ENVIRONMENTAL ASPECTS IN CULTIVATION OF PAULOWNIA IN BULGARIA. Avgusta STEPCHICH. Abstract

Transcription

1 ENVIRONMENTAL ASPECTS IN CULTIVATION OF PAULOWNIA IN BULGARIA Avgusta STEPCHICH Institute of Soil Science, Agrotechnology and Plant Protection "N. Poushkarov", Sofia, 7 ShosseBankya Str., Bulgaria *Corresponding author:astepchich@yahoo.com Abstract Paulownia is a relatively new plant species grown in Bulgaria. It is primarily associated with the extraction of timber. The tree is characterized by rapid growth in height, but also with high value of the manufactured wood. The species is of great ecological importance. There are large, bright and fragrant flowers and the big leaves facilitating the absorption of carbon. It is suitable as a honey culture and the most suitable type is Paulownia tomentosa. The plant is propagated in different ways by seeds, by cuttings and in-vitro method. The most popular method is by cuttings. The seeds are light and easily propagated by wind, but difficult to intercept alone. Because of the large amount of seeds in the seed pod, species is considered invasive for the territory of Bulgaria. The studies aimed at establishing risk of invasiveness and the possible usage of the species in Bulgaria. The studies, based on field measurements, showed that the soil and climatic conditions of the country do not premise invasiveness of the species. The species Paulownia is suitable for cultivation on reclaimed land, as well as for soil erosion control. Based on information collected from different experimental sites it is concluded that Paulownia has a great ecological importance and can be used in different areas. Keywords: Paulownia, environmental impact, cultivation, Bulgaria Introduction The ecological significance of individual plant species varies on soil and climatic conditions. The plant species Paulownia spp. has gained popularity in recent years. Cultivation is related to the possibility of using the species for different purposes. It is known for its rapid growth and decorative qualities. Paulownia best develops on light, well-aerated soils with a ph of 5.5 to 8.9. In clay or swampy soils the development of the root system is difficult and the growth is insignificantly. Intensive Paulownia cultivation is optimal to an altitude of m and temperatures at which maximum growth is observed in the range of C. Regarded to wind, it is recommended that plantations be established in locations with a wind speed of not more than 28 km/h. The plant is propagated in different ways - by seeds, cuttings and in-vitro method. The most popular method is cuttings. Due to the presence of a large quantity of seeds in the seed pod, the species was considered invasive for the territory of Bulgaria. The seeds are light and easily transported by wind, but are difficult to strike root on their own. The flowers are large, bright and aromatic, hanging on long cm thick twigs. The planting pattern is determined depending on what the resulting timber will be used for. Lawrence (2011) gives an example with plantations from Western Australia, Queensland, where the scheme used ranges from 6x5 m to 6x7 m, rarely 7x7 m. Kalmukov (2009) indicates the use of two distances between adjacent rows- 1.5 m and 2.0 m three densities between each two plants within the row m, 1.0 m and 1.5 m. Paulownia wood is suitable for both biomass and wood production. The price of wood is high, as the World Paulownia LLC proposed for 1704

2 m 3 wood is US $ 275. Diseases of Paulownia are most often caused by fungi, viruses, sunburn or over-wetting, which mainly affect the root, the trunk and the leaves. There are also a number of pests. Materials and methods The article is based on a review of primary and secondary data. Field experiments have been set up under different soil conditions. The trials were carried out on the territory of village of Pravda (Dulovo municipality) and village of Lyulin (Pernik municipality). To determine the morphological structure, composition and soil properties, soil profiles were made and soil samples were taken from the two sites. The climate is tracked according to the National Institute of Meteorology and Hydrology. For the village of Pravda, plantations have been observed since The planting pattern is 3x3 m in chess scheme. This scheme is widely used for growing timber. Plantation in Lyulin is made The planting pattern is 3x3 m in straight rows. Measurements of the height of individual plants for each site were carried out. Three maps have been created using soil, climate and irrigation data to produce maps showing the appropriate areas for paulownia, meeting the requirements of culture. The first map shows territories that cover all the required factors (soil, climate and irrigation). The second map limits places with an average temperature of up to C, and the third indicates places with irrigated mode. Observations have also been carried out on invasiveness of the species. Results and discussion The reason why the plant has gained great popularity in recent years is the extremely fast growth. Various sources describe the growth of the tree, which in 8 years reaches over 20 m. The height of a 3 year old poplar is from 9 to 12 m, while in paulownia it is from 10 to 15 m. Plant development is traced under different soil and climatic conditions on the territory of two plantations in different parts of Bulgaria. The first site is in the village of Pravda (Dulovo municipality). From the soil profiles made on site, it was found that the soil is Luvic Chernozems, heavy sandy-clay (Clayic). By mechanical composition the soil is characterized as heavy sandy clayey (54.3% physical clay in the surface horizon). The humus content in the surface horizon is 2.20%, which characterizes it as low humus soil. The nitrogen content of the soil is very low mg / kg. The phosphorus content is 12.8 mg/kg, and with potassium content of 20.2 mg/kg the soil is considered as well stocked. The reaction of the soil is very strongly acidic (ph in water 4.9), and carbonates are not found at the depth of the profile. In climatic terms the territory of Pravda is characterized by temperatures of 12.7 to 13.1 C. High annual precipitation values are reported - from 789 mm to 813 mm. No frost for the studied period was recorded at the plantations in Pravda. Plants show a significant growth since the first year of planting. The average growth in height of the plants is shown in Table 1. Table 1. Average height (m) of plants in village of Pravda Year Average height 2.4 m 4.7 m The data from the measurements made indicate the possibility of the species to develop rapidly in the soil-climatic conditions of the village of Pravda. For 2012, the average height increase is 2.4 m. For is 4.7 m, which is double compared to the previous year. No tree pruning was performed for the observed period. This allows tracking their growth from the planting period. 1705

