Our current research focuses on how multiple, co-occurring forms of environmental change impact soil biology and biogeochemistry. Our work focuses on two "extreme" ecosystems: the Sonoran Desert and Antarctica, but also extends beyond these two systems to gain a broad-scale perspective on biogeochemical processes.
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Check out our two themed research blogs:
Ecological Succession after Glacial Retreat in Antarctica
As Antarctica is warming with climate change, glacier retreat is leading to expansion of ice-free areas. Primary succession occurs in these newly exposed areas, and eventually vegetation establishes, ultimately driving future community structure and ecosystem processes. Yet, the mechanisms of primary succession in terrestrial Antarctica are poorly understood. Once established, plants can profoundly alter ecosystems, driving soil, water, and biotic processes. However, despite advances in understanding these interactions in the Arctic, we know virtually nothing about how inter-specific variation in plant functional traits works to influence terrestrial biogeochemistry, soil functioning, and soil communities in Antarctica.
We are conducting a multi-year experiment that explores how plant colonizers across successional stages influence soil communities and beiogeochemical fluxes. Our data will be the first comprehensive measures of the relative importance of plant functional types during glacial retreat and vegetative expansion from climate change in Antarctica. Understanding these processes are critical to understanding how plant functional group diversity and abundance are changing in a greening Antarctica and how soil communities and processes are influenced by these expanding plant communities.
Urbanization in the Sonoran Desert
In the Sonoran Desert, the Phoenix metropolitan area is home to 4.6 million people and is one of the largest and fastest-growing metropolitan areas in the U.S. Such rapid urbanization and human activity leads to alterations in biodiversity, environmental chemistry, and local climate. We are working with the Central Arizona-Phoenix Long-Term Ecological Research (CAP-LTER) to understand the impacts of urbanization on soil biology and biogeochemistry in the Sonoran Desert in and surrounding the Phoenix Metropolitan Area.
The Sonoran Desert is experiencing multiple concurrent forms of environmental change associated with human activity, including atmospheric nitrogen deposition, species invasions, urbanization, and altered precipitation patterns associated with climate change. We are working on a variety of projects that investigate how these human-induced changes influence soil biological communities and biogeochemical fluxes, such as soil respiration plant litter decomposition. In doing so, we are also investigating the underlying mechanisms for biological processes that are often poorly-understood in dryland ecosystems.
Using CAP-LTER's long-term Desert Fertilization Experiment, we are studying the consequences of atmospheric nitrogen (N) deposition, which is increasing due to fossil fuel combustion and agricultural sources. Most research about the impacts of nitrogen deposition has been conducted in more mesic ecosystems, such as forests and grasslands, not in desert ecosystems. The growing body of work on desert ecology suggests that the consequences of nitrogen pollution in deserts differ from our current understanding, but are not well understood. We are investigating the impact of excess nutrients on soil biological processes, such as microbial respiration, uptake into biocrusts and plants, and subsequent recycling during decomposition.
Soil Biodiversity in Maritime Antarctica
The Antarctic Peninsula is experiencing rapid environmental changes, which will influence the community of organisms that live there. However, we know very little about the microscopic organisms living in the soil in this region. Soil biology (including bacteria, fungi, and invertebrates) are responsible for important biogoechemical processes that sustain ecosystems. Without understanding the environmental conditions that influence soil biodiversity along the Antarctic Peninsula, our ability to predict the consequences of global change is strongly limited. We are working to identify the soil community along a >2,000 km transect spanning 60-75°S along the Scotia Arc and Antarctic Peninsula to discover how the microscopic soil community changes with the severity of environmental conditions, and how this relates to the plant community generating those soil conditions. Understanding more about the ways in which plant cover and climate conditions influence soil biodiversity will allow us to predict how communities will respond to future changes such as climate warming and invasive plant species. Thus, not only are we increasing our understanding of Antarctic soil biogeography, but also describing the nature and strength of plant-soil linkages in influencing soil community composition and diversity over local-to-regional spatial scales.
The Chemistry of Plant Litter Decomposition
Decomposition of plant litter is a fundamental ecological process, integral to energy flow in foodwebs, biogeochemistry and soil formation. As such, it's a process that has been studied in ecosystems for decades, yielding copious amounts of information about what drives the rate of litter decay. Much of our research explores the less-studied aspects of decomposition, including late-stage chemical dynamics and processes across the litter-soil interface.
Much of our understanding of decay dynamics focuses on rates of litter mass loss and therefore carbon dynamics, with relatively less exploration of the
chemical nature of litter decomposition. Additionally, most studies that incorporate litter chemistry focus only on initial chemistry as an indicator of how litter will behave throughout decomposition. This limits our understanding of later stages of decay, which are important for long-term ecosystem processes and biogeochemical cycling. We are using archived litter decomposition samples and data to investigate the trajectory of a comprehensive array of litter chemistry, including nutrient, structural, and metabolic parameters, across a wide variety of plant functional types and ecosystems. The results from this project will significantly expand our understanding of the nature of litter chemical changes throughout decomposition, thus informing the design of future experiments
and models of litter decomposition.
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