Zornitsa Karcheva (1)*, Stilyan Angelov (1,2), and Svetoslav Anev (1)

1. Department of Dendrology, Faculty of Forestry, University of Forestry, 10 Kliment Ohridski Blvd., 1797 Sofia, Bulgaria. *E-mail: z.karcheva@ltu.bg
2. Executive Forest Agency, 55 Hristo Botev Blvd., 1606 Sofia, Bulgaria

Large-scale natural disturbances in forest ecosystems drastically alter the light regime for residual saplings within the affected areas, placing their survival under considerable threat. Light acclimation of photosynthesis represents a key physiological mechanism for maintaining a positive carbon balance, thereby enabling plants to preserve their protective functions within altered environments. The aim of this study was to assess interspecific differences in photosynthetic light acclimation and carbon-use efficiency in saplings of three forest tree species – Fagus sylvatica L., Populus tremula L. and Acer platanoides L. – following large-scale natural disturbances. These species were selected due to their contrasting ecological strategies: the shade-tolerant F. sylvatica, the light-demanding pioneer P. tremula, and the moderately plastic A. platanoides. A comparative analysis of parameters, such as AMAX, RD, LCP, and LSP reveals pronounced species-specific responses, reflecting divergent functional–ecological strategies. These findings provide deeper understanding of the mechanisms underpinning light acclimation and offer valuable insights for adaptive forest management, particularly considering the increasing frequency and intensity of climate-induced disturbances. The results may support improved predictions of regeneration dynamics and species resilience under future forest conditions.

 Received: 23 May 2025 / Accepted: 04 August 2025 / Available online: 20 August 2025

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

Hristo Lukanov (1)*, Todor Petrov (1), and Ivana-Antonia Gaydarova (2)

1. Faculty of Agriculture, Trakia University, Student campus, 6000 Stara Zagora, Bulgaria.
*E-mail: hristo.lukanov@trakia-uni.bg
2. Faculty of Veterinary Medicine, Trakia University, Stara Zagora, Bulgaria.

The aim of the study was to perform a colorimetric assessment of eggshell colour variations in Common Pheasant (Phasianus colchicus Linnaeus, 1758) used for resettlement in Bulgaria. A total of 360 eggs were divided into five groups according to eggshell colour. Using a colorimeter, the colour characteristics were determined in the CIE L*a*b* colour space, and chroma (C) and the Shell Color Index (SCI**) were calculated. The highest lightness (L*) values were observed in the beige eggshells (68.62 ±1.62), while the lowest were found in the olive-green eggshells (55.89 ±0.49) (P < 0.001). Low negative mean values for the a* coordinate were observed only in the green eggs (−1.41 ±0.78), while low positive values were recorded for the other groups, reaching 6.8 ±0.93 for olive-green eggshells. Positive values were recorded for the b* coordinate, ranging from 13.96 ±0.80 (green) to 21.90 ±0.77 (beige), indicating a yellow spectrum position (P < 0.001). Shell Color Index (SCI**) had the lowest values for olive-green eggshells (−35.07 ±1.42) and the highest values for green eggshells (−53.07 ±2.17) (P < 0.01). The study revealed significant variations in the pigment distribution in the eggshells of the Common Pheasant, with differences in the colour index ranging up to 51.67 % between the maximum and minimum individual values. It is possible that these differences in eggshell colouration are linked to the genetic purity of the most widely bred subspecies of the Common Pheasant (Phasianus colchicus mongolicus Brandt, 1844) in the country’s game farms. Conducting a phylogenetic analysis of the population could shed light on this issue.

Received: 18 June 2025 / Accepted: 06 August 2025 / Available online: 18 August 2025

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

Rumen Tomov* and Boryana Plashkova

Department of Plant Protection, Faculty of Agronomy, University of Forestry, 10 Kliment Ohridski Blvd., 1797 Sofia, Bulgaria. E-mails: rtomov@ltu.bg*, jeboremy@abv.bg

The common walnut (Juglans regia L.) is widely distributed in Bulgaria, commonly cultivated in private gardens, along streets and intercity roads, and in orchards. It currently ranks third among fruit tree species in terms of cultivated area in the country. Walnut is also important in agroforestry systems, including alley cropping, silvopastoral, and forest farming. This study aimed at the early detection of alien insect species in Bulgaria. Field surveys were carried out in August and September 2024 in urban and suburban localities of southern Bulgaria where common walnut trees are established. Larvae and pupae of Carob moth Apomyelois ceratoniae (Zeller, 1839) were found in dry walnut fruits collected in areas of Belovo, Chernichevo, Chernomorets, Gorski izvor, Kapitan Andreevo, Lyubimets, Plovdiv, Purvomay, Simeonovgrad, and Svilengrad. This is the first report of A. ceratoniae as a pest of common walnut in Bulgaria. The species appears to be widely distributed and may be more prevalent than currently documented.

