Exploring the biogeography of herbivore – plant community interactions and ecosystem functioning

Background/Question/Methods

Biotic interactions shape landscape-scale ecosystem processes, thus understanding the connections between the biogeography of interactions and ecosystem function will enhance our ability to inform management decisions. The presence of herbivores, via their interaction with plant communities, can alter fire regimes. However, it is less clear if the impact of small mammals, which are common in managed ecosystems, on fire regimes is similar to that of herbivores like elephants. Using a rodent-exclusion manipulation, we found the presence of small rodents reduced the amount of area burned during a fire by 61% (F = 209.38, p < 0.001), indicating rodents can alter how a fire disturbance moves through an old-field ecosystem in the United States. However, plant response to herbivory is not globally constant; it would follow, therefore, that herbivore effects on fire regimes depend upon a combination of local mitigating factors. By building a global-scale database to explore how mammal-plant interactions may vary globally I will discuss: (1) are there global patterns in rodent-plant community interactions; (2) are there global patterns of large herbivore effects on fire regimes; (3) will combining the results from my first two questions provide insight on how rodents may influence ecosystem response to changing fire regimes.

Results/Conclusions

Preliminary data indicate that the effects of large herbivores on fire regime are highly dependent upon grazer type, precipitation, and past land use history across ecosystem-types. These results suggests that the current research approach that seeks to predict how species, and ultimately ecosystems, will respond to climate change without considering interactions is flawed and may lead to poor management decisions. Thus integrating interactions into predictions will better inform local, regional, and global conservation strategies (e.g. ecosystem maintenance) and management choices (e.g. timing of prescribed fires).