Facilitation Drives the Positive Effects of Plant Richness on Trace Metal Removal in a Biodiversity Experiment

Abstract

BackgroundPhytoextraction is an environmentally acceptable and inexpensive technique for mine tailing rehabilitation that uses metallophyte plants. These plants reduce the soil trace metal contents to environmentally acceptable levels by accumulating trace metals. Recently, whether more trace metals can be removed by species-rich communities of these plants received great attention, as species richness has been reported having positive effects on ecosystem functions. However, how the species richness affects trace metals removal of plant communities of mine tailing is rarely known.Methodology/Principal FindingsWe examined the effects of species richness on soil trace metal removal in both natural and experimental plant communities. The root lengths and stem heights of each plant species were measured in order to calculate the functional diversity indices. Our results showed that trace metal (Cu, Cd, Pb and Zn) concentrations in mine tailing soil declined as species richness increased in both the natural and experimental plant communities. Species richness, rather than functional diversity, positively affected the mineralomass of the experimental plant communities. The intensity of plant-plant facilitation increased with the species richness of experimental communities. Due to the incremental role of plant-plant facilitation, most of the species had higher biomasses, higher trace metal concentrations in their plant tissues and lower malondialdehyde concentrations in their leaves. Consequently, the positive effects of species richness on mineralomass were mostly attributable to facilitation among plants.Conclusions/SignificanceOur results provide clear evidence that, due to plant-plant facilitation, species richness positively affects the removal of trace metals from mine tailing soil through phytoextraction and provides further information on diversity conservation and environmental remediation in a mine tailing environment.

Plant biodiversity effects in reducing fluvial erosion are limited to low species richness

“…This is important because many of the ecosystem services provided by plants may in fact be more related to root structural traits than simple root biomass. For example, in a study investigating effects of plant species richness on metals removal in soils affected by mine tailings, Wang et al ( 2014 ) found that the functional diversity metrics using community-weighted mean trait values of root length were related to the amount of Cu, Cd, and Zn incorporated into plant tissue. Thus a sole focus on root biomass may miss important biodiversity effects on root traits, which can strongly affect ecosystem processes independently of root biomass.…”

Using phytostabilisation to conserve threatened endemic species in southeastern Democratic Republic of the Congo

“…Facilitation is a positive interaction in assembling ecological communities and is recognized as an important conditional factor for the success of phytoremediation strategies (Fre´rot et al 2006;Brooker et al 2008;Parraga-Aguado et al 2013;Wang et al 2014). It occurs when a plant species, referred to as a nurse plant, facilitates the establishment of other species by locally changing biotic and/or abiotic conditions, such as light and nutrient availability (Brooker et al 2008;Soliveres et al 2010;Bonanomi et al 2011;Beltra´n et al 2012).…”

“…It occurs when a plant species, referred to as a nurse plant, facilitates the establishment of other species by locally changing biotic and/or abiotic conditions, such as light and nutrient availability (Brooker et al 2008;Soliveres et al 2010;Bonanomi et al 2011;Beltra´n et al 2012). The identification of nurse plants is important to improve germination, growth, and survival of a diversity of plant species in heavy metal-polluted environments (Fre´rot et al 2006;Padilla and Pugnaire 2006;Parraga-Aguado et al 2013;Wang et al 2014).…”

A new family of standardized and symmetric indices for measuring the intensity and importance of plant neighbour effects

“…Recently, the numerical values of the indices are used in more involved calculations, such as relating them with other types of ecosystem properties (Wang et al . ), using them to estimate the relevance of indirect interactions (Michalet et al . ), to compare beneficiary effects with the feedback effect of the target species on its benefactor (Schöb et al .…”