Scots pine (Pinus sylvestris L.) is one of the most widespread coniferous species in boreal zones and it has a considerable economic importance in the Baltic countries. The impact of fungi on Scots pine has been known also historically, but it is predicted that it will increase in future due to climate changes that will have a positive effect on incidence and vitality of various species of fungi. The aim of the study was to characterize the occurrence of Lophodermium spp. in young stands of Scots pine in Latvia. Needle samples were collected from young pine stands (aged 1 – 14 years) located in all regions of Latvia. DNA extraction from needles was done using modified CTAB protocol, presence of Lophodermium in total extracted DNA was detected using a PCR method. Meteorological data – air temperature and precipitation – were obtained from all 34 observation stations of the Latvian Environment, Geology and Meteorology Centre. The presence of Lophodermium spp. was detected in all surveyed stands, and occurrence differences between the western and eastern regions were significant (p = 0.004). The occurrence of Lophodermium spp. in the eastern and western regions was affected by the meteorological conditions in autumn and winter of the previous years, as well as differences in the given years’ air temperature and precipitation. In 2016, the eastern region of Latvia had a higher May−August precipitation and, to a lesser extent, temperature, which correlated with a higher occurrence of Lophodermium spp.

Zemgale geobotanical region historically was dominated by large broad-leaved forests, but last centuries the high anthropogenic pressure on these territories has reduced the area of these forests. In fragmented landscape small patches of natural broad-leaf forests are protected to preserve the forest structural features, which also function as habitats for rare and protected species. The aim of this study was to compare the natural broad-leaf forest habitats and structural elements and vegetation in woodland key habitats in production forests and protected areas (nature park ''Tērvete'' and nature reserve ''Ukru gārša'') in Zemgale. In total, 12 sample plots were established (the size of sample plot 0.1 ha) in Aegopodiosa forest type. In all sample plots forest structural features were measured and vegetation survey using Braun-Blanquet method was made. In this study, we found that average amount of dead wood varies between 78.7 m**3 haE-1 in woodland key habitats in production forests and 133.0 m**3 haE-1 special protected areas. Considerable amount of broad-leaf natural forests represented by nemoral species (50 – 58% of species richness), which corresponds to these forest type communities in the region.

Importance of the study is determined by increasing consumption of woody biomass as a renewable energy source. Whole-tree harvesting is commonly applied for bioenergy use, however intensified biomass removal from forests can cause significant nutrient loss in soil. Nutrients can be returned to forest ecosystem by fertilizing soil with wood ash, which is generated as a by-product of combustion in wood-burning power plants and heating plants. Studies on ash spreading technological processes and costs so far have been insufficient. Aim of the study is to compare the productivity and prime cost of ash spreading with modular spreading trailer and Amazone mineral fertilizer spreader. According to study results productivity of modular trailer is 0.57 ha hE-1 and the spreading costs are 88 EUR haE-1, but that of mineral fertilizer spreader Amazone – 0.61 ha hE-1 and 41 EUR haE-1, respectively. Despite lower productivity modular trailer is more suitable for spreading wood ash, because a larger amount can be delivered and ash is applied more evenly. Productivity of modular trailer can be increased by technical improvements, like equipping the tractor with a crane and a small excavator bucket. Comparing costs of ash spreading and deposition, additional 8.72 EUR haE-1 were required, when using modular trailer, whereas, when using mineral fertilizer spreader, 77.52 EUR haE-1 can be saved. The main reason for the difference is smaller dosage when using modular spreader and additional loading costs.

The biological control agent Rotstop, composed of spores of Phlebiopsis gigantea, is used for treatment of conifer stumps to reduce the spread of Heterobasidion root rot in commercial forests. Two experiments were conducted to compare the antagonistic ability of the Rotstop isolate and nine Latvian isolates of P. gigantea against root rot fungus Heterobasidion, in wood of Scots pine and Norway spruce. Billets of conifer trees were first sprayed with a spore suspension of P. gigantea and then with Heterobasidion at different concentrations. The presence of fungi in billets was evaluated by morphological characteristics of mycelium. The Latvian isolates of P. gigantea showed similar or even higher values of efficacy against Heterobasidion (average efficacy 84% in spruce and 89% in pine) than the commercially manufactured Finnish preparation Rotstop (61% in spruce and 90% in pine). Latvian isolates of P. gigantea have a potential to be used for preparation of biological control agents in the future.

Norway spruce (Picea abies (L.) H.Karst.) is amongst the most important tree species for forestry in Latvia. It has been suggested that due to the foreseen climate change the productivity of Norway spruce in Latvia may decrease. Continuous observations of radial increment allow to identify periods with different growth intensity and to study the effect of environmental conditions on radial increment during them. The aim of this study was to analyse stem radial variation of Norway spruce in mixed-species stand in response to meteorological conditions over one growing season. Stem radial variation of one Norway spruce tree was monitored by band dendrometer throughout the growing season of 2013. Cumulative radial increment was divided into contraction, recovery and increment phases by the stem cycle approach. Four periods with distinct apportionment of these phases were identified – winter/spring dormancy, spring/ summer growth, growth termination and autumn hydration fluctuations. Radial increment began in the second part of May and the most active increment was observed during period of spring/summer growth. This period lasted for 42 days with the mean amplitude of stem radial variations reaching 0.06 mm while the length of increment phase reached up to two days. Throughout the growing season increment was facilitated by an increase in the temperature. Meanwhile, the effect of precipitation was insignificant, presumably due to sufficient water availability and low interspecies competition for it, characteristic in mixed species stands due to differences in depth and distribution of root systems between the species.

