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Māris Zunde, Agrita Briede and Didzis Elferts

Influence of Climatic Factors on the Annual Radial Growth of Scots Pine (Pinus sylvestris L.) in Western Latvia

Dendroclimatological research has been perfomed in Latvia after a break of about 25 years. The growth pattern of Scots pine (Pinus sylvestris L.) in six districts of western Latvia is analysed in relation to climatic factors (monthly and seasonal mean air temperature and precipitation). Applying various statistical techniques, it was observed that in this area the growth of pine on mineral soils with normal moisture conditions has been affected most significantly by the mean air temperature during the period from the second half of January to the first half of April of the same year. Thus, the period when mean air temperature is the most significant influence is similar across an area at least from Lithuania (inclusive) to southern Scandinavia, while further north it is mean summer air temperature that gradually becomes the determining factor in the radial growth of pine. Also the quality of the dendrochronological signal in tree-ring chronologies of pine growing in the environmental conditions of Latvia was determined and signature years during the 20th century were identified, when the majority of pines throughout the territory of the Baltic States exhibit a similar change in annual radial growth.

Open access

Didzis Elferts, Iluta Dauškane, Guna Ūsele and Agita Treimane

Effect of water level and climatic factors on the radial growth of black alder

Black alder (Alnus glutinosa (L.) Gaertn.) is a widespread tree species in Europe and the western part of the temperate climate zone. The area of forest in Latvia dominated by this tree species has substantially decreased due to wide-spread forest drainage. To predict future changes due to environmental change, it is extremely important to understand the function of ecosystems with black alder and their dynamics. Tree rings can be used as a proxy of past environmental factors. The aim of the study was to determine the effects of meteorological and hydrological factors on radial growth of black alder at two study sites (Dursupe and Raķupe) in Latvia. The response of black alder trees to the influence of climatic and hydrological factors was found to depend on site conditions, i.e. a climatic effect was observed in conditions when the water level was low. Spatial variation in the strength of the relationship of black alder growth to temperature, precipitation, and river level suggests that alder growth is more susceptible to drought stress on higher river banks, where the water table is deeper. Black alder trees growing on low river banks can potentially be used to reconstruct past water-levels.

Open access

Elga Apsîte, Didzis Elferts and Inese Latkovska

Abstract

This paper presents the results of the study of long-term changes of Daugava River ice phenology, i.e. the freeze-up date, the break-up date, and the duration of ice cover from 1919/1920 to 2011/2012, under the impact of the cascade of hydro power plants. The long-term changes of ice phenology were determined by global climate warming at the turn of the 20th and the 21st centuries and anthropogenic activities after the year 1939. The Mann-Kendall test showed that the ice freeze-up date has a positive trend, while the ice break-up date and the duration of ice cover had negative trends. The changes were statistically significant. Data series covering twenty years before and after construction of the hydro power plants were used for assessing the impact of each hydro power plant on changes of Daugava River ice phenology parameters. The study results showed that the duration of ice cover was significantly longer in water reservoirs, i.e. the freeze-up date was earlier and the break-up date was later. Downstream of dams duration of ice cover was shorter with later freeze-up dates and earlier break-up dates. The impact of hydro power plants on ice phenology parameters gradually decreased with distance down from the dams.

Open access

Viesturs Melecis, Zaiga Krisjane, Maris Klavins, Juris Aigars, Didzis Elferts and Janis Viksne

Preliminary Characteristics of Ecological and Socioeconomic Components and their Interaction within the Long Term Socioecological Research Platform of Latvia

Review of previous ecological and socioeconomic studies performed in the drainage basin of Lake Engure - the long-term socioecological research region (LT(S)ER) of the National LTER network of Latvia has been given. A number of studies on biodiversity and ecosystem structure of the region were published during the last century. There have been no special socioeconomic studies of the region till now. The data should be collected mostly from different archives and statistical summaries. Biodiversity of the region has been formed over the centuries and is strongly dependent on socioeconomic factors.

Open access

Astrīda Krūmiņa, Liāna Pliss, Gunita Zariņa, Agrita Puzuka, Agnese Zariņa, Baiba Lāce, Didzis Elferts, Andrey Khrunin, Svetlana Limborska, Jānis Kloviņš and Linda Gailīte Piekuse

Abstract

This article presents a review on population genetics of Latvians, which alongside Lithuanians are the two extant Baltic speaking populations. The article provides a description of genome-wide single nucleotide polymorphism (SNP) data and contains a comparative analysis of the results of studies performed on classical autosomal genetic markers, mitochondrial DNA (mtDNA) and the non-recombining part of the Y chromosome (NRY), with data on neighbouring populations. The study also covers data of recently performed ancient DNA (aDNA) studies carried out on samples from the territory of today’s Latvia. The results of population genetic studies have shown a mixture of eastern and western genetic traits in present-day Latvians with only small differences between Latvian subpopulations. Studies of the Baltic “tribal gene” LWb, as well as the gene’s SERPINA1 allele PIZ have indicated the presence of a considerable Baltic admixture in the neighbouring Finno-Ugric and Slavic populations. Although mtDNA analyses have shown that Latvians genetically in general belong to the same common gene pool as most of the Europeans, the Y-chromosomal lineage composition suggests that they are most similar to Northern and Eastern European populations of Lithuanians, Estonians, and Eastern-Slavic populations, which are ethnogenetically closest to them. The analysis of aDNA from the Early and Middle Neolithic did not present any genomic evidence of gene-flow from Central European farmers or any mitochondrial or Y-chromosomal haplogroups that are typical for them in the hunter-gatherers from the territory of today’s Latvia and Lithuania.