Issues

Lipids are main components of bee pollen grains, and vary among different pollen taxa. The objective of this study was to determine the lipid content in pollen of 20 popular bee plants and the impact of lipids to honey bees. The analysis showed, that the percentage of the total lipid content in the examined bee pollen ranged from 0.87 % for Zea mays L. to 13.6 % for that of Echinops ritro L., and the average was 3.91 %. The average level of lipids for the entomophilous plants was 4.20 % and 1.31 % for anemophilous, for Asteraceae was 5.42 % and 1.88 % for Fabaceae. The average weight of one hundred worker bees fed on pollen from Z. mays was 8208.2 mg, whereas it was 9882.2 mg for the bees fed on pollen from E. ritro. The weight of bees that consumed pollen with higher lipid content is higher compared to that consumed pollen with lower lipid content.

Knowledge of protein food used by honey bees is important, as proteins are main component of pollen. The objective of this research was to determine and compare the protein content of bee pollen from different forestry areas in Bulgaria of some popular bee plants. The analysis showed that in pollen it depended on the botanical origin. The protein content in the pollen from Oryahovo ranged from 12.8 % for Taraxacum officinale L. to 25.35 % for Cornus sanguinea L., and the average was 20.66 %, from Borushtitsa ranged from 12.3 % for Chondrilla juncea L. to 27.51 % for C. sanguinea, and the average was 21.16 %. The protein content in pollen from Brassica napus L., Cornus mas L., C. sanguinea, Robinia pseudoacacia L. and Salix sp. showed variability for both forestry areas.

Modern agriculture often leads to a reduction in small game species and loss of biodiversity. The study area includes MG-14 (35 T) square of the Universal Transverse Mercator (UTM). The density of hares during the study period varied between 0.7–2.7 ind./km2. Their number reported in 2014–2015 is significantly higher than in the other years. In 2018, the lowest hare density was reported in the study area. Most were counted in May. The density of hares was positively related to habitat diversity and negatively to Wild cat density.

The moss Hypnum cupressiforme Hedw. was used as biomonitor in three urban and five mountain sites with different pollution loads. The concentrations of 22 macro- and microelements were determined in moss-bags and were compared with those of the same elements in moss samples naturally growing in the Rhodope Mountains area. Most of the elements had highest concentrations in moss-bags exposed in Plovdiv. Strong accumulation of Cd and Pb was registered in all moss-bags with maximum in moss-bags from Sofia, reflecting that urban activities could induce more severe air pollution than mining. Cd reached saturation at the 30th day of  exposure, while Pb continued to accumulate. Analysed levels of Hg and Pb during passive monitoring confirmed the Rhodope Mountains as a region with constant high toxic element levels.

The aim of this study was to estimate the aboveground carbon sequestration and the amount of CO2 emissions at logging operation in Hyrcanian forests of Iran. Required data, such as forest standing stock, annual growth increment of trees, wood density and timber harvesting, were collected from secondary sources. Allometric equation was used for estimating the carbon sequestration. The amount of CO2 emission was calculated. Results showed that the annual growth per hectare and the amount of carbon sequestration per growth were 3.37 m3·yr-1 and 1.14 t·ha-1, respectively. Results also indicated that the value of aboveground sequestrated carbon and its net present value were 71,217.63 (10,000 IRR∙ha-1) and 12,668.28 (10,000 IRR∙ha-1), respectively. Finally, the amount of carbon emission per hectare was calculated, as it was 0.01078 t∙h-1 per year. The results of emission and carbon sequestration per hectare of the forest show that not only logging per hectare of forest will eliminate annual carbon sequestration, but also leads to an increase in CO2 into the atmosphere due to harvest activity.

The aim of the present study was to improve the use and operational efficiency of the truck-mounted tower yarders in deciduous stands and to determine the time, log’s volume transported per turn by the yarder, as well as the yarding costs. The study was carried out in the Sredna Gora Mountains, Central Bulgaria, in deciduous stand with species composition of European beech (90 %), European hornbeam (10 %). The mean productivity of truck-mounted tower cable yarder at shift level is close to the maximum for that type (9.12 m3·PMH-1 and 8.41 m3·SMH-1). In order to improve the yarder productivity a remote control of the carriage is advisable to be used, also used by the choker-setter. In this way the loaded carriage could wait for the operator before the landing. Another option to reduce choker-setter‘s fatigue and to decrease the time for lateral outhaul and hook is to use a carriage with mechanical slack-pulling. The gross costs for yarding uphill a whole deciduous tree by the studied tower yarder were calculated at 146.52 € per productive machine hour and 13.02 € per m3. In the distribution of the gross costs, labour costs (21.44 %) are lower than variable costs (29.86 %) and fixed costs (26.84 %). The results from the study are useful to integrate the cable yarders in group shelterwood system and to achieve economic and environmental efficiency of timber transportation in deciduous forests in sensitive sites.

