LSFRI Silava

Salaspils, Latvia

LSFRI Silava

Salaspils, Latvia
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Zeps M.,LSFRI Silava | Jansons A.,LSFRI Silava | Matisons R.,LSFRI Silava | Stenvall N.,Natural Resources Institute Finland Luke | Pulkkinen P.,Natural Resources Institute Finland Luke
Agricultural and Forest Meteorology | Year: 2017

During the autumn, plants undergo a physiological process of cold hardening to limit damage caused by the low temperatures of winter. Under a warming climate, plants may be less cold hardened and hence more susceptible to the effects of a sudden temperature drop. During the growth season of 2010–2011, growth and cold hardening of European aspen (Populus tremula L.) seedlings from native wild populations were examined under ambient and projected climate scenarios in greenhouses at the Haapastensyrjä research station in Southern Finland. Using locally obtained seedlings, we manipulated temperature and soil moisture during the normal growth period and then subjected them to an artificial freezing treatment during September–November 2010. At the end of the experiment, we determined seedling height, survival and the extent of stem damage, and analysed their variation with mixed effect models. Among the treatments tested, temperature was the main factor affecting survival, cold hardening, and frost damage to seedlings. The higher temperature (4 °C increase) of the 2100 future climate regime was associated with a 35% decrease in seedling survival (from 66 to 31%) during the growing period. Increased irrigation had a positive, but considerably weaker effect on seedling survival (improved survival by ca. 8%). Height of seedlings after the first growth season was enhanced by increased soil moisture and temperature, but these effects were negated the following spring by increased frost damage caused by warmer growth conditions. Although cold hardiness increased as the season progressed, increase of temperature by 1 and 4 °C severely diminished it, and survival after the freezing dropped from 55% (control) to 48% and 14%, while stem damage increased from 58% (control) to 90% and 96%, respectively. These results suggest that regeneration of north European aspen might become burdened in a warmer climate. Although survival was clearly affected, several seedlings grown under the future climate regimes survived freezing and overwintered with negligible damage, suggesting an adaptive capacity of the local population. The intraspecific competition that occurred as a side effect of the experimental setup also affected cold hardening, suggesting that stand structure might be managed to improve the resilience of aspen to frost damage. © 2017 Elsevier B.V.


Puspure I.,LSFRI Silava | Gerra-Inohosa L.,LSFRI Silava | Matisons R.,LSFRI Silava | Laivins M.,LSFRI Silava
Baltic Forestry | Year: 2017

The spreading dieback of European ash (Fraxinus excelsior L.) that is a serious threat to the existence of the species in Europe, has been related to climatic changes. Still, not all trees in stands are damaged equally, suggesting that sensitivity to weather conditions might have affected the susceptibility to the disease. Climate-growth sensitivity of ash with visually healthy and damaged crowns growing in four stands in the central and eastern part of Latvia was assessed by dendrochronological techniques. The patterns of tree-ring width variation showed high diversity amongst trees, stands and regions; differences were observed between the damaged and healthy trees. Tree-ring patterns showed higher diversity amongst the healthy trees in the central part of Latvia, but, in the eastern part of Latvia, amongst the damaged ones. Mainly, the damaged trees were ca. 10–15 years older than the healthy ones suggesting age related differences in susceptibility, which might be related to vigour. The damaged and healthy trees differed also by growth trends, suggesting affiliation to different crown class, particularly at younger age. The sets of the significant climatic factors differed between the central and eastern part of Latvia. In the central part of Latvia, ash was mainly affected by the precipitation and daily temperature difference in the summer preceding formation of the tree-ring. Although the damaged trees were more sensitive to daily temperature difference and precipitation in the preceding August, the healthy trees were also additionally affected by maximum temperature in the preceding August. In the eastern part of Latvia, the sets of the significant factors were site specific, however, trees were mainly affected by temperature in the preceding autumn and current spring. In one site, the damaged ashes were more sensitive to temperature in July and September, while in other site the damaged trees were more affected by precipitation in July; the healthy trees were additionally affected by precipitation in September and temperature in April. Hence, the susceptibility to the disease appears partially related to the climatic sensitivity of trees. © Lithuanian Research Centre for Agriculture and Forestry.


