Connecting Undergraduate Conceptions of Biogeochemical Cycles to Earth Systems Thinking Skills

Research has shown the highest level of understanding in the geosciences to be the ability to think about the Earth as a dynamic system. Biogeochemical cycles, such as the carbon nitrogen, and phosphorous cycles, are fundamental constructs linking all components of the Earth system. As these cycles link the major spheres of the Earth system through the movement of matter and energy, they provide a valuable tool to give insight into undergraduate students' systems thinking abilities. This work uses qualitative and quantitative methods to analyze student drawings and descriptions of biogeochemical cycles to understand differences in Earth systems thinking abilities among students of different majors. Qualitative analysis of drawings and interviews revealed that undergraduate students across disciplines tend to hold a "bio-centric" view of the carbon cycle and have more limited conceptions in terms of detail and breadth of the nitrogen and phosphorous cycles. Additionally, drawings revealed a notable absence of the hydrosphere in students' mental models of all three cycles. Students who took more STEM courses and were in more interdisciplinary fields (i.e. geology, science education) tended to have more nuanced (though not necessarily complete) conceptions of these cycles. Quantitative results suggest that students from STEM disciplines draw cycles with significantly more fluxes and reservoirs than their non-STEM peers. Additional analysis also shows that the number of chemistry and biology courses are most correlated to the number of fluxes and reservoirs depicted. Principal components analysis of drawings showed two major archetypes of carbon cycle drawings: bio-centric and geo-centric, with most participants and all non-STEM participants producing bio-centric drawings. This work provides a framework for using qualitative and quantitative approaches to analyze student drawings and emphasizes the importance of biogeochemistry in developing Earth systems thinking skills.