Over the last decades, climate change has triggered an increase in the frequency of spruce bark beetle (Ips typographus L.) in Central Europe. More than 50% of forests in the Czech Republic are seriously threatened by this pest, leading to high ecological and economic losses. The exponential increase of bark beetle infestation hinders the implementation of costly field campaigns to prevent and mitigate its effects. Remote sensing may help to overcome such limitations as it provides frequent and spatially continuous data on vegetation condition. Using Sentinel-2 images as main input, two models have been developed to test the ability of this data source to map bark beetle damage and severity. All models were based on a change detection approach, and required the generation of previous forest mask and dominant species maps. The first damage mapping model was developed for 2019 and 2020, and it was based on bi-temporal regressions in spruce areas to estimate forest vitality and bark beetle damage. A second model was developed for 2020 considering all forest area, but excluding clear-cuts and completely dead areas, in order to map only changes in stands dominated by alive trees. The three products were validated with in situ data. All the maps showed high accuracies (acc > 0.80). Accuracy was higher than 0.95 and F1-score was higher than 0.88 for areas with high severity, with omission errors under 0.09 in all cases. This confirmed the ability of all the models to detect bark beetle attack at the last phases. Areas with no damage or low severity showed more complex results. The no damage category yielded greater commission errors and relative bias (CEs = 0.30–0.42, relB = 0.42–0.51). The similar results obtained for 2020 leaving out clear-cuts and dead trees proved that the proposed methods could be used to help forest managers fight bark beetle pests. These biotic damage products based on Sentinel-2 can be set up for any location to derive regular forest vitality maps and inform of early damage.

Different variants of regeneration felling or different light conditions (total site factor 15-95%) and weed control were evaluated in relation to the 4-year development of individuals of regenerated sessile oak. The regeneration density is not dependent on light conditions. The highest mortality occurs on the open area of clear felling. For a certain time in youth, it is possible to consider oak as a shade-tolerating species. With the increasing light intensity the diameter and height growth of oak seedlings increases proportionally, being the highest at 100% light intensity. However, to support at least medium-fast growth, the species requires minimally 50% light intensity (smaller closed clear-felled areas). On the other hand, more extensive unprotected cleared areas appear to be quite unsuitable at the initial stages of regeneration. The positive effect of weed control on the success and growth of natural regeneration is questionable. We recommend developing the regenerated stand by means of a series of small-area (about ≤ 0.3 ha) two-stage felling with a medium-long regeneration period (15-20 years).

(1) Sessile oak (Quercus petraea (Matt.) Liebl.) is one of the most important commercial species cultivated at low altitudes in the Czech Republic, and overaged coppices are a significant part of oak stands in the region. In order to secure a high-valuable timber production (e.g., through conversion of such stands into coppices-with-standards), knowledge of the potential and limits of generative regeneration is essential. This study was conducted in three oakdominated over-aged coppice stands in different stages of conversion into coppices-with-standards and characterized by different basal area (BA, from 9.3 to 14.1 m 2 ha -1 ) and relative diffuse radiation (ISF, from 12.1 to 35.5%). The study stands were compared with respect to seed predation following acorn fall and oak regeneration parameters. At the time of their fall the acorns represented a sought-after source of food for large mammals (particularly wild boar). At the end of acorn fall, 13-67% acorns were lost due to animal predation. A control evaluation conducted the following spring revealed a decrease of 92-97% in fallen acorns. Despite the major animal impact, a high reserve of acorns and saplings remained in the stands (4 600-29 000 acorns and 66 000-310 000 saplings per ha). With increasing light intensity the oak regeneration density decreased, while the height and age variability of oak regeneration increased. Although saplings were capable of surviving several years under unfavorable light conditions (even below 12% ISF), they require a minimum of 20% ISF (i.e., BA < 16 m 2 ha -1 ) to achieve sustainable height increment. Based on our results, for conversion of such stands into coppices-with-standards we recommend a maximum of 200 reserved trees (BA = 16 m 2 ha -1 ) to achieve successful height growth of the understorey.

Pedunculate oak (Quercus robur L.) is considered the main commercial tree species in conditions of floodplain forests of central Europe. In the Czech Republic clear-cutting silvicultural system represents a prevailing regeneration method of oak stands in floodplain forest.

