Kansas State University

Division of Biology Seminar May 6

Submitted by Division of Biology

Sharon Billings, University of Kansas, will present "Scaling from Small-Scale Experiments to the Critical Zone to explain Ecosystem Patterns of Soil Organic C Dynamics" as part of the Division of Biology Seminar Series at 4 p.m. Friday, May 6, in 221 Ackert Hall. A reception will precede the lecture at 3:30 p.m. on the first floor atrium in Chalmers Hall. 

Illumination of the mechanisms governing ecosystem-scale processes — equivalent to the scale of the critical zone — often requires controlled, mechanistic laboratory studies. However, scaling phenomena observed in small, reductionist systems up to the scale of the critical zone in both space and time is challenging. 

For example, historically agricultural plots at the Calhoun critical zone observatory likely experienced reduced inputs of organic matter deep within the profile for >150 y. Many of those same plots also experienced erosional loss of the original surface horizon. As a result, forests re-growing on former agricultural land are supported by previously deeper horizons whose organic matter stocks are small compared to soil profiles in intact, old-growth hardwood stands.

Given the importance of soil organic matter mineralization for ecosystem productivity, these large-scale features of the landscape likely influence contemporary ecosystem function. However, the fundamental microbial mechanisms linking depth-related variation in soil organic matter characteristics to modern forest C balances remain unclear.

Billings' lab is working across scales to address these issues by conducting microcosm studies of isolated soil bacteria, mesocosm studies of soil organic matter decay and mineralization, and ecosystem studies of altered soil profiles in both upland and lower landscape positions. Using stoichiometric characteristics of eroded and intact soil profiles as guides, the lab is varying the ratios of resources available to bacteria growing at a known rate and quantifying C flow into their biomass vs. CO₂. The lab compares these rate responses to resource ratios with those observed during decay and mineralization of incubating soil organic matter from multiple depths which exhibit similar, natural variation in resource ratios.

Preliminary results from this ongoing project suggest that by working across scales and incrementally increasing the complexity of our experimental systems, we can elucidate some of the fundamental, small-scale mechanisms driving ecosystem processes observed across far greater temporal and spatial scales.

If you would like to visit with Billings, contact Kim O'Keefe at kokeefe@k-state.edu. The seminar is co-sponsored by the Division of Biology and K-State's chapter of Sigma Xi.