Biological weathering in model systems across scales

Plants and microorganisms derive mineral nutrients needed for their development and growth from dissolution of the minerals present in the soil. There is strong evidence that plants and microorganisms can increase the weathering and nutrient supply through active and passive mechanisms. However, biological weathering is challenging to quantify, particularly in natural systems, due to complex interactions between rock/parent material, hydrology of the site, and biota. Because of this, model experimental systems are often used to examine weathering in general and biological weathering in particular. This presentation focuses on several experiments that examined rock weathering as influenced by biota – non-vascular and vascular plants, free living microorganisms, and microorganisms in symbiotic relationships with plants – across different space and time scales from small mesocosm experiments to Landscape Evolution Observatory, a facility at the University of Arizona Biosphere 2 with three replicate 30 by 11 m hillslopes. The majority of these studies represent incipient weathering, where unweathered rock is used as a medium for plant growth. We will discuss evidence for biological weathering, partitioning of weathering products, and fluxes of CO₂ related to weathering processes. Influence of natural succession and biological complexity on weathering will also be discussed.