Bio-mining of Lanthanides from Red Mud by Green Microalgae

Red mud is a by-product of alumina production containing lanthanides. Growth of green microalgae on red mud and the intracellular accumulation of lanthanides was tested. The best growing species was Desmodesmus quadricauda (2.71 cell number doublings/day), which accumulated lanthanides to the highest level (27.3 mg/kg/day), if compared with Chlamydomonas reinhardtii and Parachlorella kessleri (2.50, 2.37 cell number doublings and 24.5, 12.5 mg/kg per day, respectively). With increasing concentrations of red mud, the growth rate decreased (2.71, 2.62, 2.43 cell number doublings/day) due to increased shadowing of cells by undissolved red mud particles. The accumulated lanthanide content, however, increased in the most efficient alga Desmodesmus quadricauda within 2 days from zero in red-mud free culture to 12.4, 39.0, 54.5 mg/kg of dry mass at red mud concentrations of 0.03, 0.05 and 0.1%, respectively. Red mud alleviated the metal starvation caused by cultivation in incomplete nutrient medium without added microelements. Moreover, the proportion of lanthanides in algae grown in red mud were about 250, 138, 117% higher than in culture grown in complete nutrient medium at red mud concentrations of 0.03, 0.05, 0.1%. Thus, green algae are prospective vehicles for bio-mining or bio-leaching of lanthanides from red mud

Biotic homogenization destabilizes ecosystem functioning by decreasing spatial asynchrony

Our planet is facing significant changes of biodiversity across spatial scales. Although the negative effects of local biodiversity (α diversity) loss on ecosystem stability are well documented, the consequences of biodiversity changes at larger spatial scales, in particular biotic homogenization, that is, reduced species turnover across space (β diversity), remain poorly known. Using data from 39 grassland biodiversity experiments, we examine the effects of β diversity on the stability of simulated landscapes while controlling for potentially confounding biotic and abiotic factors. Our results show that higher β diversity generates more asynchronous dynamics among local communities and thereby contributes to the stability of ecosystem productivity at larger spatial scales. We further quantify the relative contributions of α and β diversity to ecosystem stability and find a relatively stronger effect of α diversity, possibly due to the limited spatial scale of our experiments. The stabilizing effects of both α and β diversity lead to a positive diversity–stability relationship at the landscape scale. Our findings demonstrate the destabilizing effect of biotic homogenization and suggest that biodiversity should be conserved at multiple spatial scales to maintain the stability of ecosystem functions and services

Plant diversity effects on grassland productivity are robust to both nutrient enrichment and drought

Global change drivers are rapidly altering resource availability and biodiversity. While there is consensus that greater biodiversity increases the functioning of ecosystems, the extent to which biodiversity buffers ecosystem productivity in response to changes in resource availability remains unclear. We use data from 16 grassland experiments across North America and Europe that manipulated plant species richness and one of two essential resources—soil nutrients or water—to assess the direction and strength of the interaction between plant diversity and resource alteration on above-ground productivity and net biodiversity, complementarity, and selection effects. Despite strong increases in productivity with nutrient addition and decreases in productivity with drought, we found that resource alterations did not alter biodiversity–ecosystem functioning relationships. Our results suggest that these relationships are largely determined by increases in complementarity effects along plant species richness gradients. Although nutrient addition reduced complementarity effects at high diversity, this appears to be due to high biomass in monocultures under nutrient enrichment. Our results indicate that diversity and the complementarity of species are important regulators of grassland ecosystem productivity, regardless of changes in other drivers of ecosystem function

Multiple Facets of Biodiversity Drive the Diversity-Stability Relationship

A significant body of evidence has demonstrated that biodiversity stabilizes ecosystem functioning over time in grassland ecosystems. However, the relative importance of different facets of biodiversity underlying the diversity–stability relationship remains unclear. Here we used data from 39 biodiversity experiments and structural equation modeling to investigate the roles of species richness, phylogenetic diversity, and both the diversity and community-weighted mean of functional traits representing the ‘fast–slow’ leaf economics spectrum in driving the diversity–stability relationship. We found that high species richness and phylogenetic diversity stabilize biomass production via enhanced asynchrony. Contrary to our hypothesis, low phylogenetic diversity also enhances ecosystem stability directly, albeit weakly. While the diversity of fast–slow functional traits has a weak effect on ecosystem stability, communities dominated by slow species enhance ecosystem stability by increasing mean biomass production relative to the standard deviation of biomass over time. Our results demonstrate that biodiversity influences ecosystem stability via a variety of facets, thus highlighting a more multicausal relationship than has been previously acknowledged

Different germination success may explain lower species richness of herbaceous vegetation below non-native than native shrubs

Mechanisms by which invasive species affect native communities have been intensively studied. Invasive plants may influence other species through competition, altered ecosystem processes, or other pathways. It has been suggested that allelochemical interference is the key mechanism explaining a lower species richness of herbaceous plants below non-native than native shrubs. We studied plant recruitment from seeds sown inside and outside patches formed by Sorbaria sorbifolia, a shrub non-native to Finland, and a native shrub Rubus idaeus. Recruitment of seedlings was lower below non-native than native shrubs, in contrast to recruitment outside the shrub patches. Biotic filtering of subdominant plants was a stepwise process affected by the difference between non-native and native shrubs. Our results suggest that allelochemicals released by non-native species may be responsible for this difference. They thus give support to the hypothesis emphasizing the importance of allelopathy in the invasion of non-native plants. The slow and stepwise action of biotic filtering cautions against defining plant community membership merely based on the presence of seedlings.</p

