Prolonged summer drought periods are forecasted for the Baltic Sea region during the 21st century, thus increasing the risk of drought stress of saplings used in forest regeneration. Nevertheless, the vitality of young stands might be increased by the selection of suitable planting material. The aim of this study was to estimate the effect of changes in distribution of summer precipitation on height increment, biomass distribution and root morphology of Scots pine and silver birch planting material commonly used in the forest regeneration in Latvia. Containerized pine and bare rooted birch saplings, planted in three different soil types, were subjected to altered distribution of summer precipitation, provided by the use of automated shelter. Sheltered saplings were weekly irrigated with the sum of precipitation of a corresponding period, while afield planted saplings had an unchanged precipitation regime and served as control. Height increment was measured once per week and estimation of morphology of saplings was done after the end of every vegetation season. Significant (p is less than 0.05) differences in height increment, and shoot and root biomass were observed among the same planting material in different irrigation regimes and soil types. In the control plots of peat soil, pine had a significantly (p is less than 0.05) larger height increment while birch-significantly (p is less than 0.05) smaller compared to experiment. Forecasted longer drought periods might reduce the growth of Scots pine in fertile forest types but silver birch growth might be affected in fertile mineral soils in future.

Wet soils play an important role in hydrological, biological and chemical processes, and knowledge on their spatial distribution is essential in forestry, agriculture and similar fields. Digital elevation models (DEM) and various hydrological indexes are used to perform water runoff and accumulation processes. The prerequisite for the calculation of the hydrological indexes is the most accurate representation of the Earth’s surface in the DEM, which must be corrected as necessary to remove surface artefacts that create a dam effect. In addition, different resolutions for DEM give different results, so it is necessary to evaluate what resolution data is needed for a particular study. The aim of this study is to evaluate the feasibility of using existing ditch vector data for DEM correction and the resulting implications for soil moisture prediction. Applied methodology uses a network of available ditch vectors and creates gaps in the overlapping parts of the DEM. The data were processed using open source GIS software QGIS, GRASS GIS and Whitebox GAT. Ditch vector data were obtained from JSC Latvian State Forests and the Latvian Geospatial Information Agency. The results show that by applying the bottomless ditch approach in forest lands on moraine deposits, depending on the accuracy of the ditch vector data, the values of the prediction of the soil wetness both increase and decrease. On the other hand, in forest lands on graciolimnic sediments it is visible that predicted soil wetness values increase in the close proximity of ditches. For forest lands on glaciofluvial and eolitic sediments there were no visible changes because of lack of ditches.

A demand for wood resources is increasing. In addition to drainage and appropriate regeneration and thinning, the forest soil fertilization may increase the future harvest rates. Therefore, the improved growth of forest stands raises in priority among the research topics related to forestry. The objective of the study is to evaluate the impact of nitrogen fertilizer on soil water and throughfall water chemical composition to elaborate recommendations for the forest fertilization. The trials were conducted in a birch stand and in three coniferous stands. Nitrogen containing mineral fertilizer (ammonium nitrate) was distributed in the study sites, while the control plots were left without any treatment. The water samples were collected a season before and a season after the soil treatment. The pH level, total nitrogen, potassium and phosphate were determined in throughfall and soil water samples. The chemical properties of throughfall water differed depending on the forest stand type. The concentration of nitrogen was higher in throughfall water samples collected from the birch stand. The mean concentration of total nitrogen was 1.6 ± 0.3 mg LE−1 in the throughfall water samples from the birch stand compared to 1.03 ± 0.11 mg LE−1 in the throughfall water samples from the coniferous stands. Although the forest soil was enriched with the nitrogen fertilizer, there was a significant increase in concentrations of potassium and phosphate in soil water samples from certain stands. It can be explained with changes in pH level that occurred after the forest soil treatment with ammonium nitrate. There was also a significant increase in total nitrogen concentrations in soil water samples at the depth of 30 cm from the treated plots of the coniferous stands – 15 ± 6 mg LE−1, compared to 1.5 ± 0.03 mg LE−1 in the samples from the control plots. However, the concentrations decreased within two months and remained at a steady rate – slightly above the control level.