Temporal variation of root decomposion in oak and hornbeam stands

In this study, the temporal changes in root decomposition were investigated in the oak (Quercus frainetto Ten.) and hornbeam (Carpinus betulus L.) stands in the Istanbul University-Cerrahpaşa Faculty of Forestry Education and Research Forest between 2021 and 2022. Decomposition bags were prepared for different diameter classes for both species. The remaining mass of roots placed in these decomposition bags, decomposition coefficient "k", lignin and cellulose content, carbon and nitrogen content in the roots, and nutrient contents were examined, while the soil samples affecting decomposition were analyzed for soil temperature, soil moisture, soil pH, soil carbon and nitrogen content, microbial respiration, and microbial biomass carbon and nitrogen content. During the one-year study period, approximately 33% of fine roots and 30% of coarse roots of oak underwent decomposition, while in hornbeam, approximately 36% of fine roots and 48% of coarse roots underwent decomposition. The decomposition coefficient "k" showed a temporal decrease in both species, ranging from 0.56 to 0.52 in oak fine roots and 0.55 to 0.80 in hornbeam fine roots. Additionally, the time required for 95% decomposition for both root classes was determined to be 5.4 years for fine roots and 5.8 years for coarse roots in oak, while in hornbeam, it was 5.5 years for fine roots and 3.8 years for coarse roots. The lignin content in oak roots averaged 60.91% in fine roots and 59.54% in coarse roots, while in hornbeam roots,it was 58.25% in fine roots and 62.3% in coarse roots. The carbon content in oak roots ranged from 41% to 49.9% in fine roots and from 43.5% to 49.54% in coarse roots, while in hornbeam roots, it ranged from 43.2% to 50.68% in fine roots and from 41.79% to 48.5% in coarse roots. The nitrogen content in oak roots ranged from 1.37% to 1.66% in fine roots and from 1.28% to 1.61% in coarse roots, while in hornbeam roots, it ranged from 1.37% to 1.66% in fine roots and from 1.28% to 1.61% in coarse roots.Plant nutrient elements were evaluated as macro (P, K, Mg, Ca and Na) and micro (Al, Fe, Mn, Zn, and Cu) nutrient elements. Macro and micro elements were found to be at high levels in fine roots in both species. Soil samples were analyzed for microbial respiration, microbial biomass nitrogen, and microbial biomass carbon. Microbial respiration in oak soils was highest in June and lowest in September, while in hornbeam stands, it was highest in March and April and lowest in December. Both species showed a decrease in microbial respiration during winter months. The microbial biomass nitrogen in oak soils was highest in October and lowest in May, while microbial biomass carbon was highest in April and lowest in January. In hornbeam, microbial biomass nitrogen was highest in July and lowest in November, while microbial biomass carbon was highest in April and lowest in May. Correlation analysis based on root classes revealed a negative relationship between remaining mass and decomposition coefficient, microbial biomass nitrogen, and microbial biomass carbon in oak roots. Among soil properties, a strong negative relationship was found between soil moisture and soil temperature, soil carbon, and soil carbon/nitrogen ratio. In hornbeam, a positive correlation was observed between remaining mass and root carbon/root nitrogen ratio, while a negative correlation was observed with root nitrogen content, microbial biomass carbon, and microbial biomass carbon/microbial biomass nitrogen. Evaluation of the relationship between soil properties showed a negative relationship between microbial respiration and soil nitrogen content and a positive relationship with soil carbon/nitrogen ratio. Soil moisture was negatively correlated with soil temperature and pH. In conclusion, the study indicated that mass loss was higher in the first three months and varied seasonally in both tree species. However, it has been shown that there are different influencing factors on decomposition within the same growing environment and that there are complex relationships