/ In Yellowstone National Park, tailings and associated trace metals from past mining have been deposited along 28 km of Soda Butte Creek by large flood events. This study documents grass species diversity, density, and biomass; trace metal concentrations in soils; and soil pH, salinity, and clay content in four selected floodplain meadows contaminated by these tailings. Trace metal levels frequently exceed acceptable concentrations for agricultural soils at sampling points within the meadows. pH levels within flood-deposited tailings are strongly to moderately acid, while pH levels outside of tailings deposits are neutral. The data analysis: (1) shows that metals and acidity associated with tailings affect plant biomass, density, and diversity; (2) documents that the vegetation/metal and vegetation/pH associations are more of a threshold than a linear relationship; and (3) suggests that other factors may be involved in structuring the community. Vegetation diversity, density, and biomass decrease at threshold levels of trace metal concentrations and soil pH in all four meadows. CuSum plots of diversity in relation to trace metal levels show a decrease in mean diversity at 315 ppm copper, 22 ppm arsenic, 4.2% iron, 65 ppm lead, and 170 ppm zinc. Densities of Phleum pratense and Poa pratensis were significantly lower (P </= 0.001) on plots with more than 250 ppm copper. Above-ground biomass of Phleum pratense was also significantly lower on plots with copper levels above 250 ppm. Decreased mean grass density was found on plots with pH < 6.4, but the only statistically significant difference was for Juncus balticus, which had increased density on plots with pH < 6.4. In contrast to the clear impacts of trace metals and pH on vegetation, other site characteristics did not alter measured vegetation characteristics.
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"In many regions of North America, sedimentary deposits were produced by accelerated erosion associated with intensive land clearance and agriculture following EuroAmerican settlement (Happ et al., 1940; Happ, 1945; Knox, 1972, 1977, 1987, 2006; Trimble, 1974; Costa, 1975; Magilligan, 1985; Jacobson and Coleman, 1986; Faulkner, 1998; Lecce and Pavlowsky, 2001; Florsheim and Mount, 2003; Jackson et al., 2005; Walter and Merritts, 2008; Gellis et al., 2009; Merritts et al., 2011; Hupp et al., 2013). Mining also generated large sedimentation events in North America (Gilbert, 1917; Knox, 1987; James, 1989; Leigh, 1994; Lecce, 1997; Stoughton and Marcus, 2000; Marcus et al., 2001; Bain and Brush, 2005; Lecce et al., 2008). These anthropogenic deposits are being increasingly referred to as 'legacy sediment' (LS) by environmental scientists. "
[Show abstract][Hide abstract] ABSTRACT: Extensive anthropogenic terrestrial sedimentary deposits are well recognized in the geologic literature and are increasingly being referred to as legacy sediment (LS). Definitions of LS are reviewed and a broad but explicit definition is recommended based on episodically produced anthropogenic sediment. The phrase is being used in a variety of ways, but primarily in North America to describe post-settlement alluvium overlying older surfaces. The role of humans may be implied by current usage, but this is not always clear. The definition of LS should include alluvium and colluvium resulting to a substantial degree from a range of human-induced disturbances; e.g., vegetation clearance, logging, agriculture, mining, grazing, or urbanization. Moreover, LS should apply to sediment resulting from anthropogenic episodes on other continents and to sediment deposited by earlier episodes of human activities.
Given a broad definition of LS, various types of LS deposits are described followed by a qualitative description of processes governing deposition, preservation, and recruitment. LS is deposited and preserved where sediment delivery (DS) exceeds sediment transport capacity (TC). This can be expressed as a storage potential ratio that varies within and between basins and through time. When DS/TC < 1, recruitment and transport of LS dominate, but if DS/TC > 1, deposition and preservation are likely. When DS/TC ≫ 1, abundant deposition and graded deposits are likely even without barriers or sinks. Thus, spatial patterns of LS deposits may reveal information about past land-use history and hydrodynamics in a catchment.
"Fresh active pyrite mud is deposited in floodplains during floods , giving rise to acid production and dec - alcification of the soil when the water table drops and soil becomes oxygenated again ( Gallart et al . 1999 ; Stoughton & Marcus 2000 ; Lin et al . 2005 ) . "
[Show abstract][Hide abstract] ABSTRACT: Question: Which biogeochemical processes are responsible for the decline of endemic metallophyte vegetation in floodplain grasslands?
