ABSTRACT:In total, 67 parallel plots were chosen from the database of 153 phytosociological relevés made in the Douglas-fir and parallel Norway spruce, European Beech and oak-dominated stands to find influences of this introduced tree species on the understorey layer in totally 12 localities in the whole Czech Republic territory. Douglas-fir stands influence their habitats, which was indicated by species composition changes in the ground vegetation, as well as by abundance and dominance of particular species. Douglas-fir cultivation increases species diversity of the stands, but decreases their abundance. Described differences in understorey are not so noticeable when European beech and sessile oak stands are substituted by Douglas-fir once. But even the significant phenomenon of striking nitrophilous species such as Geranium robertianum, Urtica dioica and Galium aparine occurs here. This indicates a high content of available nitrates in the humus and top-soil horizons.

(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.

Europe has a history rich in examples of successful and problematic introductions of trees with a native origin outside of Europe (non-native trees, NNT). Many international legal frameworks such as treaties and conventions and also the European Union have responded to the global concern about potential negative impacts of NNT that may become invasive in natural ecosystems. It is, however, national and regional legislation in particular that affects current and future management decisions in the forest sector and shapes the landscapes of Europe. We identified all relevant legal instruments regulating NNT, the different legal approaches and the regulatory intensity in 40 European countries (no microstates). Information on hard and effective soft law instruments were collected by means of a targeted questionnaire and consultation of international and national legislation information systems and databases. In total, 335 relevant legal instruments were in place in June/July 2019 to regulate the use of NNT in the investigated 116 geopolitical legal units (countries as well as sub-national regions with their own legislation). Countries and regions were empirically categorized according to ad hoc-defined legislation indicators. These indicators pay respect to the general bans on the introduction of non-native species, the generally allowed and prohibited NNT, approval mechanisms and specific areas or cases where NNT are restricted or prohibited. Our study revealed a very diverse landscape of legal frameworks across Europe, with a large variety of approaches to regulating NNT being pursued and the intensity of restriction ranging from very few restrictions on species choice and plantation surface area to the complete banning of NNT from forests. The main conclusion is that there is a clear need for more co-ordinated, science-based policies both at the local and international levels to enhance the advantages of NNT and mitigate potential negative effects.

ABSTRACT:The paper analyses the influence of an extended period of cold stratification on the germination capacity, emergence rate and yield of seedlings in the Douglas fir as well as on the morphological parameters of one-year-old seedlings. A total of ten seed lots were used for evaluating germination capacity, originating from the Czech Republic, Slovakia, France and the USA. Germination capacity, emergence rate and yield of seedlings were analysed for two seed lots of Czech provenance on seed beds in the settings of a forest tree nursery. Tested variants involved (a) no pre-sowing treatment, (b) seed stratified for 21 days, and (c) seed stratified for 49 days. The germination capacity of the stratified seed was higher than that of the control variant for all of the seed lots. The effect of the stratification period length was zero for both germination capacity and emergence rate. Differences were identified between the stratification variants as regards germination energy and emergence rate. For the control variant, seedling yield reached only 1% and 2%. For the stratified seed, yield of seedlings of two selected Czech provenances was 18% and 16% (variant 21) and 26% and 36% (variant 49). Differences in the morphological parameters of seedlings were not straightforward.

AbStrAct:The condition and snow damage to stands dominated by birch were studied in the area of interest in Northern Moravia. Based on basal area, the share of birch ranged from 68 to 88%. The stands came to existence on fertile sites through natural regeneration and exhibited growth at a level of the best site classes for the Czech Republic. The most severe snow damage to the stands was recorded at the upper stand height of 8-15 m. The extent of damage in the analyzed stands amounted to 67-95% of all trees. The unambiguously predominant type of damage was bending while breakages were recorded only in up to 4% of trees. Slenderness ratios of intact trees differed according to the age (height) of stands. The highest values of about 180 were observed in the youngest, ca 5-years-old and about 5 m high stand. Slenderness ratio values of intact trees in a 17-m high stand ranged about 100. The analyzed stands did not show any differences in the slenderness ratio values between intact and damaged trees. Lower values of the ratio for solitary trees (ca 130) in a 5-years-old stand were accompanied by markedly longer crowns (80% of stem) as compared with trees growing in the stand (60% of stem). Differences in the root system architecture were revealed between intact and damaged trees within a stand of about 9 m in height.

