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Kaspars Liepiņš, Jānis Liepiņš and Roberts Matisons

Abstract

In Latvia, common ash (Fraxinus excelsior L.) can form ecologically stable monoculture stands in localities with optimum growing conditions, but they are mainly found in mixed forests throughout the country on sites with fresh, fertile, sufficiently moist, yet well-drained soils. Over the last two decades, ash decline has become a serious problem for the whole of Europe; the causal agent for it is also present in Latvia. The aim of the given study was to investigate the growth patterns of ash in different populations at the age of maturity (over 80 years), tracing back their course of growth, and identify the spatial distribution of ash to identify localities with appreciable concentration of ash-dominated stands. The study revealed high variation in the juvenile growth of ash, and confirmed that the height and diameter growth for common ash peaks at an early age. Analysis of the spatial distribution of ash indicated considerable expansion of common ash over the country during the second half of the 20th century, to some extent complementing natural overgrowing of abandoned lands by forest. Apart from the Zemgale Plain in the middle of Latvia, the highest concentration of ash stands is in upland areas with highly varying land relief conditions.

Open access

Roberts Matisons, Linda Gerra Inohosa and Māris Laiviņš

Abstract

The effect of climatic factors on tree-ring width (TRW) of European ash (Fraxinus excelsior L.) with healthy and damaged crowns growing in the central and eastern part of Latvia was assessed by dendrochronological techniques. Pointer year indices were calculated to assess the variability of TRW. Positive pointer years were more frequent than negative, similarly for damaged and healthy trees, suggesting similar limiting factors. The relationships between TRW and climatic factors differed regionally and locally. In the eastern part of Latvia, TRW was affected by temperature in spring of current and preceding years. In the central part of Latvia, weather conditions in current and preceding summer mainly affected TRW; temperature and precipitation had positive effect suggesting occurrence of water deficit, but the daily range of temperature had a negative effect. Hence, regional diversification of radial growth patterns might be expected. Some differences in sensitivity to climate were observed between the damaged and healthy trees. In the central part of Latvia, the damaged trees appeared additionally sensitive to temperature in summer. In the eastern part of Latvia, damaged trees were additionally sensitive to temperature in May. Nevertheless, some additional factors were significant for the healthy trees.

Open access

Ilze Pušpure, Māris Laiviņš, Roberts Matisons and Tālis Gaitnieks

Abstract

Intense dieback of Fraxinus excelsior L. has been causing rapid changes in advance growth of trees and understory shrub growth of the affected stands. In this study, changes in composition and density of understory were studied in 15 permanent plots (each 235.6 m2), repeatedly sampled in 2005, 2010, and 2015. Within each plot, the number and average height of understory individuals were determined. The successional changes in understory were assessed by Detrended Correspondence Analysis. In total, 11 advance growth and 20 undergrowth species were recorded. A significant increase in the density of understory was observed only in 2015, mainly due to understorey growth of Corylus avellana L., Padus avium Mill., and Lonicera xylosteum L. Regarding advanced growth, the highest density was observed for Ulmus glabra Huds., F. excelsior and Acer platanoides L.; the density of A. platanoides and F. excelsior increased particularly in the period from 2010–2015. The observed successional changes suggested individuality of development of the affected stands according to the composition of the remaining and neighbouring canopy trees.

Open access

Aris Jansons, Roberts Matisons, Agris Pobiarzens, Linards Sisenis and Una Neimane

Abstract

In forestry, alien tree species are planted to maximize yield from a stand by increasing productivity and decreasing environmental risks. In Eastern Europe, lodgepole pine (Pinus contorta var. latifolia) might be used as a source of biomass and industrial wood; however, before any recommendations are given, possible gains of the novel species should be scrupulously evaluated. In this study, we compared volume and proportion of knotty stemwood (VKN) of native Scots pine (Pinus sylvestris) from first generation seed orchards and provenances of alien lodgepole pine [Fort Nelson (58°38’ N, 122°41’ W) and Summit Lake (54°24› N, 122°37› W)] at the age of 27 years growing in central Latvia. We also assessed the relationships between VKN and several morphometric parameters.

Stem diameter of both species was similar; however, Summit Lake provenance of lodgepole pine exceeded Scots pine in height, while Fort Nelson provenance was lower than Scots pine. Although Scots pine produced nearly two times less whorls than lodgepole pine, volume of knotless stemwood did not differ significantly between the species; though it was higher for Summit Lake provenance of lodgepole pine compared to Scots pine. In contrast, the proportion of VKN differed significantly between both the species and the provenances. Scots pine showed the lowest proportion of VKN (~ 9%) and Fort Nelson provenances of lodgepole pine showed the highest proportion of VKN (~ 14%). Thus, Summit Lake appears more suitable for the production of industrial wood amongst the provenances of lodgepole pine; nevertheless, higher quantity of leftover material is expected. Some morphometric parameters correlated with VKN and the proportion of VKN, but these relationships differed between species and provenances. The total cross-section of branches was the best predictors of VKN for Scots pine and Fort Nelson provenance of lodgepole pine, while stem diameter showed the strongest correlation for Summit Lake provenance. Number of whorls and mean diameter of living branches were the best predictors of the proportion of VKN for lodgepole pine and Scots pine, respectively. Accordingly, morphometric parameters might be useful for the selection of the best trees of lodgepole pine.