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Simple Summary: Global climate change has a significant impact on soil decomposition processes through the alteration of temperature and precipitation and, in connection with them, through changes in the quantity and quality of biomass production in ecosystems. The role of soil organic matter (SOM) is particularly important, as the consequences might rapidly affect soil carbon stocks. These processes have a global impact on the CO2 content of the atmosphere and a local impact on the fertility of soils. In our research, which is based on a transcontinental litter manipulation, detritus input, and removal treatment (DIRT) project, we investigated how quantitative and qualitative changes in litter inputs can affect decomposition processes and carbon storage capacity of soils in relation to SOM content. The main question of the study is how various litter treatment sites respond to additional and/or removed organic matters through assessed soil-biological parameters. The changes were monitored with some potential soil-biological indicators, such as through examining enzyme activity, CO2 emissions, and labile carbon stocks (POXC) used by organisms in performing decomposition processes. The model experiment provided a great background highlighting organic matter's importance in soil-biological processes and soil ecosystem functioning. Soil organic matter is a biological system that functions as an integrated whole. These assemblies have different properties, functions, and decomposition times. SOM is one of the main determinants of soil productivity. Our studies were carried out in a temperate deciduous oak forest on Luvisols soil. In the DIRT Project (Detritus Input and Removal Treatments), the following treatments were applied: Double Litter, Double Wood, Control, No Litter, No Root and No Input. Our objective was to compare the effect of withdrawal or doubling of organic matter on the protein pattern of the soil and the biological activity and changes in labile C (permanganate-oxidizable carbon) content in a long-term organic matter manipulation experiment. Patterns of thermostable proteins, soil dehydrogenase enzyme activity, CO2 emission, and POXC content were measured at the most biologically active soil depth of 0–5 cm after 23 years of treatment. Our results show that the enzyme activities of the litter removal treatments were significantly reduced compared to the doubling treatments, as were the values of soil respiration. The same significant difference was also detected in the C content of the soils of the treatments. Based on cluster analysis of the protein profile of the soil samples, the No Litter and No Input treatments were significantly different from the other treatments. This shows that specific organic matter is needed to enhance soil biological activity and the associated POXC content. [ABSTRACT FROM AUTHOR]

Carbon in soil is one of the most important indicators of soil fertility. Part of the carbon stored in them is returned to the atmosphere during soil respiration. Climate change and inappropriate land use can accelerate these processes. Our work aimed to determine how soil CO2 emissions change over ten years as a result of litter manipulation treatments. Plots at the Síkfőkút DIRT (Detritus Input and Removal Treatments) experimental site include doubling either leaf litter or wood, and removing all aboveground litter, all root inputs, or removing all litter inputs. With the help of this, we were able to examine not only the effects of the different organic matter intake but also the effects of the different microclimates that occur as a result of the treatments. Total soil respiration (root and microbial respiration) is a result of a persistent lack or excess of soil organic matter relative to soil moisture. Based on our studies, the increase in the intensity of root respiration on wetter soils was only half of the increase in respiration associated with decomposition activity. The sustained growth of leaf litter significantly increases soil respiration, which can be partly explained by the more favorable supply of nutrients to the decomposing organisms, and partly by the more favorable microclimatic conditions, however, these effects were only valid in the case of wetter soils. In the dry summer environment, we experienced higher CO2 emissions during litter removal treatments. In the first period between 2002 and 2004, even wetter root removal treatments showed a significantly higher CO2 emission, while in the period 2010–2012, surface litter removal treatments. The permanent removal of surface litter in the drier summer period resulted in the formation of a dense crack network, which increased the CO2 emission of these soils, which increases the soil organic carbon loss of the soil. Our study proves the advantages of mulching in terms of a more favorable microclimate of the soil surface and a balanced carbon balance of the soil–plant system. [ABSTRACT FROM AUTHOR]

Soil organic matter supply is mainly derived from plant litter. The early stages of litter degradation is a very dynamic process. Thus, its study is important for understanding litter degradation and the control factors of different biomes and ecosystems. In the frame of the Síkfőkút DIRT (Detritus Input and Removal Treatments) Project, the effect of organic matter treatment was studied on the rate of decomposition of organic matter by applying different kinds of organic materials (leaf and wood litter, green and rooibos tea material, and cellulose cotton wool). During long-term experiments, we intended to investigate how the different organic matter manipulations changed by the soil microbial community and how it affects the degradation of different quality organic matter in the soil. The important main purpose of the research was to investigate litter degradation and its main regulators, contributing to both current and future climate scenarios. According to our results, in the case of litter-doubling treatments, we experienced a greater loss of organic matter compared to the weight of the litter bags placed in the soil of organic matter-withdrawal treatments. Furthermore, based on our results, we found that the decomposition rate is influenced by litter quality (leaf and cellulose wool) that is to be decomposed and by the applied litter treatments depending on the time allowed for decomposition. A drier climate by slowing down the degradation processes and by increasing the proportion of recalcitrant molecules in the detritus may increase the turnover time, which may lead to an increase in soil organic carbon (SOC). [ABSTRACT FROM AUTHOR]