Beech forests occupy considerable areas in the Bulgarian mountains. They are represented by communities of Fagus sylvatica (incl. F. moesiaca) and F. orientalis, and also by mixed stands of beech with Abies alba, Carpinus betulus, Quercus cerris, Q. dalechampii and Q. polycarpa. 494 relevés sampled across the country were analysed by numerical methods. They were classified into 12 groups of Fagus sylvatica forests and 3 groups of Fagus orientalis forests. The analysis of Bulgarian Fagus sylvatica communities did not show a distinct pattern of geographic differentiation and did not support the concept of the alliance Fagion moesiacum, as accepted by many earlier authors. The differentiation patterns in the Bulgarian Fagus sylvatica forests mainly follow the gradients in soils and climate, and are similar to those in the Central European beech forests. Therefore we accept a syntaxonomical scheme, which emphasizes variation due to edaphic and local topoclimatic factors rather than due to large-scale geographical differentiation. This scheme is very close to that proposed by Willner (2002) for the southern Central European beech forests, and includes the alliances Luzulo-Fagion (acidophilous beech forests), Asperulo-Fagion (nutrient-rich beech forests), and Cephalanthero-Fagion (thermophilous beech forests). The communities of Fagus orientalis are markedly different from the communities of Fagus sylvatica, have a distinct floristic composition, and belong to the Euxinian alliance Fagion orientalis.

Juniperus excelsa M. Bieb and J. sabina L. contain essential oil (EO), while J. sabina also contains podophyllotoxin, which is used as a precursor for anti-cancer drugs. Two studies were conducted. The first assessed the variability in the EO profile and podophyllotoxin concentration of the two junipers, depending on the location and tree gender. The main EO constituents of J. excelsa were α-cedrol, α-limonene and α-pinene, while the constituents in J. sabina were sabinene, terpinen-4-ol, myrtenyl acetate and α-cadinol. The podophyllotoxin yield of 18 J. sabina accessions was 0.07–0.32% (w/w), but this was not found in any of the J. excelsa accessions. The second study assessed the effect of hydrodistillation (Clevenger apparatus) and steam distillation (in a semi-commercial apparatus) on the EO profile and bioactivity. The extraction type did not significantly alter the EO composition. The EO profiles of the two junipers and their accessions were different and may be of interest to the industry utilizing juniper leaf EO. Breeding and selection programs could be developed with the two junipers (protected species) in order to identify chemotypes with (1) a high EO content and desirable composition, and (2) a high concentration of podophyllotoxin in J. sabina. Such chemotypes could be established as agricultural crops for the commercial production of podophyllotoxin and EO.

Municipal solid waste (MSW) landfills are among the major sources of greenhouse gas (GHG) emissions affecting global warming and the Earth’s climate. In Bulgaria, 53 regional non-hazardous waste landfills (RNHWL) are in operation, which necessitates conducting studies to determine the environmental risk from the emitted GHGs. This study attempted to assess the CH4 and CO2 emissions from three gas wells of a cell (in active and closed phases, each of 2.5 years duration) in an RNHWL, Harmanli (41°54′24.29″ N; 25°53′45.17″ E), based on monthly in situ measurements by portable equipment, using the Interrupted Time Series (ITS) ARMA model. The obtained results showed a significant variation of the CH4 and CO2 concentrations (2.06–15.1% v/v) and of the CH4 and CO2 emission rates (172.81–1762.76 kg/y) by gas wells (GWs), months and years, indicating the dynamics of the biodegradation of the deposited waste in the areas of the three GWs. Throughout most of the monitoring period (2018–2022), the CH4 concentrations were higher than the CO2 concentrations (% v/v), while CO2 emissions were lower than CH4 emissions (kg/y), a fact that could be explained by the differences in the mass of the two gases. The emissions rates of both gases from GW2 dominated over those from GW1 and GW3, giving a reason to determine the zone of GW2 as a hotspot of Cell-1. On the whole, CH4 and CO2 emission rates were higher in the winter (December–February) and partly in the spring (March–May) compared to summer–autumn (June–November). However, the CH4 and CO2 concentrations and emissions decreased drastically after the Cell-1 closure. The CH4/CO2 ratio (0.68–2.01) by months and gas wells demonstrated a great sensitivity, making it a suitable indicator for the assessment of organic waste biodegradation level in the landfills. The ITS ARMA model confirmed the negative and significant effect of the cell closure on CH4 and CO2 emissions; the correlations found between predicted and observed values were strong and positive (0.739–0.896).

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