Biodegradation of substrates used for soil erosion prevention 59 One of the main stages in the research of erosion prevention technologies is to determine the expedience of the substrate to the plants. The next equally important stage is to study substrate biodegradation. The investigation of substrates fell on the middle of the summer time. The coast sand and sand- ground samples were put into 10 l buckets. According to the experimental scheme, different layers of hydrolytic lignin (0, 2, 5 cm) were placed on the top of the soil LSTM 2 and LSTM 1 + promoter polymers were spread (200 ml m –2 ) on the lignin layers. The buckets with the substrate were exposed to the influence of atmospheric conditions during the whole period of the experi- ment. Samples for microbiological research were taken at the beginning of the experiment and four, eight as well as forty five weeks later. Simultane- ously drain water, soil and lignin chemical analyses were carried out. At the beginning of the experiment, bacteria were active in the degrada- tion of the coast sand organic matter, thus their number was high enough even without lignin. Later the thickness of the lignin layer influenced the fluctuation of bacteria amount. The micromycetes were the main factor in the hydrolytic lignin degradation process. The number of micromycetes in the coast sand substrate at the beginning of the experiment was statistically sig- nificantly influenced by the thickness of the hydrolytic lignin layer r = 0.84; after 4 weeks from the beginning of the research this coefficient decreased to r = 0.64, and 8 weeks later it was r = 0.48. In the sandground where carbon store was more abundant (C = 1.25%), bacterial microflora took the main part in the degradation process. The C/N ratio of 25–30 indicated that the lignin degradation process in the substrates was going on. In other cases organic matters were already degraded and transformed into nutrients. The research results indicate that the substrates made of lignin and poly- mers can be mineralized by natural microorganisms, however, they cannot be used for soil erosion prevention or growing plants without additional nitrogen compounds. Key words: hydrolytic lignin, modified polymers, soil, biodegradation, bac- teria, fungi, C/N ratio Dalia Ambrazaitienė, Olga Belous, Audronė Žukauskaitė Klaipėda University, 84 H. Manto St., LT-92294 Klaipėda, Lithuania Galia Shulga Latvian State Institute of Wood Chemistry, 27 Dzerbenes St., Riga, Latvia Biodegradation of substrates used for soil erosion prevention EKOLOGIJA. 2006. Nr. 2. P. 59–65 © Lietuvos mokslų akademija, 2006 © Lietuvos mokslų akademijos leidykla, 2006 INTRODUCTION Most marine countries have researched into their coast- lines and prepared coast protection programs (Nichols, 1992; Zeidler, 1992; Pethick, 1993; Diehl, 1998). The coastline stability insurance being one of the major ob- jectives of such programs necessitates the search for coastline zone soil erosion reduction means with an emphasis on the preservation of stable vegetation in the forested parts of dunes. Fast formation of plant cover and its stability assures better growth and moisture con- ditions in the afforested plots which are strengthening the dunes. There are technologies where synthetic polymers are used for sand strengthening, however, this method is neither effective nor environmentally friendly, therefore, the use of natural materials is suggested. Lignin, which appeared as a natural product of the evolution process, is one of them. When plant cells were infected with symbiotrophical or parasitical fungi, the evolutionary protection mechanism was evoked, with the formation of a triple complex aromatic alcohol polymer known as lignin (Сидоров, 2003). On the other hand, the fermentative system for lig- nin digestion has developed in fungi, particularly in basidiomycetes. The mineralization of decayed plants