Abstract
Short rotation coppice (SRC) with metal tolerant plants may attenuate the pollution of excessive elements with potential toxicity in soils, while preserving soil resources and functionality. Here, we investigated effects of 6 years phytomanagement with willow SRC on properties including heavy metal levels, toxicity tested by BioTox, microbial biomass, enzyme activities, and functional gene abundances measured by GeoChip of soils contaminated by As, Cd, Pb and Zn, as compared to the same soils under non-managed mixed grassland representing no intervention treatment (Unt). Though metal total concentrations did not differ by SRC and Unt, SRC soils had lower metal availability and toxicity, higher organic carbon, microbial biomass, phosphatase, urease and protease activities, as compared to Unt soils. Significantly reduced abundances of genes encoding resistances to various metals and antibiotics were observed in SRC, likely attributed to reduced metal selective pressure based on less heavy metal availability and soil toxicity. SRC also significantly reduced abundances of genes involved in nitrogen, phosphorus, and sulfur cycles, possibly due to the willow induced selection. Overall, while the SRC phytomanagement did not reduce the total heavy metal concentrations in soils, it decreased the heavy metal availability and soil toxicity, which in turn led to less metal selective pressure on microbial communities. The SRC phytomanagement also reduced the abundances of nutrient cycling genes from microbial communities, possibly due to intense plant nutrient uptake that depleted soil nitrogen and phosphorus availability, and thus site-specific practices should be considered to improve the soil nutrient supply for phytomanagement plants.
Highlights
Diffuse soil contaminations by heavy metals (HMs) and metalloids are the side effect of the worldwide industrial boom in the early to mid-1900’s, when pollution containment measures were not efficient. Panagos et al (2013) estimated that the European Union (EU) hosts more than 8.7 × 105 HM contaminated sites, of which at least 10% need urgent remediation actions as posing risks to human health
Long-term Short rotation coppice (SRC) management with a metal tolerant willow clone led to distinct microbial functional gene compositions, which could be explained by the microbial selection occurring with the fast-growing willow (Berg et al, 2009), as compared to the mixed vegetation of Unt soils
SRC management resulted in lower HM availability and soil toxicity by BioTox test, likely leading to less metal selective pressure on microbial communities
Summary
Diffuse soil contaminations by heavy metals (HMs) and metalloids are the side effect of the worldwide industrial boom in the early to mid-1900’s, when pollution containment measures were not efficient. Panagos et al (2013) estimated that the European Union (EU) hosts more than 8.7 × 105 HM contaminated sites, of which at least 10% need urgent remediation actions as posing risks to human health. Diffuse soil contaminations by heavy metals (HMs) and metalloids are the side effect of the worldwide industrial boom in the early to mid-1900’s, when pollution containment measures were not efficient. Heavy metals accumulate in soils due to wet and dry depositions from the atmosphere and other routes, with the potential of being excessive in natural and cropped plants (Mench et al, 2010) and impacting other organisms and human health through groundwater and food web (Peng et al, 2016). HM contaminated soils typically contain low microbial biomass and slow SOM decomposition activity (Tyler et al, 1989), due to lower microbial biomass, functional diversity and less efficient metabolism of HM-resistant microorganisms within the soil microbial community (Mergeay, 2000)
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