This paper provides first report for European white elm potential for biomass production. High density plantation (71,428 seedlings ha^-1) was established on spring 2012^th near Belgrade from one-year-old seedlings, produced from seed. Weed control and irrigation was practiced only in the first growing season, without fertilization. In a three year rotation, European white elm plants in a high density plantation reach average height of 341.11 cm and average root collar diameter of 31.9 mm, with height increase of about 1 m, diameter increase of about 1 cm per year. At the end of three-years rotation total produced biomass was 90 odt ha^-1, or 30 odt ha^-1 year^-1. Biomass production of European white elm is in range or higher compared to traditionally used species, indicating the need for further research on planting material, plant density and cultural practices.  

The conference on "Reforestation Challenges" took place on 20-22 June 2018 in Belgrade, Serbia, at Faculty of Forestry of the University of Belgrade. This was the fourth meeting on reforestation challenges, after three successful meetings in three previous years (2015 – Belgrade, Serbia; 2016 – Krakow, Poland; 2017 – Session at the IUFRO Congress in Freiburg, Germany). This Conference, like the first one, was organized by Faculty of Forestry of the University of Belgrade, IUFRO (specifically by IUFRO Unit: 3.02.00 - Stand Establishment and Treatment), and Reforesta Scientific and professional Society.

Beech is the most important tree species in forests of Serbia. However, despite its significance, the taxonomic status of beech in Serbia is unclear. Morphology of the cupules can be successfully used to distinguish species and within species taxa. In this paper we report results on cupules morphology, measuring the same attributes reported by Mišić (1955): 1) Length of the longest valve of cupule, 2) Width of that valve (at widest point), 3) Distance between base of the longest valve and peduncle, 4) Length of cupule without peduncle, and 5) Length of peduncle. The length of cupule and peduncle length from 12 populations in Serbia are in the range reported for Fagus sylvatica in Serbia and western Eurasia. Results of cluster analysis shows a grouping of populations in two groups:1) the southeast group, and 2) group consist of populations from northwest, east and southeast of Serbia. Populations from this southeast group also consist the group of populations on altitude over 850 m, indicating presence of ecotypes. The exception is population from Stara Planina (1,520 m a.s.l.) which is grouped with populations from altitudes under 850 m.

Aiming to produce forest reproductive material at the family level, we tested quality of twenty Fraxinus angustifolia Vahl half-sib lines in the nursery experiment. We measured height (HT) and root collar diameter (DIA) of one-year old seedlings, and we monitored germination rate and mortality during the first growing season. Seeds of 20 half-sib lines originating from Sombor area (north Serbia) were sown in seedbed on autumn 2016. The seed dormancy was not broken in all seeds equally, resulting with un-uniform germination over a two months period. All measured attributes shows a statistically significant differences, indicating a strong effect of genetic control. The highest average and DIA were measured in half-sib line 7 (22.62 cm; 5.79 mm, respectively). The lowest average DIA was measured in half-sib lines 18 (2.85 mm) and 19 (2.94 mm), which can be result of growing density effect (104 seedlings m^-2 for line 18 and 126 seedlings m^-2 for line 19, compared to 40 seedlings m^-2 for line 7). The correlation between DIA and HT is strong and positive (R=0.90). Due to its morphological superiority, half-sib line 7 could be recommended for mass production of Fraxinus angustifolia seedlings at the family level.

In North America, most tree nursery nutrition publications during the past two decades involved either container-grown stock or stock grown in greenhouses. In contrast, most bareroot nursery fertility trials in North America were published during the last century. As a result, some bareroot fertilization recommendations have remained the same since 1980 and some practices continue to be based on myths and assumptions. The bareroot nursery industry in the USA might benefit if the next generation of graduate students will consider testing old and new theories about nursery fertilization. Hopefully, they will discover new facts so that future fertilization regimes will be based on science. This paper provides various fertilizer trials that should be established in bareroot nurseries.

Stock types used in reforestation projects can influence plantation success, as they determine the morphological attributes of the planted seedlings. They can also interact with silviculture treatments to influence early seedling survival and growth. As nurseries develop and produce new stock types in response to –and in interaction with– manager needs, research efforts must be pursued to validate early seedling performance and long-term growth and yields. In this context, we aimed to evaluate the main and interactive effects of mechanical site preparation and stock type on planted black (Picea mariana [Mill.] BSP) and white spruce (P. glauca [Moench.] Voss) seedling dimensions at 16-y, and estimate the long-term impact of stock type on the merchantable volume at rotation age for white spruce. We hence compared medium (200 cm³ root plug) and large (350 cm³ root plug) containerized seedlings, as well as large bare-root seedlings of both species, in a field experiment established in Quebec (Canada), where there is a ban on the use of chemical herbicides for vegetation management treatments. Our results confirm that there is a significant, although limited impact of stock type on the size of black and white spruce at the juvenile stage, when medium and large stock types are compared, but that these small differences have a negligible effect on the estimated merchantable volume produced at rotation age (60 years). Mechanical site preparation does not promote seedling growth on these rich sites with thin humus. Therefore, selection of a medium or larger stock type for reforestation projects and application of mechanical site preparation in ecosystems similar to the one studied here should be based on other considerations than growth and yield, such as seedling availability, production and planting costs, or operational constraints.

