• Energy Research

AbstractForest vegetation and soils have been suggested as potentially important sinks for carbon (C) with appropriate management and thus are implicated as effective tools in stabilizing climate even with increasing anthropogenic release ofCO2. Drought, however, which is often predicted to increase in models of future climate change, may limit net primary productio (NPP) of dry forest types, with unknown effects on soil C storage. We studied C dynamics of a deciduous temperate forest of Hungary that has been subject to significant decreases in precipitation and increases in temperature in recent decades. We resampled plots that were established in 1972 and repeated the full C inventory by analyzing more than 4 decades of data on the number of living trees, biomass of trees and shrubs, and soil C content. Our analyses show that the decline in number and biomass of oaks started around the end of the 1970s with a 71% reduction in the number of sessile oak stems by 2014. Projected growth in this forest, based on the yield table's data for Hungary, was 4.6 kg C/m2. Although new species emerged, this new growth and small increases in oak biomass resulted in only 1.9 kg C/m2increase over 41 years. The death of oaks increased inputs of coarse woody debris to the surface of the soil, much of which is still identifiable, and caused an increase of 15.5%, or 2.6 kg C/m2, in the top 1 m of soil. Stability of this fresh organic matter input to surface soil is unknown, but is likely to be low based on the results of a colocated woody litter decomposition study. The effects of a warmer and drier climate on the C balance of forests in this region will be felt for decades to come as woody litter inputs decay, and forest growth remains impeded.

Indoor farming in the global vertical farming market has been growing by more than 8% annually since 2010 and 31.6% growth is expected by 2025. It promises to be a possible future form of agricultural practices producing local, fresh, high quality, lower-carbon food year-round. Indoor farming experiment was designed to using LED and neon lights and water source of a dehumidifier. Lettuce (Lactuca sativa L. var. capitata) was grown for 12 weeks in a naturally available forest surface soil, including its native biodiversity and biological activity. Two different levels of water supply were used, full- at 66%- and half- at 33% of the total water-holding capacity (WHC100%) of soil. Some of the physical-chemical, and soil-biological parameters, such as dehydrogenase- (DHA) and fluorescein diacetate (FDA) enzyme activities and the most probable number (MPN) of fungi and bacteria were assessed prior to and after lettuce cultivation. Although the abundance of countable microorganisms decreased appreciably by the end of the lettuce experiment, the growth of plants could result in an enhanced soil-biological enzyme activity of the used natural soil. DHA increased 4.2-fold at drought condition, and 2-fold at the optimal water supply. One can conclude that used natural forest soil with great fertility and biodiversity potential can provide a good facility for the indoor lettuce cultivation. Reduction of water supply can be further optimized with the required biomass-production of lettuce.

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).

Biochar is a solid material obtained from reductive, oxygen-free processes, i.e. the thermo-chemical conversion of biomass in oxygen-limited environment. The obtained products have high carbon sequestration potential and strong nutrient-water absorption capacities because of the enlarged carbon surfaces. It is not yet clear how carbon stimulates agrochemical parameters in soil and how those characteristics are developing as time goes on a long-term basis. Samples of ancient (25, 35, 80 years old) plant coal-affected soils were collected in a temperate deciduous forest site located in the south part of the Bükk Mountains (in North Eastern Hungary). Physical-chemical soil characteristics, such as soil pH, cation exchange capacity (CEC), the organic and inorganic nitrogen (NH4+, NH3-) and the available nutrients (P2O5 and K2O), were estimated beside organic matter (SOM) content, measured by two different methods. Levels of polycyclic aromatic hydrocarbon (PAH) compounds in soil and in various biochar samples were assessed in relation with permissible limit values and potential toxicity. Positive correlation was found between the amount of available nutrients, total organic nitrogen content, cation exchange capacity and the age of plant coal-affected soils. The sample soils were exposed to continuous plant coal biochar effect for 25 years, during which macronutrients absorbed and accumulated in the plant coal surfaces. After this period, the degradation of carbon developed simultaneously with the reduction of the amount of available nutrients, till the end of the studied 80-year-affecting period. Measured CEC level indicated positive correlation with nutrient availability and the age of biochar-affected soils. Our results support the hypothesis that biochar in soil can improve its general agrochemical characteristics in relation with its persistence in a specific soil-plant system. Potential PAH content and toxicity of biochar products are key issues of developing proper application rates in sustainable agricultural practices.