Ants (Hymenoptera: Formicidae) and earthworms (Oligochaeta) are considered ecosystem engineers because they form biogenic structures in the soil that modulate resource supply.  The importance of these consumers in ecosystems is well established, but the recovery of ants and earthworms in response to restoration following long-term disturbance is poorly understood as grassland restoration is typically focused on planting historic vegetation.  Understanding the recovery dynamics of belowground engineers is needed to evaluate their potential role in the restoration of ecosystem properties and processes during grassland restoration on formerly cultivated soil, as ants and earthworms influence soil structure and function.  Our objectives were to: quantify changes in the abundance of ants and earthworms across a chronosequence of restored prairie, and elucidate whether recovery of these groups is associated with changes in key plant and soil properties (i.e., aboveground net primary productivity, root biomass, litter, soil carbon, and plant richness).  Soil monoliths were extracted from currently cultivated fields (n=2), restored prairies ranging from 1-21 years in age (n= 17), and native prairie remnants (n=2). 

Results/Conclusions

Ant abundance peaked in the 8 and 9 year old restorations (P<0.05, r²= 0.44) and abundance was 198 times greater than cultivated fields and > 3 times greater than remnant prairie during this peak abundance period.   Earthworm abundance increased across the chronosequence (P=0.01, r²=0.31) and sites restored for >20 years contained >2 times the density of earthworms than cultivated fields and a density within the range of native prairie.  Earthworms also exhibited a seasonal differences in abundance, with greater in the fall than spring (P= 0.03).  Earthworms showed no response to any of the measured soil and plant properties, but ant abundance was positively correlated with plant richness (P=0.02).  These results demonstrate concomitant recovery of ants and earthworms with the restoration of tallgrass prairie vegetation within a decadal time scale.  Furthermore, restoration practice that aims to promote plant diversity may also benefit the abundance of some belowground engineers (i.e., ants).