Global trends in soil monitoring research from 1999–2013: a bibliometric analysis

A bibliometric analysis of soil monitoring during the period of 1999–2013 was performed based on Science Citation Index Expanded and Social Science Citation Index databases. The measuring parameters included scientific outputs, subject categories and major journals, international collaboration and geographic distribution of authors and countries, keywords, and hot topics. This research demonstrated a significant increase in the field since 1999. The USA was the largest contributor, generating 26.7% of the total articles with a total number of cited times per paper (CPP) of 17.4. The USDA ARS was the most productive institute with a CPP of 19.0. Hot topics were classified into two major groups according to the author keywords analysis: (1) monitoring objectives and indicators, e.g. climate change, land use and agriculture, soil moisture and heavy metals, which reveal the relationships between the soil and environmental factors; (2) monitoring techniques and monitoring scales, e.g. remote sensing and integrated ‘3S’ techniques, and the varied scales aiming at the comprehensive detection of various soil attributes change. We found that environment policy should be formulated regarding heavy metal pollution which raised great concern about soil monitoring. Biodegradation and bioremediation were popular methods to restore the changes in microbial communities, soil water quality, soil organic matter and inorganic matter. What is more, the integration of ‘3S’ techniques at a regional scale guaranteed the rapid data acquisition and facilitated soil mapping and its spatio-temporal pattern analysis, which should be a future research direction.