Volume 33 (2015): Issue 1 (July 2015)

Cumulative impact evaluation is one of the most actual problems in air quality monitoring. At the same time, it is also the most problematic factor to evaluate due to lack of appropriate methodology. The aim of this study was to assess the opportunity to use a new method – Cumulative Pollution Index (CPI) in cumulative impact calculation from two different sets of data – bioindication survey with Index of Atmospheric Purity method and air pollution dispersion modelling. Results show that the usage of modelling data, instead of measurements, in cumulative impact evaluation can be quite difficult due to the fact that dispersion models not always give sufficiently accurate data. Despite the issues with modelling specifics, the use of dispersion modelling in CPI calculation shows that the use of this approach not only gives plausible data – obtained values correlate with pollution level and forming strong clustering in spatial distribution, but also reveals new facts about cumulative impact – demonstrates the city microclimate importance in forming of cumulative effect due to geometry of street canyons.

Phomopsis vaccinii cause a serious disease of blueberry, cranberry and other Vaccinium crops in the North America and Europe as well. Over 1000 species names are described by Phomopsis spp., but their biology and life style are mostly unknown. Identification of P. vaccinii by methods of classical phytopathology is difficult and complicate, because many species are morphologically similar to P. vaccinii, and P. vaccinii itself has diverse patterns of colony morphology. For this investigation P. vaccinii isolates were obtained from five cranberry plantations in different locations of Latvia (Babite, Alsunga, Rucava, Ape and Pargauja municipality) from berries affected by viscid rot at harvest and storage in 2010. Altogether 44 P. vaccinii isolates were cultivated on potato dextrose agar for description of colony morphology. In order to find some relationships between samples, the isolates were arranged in different groups on the basis of mycelium color and structure (zoning), reverse pigmentation, pycnidium formation time, size, location, number and size of conidia. During this study the colonies of P. vaccinii from cranberry in Latvia showed different morphological features in culture and no relationships between growing regions and groups of isolates were found. P. vaccinii is easy to confuse with other Phomopsis species if only classical phytopathological methods are used.

Climate changes are expected to create favourable conditions for development and spread of diseases. Therefore, the impact of meteorological factors on needle cast damage, and relationship between degree of damage and growth of trees had been assessed in the study. Analysis was carried out in open-pollinated progeny trial of Norupe seed orchard clones, established in the spring of 2006, in Ltd. “Rīgas meži” (LLC “Riga Forests”). In this trial needle cast damage was assessed in three consecutive years using a fivegrade scale, dependent on the level of damages on current year needles. At the end of each growing season a tree height was measured. Plantation was significantly affected by infection average more than 66% of current year damaged by the disease. Significant (p<0.001) correlation was detected between the degree of needle cast damage and tree height increment as well as the tree height. Significant (p<0.001) differences in needle cast infection level as well as tree height and height increment were found also between open-pollinated families. The results suggest a potentially increasing needle cast infection due to predicted increase of temperature and precipitation, as well as the potential to select more resistant families against damages of this disease in tree breeding process.

Leaf area index (LAI) is widely used to describe the main characteristics of forest stands such as cover intensity at different forest levels from moss to tree as well as main stand dendrometric parameters. Hemispherical canopy photograph was used for analyzing quality and quantity of coniferous forest in Aukstaitija national park. Different sampling systems from single plots to aggregating them into stands allowed assessing significance of LAI detected by the HemiView system in forestry without special preparation. The obtained data revealed that the use of hemispheric photograph for LAI estimation in multi-aged and multi-layered mature and over mature pine and spruce stands was rather problematic. Only cover intensity of understory vegetation (grasses and mosses) was reflected best. In pure pine stands LAI also significantly reflected spatial changes in cover intensity of shrubs, grasses and mosses levels and in addition - spatial changes in main dendrometric stand parameters. Key findings - significant relationships between LAI detected in November and pine needle litterfall over September-October. It allowed detecting significance of LAI in mass balance of the main nutritional and contaminant components calculations. LAI increase by 1 m² m⁻² increased total litterfall amount by 1.7 t ha⁻¹ in a pure mature pine forest. The obtained results indicated good perspectives of LAI detected by HemiView system in forestry even without special their preparation.

Winter oilseed rape (Brassica napus L.) significance among field crops is unchangeable in Latvia in the last decade. Plant density of winter oilseed rape during growth period is influenced by plant development in autumn and plant wintering. The aim of four year (2008 – 2011) research in the LLU Research and Study farm “Vecauce” was to investigate the influence of agronomical factors (sowing date, sowing rate, fungicide (metkonazole)) application and meteorological factors on two type (line, hybrid) winter oilseed rape varieties plant density changes from sowing till harvesting. Plant density in autumn, spring and during harvesting was influenced also by meteorological parameters such as air temperature and precipitation. On four year average, field germination was observed from 66% to 95%. Sowing date significantly (p<0.05) impacted plant survival during winters in all trial years for both varieties – ‘Californium’ and ‘Excalibur’, except for ‘Excalibur’ in the year 2008. Plant survival during winter for ‘Excalibur’ (hybrid) was higher compared to ‘Californium’ (line). Higher plant losses during winter were noted on the latest sowing date for both varieties. Winter oilseed rape plant survival was not significantly (p>0.05) influenced by fungicide as growth regulator application in autumn in any trial year. Influence of sowing date and sowing rate on the total plant density at harvest time was significant in all trial years (p<0.05) for both varieties. At higher sowing rate the plant loss during growing period was higher than at lower rates.

Precise and reliable meteorological data are necessary for building performance analysis. Since meteorological conditions vary significantly from year to year, there is a need to create a test reference year (TRY), to represent the long-term weather conditions over a year. In this paper two different TRY data models were generated and compared: TRY and TRY-2. Both models where created by analysing every 3-hour weather data for a 30-year period (1984–2013) in Alūksne, Latvia, provided by the Latvian Environment Geology and Meteorology Centre (LEGMC). TRY model was generated according to standard LVS EN ISO 15927-4, but to create second model - TRY-2, 30 year average data were applied. The generated TRY contains typical months from a number of different years. The data gathered from TRY and TRY-2 models where compared with the climate data from the Latvian Cabinet of Ministers regulation No. 379, Regulations Regarding Latvian Building Code LBN 003-01. Average monthly temperature values in LBN 003-01 were lower than the TRY and TRY-2 values. The results of this study may be used in building energy simulations and heating-cooling load calculations for selected region. TRY selection process should include the most recent meteorological observations and should be periodically renewed to reflect the long-term climate change.