Bacterial Community Changes during Plant Establishment at the San Pedro River Mine Tailings Site

Abstract

Mine tailings are moderately to severely impacted sites that lack normal plant cover, soil structure and development, and the associated microbial community. In arid and semiarid environments, tailings and their associated contaminants are prone to eolian dispersion and water erosion, thus becoming sources of metal contamination. One approach to minimize or eliminate these processes is to establish a permanent vegetation cover on tailings piles. Here we report a revegetation trial conducted at a moderately impacted mine tailings site in southern Arizona. A salt and drought-tolerant plant, four-wing saltbush [Atriplex canescens (Pursh) Nutt.], was chosen for the trial. A series of 3 by 3 m plots were established in quadruplicate on the test site to evaluate growth of four-wing saltbush transplants alone or with compost addition. Results show that >80% of the transplanted saltbush survived after 1.5 yr in both treatments. Enumeration of heterotrophs and community structure analysis were conducted to monitor bacterial community changes during plant establishment as an indicator of plant and soil health. The bacterial community was evaluated using denaturing gradient gel electrophoresis (DGGE) analysis of 16S rDNA PCR gene products from tailings samples taken beneath transplant canopies. Significant differences in heterotrophic counts and community composition were observed between the two treatments and unplanted controls throughout the trial, but treatment effects were not observed. The results suggest that compost is not necessary for plant establishment at this site and that plants, rather than added compost, is the primary factor enhancing bacterial heterotrophic counts and affecting community composition.

Organic amendments: effects on cereals growth and cadmium remediation

“…This might be due to improved soil structure, nutrient, and water-holding capacity of soil in response to organic amendments, as similar effects on soil properties after the addition of compost and BGS were observed earlier by Oldare et al (2011). Organic amendments increased biomass of studied crops in Cd-contaminated soil, which is in line with and in contrast with Rosario et al (2007). This alleviation of phytotoxicity in response to organic amendments may be credited to improved physical health of soil and nutrient availability (Oldare et al 2011;Abubaker et al 2012).…”

Growth and metal uptake of energy sugarcane (Saccharum spp.) in different metal mine tailings with soil amendments

“…Without proper storage and rehabilitation, the tailings may leach into soil and water bodies (Kien et al, 2010), resulting in environmental contamination and then human health concerns. Furthermore, mine tailings threaten natural vegetation owing to their lower pH and a composition consisting of mostly silt or sand-sized particles, lacking water retention capacity and fertility (Mendez et al, 2007;Rosario et al, 2007;Ye et al, 2002). In China, mining activities have generated about 3.2 Mha wasteland, and the area impacted is still increasing at a rate of 46,700 ha per year (Li et al, 2007).…”

Effects of Compost on Colonization of Roots of Plants Grown in Metalliferous Mine Tailings, as Examined by Fluorescence In Situ Hybridization

“…Recent research has explored the minimum compost amendment required for sustained plant growth (7,11,16). Significant incremental increases were observed in total plant biomass for plants grown in extremely (pH 2.7) and moderately (pH 5.7) acidic mine tailings amended with 0, 5, and 10% compost.…”

“…Thus, no correlation was observed between the increases in plant biomass associated with increasing levels of compost amendment and the final rhizosphere bacterial counts. The specific question addressed in this effort is whether the rhizosphere population dynamics observed in previous studies (11,16) accurately reflect the actual bacterial colonization patterns of the root surface. Our goal is to better understand how the compost amendment of mine tailings affects the development of root-microbe associations during the revegetation process, as the rhizosphere community is critical for plant health.…”

“…Mine tailings have drastically reduced and functionally altered microbial communities that are not suited to support plant establishment in tailings (13). In fact, previous work has documented major transitions in the microbial communities of tailings during successful plant establishment in tailings (8,11,14,16). For example, in a recent field study in a neutral tailings site, a temporal sample series taken in the rooting zone underwent significant bacterial community changes during an 18-month field trial compared to unplanted controls (16).…”