Comparison of Polish and Hungarian floodplain soils’ reaction to the climate change

We made our investigation in the Gemenc forest, which is situated beside the Danube river near to the southern border of Hungary. Mainly 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 CaCO₃ to this area with its sediment. The flooded areas are built from fine sediment materials. Meadow soils rich in CaCO₃ 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. On our Polish investigation we took samples from the northern floodplains of Vistula, in 2 different areas, which located on the saved side. Overall the samples were very similar to the Hungarian ones.

Forest ecosystems of this area are probably one of the most important members of the continental vegetation that store carbon. Because of their size, they take a huge part of the global carbon cycle. During our examinations, we visited six Quercus petraea and Robinia pseudoacacia forests and took samples from the soil profiles 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.

In the Polish samples, the SOM varied between 0,4 and 20,9 %, with an extremety of a soil with peaty features. The ph varied between 2,0 and 8,0, with the former also being the „extremety”, otherwise the avarage value being 7,7. If we compare the two study areas, we can conclude that the soils themselves are less vulnerable to the effects of the climate change, due to the differences in the microclimate, the precipitation and the evaporation

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.