Relationship between spatio-temporal evolution of soil pH and geological environment/surface cover in the eastern Nenjiang River Basin of Northeast China during the past 30 years

Abstract

Soil pH plays an important role in crop growth and soil fertility. The status, variations and controlling factors of soil pH are of great significance to understand soil acidification and alkalization processes and to make decisions on maintaining soil productivity and ecological functions. In this paper, we analyzed the distribution and spatio-temporal variation characteristics of soil pH in the Nenjiang River Basin and the geochemical driving mechanism of soil pH distribution pattern, based on the National Multi-objective Regional Geochemical Survey data of topsoil, the Second National Soil Survey data and Normalized Difference Vegetation Index (NDVI). The results demonstrated that the topsoil pH had changed from neutral and alkaline levels to acidic and strongly alkaline levels in the past 30 years. NDVI decreased with the increase of soil pH when soil pH > 8.0, and decreased with the decrease of soil pH when soil pH < 5.0. There were significant differences in soil pH with various surface cover types. The weathering products of rocks and minerals rich in K2O, Na2O, CaO and MgO from the Daxing'an Mountains and Xiaoxing'an Mountains entered into the southern low plain and were enriched in different parts by water transportation, river and lake deposition.