My research aims to understand what creates and maintains biodiversity AND how global change alters those relationships as well as what the consequences of biodiversity and changes in biodiversity are for ecosystem function.
Humans are drastically altering the ecological drivers of most ecosystems; climate change is a global phenomenon, historical disturbance regimes are being modified and often times completely eliminated or drastically intensified, and land-use change and invasion are increasingly the norm rather than the exception.
These changes can have drastic consequences for communities on both the local and landscape level. For example, richness can be lost, species and functional composition can shift, and landscapes can be homogenized.
All these consequences, in turn, affect ecosystem function. Animal communities have numerous ecosystem function including seed dispersal and often control plant biodiversity and plant communities have long been linked to production, stability, and invasion resistance.
Grassland Community Diversity And Composition
Grasslands around the world are maintained by three key drivers - grazing, fire, and precipitation - all of which impact the amount and availability of limiting resources such as light, nutrients, and water. Through numerous studies I have examined the independent and interactive effects of disturbance (fire and grazing), precipitation (amount and pattern), and nutrient availability on plant community diversity and composition. Key elements of my research are understanding how grasslands respond to these drivers, what is the generality of the response seen across all grasslands, and how future changes in each of these drivers due to humans will impact global patterns of grassland biodiversity and ecosystem function.
Landscape Level Community Patterns
Globally, grasslands exhibit patch structure due to various disturbances, and this patch structure occurs over a range of spatial scales. A patch is defined as a region in an environment where the abundance of something (organism or resource) is high. On larger scales, a patch can be a watershed burned by fire or a grazing lawn created by bison. On smaller scales in plant communities, patches are expressed as distinct groupings of species. How these patches are maintained in grasslands is a focus of my research. In addition to the controls of landscape level patterns, I am also keenly interested in the consequences of these patterns on ecosystem properties such as beta diversity, habitat heterogeneity, and stability through time.
Community diversity and composition as well as landscape level community patterns often exert large influence over ecosystem function. Global change does and will continue to have direct effects on ecosystem function, but often ignored are the less immediate and indirect effects which global change has on ecosystem function through the plant community. The long-term impacts of any global change driver on ecosystem function cannot be fully understood until the plant community response and its effect on ecosystem function is incorporated into the process. Currently, I am working on several collaborative projects which elucidate the importance of this linkage.
Tropical Forest Ecology
Tropical forests worldwide are being emptied of their animals. Of these, the forests of Central Africa have withstood forces of defaunation the longest, largely because of their remoteness and relative lack of industrial exploitation. However, most Central African forests are now locked up in logging concessions and under growing pressure from infrastructure development and extractive industries (palm oil, agriculture and mining), which in turn greatly increase hunting pressures due to increased human encroachment on once remote forest areas. The greatest potential to alter conservation outcomes in this setting lies in our ability to understand and manage the incremental decline of animal species and gradual shifts in forest plant communities throughout the process of defaunation. Currently, in collaboration with Dr. John Poulsen, I am examining how human induced global change is altering large animal (birds and mammals) and plant community dynamics in Gabon. (Photo Credits: Cooper Rosin)