3 The second site is village of Lyulin. From the soil profile made on site, it was found that the soil is anthropogenic, light loam. By mechanical composition soil is slightly clayey (65.44% physical clay in the surface horizon). The humus content in the surface horizon characterized it as humus soil %. In nitrogen content 37.7 mg/kg and in phosphorus content 4.5 mg/kg the soil is poorly stocked. But in potassium content - 23,6 mg / kg, it is well stocked. The soil reaction is slightly alkaline (ph in water 8.1) and carbonates are established over the entire depth of the soil profile. In climatic terms the territory of Lyulin is characterized by temperatures of 10.0 to 10.4 C. The annual rainfall in 2013 is 433 m and in 2014 it is twice the amount (808 m). As a result of the reported frost in 2013 the leaves froze, which led to their subsequent fall. Plants in the village of Lyulin are also characterized by rapid growth during the years. The pruning has been performed for the measurement period. The average height increase for 2013 is 0.72 m and for m. After the pruning at the end of 2013, the plants begin their development from the root. This is also the reason for the lower results during second year of their planting (Table 2). Pruning has been done to ensure faster growth. This is a commonly used method for growing the species for the needs of the forestry industry. Table 2. Average height (m) of plants in village of Lyulin Year Average height 0,72 m 0,24 m To compare the results, Gyuleva (2010) gives data about the first year of planting the species in different regions of the country. For the territory of Svilengrad there is an average height of one year old plants of 0.57 m. For Karlovo is 0.67 m and for Lukovit is 1.19 m. From the data shown above it is obvious that the increase of the plants in Lyulin is very good. The impression is made by the much larger increase in the village of Pravda, due to the soil and climatic conditions. Trees planted in 2009 are used for the calculation of the volume of the wood planted in the territory of Dulovo municipality. The main reason for this is that by the third year the trees have a hollow core, making them extremely susceptible to strong winds. The plants from the village of Lyulin have not been calculated because of the pruning at the end of the first year. The average volume of wood was calculated per cubic meter per year per hectare (m 3 /y/ha). Plants are measured over a three year period ( ). For 2012 the values are m 3 /ha. For 2013, the volume is calculated at m 3 /ha and for 2014 it is m 3 /ha.some sources point out that under perfect conditions Paulownia starts to give 1 cubic meter of tree wood growth after the seventh-eighth year. With the help of the observations and the information gathered, three maps were prepared for the territories in Bulgaria suitable for Paulownia breeding. (Figures 1, 2 and 3). 1706

4 Figure 1. Map of soil-climatic areas with optimal, natural conditions for the development of Paulownia With all the factors for the development of the plants, the lands along the Struma River and parts of the Sakar Mountain, part of the Arda River and the southern parts of the Black Sea coast. Figure 2. Map of the territories with optimal annual temperature +13,5 С When temperature is reduced, there is a greater fragmentation of the Paulownia growing areas. There are parts of southern Bulgaria overlapping with the territories from the first map. Besides them, parts of the Balkan Range and the eastern parts of Stara Planina are also suitable. Figure 3. Map of the territories with irrigated conditions 1707

