected across different forest types in the central part of Latvia, and a subset of 21 stands were inventoried again at the end of 2012. In each stand, 20 sample plots were systematically established where trees with and without lammas shoots were counted and micro-environmental factors (moisture, competition, and browsing) were assessed on a three-grade scale.On average, the proportion of trees with lammas shoots was 6.5%. There was no significant effect of the stand age (from 3 to 7 years) on the proportion of trees with lammas shoots nor was there any age-related trend. The effect of forest type on the presence of lammas shoots was not significant. Micro-environmental factors had an important influence on the proportion of trees with lammas shoots. The proportion of lammas shoots in stands with no competition was significantly higher (14.5%) compared to stands with medium and high competition (6.0% and 2.2%, respectively). Similarly, a significantly higher proportion of trees with lammas shoots (11.7%) was observed in sites with normal moisture regime than in sites with slight or notable excess moisture, reaching 4.8% and 1.7%, respectively. Although the influence of browsing damage was not statistically significant, its trend was similar to that observed for competition and moisture regime. Overall, the proportion of trees with lammas shoots was highest in stands showing the most suitable micro-environmental conditions for Norway spruce.

The long-term (50 years) effect of whole-tree harvesting (stump harvesting) on ground vegetation in experimental drained Norway spruce (Picea abies (L.) Karst.) stands was studied. We used a chronosequence approach to assess the long-term impact of whole-tree harvesting (WTH) on stands’ ground vegetation. WTH stands were compared with four control stands with different age and with the same forest type: young stand (15 years), middle-aged stand (45 years), mature stand (110 years) and over-mature stand (140 years). Species richness was similar between the WTH stand and middle-aged stand (61 and 60 species, respectively). Shannon-Wiener diversity indices in the WTH and middle-aged stand (3.40 and 3.19, respectively) indicated that the stands were similar to each other. A community similarity analysis showed that the composition of vegetation was similar between the WTH and middle-aged stand, although some species like Lycopodium clavatum and Diphasiastrum complanatum occurred only in the WTH stand. The study showed that a period of 50 years is sufficient for ground vegetation of a typical drained spruce forest to recover after WTH management.

Biogeosciences and Forestry Biogeosciences and Forestry Genetic control of intra-annual height growth in 6-year-old Norway spruce progenies in Latvia Roberts Matisons (1) , Pauls Zeltiņš (1) , Darius Danusevičius (2) , Baiba Džeriņa (1) , Iveta Desaine (1) , Āris Jansons (1) Coupling growth with periods of favourable weather conditions minimizes risks of frost damage and maximizes annual height increment. The phenology of the formation of height increment is therefore a trait related to the adaptability of trees to annual weather fluctuations. Strong genetic control of the timing of the onset and cessation of shoot elongation has been reported for Norway spruce, but little is known about its fluctuations that occur during the growth period. The strength of the genetic control of the height growth rate was assessed for young (6 years old) Norway spruce progenies originating from six open-pollinated stands from two local provenance regions. In 2010, the length of the growing period for the studied trees was ca. 60 days. Trees from the more continental provenance region, which had later onset and cessation of height growth (by ca. 2.5 days), exhibited slightly lower increments (by ca. 1%). Accordingly, the provenance region had a significant effect on height growth at the beginning and end of the growing period. Nevertheless, considerable genetic control of the growth rate was found throughout the entire growing period (particularly at the beginning and cessation, ha 2 ≥ 0.20), except for a week-long interval around midsummer (ha 2 = 0.07). Similarly, the coefficient of additive genetic variation suggested that breeding could be applied for the improvement of height growth intensity throughout the season. The phenotypic correlations between weekly growth rates and tree height (before growth) were mostly non-significant, suggesting varying mechanisms of control, hence possibility for simultaneous improvement of the traits by breeding.