Vertical distribution of alkali and alkaline earth metals in the soil profile of a wetland - terrestrial ecosystem complex in India

Abstract

We examined the ammonium acetate extractable forms of alkali (Na, K) and alkaline earth (Ca, Li, and Mg) metals in the soil system in a world heritage site, Keoladeo National Park, Bharatpur, India for 3 consecutive years—2003, 2004, and 2005. The metals were assessed along the soil profile, from surface to 1.00 m depth (as 5 layers, at 0, 0.25, 0.50, 0.75, and 1.00 m). Sodium and K were negatively correlated (P < 0.05) and were found in the range 40–4533 and 77–1802 mg/kg, respectively. The distributions of these metals were significantly different among habitats (Na: F = 17.035, K: F = 30.56; P < 0.05). The lowest and highest values of Ca were 548 and 5976 mg/kg, and for Mg 230 and 5654 mg/kg. The variation in Ca was significant among the soil layers (F = 11.9) and among the habitats (F = 117.3, P < 0.05). Li was found in the range 1.74–15.00 mg/kg soil and varied significantly among the soil layers (F = 71.7) as well as habitats (F = 105.9, P < 0.05). Potassium was positively correlated with Ca, Li, and Mg during 2004 and 2005 (P < 0.05). The terrestrial areas in the Park had higher values of Na/K ratio, indicating the dominating presence of Na salts. Calcium-type enrichment in the wetland and Na-type enrichment in the woodland and grassland differentiated the soil in the Park. A low Mg/Ca molar ratio with a range 0.089–1.681 suggests that CaCO3 rocks would not be the major source of Ca in this Park. Since some of the elements were comparatively higher in the soil, the phytocycling of biogenic elements such as Mg and Ca would ultimately improve the fertility status of the soil system in the Park. Although not addressed here, this issue needs to be considered.