Trace element budget in an African savannah ecosystem

Abstract

Abstract. The concentration of selected trace elements (Co, Cu, Fe, Mn, Mo, Se, and Zn) were analysed in soils, grass, bush, and tree samples from the Mole National Park, Ghana. The distribution of the essential nutrients: cobalt, copper, manganese, and selenium is controlled by bedrock geology, whereas iron, molybdenum, and zinc distribution is controlled by soil and hydrological processes. In the soils, iron, manganese, and cobalt are largely fixed in the mineral fraction while most of the copper, molybdenum, and selenium in the soils can be extracted by disodium ethylenediaminetetracetate. Copper, cobalt, and manganese appear to be preferentially concentrated in grass species while molybdenum and selenium are concentrated in browse plants.Variations in uptake exist between wet and dry seasons with all trace elements studied, except iron and manganese, showing a marked increased availability in the wet season and increased concentration in the residual fraction of the mineral and organic soils in the dry season. In the dry season the plant concentration of molybdenum and selenium decreased while copper and zine showed increased concentrations and this may be related to a lower pH of the groundwaters at this time.A budget of metal input and output in the ecosystem at Mole has been computed. From this potential dietary deficiencies in cobalt can be observed, however for other metals soil and plant concentrations are sufficient to prevent straightforward deficiencies while the concentrations of molybdenum and selenium are sufficiently low to be considered safe.

Regulation of nitrogen fixation from free-living organisms in soil and leaf litter of two tropical forests of the Guiana shield

“…Just as in soils, however, and in spite of its importance for N fixation (Kaiser et al 2005;Seefeldt et al 2009), we found no evidence to support a regulatory role for Mo content. Similar as in soils, litter Mo concentrations were ten-fold higher than those reported from other tropical sites (Barron et al 2009;Bowell and Ansah 1993;Reed et al 2013;Wurzburger et al 2012) and likely too high to render a regulatory role to Mo in litter FLNF rates.…”

Grazing behaviour of the giraffe in Hwange National Park, Zimbabwe

“…In contrast, some of the giraffes’ preferred browse species reach their maximum protein content during this time (Sauer, ). We therefore assume that the function of feeding on herbs during the dry season is not principally to supplement protein/energy intake, but rather to access other nutritional factors not currently present in sufficient amounts in browse, because previous studies imply that the herb layer sometimes has more available micronutrients than browse (Bowell & Ansah, ; Milewski & Diamond, ). Giraffes are likely to require large amounts of minerals (Milewski & Diamond, ; Mitchell & Skinner, ), which is also assumed to be the driving force behind osteophagy (Wyatt, ; Kok & Opperman, ).…”

Impact of Nutrient Additions on Free‐Living Nitrogen Fixation in Litter and Soil of Two French‐Guianese Lowland Tropical Forests

“…However, the unchanging litter BNF rates following Mo additions alone (Figures 1 and 2a) provide strong evidence that in leaf litter, Mo is not limiting BNF rates. In both forest sites, the litter Mo concentration was high (Table 1) compared to the litter Mo concentration reported for other tropical sites (Barron et al., 2009; Bowell & Ansah, 1993; Reed et al., 2013; Vitousek & Hobbie, 2000). In this framework of litter stoichiometry at our forest sites, it is very likely that P and not Mo are limiting litter BNF.…”