Researchers indicate that soil rock fragment is a critical but unquantified factor affecting terrestrial carbon and nitrogen cycles
Rock fragment (RF) is defined as the mineral particles with diameter > 2 mm, and is widely distributed in the soils over the world, especially in mountainous areas. During recent decades, because of the increasing demand of agricultural land, soils in mountainous areas which contain significant amounts of RF have been intensively converted for agricultural uses, and caused serious environmental issues. Accordingly, roles of RF on soil physical, chemical and biological processes have received a growing attention.
However, few previous studies focused on the possible relationships between RF and soil carbon (C) and nitrogen (N) cycles. RF has been widely documented affecting soil hydraulic properties and hydrological status, temperature and soil C and N stocks, which are key factors controlling soil C and N biogeochemical and physical processes. Therefore, assuredly, RF can exert great influences on soil C and N cycles.
Based on the above cognition, researchers led by Prof. ZHU Qing from Nanjing Institute of Geography and Limnology of the Chinese Academy of Sciences reviewed and summarized the possible effects of RF on soil C and N cycles, discussed the limitations in mechanisms and approaches to accounting for RF in soil C and N cycles, and proposed the solutions for future consideration of RF in soil C and N cycling research. This review was published in Geoderma.
In this review, researchers concluded that RF can directly and indirectly affect the soil C and N cycles, through affecting soil C and N stocks, hydrology, temperature, and via chemical weathering that releases C, N, cations and anions, consumes CO2 and regulates pH. Therefore, to better describe the soil C and N cycles and their responses to global change, it will be critical to incorporate information of soil RF in experiments as well as statistical and process models.
Researchers proposed three key points for investigating the roles of RF on soil C and N cycles. Firstly, new and improved mechanisms and approaches for sampling, measuring and mapping are needed to quantify the effects of RF. Secondly, the influencing mechanisms and evolutions over time of RF should be together used to improve mechanism investigations and model simulations that span spatial and temporal scales. Thirdly, studies on the effects of RF should be deployed from the perspective of earth’s critical zone, and upscaled to the global perspective to investigate the roles of RF on global C and N cycles and future changes.
This review will improve our understandings of RF and terrestrial C and N cycles, and their responses to global changes.
Fig. 1 A conceptual framework for investigating the roles of RF on terrestrial C and N cycles from the scope of earth’s critical zone to global scale. (Image by LAI Xiaoming)
Nanjing Institute of Geography and Limnology