Seasonal variation of litter accumulation and putrefaction with reference to decomposers in a mangrove forest in Karachi, Pakistan

Abstract

Litter production and its decomposition is a major source of nutrients for mangrove ecosystems. This study was conducted on a naturally growing mangrove population in the Sandspit area in Karachi, Pakistan, during 2007 and 2008. Avicennia marina (Forssk.) Vierh. forms an almost pure population in Sandspit mangrove swamps. To examine the details of temporal fluctuation in litter accumulation and its decomposition, observations were taken at monthly intervals. Results showed that the maximum litter accumulation occurred during the monsoon and post-monsoon season with the maximum accumulation in August (68.76 ± 8.72 g/ m2), while minimum litter accretion occurred in January (13.61 ± 1.46 g/m2). The decomposition rate was highest (47.7%) in June and almost completed in 8 months. The exponential curve model showed highly significant differences between the rates of decomposition in various months both at ground level and at a 5-cm depth below the surface. Soil fungi and major bacterial groups were examined as decomposers. Aspergillus Micheli was the most diverse group of the soil-borne microflora in the mangrove habitat. The fungal spore load in the soil was greater in summer and lower in winter.