Agroecology Lab

 

Plant and Environmental Drivers of Ecosystem Recovery during C4 Grassland Development


PI’s: Sara Baer and Johan Six
Students: Ryan Klopf and Elizabeth Bach
Participants: Clinton Meyer
Funded by the Mellon Foundation


In tallgrass prairie, above- and belowground net primary productivity are the primary sources of energy for belowground microbial communities that, in turn, mineralize nutrients required for plant growth. Factors that control productivity and nutrient cycling in tallgrass prairies have become increasingly understood in the past two decades. However, the majority of the tallgrass prairie ecosystem (>95%) has been replaced by row-crop agriculture. The conversion of these agricultural systems to native grassland vegetation has become widespread. The spatial and temporal extent of developing grasslands dominated by C4 species throughout the historic extent of the tallgrass prairie ecosystem presents an opportunity to gain a better mechanistic understanding of factors influencing the recovery of soil organic matter pools, the microbial community, soil structure and consequently ecosystem-wide nutrient cycling.

Numerous studies have documented changes in soil C and N storage resulting from conversion of cropland to native grassland and a few studies have used chronosequences to assess actual recovery rates of these ecosystem processes. However, no studies have used multiple chronosequences, with variation in important state factors, to identify controls on the recovery of belowground processes in developing C4-grasslands. In this project we use four grassland chronosequences, two in each of the western and eastern regions of the tallgrass prairie, to elucidate recovery rates of ecosystem processes as mediated by time, vegetation composition, precipitation, and soil type. We are testing the following hypotheses. 1) Within similar soil textures, faster recovery of total, stable and active soil C pools will occur in the eastern region as a result of greater precipitation. 2) Within a similar climatic region, these C pools will recover faster in soils with finer texture. 3) Increasing conservation of N, as indexed by less available mineral N and greater immobilization rates, will be tightly coupled to recovery of the active C pool. 4) Initial cessation of cultivation will produce the greatest change in soil microbial community structure, allowing for development of a larger fungal component; however, further response in the fungal:bacterial ratio in continually developing grasslands will be regulated by soil water holding capacity, as affected by precipitation, soil texture, and soil organic matter.

For more information contact Sara Baer (sgbaer@siu.edu) or Johan Six (jwsix@ucdavis.edu).