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

Abstract

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.

Active revegetation after mining: what is the contribution of peer-reviewed studies?

“…This finding could be due to several reasons. On the one hand, the effect of fertilization and the addition of amendments may depend on the functional strategies of the introduced species, since plants differ in biomass allocation when there is an increase in nutrient availability ( Oliet et al., 2013 ; Ploughe et al., 2021 ). Unlike late-successional species, pioneer species tend to allocate more resources to aerial parts than to roots ( Portsmuth and Niinemets, 2007 ); thus, the effect of nutrient addition can depend on the indicator used to assess growth.…”

“…Leaching from fertilizers can increase with increasing rainfall and temperatures ( Jabloun et al., 2015 ). In addition, organic amendments are more effective in warmer climates, since nutrients are mineralized faster and may be available to plants more rapidly ( Ploughe et al., 2021 ). In turn, in semi-arid climates, where rainfall is scarce, rapid nutrient mineralization can lead to increased salinity and, consequently, water stress ( Fuentes et al., 2007 ).…”

Mulch more so than compost improves soil health to reestablish vegetation in a semiarid rangeland

“…Despite growing research and meta‐analyses showing that organic amendments can be an effective tool for ecological restoration (Hueso‐González et al 2018; Gravuer et al 2019; Ploughe et al 2021), there remains a great deal of variability between different climates where similar amendments can have wide‐ranging effects on plants and soils. The literature we reviewed, including studies using woody organic amendments in southern Arizona, show inconsistent positive results using woody mulch for restoration (Gebhardt et al 2017; Fehmi et al 2019; Espinosa et al 2020).…”

“…Furthermore, many studies using mulch and compost in drylands were either in forested ecosystems (e.g. Jacobs 2015), used chipped woody mulch instead of whole branches (Espinosa et al 2020), used biosolids instead of composted woody waste and manure (Gravuer et al 2019; Ploughe et al 2021), or incorporated organic amendments into soils using tillage (Tejada et al 2009), which is not usually possible or cost‐effective in rocky soils, steep slopes, or remote locations that are common in rangelands of the western United States.…”

Grassland reclamation of a copper mine tailings facility: Long‐term effects of biosolids on plant community responses

“…As an alternative, treated solid residue (sewage sludge) from municipal wastewater, known as biosolids, are used as a soil amendment to assist the establishment of a vegetative cover (CCME, 2012; Wallace et al, 2016; Avery et al, 2018). The use of biosolids provides a gradual source of plant‐available nitrogen and phosphorus and improves the physical, chemical and biological properties of the soil, enhancing vegetation establishment (Cuevas et al, 2000; Martinez et al, 2003; Paschke et al, 2005; Walter et al, 2006; Gardner et al, 2010; Gardner et al, 2012; Ploughe et al, 2020; Harris et al, 2021). While traditional reclamation methods focus on the control of erosion, new methods generally aim to establish diverse, and preferably native plant communities.…”