Current research
Woody encroachment influences on carbon and nitrogen pools and processes
There has been a dramatic increase in the abundance and cover of woody plants (trees and shrubs) in grasslands and savannas globally over the past century. This proliferation of woody vegetation, as well as management approaches to combat it (e.g., prescribed burning, herbicide application, and mechanical removal), may affect local, regional, and global C and N cycles. We are currently involved in several different projects that use field studies and ecosystem modeling to explore how woody plants affect C and N pools and processes. We are particularly interested in the role of spatial and temporal heterogeneity in these systems and soil C stabilization processes.
Examples of this research:
Dryland decomposition
Litter decomposition is an important biogeochemical process. The controls over decomposition are poorly understood in arid and semi-arid systems (drylands) relative to mesic systems. Recent work suggests that abiotic drivers of decomposition such as UV photodegradation and soil-litter mixing may play a unique role in dryland decomposition. We are conducting a series of laboratory and field experiments to explore these drivers.
Examples of this research:
Global change influences on arid systems
Dryland systems are expected to be strongly affected by future changes in climate. We have several projects exploring the impacts of changing precipitation regimes on plant ecophysiology, litter decomposition, and carbon cycling. For example, we have found that increasing aridity may lead to greater heterogeneity in biogeochemical cycling between woody canopy and intercanopy microsites. Our lab is currently investigating the impact of precipitation exclusion and addition on microbial community function by using rainfall exclosures. We are also working across rainfall gradients in Australia and Namibia to understand moisture controls over carbon cycling.
Examples of this research:
Soil biodiversity impacts on ecosystem processes
Recent work has made such progress understanding relationships between plant diversity and ecosystem processes. In contrast, we have very limited understanding of impacts of soil organism diversity. Losses of soil biodiversity appear to strongly impact soil C cycling processes, although teasing diversity impacts are complicated by methodological concerns, including different possible classifications of diversity for difficult-to-study soil organisms (e.g. taxonomic, function, body size).
Examples of this research:
Animal influences on ecosystems
We are interested in how animals - from arthropods to large mammals - affect ecosystem processes. Past work in this area include insect herbivore responses to atmospheric nitrogen deposition, the role of herbivory in plant invasions, small mammal impacts on soil carbon pools, and animal impacts on leaf litter decomposition.
Examples of this research:
