After the dust has settled: Long term plant community impacts of explosive soil contamination

Background/Question/Methods

Soils contaminated with explosive compounds, a global concern, pose a number of threats to all levels of biota. Many of the studies which have focused on explosive compounds in the soil investigate individual or species level impacts while the larger plant community questions are often ignored. Our goal was to fill that gap and investigate impacts on community structure and diversity in an area contaminated with three explosive compounds/mixtures (RDX, TNT, Composition B). Community data were collected from an experimental minefield. The site was cleared 16 years ago, contaminated with explosives, and allowed to revegetate naturally. Plots within contaminated and reference sites were established. Woody and herbaceous species presence/absence was recorded and from which species diversity and richness were calculated. The presence/absence data were used in Nonmetric Multidimensional Scaling (NMS) ordinations followed by Monte Carlo simulation testing. Functional types, including habit, growth form, life history, seed dispersal mechanism, and seed size, for species present were also analyzed via ordination on a per site basis.

Results/Conclusions

Classical diversity metrics (Richness, Diversity, Shannon-Weiner index) identified trends present in community structure. NMS ordination showed sites to cluster apart depending on the contaminant, but also from reference plots. The Monte Carlo test gave a final stress value of 15, ensuring that the NMS was reliable. Ordinations involving dominant function traits showed some differentiation between reference and contaminant plots, but differences among contaminant plots were much clearer. Differences between reference and contaminant sites in species composition, diversity, and richness, suggest that the presence of soil contaminants act as a physiological filter controlling which plant species establish and prosper. Thus soil contaminants can have long lasting impacts on the ecological processes long after the initial contamination event.