Do Soil Properties Influence Successional Trajectories Following the Eradication of an Invasive Grass?.

We used a 7 year post-eradication chronosequence to assess patterns of secondary succession following the local eradication of cogongrass (Imperata cylindrica) from a longleaf pine sandhill ecosystem.  Our findings revealed a general pattern of increasing plant cover, species richness and diversity in the years following eradication. By year 7, cover and diversity were not statistically different from a native reference treatment, although species richness remained lower (13.0 vs. 14.7 species/plot). Despite this apparent recovery, there was little evidence that the composition of formerly invaded sites – even after 7 years – converged with the reference. A Mantel Test and Canonical Discriminant Analysis indicated that certain soil properties (e.g. organic matter, mycorrhizal inoculum, and pH) correlated with successional patterns. PCR clone libraries indicated that substantial alterations to AMF community assembly occurred due to invasion, and novel AMF community characteristics persisted for 3 years following eradication. All measured soil properties (OM, pH, mycorrhizal inoculum, N and P) returned to a reference state within 7 years.  The fact that soil chemical and microbiological properties return to a reference state quite rapidly following cogongrass eradication is encouraging, as it indicates that “legacy” effects are only temporary. That soil properties “recover” before native plant communities suggests that a combination of recruitment and dispersal limitations drives plant community succession following eradication.