Breaking physical dormancy in some forest seeds is a challenge for scientists and forest managers to obtain an homogeneous germination for larger seed samples. The role played by the seed coat in seed dormancy of six trees with great interest in agroforestry (Robinia pseudoacacia, Leucaena leucocephala, Erythrostemon gilliesii, Styphnolobium japonicum, Acacia dealbata and Brachychiton populneus) was tested by the effects of the pretreatment and its duration on the performance of seed germination, by considering the final germination percentage (FGP) and the mean germination time (MGT). These parameters are estimated at various times of incubation (5, 10 and 15 days) in Petri dishes and stored in darkness at (25 ± 2°C). The pretreatment consists of an immersion of seeds in concentrated sulphuric acid during 30, 60 and 90 minutes. Sowing without pretreatment (control) revealed no germination induction for B. populneus and A. dealbata, except for R. pseudoacacia, L. leucocephala and S. japonica where the germination does not exceed 12% for all the experience duration. Generally, pretreatments were very useful to improve seed germination. The time of immersion into sulphuric acid significantly affected (P < 0.0001) the FGP and the MGT in all studied species. A duration of 30 minutes of soaking was adequate to give a very high rate of germination for L. leucocephala, E. gilliesii, S. japonica and A. dealbata with respective FGP of 100%, 95%, 100% and 100%. However, an extended duration of pretreatment of 60 minutes was necessary for a maximal germination for R. pseudoacacia and B. populneus with FGP of 85% and 100%, respectively. A prolonged duration of 90 minutes of presowing was very fatal for L. leucocephala, A. dealbata and B. populneus. An excellent germinative strength is characterized by a higher FGP and a reduced MGT.

Early growth and survival of tree seedlings is often poor on reclaimed coal surface mines in Appalachia. Biochar produced in bioenergy generation has potential for use as an amendment to improve seedling performance. Mine soil was collected from a recently reclaimed coal surface mine in Wise County, Virginia and mixed with loblolly pine (Pinus taeda L.) sawdust biochar, simulating application rates of 2.3, 11.2 and 22.5 Mg ha^-1. Unplanted leaching columns and 4 L tree planting pots were filled with these biochar-soil mixtures, plus controls of pure mine soil and pure biochar. For the tree planting pots, additional pots were created where the biochar was applied as a topdressing at the same application rates as in the mixtures. One-year-old seedlings of both American sycamore (Platanus occidentalis L.) and black locust (Robinia pseudoacacia L.) were planted. Unplanted leaching columns were leached with collected rainwater for six months to simulate weathering. Trees were grown for one growing season. Black locust had higher average above-ground dry woody biomass (24.4 g) than American sycamore (17.0 g), and also higher below-ground biomass (61.0 g compared to 30.2 g). The pure biochar produced greater average below-ground biomass (99.9 g) than the pure mine soil (46.9 g). All of the biochar treatments produced greater average above-ground woody biomass (19.1 g – 33.4 g) than the pure mine soil (10.9 g). After weathering, biochar provided less available soil phosphorus, calcium and iron than the mine soil itself while increasing soil carbon and organic matter. High (22.5 Mg ha^-1) biochar applications increased soil volumetric water holding capacity to 18.6% compared to 13.4% for pure mine soil. Naturally-occurring herbaceous biomass in the pots was negatively correlated with above-ground woody biomass at r = -0.483. Topdressing and full incorporation of biochar were not significantly different in their effects on biomass. Results suggest that pine biochar either broadcast at 2.3 - 22.5 Mg ha^‑1, or mixed in planting holes with backfill soil, will promote faster above-ground growth and larger root systems in seedlings in mine soils. Further studies should test these methods in the field over multiple years and further refine recommendations of the rate of biochar to use and how best to apply it. New systems are being developed in Appalachia to produce biofuels and biochar from local biomass and to recycle biochar into the land base to enhance future biomass productivity. Applying 4 L of biochar mixed with the backfill of newly-planted trees is the top recommended practice for tree performance.

This paper adds to the evidence base in the discussion to what extent woodland development can be a means to restoring the land affected by mining. We investigate the formation of vegetation communities in sites on a former Sulphur quarry in the Roztochya district of the Lviv region in Ukraine to answer the research questions: How can the formation of vegetation cover affect the disturbed sites and what knowledge can be used in restoration practices elsewhere? We perform an experiment examining which types of vegetation are suitable for the restoration. We explore the influence of restored vegetation and re-emerged woodlands have on the process of soil rehabilitation and the increasing organic substance in it. We examine the impact of various combinations of vegetation on land rehabilitation. Explaining the degree of colonization of waste land by various types of vegetation helps us to reveal the trends of regenerative processes and identify the most promising for restoration tree species in affiliation with the ground vegetation. The results can assist decision-makers in choosing compatibility alliances of vegetation to sustain regeneration processes. Although this research is location specific, the knowledge developed can to a degree be applied to similar places, in the temperate zone.