The unifying conceptual framework driving our understanding of the tallgrass prairie ecosystem (and other mesic grasslands) considers fire, grazing and climatic variability as essential and interactive drivers responsible for the structure and function of this biome. The interplay of this biotic and abiotic template across a heterogeneous landscape leads to the high species diversity and complex, non-linear behavior characteristic of grassland ecosystems and the species therein. Two specific research questions highlight changing climate-management practices and ecosystem responses in tallgrass prairie. First, infrequent burning and the presence of large grazers alters microclimate conditions (cooler/wetter) and the physiological responses of plant species compared to frequently burned, ungrazed prairie. Second, shrub encroachment in tallgrass prairie results from altered land-use practices, similar to other grassland and savanna ecosystems worldwide.
Results/Conclusions
To address Q1, we used a sensor-network installed along a topographic gradient at the Konza Prairie (KS, USA). Data from 2008-2010 showed climate-carbon and -water flux patterns as a function of scale and landscape management. To address Q2, we assessed resource-competition in the grass-shrub ecotone. Results from 2009-10 link varying soil water provenance utilized by the two growth forms, temporal differences in canopy development, and litter produced as synergistic drivers promoting shrub expansion. Taken together, these results illustrate how changes in the frequency and magnitude of the biome drivers (fire, grazing, climatic variability) alter species composition and energy flux in tallgrass prairie.
