Reduction of agricultural production has led to abandonment of farmlands in Latvia. According to the Central Statistical Bureau, 1.4 million ha of lands, including 0.6 million ha of farmlands were set aside in 2008. Most of them transform into forests; however, information about the afforestation has been limited until recent years. The first field measurement based evaluation of forest stands on abandoned farmlands was implemented within the scope of the National statistical forest inventory (NSFI). The NSFI covers forests, farmlands, settlements, wetlands and other lands, providing valuable information about the land use and forest resources. According to the NSFI, total area of naturally afforested farmlands is 257,850 ± 3,606 ha with growing stock of 2,870.364 ± 239,088 m³. Naturally afforested lands occupy 4% of the total country area. The highest share of naturally afforested lands is in Ludza (11% of the total area) and Krāslava districts (9% of the total area). Birch (Betula pendula Roth) and grey alder (Alnus incana (L.) Moench) are the most common dominant tree species in naturally afforested areas (77,092 ± 1,861 ha and 40,285 ± 1,395 ha, respectively). In relation to the Kyoto protocol it is important to separate lands afforested before and after 1990. The total area of lands afforested after 1990 in Latvia is 170,890 ± 2,862 ha with total growing stock of 1,367.427 ± 125,482 m³ and annual increment of timber volume – 122,530 ± 10,513 m³.

Fire is a major disturbance in hemiboreal forests; it affects not only trees, but also ground vegetation. Previous studies have analysed the succession of ground vegetation after the fire, but not addressed the impact of the size of the burned area on revegetation of it. Therefore, the aim of our study was to assess the differences in post-fire ground vegetation in relation to the distance from the edge of the affected area. Vegetation data were collected using Braun-Blanquet method in three sites (122 sample plots) affected by forest fire and five clearcuts (not affected by fire) (92 plots), all regenerated by Scots pine 6 – 7 years before the assessment. The number of ground vegetation species (in all sites predominantly birds or wind dispersed) as well as their projective cover was not affected by the distance from the nearest edge of burned or clearcut, except in burned sites on dry sand soil (Vaccinosa and Myrtillosa), where herbaceous plant and shrub cover was decreasing (from 23.5% to 11.6%) and bryophyte and lichen cover – increasing (from 3% to 13.9%) with an increasing distance from the edge of the area. The total number of plants in burned areas was twice smaller than in clearcut in the same soil conditions but such large difference in projective cover was not observed. There were no significant differences between burned and clearcut areas in respect to Ellenberg’s indicator values on both soil types, as well as no trend in Ellenberg’s values for soil moisture in relation to distance from the nearest stand edge.

An important factor in the development of forest ecosystem is the ability to regenerate. Natural intensity of self thinning of a forest depends on the tree species and environmental conditions. Due to abiotic and biotic factors in a continuous forest tract, there appears a clearing, which, depending on the size, forms new growth conditions. Over time, the resulting new space is occupied by herbaceous and woody vegetation. Most often regeneration of a new forest depends on the size of the plot. The study was conducted in 2013 during the growing season in a typical broadleaf forest stand. During the study woody vegetation and projection coverage of herbaceous vegetation was registered in large clearings. Light conditions in the plots and under tree canopies, as well as soil parameters were ascertained. Based on the collected data, the view of the structure of woody vegetation, projection coverage of herbaceous vegetation, light conditions, temperature, soil moisture content and pH changes were obtained. In order to clarify the influence of microclimatic conditions on natural forest regeneration, the data on light and soil characteristics were analyzed. The aim of the study - was to determine the changes of woody and herbaceous vegetation in spruce stand clearings and to assess the impact of microclimate. During the study it was found out that in large plots dominated species demanding higher amount of light, while herbaceous vegetation was attributed to the third, fourth groups of aggressiveness. Naturally regenerated seedlings condition was mostly influenced by light conditions and soil moisture content.

Forest fires in Latvia occur every year. Research about vegetation and forest regeneration after forest fire is being carried out in Latvia, and sanitary conditions are being evaluated too; however, there are no large studies about the forest fire impact on radial growth dynamics of trees. The aim of the study was to analyse and compare the response reaction of a forest stand after fire in two forest site types – Hylocomiosa and Vacciniosa turf. mel. The object of the research was fire affected middle–aged managed Scots pine (Pinus sylvestris L.) stands in the aforementioned forest site types. The study compares radial growth dynamics of trees, tree mortality and forest stand sanitary conditions after fire in Hylocomiosa and Vacciniosa turf. mel. The observed fire impact on radial growth dynamics of trees was negative in both forest site types. Negative fire impact on sanitary conditions was observed, too.

The aim of the study is to determine how successful the initial growth of naturally grown and planted pines is after performing the shelterwood cutting. The research includes tree count and height analysis in Myrtillosa and Hylocomiosa forest types with different regeneration methods in 2018. A total of 10 sites were arranged for the research, each site having 4 sample plots. All naturally regenerated and planted pine (2009, 2012 and 2013) heights were measured. Judging by the number of trees after shelterwood cutting, most sites should not be considered regenerated, additional planting or scarification of soil is required which can improve the efficiency of natural regeneration. In all the sites both in Myrtillosa and Hylocomiosa, after shelterwood cutting it was observed that the height of artificially regenerated trees is higher than the height of naturally regenerated trees, indicating the ability of planted pines to produce more rapid height increment in the first years of life, regardless of forest type. The basal area of the stand has a significant negative impact on the increment, and it indicates the need for the subsequent shelterwood cut to be performed. Although Hylocomiosa is a more fertile forest type than Myrtillosa, the height of the planted pine trees in Myrtillosa is higher than in Hylocomiosa, where, after shelterwood cutting, no sufficiently intensive agro-technical tending has been performed.

