Revegetation of degraded ecosystems into grasslands using biosolids as an organic amendment: A meta-analysis

Questions Biosolids are a source of nutrient-rich organic material that can be used to improve degraded or disturbed soils. Research on vegetation responses to the land application of biosolids has increased in the past 20 years, but there is no consensus on how plant communities respond to biosolids applications. What factors influence productivity and vegetative cover following biosolids application for grassland reclamation? How does the addition of biosolids impact plant community responses? Location Global, but predominantly North America and Europe. Methods To explore vegetative responses following biosolids application, we used a global systematic review and meta-analysis of 59 articles. Our meta-analysis used the log response ratio (LRR) as an effect size for productivity, total cover, species richness, diversity and exotic species abundance and explored covariates addressing various site characteristics and reclamation strategies. Results We found that across sites, the land application of biosolids significantly increased productivity and cover but had no significant overall effect on species richness, Shannon diversity or exotic species abundance on degraded lands. These increases in the LRR for productivity and vegetative cover were lower on sites that experienced a fire prior to biosolids application. Climatic variables like mean annual temperature were shown to alter the response of vegetative cover, where warmer sites tended to have more positive responses to biosolids. Seeding was found to increase plant cover but decrease species richness early in the reclamation process. Conclusions This area of research is growing; most of the publications we used come from the last 20 years and were mostly conducted in North America and Europe. While we can build on the present literature, there is clearly room for more research to ensure the process of reclaiming degraded ecosystems using biosolids results in desired plant communities, e.g. high native species diversity. Future research should consistently report biosolids chemical characteristics as well as application and processing methodologies.

Automated summary

Research on the use of biosolids for soil reclamation has shown significant increases in productivity and cover, while not significantly affecting species richness, diversity, or exotic species abundance. Climatic variables, such as mean annual temperature, play a role in determining vegetative cover responses. Seeding can increase plant cover but decrease species richness during early stages of reclamation process.