Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

The Effects of Thinning on Soil Respiration and Microbial Respiration in

Oak and Hornbeam Stands
Soil respiration, which involves the emission of CO₂ during the decomposition of organic matter carried out by the metabolic activity of the plant roots and soil microorganisms, is a fundamental process in the carbon cycle and represents the main pathway whereby carbon fixed by the soil is returned to the atmosphere.
In this study, effects of thinning on oak (Quercus franietto) and hornbeam (Carpinus betulus) stands were examined between 2010 – 2012 years in Research Forest of Faculty of Forestry, Istanbul University we determined two thinning areas and two control areas under each tree species. Thinning reduced tree density by 50 % of basal area. This research is being focused on the main factors (soil temperature, moisture, carbon content, nitrogen content, ground cover biomass, forest floor and fine root biomass) which are effective on the soil respiration and microbial respiration. Soil respiration was measured bimonhtly with the soda-lime method. Microbial respiration was measured for soil and forest floor with incubation method.
The research results of annual average respiration value were significantly higher in thinned areas (1,92 g C/m²/day) than in control areas (1,79 g C/m²/day) in oak stands. On the contrary, soil respiration were not significantly different between thinned areas (1,76 g C/m²/day) and control areas (1,72 g C/m²/day) in hornbeam stands. During research period, soil respiration decreased from baseline in both oak and hornbeam stands. Soil respiration higher in thinned areas compared to control areas. Soil respiration was linear correlations with ground cover biomass, soil temperature and fine root biomass during two years in each tree species.
Soil microbial respiration were not significantly different despite of higher in thinned areas than control areas in oak and hornbeam stands evaluated in a two-year full time. Microbial respiration of forest floor in control areas significantly higher than thinned areas in oak and hornbeam stands Soil microbial respiration was linear correlations with soil nitrogen content and soil acidity while forest floor microbial respiration was linear correlations with carbon content and carbon/nitrogen ratio of forest floor.
In conclusion, ground cover biomass was main factor directing soil respiration in the stands. In addition, soil nitrogen content and soil acidity were limited factors for soil microbial respiration.