The high-resolution layers (HRLs) are Pan-European land cover datasets aimed at monitoring soil sealing (imperviousness, forest, grasslands, wetness and water, and small woody features. The main purpose of this article is to present the methodology and results from verification of two Forest HRL products for the 2015 reference year for Bulgarian territory: Dominant Leaf Type (DLT) and Tree Cover Density (TCD). The verification task aims at identifying systematic classification errors and the results are supposed to be used for improvement in future product updates. Qualitative approach for assessment of the HRL quality is applied in two steps, called General overview of data quality and Look-and-feel verification. The latter is performed within dedicated strata through non-random sampling, checking HRLs for omission and commission errors. We show results from a verification at country level based on local expertise and best available in situ data. We also provide comments and recommendations concerning commission and omission strata. Several cases of both of the above types of errors are identified and analysed in the DLT and TCD high resolution layers. Despite of errors found, both DLT and TCD receive a ‘good’ mark, and the same rating prevails in the strata level evaluation.

Climate change is among the main challenges for achieving sustainable development of aquaculture. It is likely to cause changes in the temperature and hydrological regimes of inland waters. Air temperatures in the region of Dospat Dam have been rising over the past 15 years. This impacts the water temperature in the dam and on rainbow trout (Oncorhynchus mykiss) farming in it. The average water temperatures measured in the surface layer in the 1970s (10.18 ±6.79 °C), and the 1980s (10.16 ±7.07 °C) were lower than the ones today (12.40 ±7.12 °C). Higher summer temperatures of the water in the dam have an unfavourable impact on the key biological indicators which determine the aquaculture efficiency, such as fish growth (AG, g), survival rate of fish (SR, %) and feed conversion ratio (FCR). The water temperatures in July and August are above 18–20 °C. This period is marked by the lowest fish growth and the lowest survival rate of fish. At the same time, feed conversion ratio is 3.3:1 which is higher than recommended in feed charts and it is economically inefficient. Global warming is likely to have a negative impact on the development of cold-water aquaculture in Bulgaria. It will result in a longer production cycle and higher costs.

The oak forests in Mediterranean are widespread and dynamic natural ecosystems. For millennia, oak forests have provided vital ecosystem services to humans in the Mediterranean including social, economic and environmental services and goods; however, in parallel, human exploitation has altered their structure. Consequently, targeted management approaches are required to optimize the production. In the current study we analyzed the structural characteristics of the Foloi oak forest (Quercus frainetto) in the wider area of Ancient Olympia, Peloponnese, Greece. An extensive fieldwork was applied in 29 randomly located plots in order to collect dendrometric characteristics of 938 individual trees. The collected data were used to build models for estimating tree age, tree height and canopy length from diameter at breast height (DBH). All models were found to have an adequate fit and provide useful tool for the assessment of site structural and growth characteristics. Furthermore, we present a model for assessing site quality from topographic characteristics such as slope and exposition. Finally, we employed a stand visualization tool to get a graphical representation of the stand structure, which can be used in order to adopt appropriate silvicultural practices. We believe our findings will provide useful tools to forest managers and practitioners for the sustainable management and restoration of oak forests.

Seed germination experiments were conducted at Botswana University of Agriculture and Natural Resources to determine the best possible pre-sowing treatment methods that maximize seed germination of Albizia versicolor and Faidherbia albida. The experiments were laid out in a completely randomized design (CRD) with 10 pre-sowing treatments, namely the control, mechanical scarification, soaking in concentrated sulphuric acid with four levels of time exposure (15, 30, 45 and 60 min), immersion in boiling water with three levels of time exposure (1, 3 and 5 min) and soaking in hot water (allowed to cool for 24 h). Treated seeds were germinated for 30 days at room temperature (25 °C). The raw data were subjected to analysis of variance (ANOVA). The results showed that seeds treated mechanically, sulphuric acid (all levels), boiling water (1 and 3 min) and hot water had significantly (p < 0.01) higher mean germination percentages than the control and boiling water (5 min) for A. versicolor, whereas for F. albida seeds treated mechanically and exposed to sulphuric acid (all levels) had significantly (p < 0.01) higher mean germination percentages than the rest. Significant (p < 0.01) mean germination time and index were revealed among the treatments for the two species.