In this study, a conceptual rainfall-runoff METQ model, version METQ2007BDOPT, to simulate daily runoff was applied. The model structure and parameters were fundamentally the same as in the METQ98 model with some additional improvement and semi-automatical calibration performance. The model has proved to be successful for both small (the Vienziemite Brook, 5.92 km2 ) and large (the Daugava River, 81 000 km2 ) drainage basins. The model METQ2007BDOPT was calibrated to the six different size river basins (the Pērse, the Malta, the Neriņa, the Imula, the Malmuta and the Iecava). These pilot river basins are characterised by one or two prevailing natural conditions such as hilly agricultural lands, agricultural lowlands, sandy lowlands, forested areas, swamps or lakes. The results of calibration showed good coincidence between the measured and simulated daily discharges. The Nash – Sutcliffe model efficiency coefficient NSE varies from 0.52 to 0.78 and Pearson correlation coefficient r from 0.65 to 0.88 for the six river basins with calibration and validation period from 1956 to 2015. In this study, we found some relationships between the model parameter values and physiographic sub-catchment characteristics.

Lake sediments have a broad range of elementary and organic substance content. Bottom sediments collect decaying organic debris of aquatic plants and animals mixed by water drift with mineral constituents - deposited in the bottom of the lake in anoxic conditions. Lake Alūksne is situated in Northeast Latvia and is of glacial origin. Its water and bottom sediments chemical content depends on formation conditions – influenced also by anthropogenic activities. In order to determine environmental quality for restoration purposes and sediment recovery, geochemical research is needed. This paper aims to study bottom sediments – texture, ash part, organic compounds and metals to pinpoint necessary steps that are crucial for distinguishing environmental quality of the lake through geochemistry research. Bottom sediments contain sapropel with large admixture of organic compounds and microelements that may significantly influence biota and human health if concentration exceeds natural background levels. When bottom sediments are recovered, it may improve oxygene conditions in the lake, extracted sapropel can be used as a fertilizer, therapeutic agents, supplements for farm foods. Generally, sapropel is improving the structure of agricultural soils, increasing the cation exchange capacity and serving as binding material for complexes formation; thus diminishing ecotoxicological exposure threats of heavy metals, increasing yields and albumen and protein quantity in plants cultivation products. As these sediments can be used for soil fertilizing and crop production improvement in agriculture, mechanisms of ecotoxicological impact to various soil types and agricultural plant ecology should be researched.

Eutrophication caused by water pollution with nutrients (nitrogen (N) and phosphorus (P)) is one of the main environmental problems nowadays. Poor water quality might be caused by many natural and anthropogenic factors. The most common anthropogenic factors are water pollution caused by intensive agriculture (e. g. intensive fertilizer use, high density of livestock) and discharges from municipal waste water treatment plants (WWTP). In this study, nutrient load from WWTP to the River Berze basin in time period from the year 2005 to the year 2015 was described. In total, 23 WWTPs of the study area were analysed using descriptive statistics to calculate average values of nutrient amount and concentrations discharged to River Berze basin. From 2005 to 2015 average N and P load from WWTP to the River Berze basin have been reduced, but concentration of N and P in treated wastewater (WW) have increased. The largest WWTP of the study area – Krigeri (WWTP of city Dobele) is subject to the regulations of treated WW quality set by Republic of Latvia Cabinet Regulation No. 34. The WWTP Krigeri meets the regulations, but overall situation in the study area suggests that strict control of smaller WWTP should be made.

Our previous research was focussed on evaluating spaces in the Soviet period housing estates in Riga according to theoretical model of spatial measurements. This model was based on assumption established ex situ that liking and perception of urban space is closely related to buildings. Namely, to the way walls of the buildings shape a setting in terms of its height, width, length. This current paper sets the goal to analyse the impact of landscape elements such as trees, benches, elevations of earth surface, playgrounds on the perception and preference of open spaces in situ. This is done to verify the hypothesis that landscape elements as well as the method of research play a role in our knowledge on how urban spaces are regarded. Semi-structured interviews in walk-along modus are used to talk to inhabitants about the ways they see and like yards and streets in three residential areas: ‘Agenskalna priedes’, ‘Kengarags’, ‘Zolitude’. The interview materials are analysed discursively. The extracted information is compared to the data previously acquired by using the model of spatial measurements. The results of interviews show that trees are the landscape elements that have the largest impact on how residents perceive the size of a space and how they like a setting. There are also other elements such as benches, playgrounds, elevations that play a role. The interview material displays deviations in preference and perception of the size of space compared to the model of spatial measurements. Yet these deviations can be adapted to the model.

Raw milk cheeses are known to have more intense and strong flavour and different texture due to natural microbiota and enzymes. Nevertheless, there are concerns about safety of these products. For microbial inactivation heat treatment of milk is used, but it can adversely affect the flavour, taste and texture of the product. Therefore, applying non-thermal technology such as high pressure processing is attracting alternative. The aim of this study was to examine the effects of high pressure treatment of cow`s milk at a wide range of pressures (400–600 MPa) on milk rennet coagulation time, curd firmness and curd yield. Processed milk samples were subjected to enzymatic coagulation using commercial rennet to determine rennet coagulation time, yield of coagulum and curd firmness. High pressure processing insignificantly influences coagulation properties of whole milk. However, the magnitude of changes depended on applied pressure. Rennet coagulation time and curd yield were significantly different (p is less than 0.05) among the pressure treated milk samples. The higher firmness of the curd form pressurized milk than that of raw or pasteurized milk, evaluated positively. The main effects of high pressure treatment in milk appeared to involve dissociation of casein micelles from the colloidal to the soluble phase. This study suggests that high pressure treatments of milk at 500 MPa or 550 MPa for 15 min may be beneficial for improving the coagulation properties of milk. These positive effects indicated that high pressure processing may have potential for new cheese varieties development.