Seven stands were selected in different areas of the Madhupur Sal (Shorea robusta) forest to study the seasonal variation of available nutrients in soils. Soil samples were collected after every two months at two depths (top soil 0-10 cm and 10-20 cm) and their physicochemical properties were determined. The percentage of soil moisture was found to vary in different stands and pH values of soil ranged from 4.60 to 6.28. Seasonal fluctuation of electrical conductivity was observed. An increasing trend of sodium accumulation was found in both top and sub-soil layers at all the stands. The concentration of potassium also showed a decreasing tendency in both layers. The exchangeable calcium and magnesium contents did not show significant (pH 0.05) seasonal variation. The high values of manganese and iron were confined to top soil and values decreased down the profile. Key words: Shorea robusta, soil, physico-chemical characteristics, seasonal variation.   doi: 10.3126/eco.v15i0.1936 ECOPRINT 15: 7-14, 2008

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An investigation on the effects of calcium and manganese interaction on the growth and nutrition of Epilobium hirsutum L. was carried out. The plant showed both calcium deficiency at a level of 0.08 mg•liter-1 (Ca as CaCla•6HaO) and manganese toxicity symptoms at a level of5 mg.liter1 (Mnas MnSO,•4H a O). An increase in the calcium level in the nutrient solution was effective in reducing manganese toxicity. The plant responded best to the conditions of the highest calcium level (40 mg•liter 1) and the lowest manganese level (0.05 mg•liter-1) in the nutrient solution. Uptake of manganese in the root decreased with increasing calcium level in the nutrient solution. In contrast, in shoots iron content decreased and accumulation of magnesium also decreased both in shoot and root with the increase of the manganese level in the nutrient solution.

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Investigation has been done to gain evidence on certain chemical properties of water and vegetation in area representative of the various wetland habitats which go under water during rainy season. The measurements were done with edaphic condition, water chemistry, and floristic composition. Water was neutral to alkaline and pH varied from 6.97 to 7.20 and conductivity was in the range of 97.5 m mhos to 240 m mhos. Seasonal variation of chloride content was observed throughout the year and the highest chloride (104.96 mg/l) was in the month of October. Dissolved oxygen concentration was very low (2.99 mg/l) in the month of October. With the decrease of water, the value of alkalinity became double (76.0 mg/). No distinct variation in the content of hardness was observed in the three different locations. Temporary hardness varied from 0.1 0 to 0.56 mg/l. High value of total solids in the month of July (70 mg/l) indicated that high amount of sediment are coming with the flow of water from upstream. Total suspended solids were higher than dissolved solids. Exchangeable cations were low in the beginning and an increasing tendency of Na and Ca was observed in the later stages of marsh formation. DOI: http://dx.doi.org/10.3126/eco.v18i0.9413Ecoprint: An International Journal of EcologyVol. 18, 2011 Page: 71-76 Uploaded date: 12/22/2013