ABSTRACT:One of the critical points of Douglas fir seedling production is to optimize the time of sowing and length of pre-sowing treatment. Germination and emergence of Douglas fir seed lot of the Czech origin (CZ-2-2A-DG-1740-6-3-P) were observed in simulated warm and cold conditions in two phytotrons for 3 months. Before this procedure the seeds were exposed to different prechilling duration. The temperature in control conditions of phytotrons was stable for 28 days and then it was increased: 11, 13, 17°C in cold phytotron and 13, 17, 20°C in the warm phytotron. Seeds without stratification and stratified for 3, 5, 7, 9 and 16 weeks were tested. The laboratory germination capacity of non-stratified seeds was only 58% and it was significantly (P < 0.05, Tukey's test) lower than in stratification treatments when it varied from 92% to 96%. Non-stratified seeds did not germinate in cold phytotron and they germinated very slowly (germination rate at the end of experiment was 7%) in warm phytotron. The germination capacity of seeds both in the phytotron and in the laboratory was observed in treatments with prechilling of seeds longer than 7 weeks in warm conditions and only for seeds after 16 weeks of prechilling in cold conditions. The highest emergence rate of seeds (84%) was found in the warm phytotron after 16 weeks of stratification. Comparable results were reached only for 9 weeks of stratification in the same phytotron. The results suggest that the prolongation of the standard 3-week prechilling period helps to increase germination capacity and emergence rate of seeds. Future research should focus on optimal length with regard to more seed lots and also on seedling quality parameters. JOURNAL OF FOREST SCIENCE, 60, 2014 (7): 281-287From the aspect of forestry, Douglas fi r is considered a promising tree species for the region of Central Europe (Kenk, Ehring 1995;Kantor et al. 2001;Tauchman et al. 2010). In the region of the Czech Republic it is recommended to increase its share from 0.2 to 2-4% of the total stand area (Beran, Šindelá 1996; Kantor et al. 2010). On sites without seed-producing trees and in areas where Douglas fi r has not been present so far, artifi cial regeneration is necessary. One of the critical points in artifi cial regeneration of Douglas-fi r is a small yield of seedlings in nursery practice of the Czech Republic. From many aspects which infl uence the yield of Douglas fi r seedlings the presowing treatment seems to be important because the seeds exhibit dormancy (Heit 1968;Gosling, Peace 1990;Müller et al. 1999).Cold stratifi cation of seeds has a favourable eff ect on subsequent germination and shows an increase in total germination capacity, increased germination rate and extended range of temperatures at which the seeds germinate (Gosling 1988). Th e main prerequisite for successful stratifi cation is its suffi cient duration. According to Jones, Gosling (1994), short stratifi cation (2-6 weeks) of seeds with relative dormancy improves the germination capacity as well as the germ...

Local adaptation and the evolution of phenotypic plasticity may facilitate biological invasions. Both processes can enhance germination and seedling recruitment, which are crucial life-history traits for plants. The rate, timing and speed of germination have recently been documented as playing a major role during the invasion process. Black locust (Robinia pseudoacacia L.) is a North American tree, which has spread widely throughout Europe. A recent study demonstrated that a few populations are the source of European black locust. Thus, invasive populations can be compared to native ones in order to identify genetic-based phenotypic differentiation and the role of phenotypic plasticity can thereby be assessed.• A quantitative genetics experiment was performed to evaluate 13 juvenile traits of both native and invasive black locust populations (3000 seeds, 20 populations) subjected to three different thermal treatments (18 °C, 22 °C and 31 °C).• The results revealed European populations to have a higher germination rate than the native American populations (88% versus 60%), and even when genetic distance between populations was considered. Moreover, this trait showed lower plasticity to temperature in the invasive range than in the native one. Conversely, other studied traits showed high plasticity to temperature, but they responded in a similar way to temperature increase: the warmer the temperature, the higher the growth rate or germination traits values.• The demonstrated genetic differentiation between native and invasive populations testifies to a shift between ranges for the maximum germination percentage. This pattern could be due to human-mediated introduction of black locust.