Baders E.,LSFRI Silava | Senhofa S.,LSFRI Silava | Purina L.,LSFRI Silava | Jansons A.,LSFRI Silava
Baltic Forestry | Year: 2017

The dynamics of unmanaged forest ecosystems is led by the natural disturbances, among which storms are one of the most important, especially due to occurring and predicted increase in their frequency. Mimicking of the natural disturbances is considered a part of the forest management strategy in the particular areas. However, the diversity of the possible initial stand and landscape composition leads to the various corresponding pathways of recovery after the disturbance. So far, a limited number of short term (up to 25 years after the windthrow) empirical studies have assessed them in the hemiboreal forests. In this study, the stand development 45-46 years after the stand replacing windthrow was assessed in the north-western part of Latvia, Slitere National Park. In the areas formerly dominated by Norway spruce, the post-storm tree species composition was significantly altered by the site type. Birch dominated in the overstorey; however, the dominance of spruce was found in 12 and 33% of the areas in the mesic and wet sites, respectively; the understorey and the advanced regeneration were mostly (61 and 46%, respectively) formed by spruce. In most cases, the diameter at breast height (DBH) of the overstorey spruce was similar or larger than for pioneer species (except aspen), regardless of the proportion of spruce in the stand composition. The dimensions of spruce were significantly larger in mesic than in wet sites: DBH and height was 23.8 ± 1.0 vs. 19.4 ± 1.5 cm and 22.5 ± 0.5 vs. 17.7 ± 1.0 m, respectively. Regardless of the distance from the undamaged stand, the number of the overstorey spruce was similar, indicating the sufficient seed dispersal from the windthrown trees. However, on the wet sites, the proportion of spruce from the total number of trees was significantly higher in the areas up to 50 m from spruce stand that remained after the storm. Also, the abundance of the understorey spruce had significant positive relation to the distance to the undamaged stand. The results suggest that 45 years after the stand-replacing windthrow spruce is abundant within all stand layers and might dominate the overstorey besides the pioneer species. © 2017; Lietuvos Misku Institutas. All rights reserved.


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.


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.


Purina L.,LSFRI Silava | Matisons R.,LSFRI Silava | Jansons A.,LSFRI Silava | Senhofa S.,LSFRI Silava
Silva Fennica | Year: 2016

The projections of vegetation zones suggest increasing growth potential of European beech (Fagus sylvatica L.) in Northern Europe. Such changes usually are most apparent in the marginal populations. In this study, survival of young beech growing in an experimental plantation under canopy of a mixed coniferous stand in the central part of Latvia was assessed after 33 years since the establishment. The planting material originated from an older experimental stand in the western part of Latvia. Although, at present, the studied plantation could be considered as the northeasternmost beech stand in Europe, a good survival was observed - ca. 80% of the seedlings have survived, despite several cold spells of ca. -30 °C that occurred during the recent three decades. Additionally, some self-regeneration i.e. branch sprouting was observed. The saplings were rather low, as their mean height was ca. 4 m. Still, some individuals, which were growing under canopy openings, reached considerable dimensions; their height and stem diameter exceeded 10 m and 9 cm, respectively. The distribution of sapling dimensions had the reverse-J shape that is typical for shade tolerant species, indicating normal development of the beech regrowth. The crowns of saplings were narrow and the stems were spindly, suggesting that trees with a good stem quality might be bred. Hence, our results suggest that environmental conditions in the central part of Latvia have been satisfactory for beech, thus encouraging establishment of more extensive trials within the region. © 2016, Finnish Society of Forest Science. all rights reserved.


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.


Senhofa S.,LSFRI Silava | Zeps M.,LSFRI Silava | Matisons R.,LSFRI Silava | Smilga J.,LSFRI Silava | And 2 more authors.
Silva Fennica | Year: 2016

Fast-growing hybrids of Populus L. have an increasing importance as a source of renewable energy and as industrial wood. Nevertheless, the long-term sensitivity of Populus hybrids to weather conditions and hence to possible climatic hazards in Northern Europe have been insufficiently studied, likely due to the limited age of the trees (short rotation). In this study, the climatic sensitivity of ca. 65-year-old hybrid poplars (Populus balsamifera L. × P. laurifolia Ledeb.), growing at two sites in the western part of Latvia, and ca. 55-year-old hybrid aspens (Populus tremuloides Michx. × P. tremula L.), growing in the eastern part of Latvia, have been studied using classical dendrochronological techniques. The high-frequency variation of tree-ring width (TRW) of hybrid poplar from both sites was similar, but it differed from hybrid aspen due to the diverse parental species and geographic location of the stands. Nevertheless, some common tendencies in TRW were observed for both hybrids. Climatic factors influencing TRW were generally similar for both hybrids, but their composition differed. The strength of climate-TRW relationships was similar, but the hybrid poplar was affected by a higher number of climatic factors. Hybrid poplar was sensitive to factors related to water deficit in late summer in the previous and current years. Hybrid aspen was sensitive to conditions in the year of formation of tree-ring. Both hybrids also displayed a reaction to temperature during the dormant period. The observed climate-growth relationships suggest that increasing temperatures might burden the radial growth of the studied hybrids of Populus. © 2016, Silva Fennica. All rights reserved.


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.


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.

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