Alexander Dountchev* and Petar Zhelev

Department of Dendrology, University of Forestry, 10 Kliment Ohridski Blvd.,
Sofia 1797, Bulgaria. *E-mail: alexdountchev@hotmail.com

The regeneration of montane Norway spruce (Picea abies (L.) Karst.) forests is among the most challenging silvicultural issues due to the extreme climatic conditions at high altitudes, particularly after large-scale natural disturbances. The aim of the study was to compare the development of the natural and artificial regeneration in the period 2006-2014 in a cleared windthrow area of 14 ha, which resulted from a wind-disturbance in 2001. The study area was situated in Ofeliite site, Vitosha Mountain, West Bulgaria. The forest regeneration was studied in 16 permanent sample plots of size 10 m x 10 m (100 m²). We found that the intensity of natural regeneration decreased significantly five years after the windthrow. Dominant species was Picea abies, which regenerated most frequently on decaying deadwood. The artificial regeneration had 5 times lower numbers than the natural one. This could be due to the low planting density and the higher mortality rate of planted spruce seedlings in comparison to the naturally established ones. The risk of mortality was highest among saplings lower than 0.5 m. The main reasons for the observed mortality were the withering and suppression by other plant species such as Rubus ideaus L. and Calamagrostis arundinacea (L.) Roth. Our results suggest that the natural regeneration was more important than the artificial planting for the restoration of the wind-disturbed spruce forest in Ofeliite site. In this respect, sustaining abundant seedling bank as well as sufficient quantities of decayed deadwood as regeneration substrate and microhabitat in the managed spruce forests can help adequate natural regeneration after large-scale disturbances.

Panayot Panayotov (1)*, Ivo Valchev (2), Kancho Kalmukov (3), Momchil Panayotov (1),
Stoiko Petrin (2), and Nikolay Yavorov (2)

1. Faculty of Forest Industry, Faculty of Forestry, University of Forestry,
10 St. Kliment Ohridski blvd., 1797 Sofia, Bulgaria. *E-mail: ppanayotov45@abv.bg
2. Department of Pulp, Paper and Printing Arts, University of Chemical Technology and
Metallurgy, 8 St. Kliment Ohridski blvd., 1756 Sofia, Bulgaria. E-mail: ivoval@uctm.edu
3. Experimental Station for Fast-Growing Forest Species, 18 Nove str., 5250 Svishtov, Bulgaria.
E-mail: kkalmukov@abv.bg

The potential of Black locust (Robinia pseudoacacia L.) wood for production of chemical pulp
and glucose was studied. Different clones of Black locust growing in various habitats in Bulgaria
were analysed and their chemical composition and density was compared. It was established
that the differences in the content of cellulose, lignin, pentosanes and extracted substance in
the respective clones were not high and were within the range of 10 % of the corresponding
component. Hence, the effect of the chemical composition on the pulp yield was relatively
low. The differences in the planting schemes (density) of the Black locust clones had greater
influence on the productivity and efficiency of the pulping process. The authors found that Robinia
pseudoacacia L. has the highest potential in Bulgaria for glucose production. The glucose yield
after enzymatic hydrolysis of steam-exploded Black locust is approximately higher in comparison
with corresponding treatment of maize stalks, wheat straw and fast-growing poplar and willow.
The conclusion is that there are opportunities for plantation harvesting in Bulgaria of separate
Robinia pseudoacacia L. clones for chemical pulp or glucose for production bioethanol.

Lyubcho Trichkov (1)* and Dinko Dinev (2)

1. Executive Forest Agency, 55 Hristo Botev blvd., 1040 Sofia, Bulgaria.
*E-mail: lptrichkov@iag.bg
2. Southest State Enterprise, Sliven. Address for correspondence:
Izgrev Complex, bl. 36, 8008 Burgas, Bulgaria. E-mail: dinevds@gmail.com

Having in mind the assortment and age structure, the tree composition and other specific peculiarities of Bulgarian forests, as well as the national timber market, about 70 % of the harvested timber is used for technological purposes, e.g. for production of particle boards, cellulose and for energy purposes, like firewood for residential heating. Along with the harvested logs (saw logs, pulpwood and firewood), Bulgaria has also considerable recovery of other biomass. In 2014, the share of the categories 'woods' and 'brushwood' is about 50 % of the total timber harvested volume in Bulgaria. Practically, in our country the wood waste from felling together with the brushwood is about 1.4 Mio (m³/y) of solid waste. That wood waste presents a significant energy potential but the degree of its quantitative concentration is low and often this resource is at big distances from the settlements. The most important advantages and benefits of the utilization of solid wood biofuels in the form of pellets, briquettes, charcoal and chips for energy purposes are: ecological - decrease of the carbon emissions and air pollution and economic (social in this account) - decrease of the costs of energy resources, which ensures both economic and social effect of the use of biofuels produced from wood biomass. In Bulgaria, the volume of wood energy products in 2014 is: 52,550 t pellets, 6,800 t briquettes, 11,550 t charcoal and 9,400 t wood chips, respectively. About 60 % of the number of pellet producing companies has a share of 15-20 % in the total pellet production. Such small-size firms use small-size pressing machines. The general analysis related to the sale of wood pellet and briquette shows that about 2/3 are realized for export based on preliminary signed contracts and the introduction of quality requirements. Most often the export is for Greece, Turkey and Italy. According to our assessments, the best conditions for development exist for briquettes production and wood chips designed to home market, of pellets designed to international one and of charcoal for both.

Zvezdelin Milanov

Municipality of Stara Zagora, 107 Tsar Simeon Veliki Blvd, 6000 Stara Zagora,
Bulgaria. E-mail: milanovzb@abv.bg

Red deer has been reintroduced in 18 lowland and mountain former habitats by releasing
animals from two neighbouring populations, supposed to be genetically identical. The mean values
of measurements of trophies obtained from newly-created and initial populations have been
compared by Student's t-test. The significant differences found did not depend on new habitats
remoteness, as well as on the mean age of animals hunted for trophy. Evidently, it seems that
ecological variables are the most important cause of red deer trophy size variability, and further
investigations are needed to study the relationship between altitude, climate, vegetation, etc. and
the most important trophy measurements.

Velika Jordanova* and Konstantin Marinov

Faculty of Forestry, University of Forestry, 10 St. Kliment Ohridski blvd., 1797 Sofia,
Bulgaria. E-mails: veli_jordanova@abv.bg*; kmarinov_ltu@abv.bg

Contemporary technologies for afforestation of forest areas, based on the use of specialized
milling units for soil preparation, mulching, shredding of stumps and other typical forest
operations, are characterized by relatively high environmental and quality indicators, lower
cost of labor and a smaller number of used technical means. These indicators are due to the
use of specialized milling machines, which can operate in wide range of strength and type of
deformation and interaction of the cultivated object. To achieve good results and low technology
speeds, more energy and powerful tractors are needed. This article presents results of
some basic performance of forest milling aggregate PT-400, with multi-purpose forest tiller
FAE 300/S. The survey has been carried out on experimental poplar sites and slashes along
the Danube river valley in the north-west region Bulgaria. For the purpose of the study the
following parameters were determined: fuel consumption, operating speed and operational
performance of the milling unit under certain conditions: 1) crushing stumps with diameters up
to dav = 65 cm, mulching False indigo-bush (Amorfha fruticosa) with height of 2.5–3.0 m and
clearing debris; 2) milling of the soil to a depth of 0.5 m. The obtained results will be useful
for better determination and establishment of technological capacities and performance of the
studied specialized milling unit.