Influence of spontaneous silvatization on physicochemical properties of chernozem of extrazonal meadow-steppe plant communities of Botanical Reserve “Makitra” (National Nature Park “Northern Podillia”, Ukraine)

Abstract

Meadow-steppe plant communities of the nature reserve territories of the National Nature Park “Northern Podillia”, in particular, the “Makitra” reserve located outside the steppe zone, as a result of the decrease in economic activity and the effect of the passive protection mode (absolutely reserved regime) of rare plant species populations are under the threat of spontaneous afforestation and may lose their original purpose. The changes that accompany the sylvatization process concern all components of the biogeocenosis. In the process of degradation of the grass phytocenosis, the morphological features and physical and chemical properties of the soil undergo changes too. Soil profiles were taken on the northeastern slope of Makitra Mountain, in the meadow-steppe plant association. We revealed that 12–15 years after the beginning of afforestation with Scots pine, chernozem under the primary meadow-steppe plant association possesses apparent signs of degradation throughout the depth of the profile: (1) degradation of surface organogenic horizons (Hc + Hd); (2) lowering the depth of the carbonate level in the profile by 10–15 cm; (3) loss of organic matter by 30–50 %; (4) reduction of cation exchange capacity by 15–20 %; (5) leaching of CaСО3 (>50 % from the H horizon) and other macro- (K, Na, Mg, Fe, Al) and trace elements (Cu, Zn, Mn, Ni, Pb) (up to 10–30 %). The intensity of leaching processes at the study time-point remains high, evidenced by the higher content of amorphous silica, aluminum, and water-soluble carbon in the soil at the afforestation stage, compared to virgin chernozem. The obtained results provide basics for predicting the soil development from typical chernozem under virgin meadow-steppe phytocenosis to leached chernozem (forest chernozem according to Travleev (2008)) in the process of overgrowing with Scots pine. In both cases, the soil-forming process is still within the framework of the humus-accumulative process of soil formation. However, taking into account the high intensity of degradation processes detected at the time of the research, there is a possibility of a significant increase in signs of leaching, which will indicate an impact on the development of the soil profile together with the chernozem (accumulative) and podzolic soil-forming processes.