Global climate change will lead to a decrease in the erosion resistance of Polissya and Forest-Steppe soils

Abstract

Soil erosion is an ecological process leading to both soil degradation and soil fertility reduction. The USLE empirical model incorporates the soil erosion index (K-factor), describing the susceptibility to soil erosion, which depends on the structural stability of soil aggregates. The article evaluates the spatial variability of the erodibility factor across Polissya and the Forest-Steppe regions of Ukraine and forecasts the changes in this indicator in the near-, medium- and long-term. The assessment of the soil erodibility factor K for the period 1970–2000 suggests that this indicator was at the level of 0.11 ± 0.013 t•ha•h•/ (ha•MJ•mm). The organic matter content is an important factor determining the soil's sensitivity to erosion. The highest stocks of organic matter in the region were observed in the northern part of the territory, due to the accumulation of organic matter caused by waterlogging of soils and extensive swamping processes. In agricultural areas, relatively low soil organic matter content was observed in some landscapes in the centre, south and west. The dependence of soil organic matter content on bioclimatic variables was established to predict the trend of changes in the soil erodibility factor K over time due to global climate change. Regression analysis was able to explain 79% of the variation in soil organic matter content. The statistically significant predictors of soil organic matter content were annual mean temperature, temperature seasonality, mean temperature of the wettest quarter, mean temperature of the warmest quarter, precipitation of the wettest month, precipitation of the wettest quarter, precipitation of the warmest quarter. The application of the predicted values of bioclimatic variables provided an opportunity to predict the content of organic matter in the soil and calculate the value of the soil erodibility factor K in the future. The forecast indicates that climate change is expected to result in a reduction of soil organic matter content by an average of 26.7% in 2021–2040, which would also lead to an increase in the soil erodibility factor K by 3.6%. In 2021–2040, the regional minimum organic matter content will shift from the southwest to the central part of the region. The zone of lowest erosion will decrease significantly and will be located only in the north-west of the region. The zone of highest erosion will spread in the latitudinal direction from east to west. In the period 2041–2060, climate change will not lead to significant changes in the content of organic matter in the soil, and, accordingly, the values of the soil erodibility factor K will not change significantly. The regional minimum of soil organic matter content will be observed in the southeast, and the regional maxima of soil organic matter content will be observed in the northeast and southwest. The regional minimum of soil erosion will remain virtually unchanged in the north-west of the region. In the period 2061–2080, climate change will also worsen the situation, and compared to 2041–2060, the organic matter content in the soil will decrease by 15.1%, resulting in a 1.6% increase in the soil erodibility factor K. The regional minimum of organic matter content will shift to the north and north-east. The regional maximum of soil erosion will spread in space. The differential approach allowed us to better reflect the trends in soil erosion. In the period from 1970–2000 to 2021–2040, the largest increase in soil erosion will occur in the north of the region. A decrease in erosion will occur in the south-west of the region. In the following period, the area of increased soil erosion will be localised in the east of the region. In the period up to 2061–2080, the area of increased soil erosion will cover the north and south-west of the region. Soil organic matter stock is a risk factor for increased soil sensitivity to erosion in the sense that a larger stock can be reduced to a greater extent. Thus, in the coming decades, the Polissia region should be considered the most risky in the context of the negative effects of climate change on soil erosion resistance. In the medium term, the deterioration trend will continue in the northeast of Polissia, and in the long term, threats will resume throughout Polissia