Environmental variability of some edaphic components from virgin areas of tropical mangrove forest of Sundarban, India

Abstract

Level of occurrence and characteristics of some important edaphic components were studied in the intertidal surface sediments from core mangrove forest of Sundarbans in a comprehensive way for the first time. Sediments were characterized to be dominated by finer particles of silt and clay with moderate to high carbon content (0.40 - 2.76%), low cation exchange capacity (average of 11.10 me100 g-1), low available nitrogen (about 10% of total nitrogen), high salt content with alkaline nature (pH, 7.5 – 8.2) and well supply of easily available form of phosphorous (17.75 - 57.0 mg.kg-1as P2O5) and potassium (12.7-22.5 meq.100g-1). Statistical analysis revealed that clay deposition was favored at high pH (p <0.05) and fresh water silt fraction had a strong affinity for exchangeable potassium (p <0.05). It also distinctly highlighted the prevalence of effective winnowing activity with considerable deposition of organic matter from multiple sources in the sedimentary system. This resulted in higher variability (CV > 50%) and asymmetric distribution of organic carbon and total nitrogen with large degree of peakedness. In contrast, all other edaphic components including available nutritional elements (N, P and K) were symmetrically equilibrated by natural bio-geochemical processes into various environmental segments and thus, largely could show normal distribution. Principle component analysis (PCA) also supported the existence of complexity of the system and identified well the multitude of the most dominating factors governing the sedimentary environment in this region. Thus the entire study gives an idea about the factors controlling the biogeochemical processes of this unique ecosystem.