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Salaspils, Latvia

Jansons A.,LSFRI Silava | Matisons R.,LSFRI Silava | Zadina M.,LSFRI Silava | Sisenis L.,Akademijas str. 11 | Jansons J.,Forest Competence Center
Silva Fennica | Year: 2015

Height growth of trees is a crucial parameter that influences the composition and productivity of forest stands and quality of timber; however, the relationships between annual height increment (HI) and climatic factors have been poorly studied. In this study, the effect of monthly mean temperature and precipitation sums on the HI of Scots pine in two sites in Latvia have been determined using dendrochronological techniques. Correlation and response function analyses were conducted for entire chronologies of HI and for 50-year intervals within them. Climatic factors significantly affected the HI of Scots pine; however, not only did the suite of significant factors differ between the sites, but the influence of these factors changed during the 20th century. In the site in western Latvia where climate is milder, temperature in the preceding summer was the main climatic determinant of HI. The effect of temperature in the dormant period and spring was significant during the first part of the 20th century, while the effect of temperature in the previous September and November has become significant since the second half of the 20th century. In the site in eastern Latvia where summers are hotter, HI has been affected by both temperature and water deficit related factors in the summer. However, since the later part of the 20th century, the effect of temperature in the previous October has intensified and become the main climatic determinant of HI. © 2015 Finnish Society of Forest Science. All rights reserved. Source


Jansons A.,LSFRI Silava | Matisons R.,LSFRI Silava | Purina L.,LSFRI Silava | Neimane U.,LSFRI Silava | Jansons J.,Forest Competence Center
Silva Fennica | Year: 2015

Relationships between climatic variables and tree-ring width (TRW) of dominant European larch (Larix decidua Mill.) and European beech (Fagus sylvatica L.) trees growing outside of their natural distribution area in western Latvia were studied. Chronologies of TRW, which covered the periods 1949–2012 and 1911–2012, were produced for beech and larch, respectively. Common signatures in TRW between both species were observed, but their amplitude differed. Correlation analysis showed that variation of TRW of both species was affected by drought related climatic variables. Tree-ring width of beech was affected by temperature in the previous July and August and the effect of spring and autumn temperature was observed. Since the 1980s, the effect of July precipitation has become significant. Summer precipitation was significant for larch in the mid-part of the previous century; however, temperature in the previous September has become a limiting factor since 1970s. The limiting effect of winter and spring temperature apparently lost its significance around the 1950s. © 2015, Finnish Society of Forest Science. All rights reserved. Source


Matisons R.,LSFRI Silava | Jansons J.,Latvian Forest Competence Center | Katrevics J.,LSFRI Silava | Jansons A.,LSFRI Silava
Silva Fennica | Year: 2015

The effect of climatic factors on wood anatomy of the alien red oak (Quercus rubra L.) growing in three experimental plantations in Latvia was assessed by classical dendrochronological techniques. Two tree-ring proxies - tree-ring width (TRW) and mean area of early wood vessel lumen (VLA) - were studied on 33 trees. Annual variation of TRW amongst trees was similar (mean r = 0.46), but there was more individuality in VLA (mean r = 0.26); nevertheless, chronologies of both proxies had rather synchronous variation amongst the sites. Annual variation of TRW was affected by factors related to water deficit in late summer, as suggested by the negative effect of temperature and positive effect of precipitation that have intensified during the 20th century, likely due to warming. Although weather conditions during the dormant period did not directly affect TRW, temperature during the autumn-spring period has been the main climatic determinant of VLAlikely via influence on overwintering and hence vigour of tree. This suggests that conductive properties of wood and hence the susceptibility to water deficit have been affected by weather conditions before the formation of tree rings. During the 20th century, sensitivity of VLA has shifted from temperature in winter to temperature in autumn likely due to climate change. Still, the positive effect of these factors suggests that warming of climate would increase VLA and hence the risk of embolism and xylem disfunction. Therefore, the importance of availability of water for growth of red oak in Latvia is increasing. © 2015 Finnish Society of Forest Science. All rights reserved. Source


Liepins K.,LSFRI Silava | Lazdins A.,LSFRI Silava | Liepins J.,LSFRI Silava | Prindulis U.,LSFRI Silava
Small-scale Forestry | Year: 2015

In Latvia, the management of grey alder stands is an important issue in non-state forests, where this species accounts for 14 % of the total non-state forest area. The motor-manual felling and processing of timber with a chainsaw is still a commonly used method in non-state forests, while timber harvesting in final felling is fully mechanized in state forests. This study examined the productivity and costs of the mechanized and motor-manual harvesting of grey alder following the cut-to-length CTL system and analysed factors influencing the productivity of harvesting of grey alder stands under Latvian conditions. Productivity rates achieved for mechanized and motor-manual harvesting were 7.04 and 2.99 m3 per productive work hour, respectively. Despite lower productivity, motor-manual harvesting was more cost-effective than mechanized harvesting. Improved working methods that could ensure higher production levels and increase the labour costs in the future have potential to increase the cost competiveness of the mechanized harvesting of alder stands in Latvia. © 2015, Steve Harrison, John Herbohn. Source


Jansons A.,LSFRI Silava | Zeps M.,LSFRI Silava | Rieksts-RiekstinS J.,LSFRI Silava | Matisons R.,LSFRI Silava | Krisans O.,LSFRI Silava
Silva Fennica | Year: 2014

Height growth of young hybrid aspen (Populus tremula L. × P. tremuloides Michx.) was studied in relation to weather conditions. Height of clones with different leaf flushing phenology (early, intermediate and late) was monitored during the growing periods of 2010 and 2011 in a plantation established on former agricultural land. Mean daily height increment (HI) was calculated. Multiple linear regression was used to determine which weather factors (variables) had significant effect on HI. Mean seasonal height growth (mean seasonal HI) between clones (groups) was compared by ANOVA. In both years, HI was significantly higher for clones with early and intermediate leaf flushing compared to clones with late leaf flushing. The effect of weather factors also differed between clones according to their leaf flushing phenology; it was the weakest for HI of clones with early leaf flushing compared to clones with intermediate and late leaf flushing. Mean temperature was the main factor, which positively affected HI of all clones, suggesting that warmer climate might be beneficial for height growth of young hybrid aspen in Latvia. Nevertheless, significant negative relationship between HI and potential evapotranspiration (PET) was observed for clones with delayed leaf flushing, suggesting negative effect of increasing variability of precipitation on growth. Thus, the differences in height growth intensity might be related to growth sensitivity to weather conditions. On the other hand, such differences in height growth between clones might be caused by competition (i.e. with herbs), as trees with early leaf flushing might conquer more resources and become more robust against the environmental fluctuation. © 2014 Finnish Society of Forest Science. All rights reserved. Source

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