Carbon stock of the Gemenc forest (Hungary)

We made our investigation in the Gemenc forest, which is situated beside the Danube river near the southern border of Hungary. Mainly the Danube and in the last decades, watercourse management played a significant role in landscape evolution. Most of the area is on the saved side today, so it doesn’t get flooded. The Danube usually brings calcium carbonate to this area with its sediment. The flooded areas are built from fine sediment materials. Meadow soils rich in calcium carbonate are characteristic, and the forests of this land grow healthy here (assuming that are high-quality forest types). Farther away from the river, higher plains have sand with humus soils and Chernozem soils.

Forest ecosystems of this area are probably one of the most important members of the continental vegetation that stores carbon. Because of their size, they take huge part of the global carbon cycle. The amount of carbon stored in the soil – similar to the carbon stored in wood- and the consequences of human activities on this carbon are less known in Hungary. The reason for this is the small amount of information we have about this topic. During our examinations, we visited six Quercus petraea and Robinia pseudoacacia forests and measured the carbon stock of those forest soil besides the determination of water holding capacity. The humus content of the examined soil samples varied between 0.7 and 6.9 %. Since the study areas are no longer or rarely affected by flooding, the highest organic matter content was found in the topsoil layer for each sample. SOM content gradually decreased with depth. The effect of flooding is clearly shown by the fact that we found organic matter in the samples even in the layer below 100 cm, and in several cases, we found buried humus levels. Accordingly, the organic carbon stock of these soils may be higher than average. However, the decreasing number of floods endangers the vitality of forest stands. With less flooding, decreasing groundwater level, and an increase in the temperature at night, dew formation becomes more limited, and evaporation increases. These changes also affect the decomposition processes taking place in the soil, the circulation of nutrients, and soil respiration. Increasing temperature, the speed of decomposition, and the intensity of soil respiration increase, which can further increase the decrease in the soil's C pool.

This article was made in frame of the project TKP2021-NKTA-43 which has been implemented with the support provided by the Ministry of Innovation and Technology of Hungary (successor: Ministry of Culture and Innovation of Hungary) from the National Research, Development and Innovation Fund, financed under the TKP2021-NKTA funding scheme.