Aridland Soil and Plant Ecology
Our soil ecology research is motivated by the fact that soils are the most understudied component of the Earth system and yet have enormous impacts on its function. Our research seeks to understand the ecology and biogeochemistry of soils, especially how soil carbon moves in soils across time and space, and what factors lead to these changes, particularly in aridlands encompassing over 40% of the Earth's terrestrial surface. In aridlands, soil biogeochemical activity in the region occupied and in close proximity to an individual vascular plant (e.g., shrubs and trees) often increases creating what are known as ‘resource islands’ or ‘islands of fertility,’ especially relative to plant interspaces. Resource islands are formed through interactions and feedbacks that occur between a plant and its proximate environment in arid ecosystems. Over time, these interactions make the habitat supporting an individual plant increasingly favorable for biogeochemical activity and the area outside the plant’s sphere of influence relatively less suitable for vascular plant establishment.
In aridland ecosystems, most of the SOC in aridland ecosystems is stored belowground but at significantly great depths (3 m and greater), ranging from 56 to 69 tons-C ha^-1; values approximately two times greater than aboveground pools. On a per hectare basis, organic SOC pools in aridlands are not remarkable. Instead, it is the vast area that aridlands occupy on Earth’s surface that makes them notable. On the contrary, SIC pools are indeed globally remarkable. Arid regions contain secondary carbonates, including cemented CaCO3 known as caliche. Carbonates precipitate when rainwater, soil CO2 and calcium react and it has been estimated that nearly 8 x 10^17 g of C is stored as caliche globally. The vegetation present at a particular location influences the formation and dissolution of caliche by affecting soil CO2 concentrations through root and microbial respiration. Soil CO2 can range from 10 to 100 times greater in the rhizosphere than the atmosphere, particularly after precipitation events in aridlands, and as a result of root and microbial respiration and decomposition. Consequently, changes in aridland ecosystems aboveground (e.g., removal of shrubs and trees), directly impact soil ecology and biogeochemistry belowground, which can have a major impact on soil carbon and ultimately, the global C cycle.