Seasonal Changes of Microbial Biomass Carbon, Nitrogen, and Phosphorus in Soil Under an Oriental Beech Stand

Abstract

Microbial biomass, which is both a pool and a nutrient source for plants, is commonly accepted as an index indicating the health and fertility of the soil. Soil microbial biomass at higher levels can be obtained through the presence of more favorable environments, availability of nutrients and organic carbon, soil moisture content and temperature, and residues from plants. This study investigated the seasonal variation of some -physical- chemical properties and the carbon, nitrogen, and phosphorus in the microbial biomass of the soil under an oriental beech stand in the Arit-Bartin region of Turkey. A chloroform fumigation- extraction procedure was applied to the fresh soil samples to determine the C, N, and P in their microbial biomass. The results showed that the highest mean contents of microbial biomass of carbon (C-mic), nitrogen (N-mic), and phosphorous (P mic) of soil were measured in autumn (C-mic = 650.51; N-mic = 128.39; and P-mic = 30.77 mu g g(-1)) and the lowest in spring (C-mic = 516.75; N-mic = 83.33; and P-mic = 21.40 mu g g(-1)). This can be explained by the lower levels of organic carbon (C org), total nitrogen (N-total), and available phosphorus (P) in the soil during spring. In addition, a positive correlation was found between microbial biomass and the moisture and temperature of the soil, C-org, N-total, and available P. These findings indicated that the soil temperature and soil moisture, along with the above-mentioned variables, affect the level of C-mic, N-mic, and P-mic of soil. Except for the soil reaction (pH), the C-org:N-total ratio, and soil C-mic, a notable seasonal change was found in some physical-chemical properties of the soil and in the P and N in the microbial biomass under the oriental beech stand.