ECOLOGIA BALKANICA 2019, Vol. 11, Issue 1 June 2019 pp. 191-204 Distribution, Characteristics and Ecological Role of Protective Forest Belts in Silistra Municipality, Northeastern Bulgaria Kiril V. Vassilev1*, Assen I. Assenov2, Nikolay I. Velev1, Borislav G. Grigorov2, Bilyana B. Borissova2 1 - Bulgarian Academy of Sciences, Institute of Biodiversity and Ecosystem Research, Department of Plant and Fungal Diversity and Resources, G. Bonchev str. 23, 1113, Sofia, BULGARIA; 2 - Sofia University “St. Kliment Ohridski”, Faculty of Geology and Geography, Department “Landscape Ecology and Environmental Protection”, 15, Tzar Osvoboditel Blvd. 1504 Sofia, BULGARIA *Corresponding author: [email protected] Abstract. Protective forest belts are developed as a defense against dry winds and soil moisture loss and considered as natural capital nowadays. Silistra municipality’s protective forest belts were investigated about their distribution, floristic composition, vegetation structure and syntaxomony. During 2018 field season 32 relevés were collected following the Braun-Blanquet approach. Data about diversity of invasive and melliferous plants were collected also. Vegetation types were identified by numerical classification using hierarchical agglomerative clustering (PC-ORD). Descriptive statistics about the cover of tree, shrub and herb layers as well as cover of invasive and melliferous plants were graphically summarized in vertical box-and-whisker plots. The forest belts syntaxonomical diversity is represented by 2 associations (Cotino coggygriae-Quercetum cerris, Bromo sterilis-Robinietum) and Amorpha fruticosa-Morus alba plant community. Cotino coggygriae-Quercetum cerris has closed horizontal structure with dominants Quercus cerris and Cottinus coggygria in tree and shrub layers respectively. Bromo sterilis-Robinietum is characterized by poor species composition and vegetation dominated by Robinia pseudoacacia and Fraxinus americana, whereas Amorpha fruticosa-Morus alba community has local distribution and represents a final stage of vegetation degradation. Totally five alien species (Acer negundo, Amorpha fruticosa, Erigeron annuus, Fraxinus americana and Robinia pseudoacacia) and 26 melliferous plants were identified within the forest belts. The highest cover of invasive species and melliferous plants were found within Bromo sterilis-Robinietum and Amorpha fruticosa-Morus alba. The main melliferous plant species were Robinia pseudoacacia, Amorpha fruticosa, Morus alba and Prunus cerasifera. The investigated forest belt vegetation bears the characters of a long-standing anthropogenic impact. They have been subject to cutting, burning and pasturing during the last 50-60 years. Key words: alien invasive plants, Braun-Blanquet approach, mapping, melliferous plants, numerical classification, vegetation structure. Introduction them as natural capital, providing Protective forest belts are of a particular regulating, cultural and few direct material historical importance for shielding against ecosystem/landscape goods and services, dry winds and for preserving soil moisture. but significant indirect material The contemporary interpretation considers ecosystem/landscape goods and services, as © Ecologia Balkanica Union of Scientists in Bulgaria – Plovdiv http://eb.bio.uni-plovdiv.bg University of Plovdiv Publishing House Distribution, Characteristics and Ecological Role of Protective Forest Belts in Silistra Municipality... a product of the nearby agricultural areas were applied in Romania. During this period (pollination of crops and other plants, the first plantations of protective forest belts purification of water and air, etc.). in the occupied Bulgarian Southern Geographically determined, the first Dobrudzha have been established. protective forest belt emerged in the The end of World War II saw Kingdom of Russia under the influence of a nationalization of lands in Bulgaria and Russian forester, named Nestor Karlovich Romania. State act (№ 236) was adopted in Genko (1839-1904). The continental climate, Bulgaria in 1951, concerning the characterized by insufficient rainfall and the development of agriculture, water supply emergence of dry winds, leading to erosion and electrification in Dobrudzha and in and drying of the soil, is a prerequisite for parallel with this a plan-program for the the creation of protective forest belts, creation of protective forest belts was also particularly in this part of the world. These brought to light. Soon after that an processes, along with the destruction of the expedition, studying forest belts in European forests in the period 1750-1850, Dobrudzha, was led and a book was provoked the need of the foundation and published by STOYANOV & KITANOV (1955), development of the forestry