The impact of afforestation on soil properties

Over the past hundred years, Hungary's forest area has increased from 12% to 24%, thanks to afforestation efforts. Accordingly, it is crucial to examine the impact of forests on soils.

In our study, we compared 1. a cropland, 2. a 19-year-old pedunculate oak stand, and 3. a 79-year-old pedunculate oak stand at the Szentkirály area of the Great Hungarian Plain to investigate changes in the soil. On adjacent areas with calcareous chernozem soil, undisturbed soil samples were taken every 10 cm down to a depth of 110 cm and analyzed in the laboratory.

By examining the soil pH, it was determined that the soil under the cropland and the young stand was weakly alkaline to alkaline (7.9 (pH_H2O) to 8.6 (pH_H2O)). In contrast, the upper soil layers under the old forest exhibited an acidic pH (5.4 (pH_H2O)). Intensive leaching was observed, affecting the upper 50 cm layer. The soil carbonate content values also corresponded to the pH levels. Based on particle size distribution analysis, the soil was classified as sandy loam, with no differences observed under the various land uses.

The humus content in the soil samples ranged from 0.1% to 3.5%. The lowest humus content (0.1%-1.7%) was found in the cropland, while the highest humus content was observed in the old oak forest, where the top layer contained 3.0% humus. Overall, it can be concluded that the nearly 80 years of afforestation significantly impacted soil development. Leaching intensified, and following the cessation of plowing, organic matter accumulation began in the soils. Field observations also indicated a marked improvement in soil structure. The forest improved the soil properties, creating conditions more favorable for itself.

This article was made in the 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. Some of the tools used during the research were acquired within the framework of the "Investigation of the conditions for the cultivation of wood biomass - GINOP-2.3.3-15-2016-00039" project.