Quantification of organic carbon and primary nutrients in litter and soil in a foothill forest plantation of eastern Himalaya

The present study was an effort to understand the amount of litter fall and its subsequent decomposition and quantify the release of available nutrients and soil physicochemical characteristics in plantations of four forest tree species（Lagerstroemia parviflora, Tectona grandis, Shorea robusta and Michelia champaca） in the Chilapatta Reserve Forest of the Cooch Behar Wildlife Division in the Terai zone of West Bengal, India. The most litter(5.61 Mg ha-1)was produced by T. grandis plantation and the least(4.72 Mg ha-1) by L. parviflora. The material turnover rate to the soil through decomposition from total litter was fastest during the first quarter of the year and subsequently decreased during the next two quarters. The material turnover rate was only 1 year, which indicates that more than90% of the total litter produced decomposed within a year.The available primary nutrient content in litter varied across the four plantations over the year. The plantations generally did not significantly influence the soil physical characteristics but did significantly influence the availability of primary nutrients and organic carbon at two depths（1–15 and16–30 cm） over the year. The availability of soil primary nutrients in the four plantations also increased gradually from the first quarter of the year to the third quarter and then decreased during the last quarter to the same level as in the first quarter of the year at both depths. The availability for soil organic carbon in the plantations followed a similar trend. The amount of litter produced and the material turnover in the soil in the different plantations differed, influencing the nutrient availability and organic carbon at the plantations. The amount of soil organic carbon was highest for T. grandis(2.52 Mg ha-1) and lowest for L. parviflora(2.12 Mg ha-1). Litter is the source of soil organic matter,and more the litter that is produced by the plantations, the higher will be the content and amount of soil organic carbon in the plantation.