Suchergebnisse

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.

Hydrometeorological parameters and aquatic chemistry of Lake Engure: Trends of changes due to human impact and natural variability
Lake Engure, located in Latvia, is the largest shallow coastal lake that developed after retreat of the Littorina Sea. It supports high biodiversity and has national and international importance. Engure is a hardwater lake with abundant macrophyte and charophyte vegetation. The present study determined the impact of the main meteorological indicators related to global warming, and also indicators of climate extremes. The lake water level is regulated by hydrotechnical constructions. In the the warm period (April-October) of the year the lake level tends to increase. However, from a perspective of long-term changes, there was a good relationship between the Western type of Atmospheric Circulation Index and water level in general, and also between NAO index in March and lake water level in April. Regarding water chemical composition, there has been a decrease of phosphorus concentration while ammonium and nitrate concentrations have not changed. Ionic composition of Lake Engure is characterised by dominance of hydrocarbonates, calcium and magnesium ions.

Abstract. Drought events and their impacts vary spatially and temporally due to diverse pedo-climatic and hydrologic conditions, as well as variations in exposure and vulnerability, such as demographics and response actions. While hazard severity and frequency of past drought events have been studied in detail, little is known about the effect of drought management strategies on the actual impacts and how the hazard is perceived by relevant stakeholders. In a continental study, we characterised and assessed the impacts and the perceptions of two recent drought events (2018 and 2019) in Europe and examined the relationship between management strategies and drought perception, hazard, and impact. The study was based on a pan-European survey involving national representatives from 28 countries and relevant stakeholders responding to a standard questionnaire. The survey focused on collecting information on stakeholders' perceptions of drought, impacts on water resources and beyond, water availability, and current drought management strategies on national and regional scales. The survey results were compared with the actual drought hazard information registered by the European Drought Observatory (EDO) for 2018 and 2019. The results highlighted high diversity in drought perception across different countries and in values of the implemented drought management strategies to alleviate impacts by increasing national and sub-national awareness and resilience. The study identifies an urgent need to further reduce drought impacts by constructing and implementing a European macro-level drought governance approach, such as a directive, which would strengthen national drought management and mitigate damage to human and natural assets.