Seasonal distribution of Isotomina thermophilan in a secondary succession and a homegarden in Cachar, Assam.

ABSTRACT

Present investigation was carried out in Cachar district of Assam over a period of two years (May 2007 - April 2009) to understand the seasonal ecology of Isotomina thermophila (Axelson, 1900) in secondary succession and homegarden ecosystems. Population was found to be maximum during July 2008 (7949.05 No. m-2) and September 2008 (7949.05 No. m-2) in homegarden whereas the peak was recorded in secondary succession during September 2008 (13656.05 No. m-2). Least population was encountered during March 2008 (1222.93 No. m-2) and April 2008 (1630.57 No. m-2) in homegarden and secondary succession, respectively. It may be due to the fact that, vital activity of this species effected in the dry period or migrate towards lower soil profile in search of food and moisture. Linear regression analysis established the hypothesis that all the environmental variables showed positive and significant influence on the population dynamics whereas in homegarden, rainfall (r= 0.36, p>0.05) did not show any influence. In multiple regression analysis positive and significant influences (p<0.05) were recorded for both the investigated sites. Rainfall, relative humidity and temperature facilitated the soil moisture, microbial activity, litter decomposition may favour the reproduction and growth rate of the species. Among microclimatic conditions except soil pH all other parameters exhibited significant correlations (p<0.05) with population. Based on the present investigation, it can be concluded that I. thermophilia does not differ much with the general ecology of collembolans in this sub humid climate.