Received: 25 July 2025 / Accepted: 10 August 2025 / Available online: 18 August 2025

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

Elitsa Blagoeva (1)* and Desislava Angelova (2)

1. Agricultural Academy, Agricultural Experimental Station at the Eastern Rhodopes, 6600
Kardzhali, Bulgaria. *E-mail: elica_blagoeva@abv.bg
2. Agricultural Academy, Institute for Roses and Aromatic Plants, 6100 Kazanlak, Bulgaria.
E-mail: desita7706@abv.bg

Thyme is a perennial herb from Lamiaceae family, particularly valued for its essential oils, which contain bioactive compounds with significant therapeutic and culinary properties. The oil composition varies significantly due to factors like genetic diversity and geographical distribution, resulting in distinct chemotypes. Thyme cultivation offers a valuable alternative to harvesting natural resources which disturb and diminish biodiversity and natural sustainability. A comparative field study was set up in 2021 at the Agricultural Experimental Station at the Eastern Rhodopes in town of Kardzhali with thyme species. Three genotypes were included in the study: a thymol-type cultivar ‘Deutscher Winter’ (Thymus vulgaris L.), and two Bulgarian cultivars: citral-type ‘Slava’ (Thymus sibthorpii Bentham.) and geraniol-type ‘Pagane’ (Thymus marcshallianus Willd.). Phenological and biometrical indexes were gathered and analysed, data on oil content and mass productivity were also presented. In the Eastern Rhodopes full bloom period is cultivar-dependent and occurs as follows: 10–20 May for ‘Deutscher Winter’ thyme, 1–10 June for ‘Slava’ and 5–20 June for ‘Pagane’. At the third year of thyme cultivation, the highest fresh mass per plant was gathered from ‘Deutscher Winter’ variant (445 g), followed by ‘Slava’ (345 g) and ‘Pagane’ (219 g). The highest FW/DW ratio was evaluated for ‘Slava’ (1:4). In the first years, fresh mass yield harvested per hectare varied significantly: 10–13 t·ha-1 from ‘Deutscher Winter’, 6–13 t·ha-1 from ‘Slava’ and 2–7 t·ha-1 from ‘Pagane’. Essential oil harvest quantities followed fresh mass yield – the highest oil yield was recorded for ‘Deutscher Winter’ (19.6–24.5 kg·ha-1), followed by ‘Slava’ (12.8–32.8 kg·ha-1) and ‘Pagane’ (8.1–17.3 kg·ha-1). Oil content was dependent on the year of cultivation. The highest amount was recorded for ‘Pagane’, followed by ‘Slava’ and ‘Deutscher Winter’.

Received: 30 June 2025 / Accepted: 18 August 2025 / Available online: 22 August 2025

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.

Konstantin Marinov (1)*, Dimitar Peev (1), and Konstantin Kostov (2)

1. Department of Technologies and Mechanisation in Forestry, University of Forestry, Sofia,
Bulgaria. *E-mail: kmarinov@ltu.bg
2. State Forestry, Dobrich, Bulgaria.

This paper presents results of an experimental study of a FAE SSM/HP 250 forestry tiller, powered by Fendt 939 Vario tractor with nominal power of 265 kW, used for soil preparation of open areas designated for field-protection establishment of forest belts in the Dobrudzha region in Northeastern Bulgaria. The influence of the mechanical composition and hardness of the soil, the tillage depth, and the tiller rotor rotational frequency on the operational performance and fuel consumption were studied. The experiments were conducted in open forest areas, with different mechanical composition and hardness of the soil. The experimental plots are located on clay-sandy soils with an average hardness of 345 kPa, sandy-clay soils with hardness 690 kPa and clay soils with hardness 2100 kPa. As a result of the study, functional mathematical models were developed to determine the operating performance and fuel consumption of the tilling unit, depending on the rotor rotational frequency, soil mechanical composition and hardness, and tillage depth. These results were used to determine the optimal rotor speed of the tiller based on soil type and tillage depth.

Received: 18 June 2025 / Accepted: 19 August 2025 / Available online: 25 August 2025

Open Access: This work is distributed under the Creative Commons Attribution 4.0 License.