5 Unlike the first two maps, on the third map there are more territories suitable for Paulownia breeding. Impressive is the territory along the Danube River, as well as the valley of the Osam River. The lands located in the Maritsa and Tundja rivers, as well as almost everywhere along the Black Sea coast, are suitable. Determining a crop as a honey is dependent on climatic conditions. Higher temperatures allow for a longer flowering period and vice versa - shorter blooms. Nectar in a paulownia color is significantly higher than that in one acacia white color, which is from 1,662 to 8,130 mg (Vachev, Kalmukov, 2005) and from lime-tree is from 1,414 to 10,53 mg (Tsocheva, Vachev, Karmukov, 2007). Plants begin to bloom in the third year. From an economic point of view, it is better to plant the plantations to be used as honeycombs in areas with higher air temperatures (Kalmukov, Vachev, Kanchev, 2016). From an erosion point of view, it is noted that at the beginning of its development, the culture has poor erosion protection, due to the slow increase in area coverage. When cultivating the species for the harvesting of wood is not allowed the shaping of a powerful crown. The trees are allowed to grow only at a height, thus the only area coverage is from the single leaves located on the stem. Upon growth, these leaves drop and reduce the anti-erosion effect of the culture. Unlike other species paulownia, it can also be grown as a bush species. This allows the formation of more branches and consequently increases the area coverage. An important condition for growing the species for anti-erosion purposes is that the terrain should appropriate with the requirements of the culture. The lack of key factors for its development could lead to the extinction of planted plants. In some areas, Paulownia is considered an invasive species. In Europe, it is predominantly limited in man-made habitats (Essl 2007). For the territory of Bulgaria, the species is not defined as invasive. A small pod of Paulownia contains hundreds of small seeds, and since their vitality is always high, only a few pods are required to produce a large number of seedlings. However, climate conditions in Bulgaria do not allow these seeds to spread and set off independently, which is why it is not to be described as invasive. Conclusion From the measurements and observations made, it can be noticed that the fast-growing species of Paulovnia can be cultivated for different purposes on the territory of Bulgaria. With its honey-like properties it is suitable for planting near hives. The formation of a large crown and exceptionally beautiful colors are a prerequisite for its cultivation as park vegetation. Its rapid growth, under appropriate conditions, allows it to be cultivated for the forestry industry, and thus could replace slower growing species. The increase in the volume of wood is increased every year, with the average volume of six years of planting being m 3 /ha. From the maps, a repeat of the territories suitable for paulownia cultivation in Bulgaria is observed. Under optimal conditions the lands along the Danube River and the rivers Maritsa and Struma are distinguished. It is precisely this restriction of the appropriate territories that it does not allow it to be included in the list of invasive species for the country. Depending on the way of cultivation, paulownia has the potential to protect the soil from erosion. Its growing in the form of a bush increases the area coverage, thus increasing its protective effect. The species is relatively new and unexplored for the territory of Bulgaria and this necessitates the need for further in-depth research. 1708

6 References Vachev, P., K.Kalmukov Nectar productivity and honey productivity of some species of white share (Robinia pseudoacacia L.) Acta entotmologica Bulgarica. Vol. 11, 3-4, Gyuleva V., Maria Glushkova, Katya Velinova, Proletka Dimitrova, Ecological-biological Peculiaritiesof Some Paulownia Species Growing in Bulgaria and Prevention of Potential Negative Consequence for Environment, Forest Research Institute, BAS, 132 Kliment Ohridski Str Sofia, Bulgaria. Essl F. (2007) From ornamental to detrimental? The incipient invasion of Central Europe by Paulownia tomentosa. Preslia 79(4): Kalmukov, K., Effect of Initial Density on Condition and Growth of Paulownia tomentosa L., Experimental Station for Rapid Forest-like Species, 5250 Svishtov, Bulgaria, Kalmukov, K., P. Vachev, G. Kanchev. Nectar productivity, sucrose productivity, and honey productivity of paulownia tomentosa l. Science & Technologies: Volume VI, Lawrence, James S., Paulownia technical bulletin #1, #2, 23 September 2011 Mueller, J.P., J.M. Luginbuhl, and B.A. Bergmann Establishment and early growth characteristics of six Paulownia genotypes for goat browse in Raleigh, NC, USA. Agroforestry Systems 52: Tsocheva, K., P.Vachev, K.Kalmukov, 2007, Evaluation of the effects of Tilia platyphillos and Tilia cordata on the variation of color nectro-productiveness, nectar sugar concentration and number of flowers in one inflorescence. Acta entomologica Bulgarica, vol,13, 1,2,