Spatio-temporal patterns of soil organic carbon and pH in relation to environmental factors-A case study of the Black Soil Region of Northeastern China

The Northeastern Black Soil Region plays a key role in food supply in China. Identifying spatio-temporal variation of soil properties as influenced by environmental factors has become essential for future agricultural development. A total of 5891 topsoil samples (0-20 cm) were collected and soil organic carbon (SOC) and pH were measured in the Jilin Province. Geostatistics, multiple linear regression, and redundancy analysis (RDA) were used to highlight the spatio-temporal patterns of SOC and pH and determine the relationship with environmental factors. Results showed that from 1980 to 2010 average level of SOC increased by 2.68 g kg−1 (p < 0.001). However, in the Golden-Maize-Belt Counties (i.e., the major grain-producing areas of the Jilin Province), the SOC content rapidly decreased, the largest drop reaching 24.83 g kg−1. Over the past thirty years, pH values slightly increased (0.30; p > 0.05) throughout the province. Environmental factors could explain 64% and 78% of the spatial patterns of SOC and pH, respectively. The principal factors impacting SOC and pH included: precipitation, gully density, forested land and grain yield. There was significant covariation between natural and human factors in forming these spatial patterns. Anthropogenic disturbance had a larger influence on the distribution of SOC than on the distribution of pH.