In Latvia, P.abies (L.) H. Karst stands occupy about 18% of the total forest area (3.01 million) forming pure and mixed stands. Regardless of the main goals, productivity of the future forest stands must be preserved; therefore, it is very important for forest management to identify risk factors. P.abies often suffers from various risk factors. The aim of the research was – to assess the sanitary state of Picea abies (L.) H. Karst in Oxalidosa, where the area of forest stands has been restored both anthropogenically and naturally. Selected young stands are located in Limbazi district of Latvia. Empirical data was collected in 5 spruce stands with the total area of 9.2 ha in Oxalidosa. In total, 67 sample plots were installed with radius of 3.99 m, measuring 799 trees. Diameter was measured for all trees in the sample plot. For sanitary state of P.abies young stands characterization damage caused by biotic factors was assessed visually after four-point scale: health tree (0), minor damage to 25% (1), moderately damaged 26 – 50% (2), severely damaged or dried – from 51% (3). Damage caused by P.abietina and browsing was found in several stands, while damage produced by P.abietina larvae was detected only in one pure stand. Occurrence of browsing damage is 10 – 28%, while damage intensity – 7.7 – 21.8%. There are significant differences between occurrence of browsing damage (p=0.001) and also between damaged tree damage intensity (p=0.003). Nature of browsing damage depends on the size of pure and mixed stand area, the location in forest massif and adjoining territory.

In Latvia, two European ash (Fraxinus excelsior) genetic resource forests (GRF) have been designated in Skrīveri and Bērvircava. However, as the degree of damage of ash by the pathogenic fungus Hymenoscyphus fraxineus has increased, many stands have died and many do not comply anymore with minimum requirements for GRF. The aim of the present research was to evaluate and examine the quality of ash GRFs. In each forest unit, one 20×20 m plot was established, and the first (E3) and second (E2) layer projective cover of each species was determined in August 2014. All undergrowth and advance regeneration species were counted and the degree of ash damage by H. fraxineus was determined along a diagonal 25×1 m transect in each plot. In total, 101 plots were established. Quality evaluation was carried out according to the basic criteria for selection of GRF as well as based on criteria cited in other research. Their variation was established by using principal component analysis. Ash in layer E3 was better maintained in Skrīveri, but ash regeneration there was worse, as well as a higher degree of damage by H. fraxineus was observed. Ash regeneration density is significantly influenced by its cover on layers E3 and E2 as well as by tree species dominating the growth. The most valuable GRFs have been maintained in Skrīveri where 50% of units were rated of average quality and few of bad quality. In Bērvircava, 56% of forest units were of bad and very bad quality.

Fire is a frequent disturbance in hemiboreal forests that in Latvia affects mostly Scots pine (Pinus Sylvestris L.) stands. Increased forest fire risk is predicted in future as a result of climatic changes. Therefore the aim of our study was to assess Scots pine regeneration after forest fire in different forest types and with different regeneration methods. Tree height was measured and browsing damage assessed seven years after the forest fire in six different forest types, where planting and natural regeneration (in a clearcut and without management) occurred in compartments randomly selected from a list of stands severely affected by forest fire. The height of Scots pine was significantly affected both by forest type and regeneration method. Notable advantages of planting based on tree height were found in wet mineral soils and peat soils. Trees on poor (dry, wet, peat) soils were higher in natural regeneration after clearcut than in natural regeneration without clearcut. The density of Scots pine trees was significantly affected by the forest type but not by regeneration method (planting, natural regeneration, natural regeneration after the clearcut). The most abundant tree species in natural regeneration after clearcut in all forest types was silver birch (Betula pendula Roth.). The height of silver birch exceeded that of Scots pine in all analyzed soils in clearcut areas except Vaccinososphagnosa forest type, emphasizing the importance of thinning to ensure a successful development of Scots pine stands.

The regeneration of European hornbeam (Carpinus betulus L.) has been assessed in the National Gene Reserve Forest near Lukne in the south-western part of Latvia, which is the northernmost point of hornbeam distribution in Europe. In the studied stand, six sampling plots and four transects were established to assess stand structure and the effect of irradiation parameters on stand regeneration. Successful regeneration of hornbeam was shown by its presence in all height and diameter classes. Nevertheless, in the smallest height and diameter classes, an increased abundance of other shade tolerant species (maple (Acer platanoides L.) and lime (Tilia cordata Mill.) was observed. Norway spruce (Picea abies Karst.) mainly formed a scattered second forest floor and, apparently, competed with hornbeam. Light parameters, particularly, the diffuse radiation, had a significant effect (p=0.05) on the distribution and abundance of hornbeam understory. The threshold values of irradiation parameters for hornbeam were notably higher compared to other species. The number and height of hornbeam saplings correlated tightly with the amount of available light. Nevertheless, under sufficient light conditions hornbeam showed good vitality, thus suggesting suitability of growing conditions.