Density and spatial distribution of beech (Fagus sylvatica L.) regeneration in Norway spruce (Picea abies (L.) Karsten) stands in the central part of the Czech Republic Lumir DobrovolnyThe conversion of Norway spruce monocultures to mixed forest is a long-term and costly process, and little information is available on the silvicultural use of spontaneous regeneration of native tree species to such purposes. In this context, we focused on the natural expansion of European beech in pure Norway spruce stands currently occurring in central Europe. The study was conducted in three secondary spruce stands with single adult (seed) beech trees growing on acidic sites of the fir-beech vegetation zone in the Bohemian-Moravian Highlands (Czech Republic). The regeneration strategy of beech and spruce (in terms of density and height increment) was studied under different light regimes (expressed using the indirect site factor -ISF) on the forest edge (9.7-41.2% ISF) and within gaps in the forest interior (10.7-20.8% ISF). Beech showed a broad light adaptability, being present under the spruce canopy with high density, depending on the distance from beech seed trees. Sparse beech saplings were found at a distance of more than 100 m from adult beech trees; however, abundant beech regeneration was found up to a distance of 25 m. Contrastingly, the density and growth in height of the spruce regeneration was strongly affected by light conditions. Spruce reached a density higher than beech in the understory where ISF > 17% (i.e., up to a distance of 45 m from the stand edge or within gaps no smaller than 400 m 2 ), and competed with beech in terms of height growth where ISF > 20% (i.e., at the very stand edges). Knowledge of the spatial pattern and the light strategy of both species provided useful information to support the conversion of spruce monocultural stands to mixed spruce-beech forests.

No abstract

AbsTrAcT:Recently individually dispersed adult beech trees have regenerated in spruce monocultures and this fact could be used to manage the transformation of stands into a mixed forest. Three such cases in the fir-beech and spruce-beech forest zones were analyzed. Beech regeneration is dispersed to distances of several hundred meters regardless of the configuration of the terrain. Using a model we describe this process by a dispersion curve that can be broken up into three sections: (1) directly under the crown as the result of barochory; (2) from 15 to 30 m from the trunk, where the barochoric and zoochoric dispersal of beech nuts intersects; (3) from the "breakpoint" to farther away as a result of zoochory. Regeneration is utilizable as an optimal or at least acceptable method for creating the next economically valuable stands only in sections 1 and 2. In section 3 individual trees may be the central points for the transformation of the second successive forest generation. With spontaneous development without protection from game the density is in the range of hundreds of individuals; in protected groups density can be in the range of tens of thousands of individuals per hectare. The successful regeneration of each tree species is dependent on many favourable circumstances and regeneration is not often successful, even when it is managed using the application of all available biological knowledge. Therefore, the high regeneration potential of beech, which has been recorded approximately over the last twenty years, is noteworthy. It is particularly surprising for the fact that beech advance regeneration that started with just a few isolated individuals has spontaneously penetrated deep into homogenous artificial spruce stands.A similar phenomenon has already been observed and precisely studied in the temperate zone of Europe for oak (pedunculate and sessile oak), wherein they were dispersed to areas far from the regenerating trees. Either they contributed to forest recolonization on abandoned areas and on clearings caused by natural disasters or clear cutting, or they penetrated into forest stands, most frequently pine stands, and started off a spontaneous change in the tree species composition. Interest was above all in how acorns were dispersed. It was discovered that birds play a critical role, mostly jays (Garrulus glandarius)

Forest gaps remain the optimal forest management practice in modern forestry. Upon all the physical properties of forest gaps, the ‘gap size’ feature stands out as an essential property. The effect of gap size on tree species composition and diversity of natural regeneration in forest gaps of different sizes was investigated. Eight research forest gaps were selected from the Training Forest School Enterprise, also called Masaryk Forest in Křtiny, a temperate mixed forest in the Czech Republic. By given gap sizes, small (&lt; 700 m²) and large gaps (≥ 700 m²) were defined. Forty-one (41) regeneration microsites (RSs) of 1 m² circular area at 2 m intervals were demarcated within each forest gap. These RSs served as data collection points. From the total of eleven (11) species enumerated, large gaps obtained higher species composition (10) and diversity (Simpson = 0.5 1-D; Shannon = 1.0 H and Pielou’s evenness = 0.5 J indices) records, yet, small gaps presented favourable conditions for prolific natural regeneration significantly. Light-adapted species demonstrated no significant difference (P &gt; 0.05) between small and large gaps, however, intermediate and shade-tolerant species were significantly higher (P &lt; 0.05) in small gaps. There were progressive declines in height growth of natural regeneration from 0–20 cm to 21–50 cm and 51+ cm in small and large gaps at R²= 99% and 88%, respectively. <br /> The development of herbaceous vegetation in small and large gaps had positive and negative effects on the natural regeneration of Fagus sylvatica and Abies alba species, respectively.