Determination of soil respiration in the oriental beech stands that different intensities thinnined, and adjacent oak and grassland

It is known that the increase in carbon dioxide concentrations in the atmosphere can lead to global problems such as global warming and climate change. The soil releases a significant amount of carbon dioxide accumulated in the atmosphere through respiration. Soil respiration can be affected by land use, ecosystem type, and forest exploitation due to changes in soil quality, soil fertility, and biological activities. In this study, the changes in soil respiration on a monthly, seasonal and annual basis in pure and natural Oriental beech (Fagus orientalis Lipsky.) stands thinned different intensities and adjacent sessile oak (Quercus petraea (Mattuschka) Liebl.) stands and grassland areas in the Düzce region were investigated. While 25% (Beech-25AŞ) and 17% (Beech-17AŞ) of the average chest surface were removed by regular thinning in two fields of eastern beech, thinning was not applied in the other beech field (Beech control). In the neighboring oak field, 38% of the basal area was removed at regular thinning. Three sampling areas were randomly determined within the five research areas, and soil respiration, soil moisture, soil temperature and root biomass measurements were made in 2022 and 2023. Soil respiration measurement was carried out by the soda-lime method, and root biomass measurement was carried out using a steel core of 6,4 cm diameter and 30 cm length. On average, soil respiration is between 0,6-5,51 g C m-2 day-1 in oak forests, between 0,22-5,42 g C m-2 day-1 in beech forests, and 0,33-3,25 g C m-2 day-1 in grassland. Beech control area had approximately 25% more soil respiration than Beech-17AŞ and 11% more soil respiration than Kayın-25AŞ. Comparing all sites, soil respiration of oak site is higher than beech sites and grassland. Soil respiration is similar in spring and summer and is higher than in other seasons. While the annual average soil moisture of the beech control was higher than that of the thinned beech sites, no difference was found between soil temperatures. While thinning did not have a significant effect on fine root biomass (mean:1060,2 g m-2) among beech fields, the fine root biomass of forest areas was 22% higher than that of grassland. There was a linear positive relationship between soil respiration and soil moisture in beech fields, and soil respiration showed a linear positive relationship with both soil moisture and soil temperature in all fields. No significant relationship was found between soil respiration and fine root biomass.