Print PageMany biogeochemical systems are by definition complex adaptive system because they meet four criteria: (1) the system consists of diverse agents, (2) the agents are connected, (3) the agents are interdependent, and (4) the system adapts in response to perturbations. Greatly magnified images of soil microorganisms in arid and semiarid soils, as well as lab and field experiments, indicate that soil calcium carbonate is biogenic, at least in part. The biological formation of soil carbonate was investigated to determine if this process is a complex adaptive system. (1) Diverse agents include calcium, carbon dioxide, bicarbonate, pH, water, microorganisms, root hairs, Ca-silicate minerals, atmospheric dust, plants, and climate. (2) Connectivity of the agents was determined with fungal traps and microscope slides inserted into soils. (3) Interdependency was assessed by manipulating Ca and glucose supplies. (4) Adaptability was determined by measuring the amount of calcite formed by soil microorganisms.
Results/Conclusions
Within three weeks soil fungi in both arid and forest soils produced calcium carbonate crystals when supplied with calcium acetate agar. The results reveal that the agents are connected and interdependent and that calcite biomineralization is an adaptive complex system ultimately linked to continental scale biomes and global climatic regions. Because soil carbonate is the third largest C pool in the active global carbon cycle, containing at least 800 x petagrams of carbon, thus exceeding the amount in the atmosphere (ca. 750 petagrams) or in land plants (ca. 560 petagrams) viewing soil carbonate as a biological complex adaptive system can advance our understanding of the global carbon cycle and carbon sequestration as inorganic carbon.
