Plant communities on ironstone outcrops: a diverse and endangered Brazilian ecosystem

Mountain areas are recognized centres of endemism and diversity on account of their isolation and altitudinal diversity. In tropical regions, mountain tops usually stand as islands of xeric vegetation among mesophytic assemblages. Unlike the vegetation growing on other rock outcrops lithologies, such as inselbergs (granite/gneiss) or campos rupestres (quartz/arenite), ironstone outcrop plant communities still lack systematic studies in Brazil. These outcrops (locally known as canga) share most of the characteristics of other rock outcrops, such as isolation and edapho-climatic harshness, but differ in that they are the object of opencast mining, and thus subjected to irrecoverable degradation. In addition, they are expected to harbour metal-tolerant and hyperaccumulator plant species. A botanical survey of two ironstone outcrop locations in the most important mining region of southeastern Brazil, the Iron Quadrangle, revealed a high within-site (138 and 160 species per site), and between-site diversity (only 27% of common species), totaling 64 families and 234 species among basal families and eudicots (154 species), monocots (68 species), and ferns (12 species). Canga crusts are rich in dicots, several of which play an important role in community structuring, together with the more usual monocot aggregations. Distinct plant communities are found associated to different microhabitats within the iron crust, depending primarily on the amount of soil and moisture retention in the different microtopographies. The environmental uniqueness, high diversity, lack of studies and rapid destruction of these ecosystems pose an immediate challenge for their conservation.     

Acoustical estimates of fish and zooplankton distribution in the Piaseczno reservoir, Southern Poland

Hydroacoustical surveys in the Piaseczno reservoir were performed in May and September 2002 using a Biosonics 101 dual beam echo sounder. They have revealed very scarce fish populations in pelagic waters with twice-higher abundance in autumn (530 fish ha⁻¹) as compared with spring (280 fish ha⁻¹). Small and very small fish (below 10 cm length) dominated. Apart from fish, Chaoborus larvae were producing acoustical echoes of the TS similar or slightly weaker than that of small fish. Invertebrates formed a thin layer, less than 2 m thick at the border of an anoxic zone, and were changing their depth position between 6 and 16 m, both diurnally and seasonally.     

Chemical properties of water in a flooded opencast sulphur mine

The chemical properties of water in the only flooded sulphur opencast mine in the world have been analysed. The reservoir has a depth of 22 m and is still continuously pumped, which affects the deeper tertiary aquifer. Instead of quaternary water being pumped out, tertiary water flows into the reservoir. Mineralisation of the water in this reservoir varied from 2000 to 10,000 mg dm⁻³ near the bottom. Light penetrates to 8–10 m and this photic layer is oxygenated. The hypolimnion is only partially oxygenated and contains H₂S. The monimolimnion is salty and also poisoned by H₂S. Discriminant analysis shows three layers: upper 0–10 m, transitional 10–15 m and bottom 15–22 m. Variability of the chemical properties is negligible through the year, excluding special situations such as ice melting. The transitional layer is rich in SO₄²⁻ – about 1000 mg dm⁻³ and unionized H₂S. S²⁻ oxidation is very intensive, excess CaSO₄ precipitates at a depth of 10 m resulting in opacity. Above and below, these concentrations diminish. For this zone a new name is proposed: the katalimnion. In the bottom layer, NO₃⁻ does not occur – whereas there is a high concentration of NH₄⁺. Discrimination on the basis of chemical parameters divides the vertical profile into three levels: epi- + meta- + upper half of the hypolimnion, lower half of the hypolimnion and monimolimnion. This indicates that for sampling, three levels might be sufficient. The same analysis used for time showed a low differentiation in the annual cycle. These results can help in optimizing the monitoring scheme for this pit lake and reducing its cost.     

An evaluation of the use of translocated blanket bog vegetation for heathland restoration

Abstract. The decision was taken by an opencast coal mining company to translocate on-site blanket bog vegetation, on completion of mining, at a site in Co. Durham, UK, both to preserve it and to use it to enhance recolonization. The vegetation of the treatments was monitored for seven years after site completion and this paper reports on the progress of the translocated material and its effect on recolonization. Translocation of large turves of blanket bog into carefully prepared receptor cells preserved most of the vegetation intact, but resulted in severe decline in the frequency of Sphagnum, while the design of the receptor site as strips of translocated vegetation enclosing strips of spread, stored peat accelerated recolonization of the intervening bare peat by Calluna vulgaris, but not of other target species. This attempt to translocate blanket bog vegetation and at the same time use it to accelerate recolonization was only partly successful. It was concluded that the ecological requirements of species known to be significant for ecosystem function, such as Sphagnum, must be fulfilled if translocation of blanket bog is to be attempted in future.