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Soil respiration describes the process of gas exchange between organisms and their environment. As one of the key processes in ecosystems, soil respiration is linked to ecosystem productivity, soil fertility, and the regional and global carbon cycles. The objective of this study is to investigate the impact of abiotic factors, particularly variations in air temperature and humidity, on the intensity of soil respiration in the dystric cambisols within the Quercetum montanum typicum forest community at the National Park “Fruška Gora” in the Vojvodina Province of Serbia. A total of 32 site visits were conducted in 2014–2017 period to obtain site-specific data on air and soil temperature and humidity, and soil evaporation and respiration. The key findings indicate that the variations in air temperature and humidity significantly impact soil respiration. In most cases, soil respiration positively correlates with soil temperature; however, in some years, a nonlinear response has been observed, which may indicate thermal stress at higher temperatures.

Soil microbial processes are a key component of the carbon and energy cycle in terrestrial ecosystems, with enzymatic activities and microbial respiration playing a central role in the decomposition of organic matter and the release of carbon dioxide. Dehydrogenase activity (DHA) is a reliable bioindicator of total microbial activity, while soil respiration (Rs) represents the conditions under which microbial metabolic pathways occur. In the past decade or so, numerous separate studies of soil characteristics, microbial activity and soil respiration have been conducted on Fruška Gora. So far, no study has been conducted that would contribute to a better understanding of the influence of soil temperature and humidity on microbial activity and soil respiration. The studied area is located in the NP “Fruška Gora”, GJ Popovica – Majdan – Zmajevac, 20/c, in a coppice forest of sessile oak (Quercetum montanum typicum) with an admixture of beech (Fagus moesiaca (Domin, Maly) Czecz). The terrain is very steep, altitudes 475–505 m, southeast exposure, geological base is shale, and the soil is dystric cambisol. A total of 32 field visits were conducted in the period 2014–2017. for measurements of air and soil temperature and humidity, as well as soil sampling for laboratory analysis. In this study, the relationships between soil dehydrogenase activity (DHA), soil temperature (Soil T), soil water content (SWC), and soil respiration rate (Rs) were analyzed during three growing seasons (2014, 2015, and 2017) using linear and polynomial regression models. The results show that the relationship between Soil T and DHA varies significantly depending on the year, implying that the influence of temperature likely depends on the interaction with other abiotic factors. The relationship between SWC and DHA also indicates a highly non-linear character, polynomial models significantly better explain the variability of DHA (R² = 0.641 – 0.92), which indicates that there is an optimal water content in the soil where DHA is most expressed. Analysis of the relationship between Soil T and Rs of the soil shows a positive correlation with pronounced interannual variability. The relationship between SWC and Rs emphasizes the importance of the water regime as a limiting factor for microbial activity. Analysis of the relationship between DHA and Rs indicates a potential mutual dependence of these biochemical processes, but largely dependent on the year and environmental conditions. It can be concluded that DHA and Rs are significantly related to Soil T and SWC, but are not consistent between seasons. Interactions between microbiological activity and abiotic factors show marked non-linearity, which confirms the necessity of using multi-level (polynomial) models in ecological studies of soil processes.

Hans Em Faculty of Forest Sciences, Landscape Architecture and Environmental Engineering

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