science (POPOV where soil scientists, hydrologists, botanists et al., 2017). During the period 1886-1903 and zoologists made contributions also. protective forest belts in Ulyanovska Oblast According to POPOV et al. (2017) the have been established and today they are a bulgarian government ordered the creation protected natural object. The total aerial of nine protective forest belts, covering 21 coverage of the forest belts “Genko stripes” 997 ha in total and with 800 km length (fig. in Samara Oblast is nearly 9 000 hectares and 1).The belts have 70-90 m in width and their total length is around 150 km, while plantations were planted in 1951 –1958. The their width is 640 m. tree species Quercus robur, Quercus petraea, As Genko was working on the Fraxinus excelsior, Robinia pseudoacacia, plantation of the protective forest belts, the Gleditsia triacanthos, Juglans regia and Populus same idea was adopted in the neighboring ssp. were planted according to POPOV et al. country of Romania, where BRAD (1850) (2017). As of 1980 the average height of the created the first plantations as “shelters belts was 5-15m and the stock are 389 000 m3. against wind”. Romania had a leading role Forest belts are protecting agricultural area in the creation of protective forest belts with with cells 500-600 m wide and 1200-2000 m its Barăgan plain for forest belts from 1906, long. The prevailing winds in this territory which is more than 39 years younger than come from the north, so the main belts are the plan of Roosevelt and 42 years younger oriented in east-west direction, having a than the plan of the Soviet Union for distance of 500 m in-between. According to transformation of nature, following BUCUR GEORGIEV (1960) the impact of the belts is (2016). In 1936 the plantation of forest belts divided in an equal distance from them, in the villages of Karvuna (Balchik multiplied by 25-30 height. Municipality) and Rogozino (Dobrich The protective effect of the forest belts Municipality) started and two years later can be summarized in the following way: the plantations were finished. The work in wind effect has been reduced with 25-30%, Karvuna village continued in 1939 and 1940 air moisture deficit has been reduced by 15- when according to the Treaty of Craiova 20% and physical evaporation has been these lands were returned to Bulgaria, reduced by 7-20%, according to VACHOVSKI POPOV et al. (2017). & DIMITROV (2003). Snow cover started to The October Revolution in 1917 ceazed accumulate equally at the direction of the plantations, but after World War I, special snowfall within the belts, while soil moisture measures for the creation of new forest belts was kept in the horizon between 100 and 200 192 Vassilev et al. cm with an increase of 45-50%. Among the the anthropogenic influence and distribution existing protective forest belts in Bulgaria, of alien and melliferous plants of studied the ones in Dobrudzha have the best status, forest belts. according to POPOV et al. (2017). Forest belts can be analyzed as linear Materials and Methods elements in landscape structure that directly influence ecological processes, following Study area FORMAN & BAUDRY (1984) and landscape Protective forest belts in the functions, according to MARSHALL & municipality of Silistra were the object of the MOONEN (2002). European history of current investigation and they were built-up agriculture acknowledges constructive role date back from 1951-1958. Its area covers of linear elements in the formation and 51589.1 hа of which 38754.4 hа are functioning of a wide variety of rural agricultural territories, 6827.3 hа forest areas, landscapes, following ZIMMERMANN (2006). 3622.6 hа urbanized territories, 1809.0 hа The understanding of landscape’s pattern water areas, 51.0 hа quarries and transport interactions – arable fields (matrix) and infrastructure takes up to 524.8 hа. Silistra adjacent green corridors (linear elements), Municipality comprises around 18% of the are essential for biodiversity complexity territory of the whole province (Silistra). explanation, according to MEYER et al. (2012). There are also eighteen villages and one Linear landscape elements are a valuable town - Silistra, which is the center of the indicator for the biological diversity in agro- province and the municipality (Municipal landscapes, following BILLETER et al. (2008). development plan 2014-2020). The plain Landscape Ecology considers linear relief reaches up to 200 m a.s.l. The fertile elements as sources of important ecosystem lowland of Baltata, located near Aidemir services, according to VAN DER ZANDEN et al. village, is also situated here and the (2013) and stimulates multi-functional southwestern part of the plain is taken by landscape utilization. Depending on the Srebarna