Location: Floodplain grasslands along the River Geul (the Netherlands) and metalliferous mine spoils near the River Geul (Belgium).
Methods: In order to find factors and soil processes that have caused a decline of metallophytes and an increase of pseudo-metallophytes in floodplain grasslands, a soil study was done at locations currently and formerly dominated by metallophytes. In addition, changes in soil chemistry in recent decades in floodplain grasslands were investigated. Finally, a 2-year plant growth experiment was performed in the field, to test the effects of improving soil conditions by topsoil removal.
Results: Metallophytes only occur on acidic floodplain soils (pH-H2O 5.0-5.5) with relatively high Zn availability (total Zn >40 μmol g−1; Zn/Ca>0.8; Zn-H2O>59 μmol kg−1) combined with low phosphate availability (Olsen-P≪1250 μmol kg−1). The Olsen-P and total Ca concentrations were relatively high in topsoil (0-20 cm), while total Zn was high throughout the soil profile (0-50 cm). Removal of topsoil led to recovery of P and Zn availability. Under the new soil conditions there was almost no growth and expansion of pseudo-metalliferous grasses in time, wheras metallophytes easily established, maintained and reproduced with significant increases in cover over time.
Conclusions: On a global scale, metallophyte vegetation types are increasingly under threat of extinction. Our study shows that factors leading to higher soil alkalinity inhibit Zn availability at the expense of the metallophyte vegetation. Factors leading to a higher Olsen-P concentration stimulate the growth of more competitive pseudo-metallophyte grasses. Both eutrophication and alkalinisation have contributed to the decline of metallophyte vegetation in floodplains of the River Geul. Removal of the alkaline- and phosphate-enriched soil top layer restores the original soil chemistry and enables re-colonisation by the metallophyte vegetation. The results can be applied in conservation and restoration strategies for such sites.
"However, further standard dose-response laboratory tests (Ginocchio et al. 2002, Ginocchio & Baker 2004) are needed to determine the degree of tolerance of these species to pH and metals. Reduction in grass diversity, density and productivity has been described for other meadows impacted by historie mine exploitations (Stoughton & Marcus 2000), but development of tolerance to metals in plants has been demonstrated in several studies around the word (Bradshaw 1984, Bradshaw & Hardwick 1989, Kruckberg & Wu 1992, Macnair & Baker 1994, Brooks 1998). Plant adaptation to increased metal levels can oceur rapidly, sometimes within few years of disturbance (Bradshaw 1984, Baker 1987, Tyler et al. 1989), therefore, under a long history of interaction, porphyry Cu-Mo deposits and historie mine spoils affecting surface water quality at the YLNS may have resulted in directional selection for metal and acidic water tolerant plant species. "
[Show abstract][Hide abstract] ABSTRACT: Porphyry Cu-Mo deposits have influenced surface water quality in high-Andes of north-central Chile since the Miocene. Water anomalies may reduce species abundance and diversity in alpine meadows as acidic and metal-rich waters are highly toxic to plants The study assessed the importance of surface water quality on plant abundance and diversity in high-alpine meadows at the Yerba Loca Natural Santuary (YLNS), central Chile (33°15' S, 70°18' W). Hydrochemical and plant prospecting were carried out on Piedra Carvajal, Chorrillos del Plomo and La Lata meadows the growing seasons of 2006 and 2007. Direct gradient analysis was performed through canonical correspondence analysis (CCA) to look for relationships among water chemistry and plant factors. High variability in water chemistry was found inside and among meadows, particularly for pH, sulphate, electric conductivity, hardness, and total dissolved Cu, Zn, Cd, Pb and Fe. Data on species abundance and water chemical factors suggests that pH and total dissolved Cu are very important factor determining changes in plant abundance and diversity in study meadows. For instance, Festuca purpurascens, Colobanthus quitensis, and Arenaria rivularis are abundant in habitals with Cu-rich waters while Festuca magellanica, Patosia clandestina, Plantago barbata, Werneria pygmea, and Erigeron andícola are abundant in habitals with dilute waters.
Revista chilena de historia natural 12/2008; 81(4):469-488. DOI:10.4067/S0716-078X2008000400003 · 0.65 Impact Factor