Decomposition studies on two floating leaved macrophytes,Nymphaea nouchali andNymphoides indica, of lake Kondakarla, India

Abstract

Rates of weight loss and nutrient release (N, P, Ca, Mg, Na, K) were measured in decomposing tissues ofNymphaea nouchali Burm (leaf and rhizome) andNymphoides indica (L.) O Kuntze under field (90 days) and laboratory (60 days) conditions. Dry weight loss followed the sequence ofNymphoides indica>Nymphaea nouchali leaf >Nymphaea nouchali rhizome. The rate of nutrient release (N, P, Ca, Mg) from the decomposing tissues ofNymphaea nouchali rhizome appears to be correlated with nutrient concentration in leachate (receiving water) under laboratory experiments. The concentration of nitrogen in the decomposing tissues of all the samples increased with time. No increase in sodium and potassium concentrations was observed during the study under both the conditions. The maximum elemental loss was mostly observed under laboratory experiments than in the field studies. Accumulation of nitrogen, calcium and magnesium instead of release at certain stages of decomposition is attributed to microbial immobilization. The sequence of elemental loss in the decomposing tissues of these macrophytes is Na>K>P>Mg>Ca>N.