Effects of site preparation methods on soil productivity in eastern beech (Fagus orientalis, Lipsky) ecosistems

Forestry operations have an impact on soil physical, biological and chemical properties. Extend of impact may vary with soil and forest types. However, extend and durations of these changes have not clearly documented. Data are available for short-term studies. But, results from short-term experiments may not be adequate to speculate for the long-term predictions.Eastern beech (Fagus orientalis Lipsky) is one of the most important tree species of Turkey in terms of wood production. The understories of beech forest in the Black Sea region are occupied with very dense purple ?flowered rhododendron (Rhododendron ponticum L.). Since these woody weed prevent seed germination and seedling growth it must be cleared from the site during the regeneration of beech stands.Different site preparation and weed control techniques have been used for many years. However, machine (bulldozer equipped with a rake) becomes the sole technique lately. But, using machine for site preparation may remove some of the top soil during the operation. Thus these methods may result in significant nutrient losses from the ecosystem and eventually reduce seedling growth.The objectives of this study, to investigate the effects of different site preparation methods on some of the soil physical and chemical properties and long-term site productivity in beech natural regeneration sites in the western Black Sea region.Two of the experimental sites were chosen from beech stands located in the Deredibi Forest Management Cheifship of the Akçakoca Management Directorate (310 07? 53?? N, 400 59? 46?? E and (310 07? 37?? N, 400 59? 46?? E). These two experimental sites are 750 m above the sea level and one is on the north aspect with an average 35 % slope and the other One is facing northwest aspect with 10- 20 % slope. The third block is located in an inland site compared to the other two blocks (400 41? 04?? N, 310 19? 17?? E). The elevation of the third block is about 1050 m and it is facing North aspect with an average of 30 % slope.Randomized block design were used for the experiment. Weeds were cleared from the sites using labor force (grubbing), prescribed fire and bulldozer during a mast year of the beech in 2006. Understory were sampled on 6 randomly chosen 1 m2 sampling quadrates before the treatment on each block. Biomass of above and below-ground part of understory and their macro-nutrient contents were calculated as kg on a hectare base. Forest floor organic matter (OM) was sampled on 5 randomly chosen spot on each experimental unit. Then OM biomass and nutrient contents were calculated. Intact soil core samples were taken from 0-10 and 10-20 cm depth on 5 randomly chosen locations on each experimental unit. And 5 soil profiles on randomly chosen spots on each block were dug. Then soil depth, nutrient content, pH, texture of soil were determined.Data revealed that there are 45 ton understory biomass containing at least 22 ton carbon ( C), 300 kg nitrogen (N), and 15 kg phosporus (P) per hectare forests. There are 64 % less forest-floor organic matter (OM) biomass on burned and machine cleared sites than those of the grubbing sites. Organic matter C on the machine site is 3.5 times less than those of the control and grubbing sites. Nitrogen, P, calcium (Ca) and magnesium (Mg) content of the OM on machine site were 4.4, 4.2, 7.3 and 4.1 times less than those of control and grubbing sites, respectively. Potassium content of OM on machine site is 3.4 times less than that of grubbing site.Soil bulk densities in the first 10 and 20 cm soil depth are 34 % and 26 % higher on machine sites than those of the other treatments, respectively. Soil cation exchange capacities (CEC) are 31 % lower in control and machine sites than those of the grubbing and burning sites. Grubbing and burning sites have half a degree higher soil pH than those of machine and control sites.The first 20 cm soil depth have 32 and 20 % lower C and N content in machine site than those of the burned and control sites. Soil K content on machine site is 45 % lower than those of grubbing and control sites. Soil Ca content on machine site is 4.2 times less than that of grubbing site.Key words: Ecosystem, sustainability, productivity, beech, rhododendron, site-preparation, Düzce