Plant communities as a key factor in biogeochemical processes involving micronutrients (Fe, Mn, Co, and Cu) in Antarctic soils (Byers Peninsula, maritime Antarctica)
X.L. Otero, S. Fernández, M.A. de Pablo Hernandez, E.C. Nizoli, A. Quesada
Departamento de Edafoloxía e Química Agrícola, Facultade de Bioloxía, Universidade de Santiago de Compostela, 15785 Santiago de Compostela, Spain.
The main objective of this study was to establish the effects of plants and microorganisms on soil formation and the geochemical mobility of certain micronutrients in soils from Byers Peninsula (Antarctica). For this purpose, 14 sampling sites were selected to cover the existing range of lithological and geomorphological variability in the area. Soils were sampled at the surface (0–5 cm) and subsurface (from 5 cm to 30 cm or until contact with the bedrock or permafrost). Soil samples were physicochemically characterized by analysis of pH, electrical conductivity, size particle distribution, total organic carbon, total nitrogen and dissolved organic carbon. Sequential extraction of Fe and Mn and of micronutrients (Co, Cu) was also carried out.
The analytical results revealed significant differences between sites in relation to plant cover. The total organic carbon was 1.5 times higher, the total nitrogen was 1.6 times higher, the dissolved organic carbon was more than 3.6 times higher and the pHKCl (pH in 0.1 M KCl) was lower in the sites colonized by plants (mainly mosses) than in the sites without any plant cover. The sequential extraction of biolimiting nutrients (Fe, Mn, Co, and Cu) also revealed significant differences in the fractions in relation to the presence of plants. Specifically, the most labile and mobile fractions (amorphous Fe oxyhydroxides, easily reducible Mn, and metals soluble in sodium pyrophosphate) were present at higher concentrations in the sites colonized by vegetation than in the sites without plants. The latter aspect may be of particular importance within the context of global climate change, as increased temperatures will favour expansion of vegetation and the flow of biolimiting nutrients towards oceans and lakes, which may have direct effects on primary productivity.