Non-native and native shrubs have differing impacts on species diversity and composition of associated plant communities

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Data from: Seasonality promotes grassland diversity: interactions with mowing, fertilization and removal of dominant species

1. Current biodiversity declines in species-rich grasslands are connected with the cessation of management, eutrophication and the expansion of dominant grass species. One of the theoretical mechanisms limiting biodiversity loss is the ability of subordinate species to avoid competitive exclusion by seasonal niche separation from dominant species. Here we explore how seasonality underpins the maintenance of diversity in temperate meadows under different management regimes and competition intensities in relation to species functional traits. 2. We studied eight different communities in a long-term meadow experiment that manipulated mowing, fertilization and dominant species (Molinia caerulea) removal. In each community, species-specific trait and biomass data were taken five times during the year to test whether seasonal variation in species composition and functional strategies enable species to coexist. 3. Mown unfertlized meadows exhibited pronounced seasonal variations in community composition and structure, linked to differences in resource-use strategies between mid-summer dominants and the spring and autumn subordinates. Higher specific leaf area and foliar nitrogen concentration in the fast-growing dominants, and increased water use (δ13C) and nutrient acquisition (δ15N) efficiency in resource-retentive subordinates, best predicted their temporal niche separation. Seasonal segregation of species with contrasting strategies increased after mowing cessation, and the resulting summer dominance of Molinia. Conversely, the seasonal dynamics were markedly reduced by fertilization, promoting tall grasses over sedges and forbs throughout the entire year, thereby decreasing the overall taxonomic and functional diversity. When Molinia was removed the compositional changes during the season became less pronounced, being significant only in mown unfertilized plots. 4. Seasonal shifts in community composition reduced the competitive interactions and promoted the coexistence of dominant and subordinate species. Seasonality reversed the negative mid-summer diversity-productivity relationship to a positive one during the spring and autumn, and seasonality only prevented diversity loss in unfertilized conditions possibly because competition is most intense in summer. In fertilized meadows, subordinate species are not able to escape competitive exclusion by shifting their phenological peaks to the spring or autumn periods because asymmetric competition is intense over the entire growing season. Studying seasonal dynamics is key to understanding the maintenance of grassland diversity under ongoing land use change

Dolezal_JEcol-2018 Seasonality

Data were collected in the field in eight different communities in a long-term meadow fully-factorial experiment that manipulated mowing, fertilization and dominant species (Molinia caerulea) removal. In each community, species-specific trait and biomass data were taken five times during the year. We collected vegetation data in each permanent plot (24 in total) by clipping the aboveground biomass in April 2004, June 2004, August 2004, October 2004 and March 2005. We measured several plant traits relevant to competitive ability (plant height), nutrient acquisition (δ15N), water use efficiency (δ13C) and allocation (SLA - specific leaf area, LNC - leaf nitrogen concentration, LDMC and StDMC - leaf and stem dry matter content, respectively)

Detecting local adaptation in widespread grassland species - the importance of scale and local plant community

1. Adaptation of plant populations to local environments has been shown in many species but local adaptation is not always apparent and spatial scales of differentiation are not well known. In a reciprocal transplant experiment we tested whether: (i) three widespread grassland species are locally adapted at a European scale; (ii) detection of local adaptation depends on competition with the local plant community; and (iii) local differentiation between neighbouring populations from contrasting habitats can be stronger than differentiation at a European scale. 2. Seeds of Holcus lanatus, Lotus corniculatus and Plantago lanceolata from a Swiss, Czech and UK population were sown in a reciprocal transplant experiment at fields that exhibit environmental conditions similar to the source sites. Seedling emergence, survival, growth and reproduction were recorded for two consecutive years. 3. The effect of competition was tested by comparing individuals in weeded monocultures with plants sown together with species from the local grassland community. To compare large-scale vs. small-scale differentiation, a neighbouring population from a contrasting habitat (wet-dry contrast) was compared with the ‘home’ and ‘foreign’ populations. 4. In P. lanceolata and H. lanatus, a significant home-site advantage was detected in fitness-related traits, thus indicating local adaptation. In L. corniculatus, an overall superiority of one provenance was found. 5. The detection of local adaptation depended on competition with the local plant community. In the absence of competition the home-site advantage was underestimated in P. lanceolata and overestimated in H. lanatus. 6. A significant population differentiation between contrasting local habitats was found. In some traits, this small-scale was greater than large-scale differentiation between countries. 7. Our results indicate that local adaptation in real plant communities cannot necessarily be predicted from plants grown in weeded monocultures and that tests on the relationship between fitness and geographical distance have to account for habitat-dependent small-scale differentiation. Considering the strong small-scale differentiation, a local provenance from a different habitat may not be the best choice in ecological restoration if distant populations from a more similar habitat are available