JS6-3:

Nitrogen mineralization in soils and its relationship with microbial community diversity along a vegetation gradient in Miyakejima island

Nitrogen mineralization in soil is one of the fundamental processes in terrestrial ecosystem. This process is strongly regulated by various microbes and produce dissolved inorganic nitrogen, such as NH+ 4and NO− 3, which are limiting nutrients for plant growth especially in harsh environments. Since bareland or severe damaged ecosystems after volcanic eruption are generally in low nutrient conditions, the nitrogen mineralization in these ecosystems are of importance. Miyakejima island, one of the active volcano in Japan was erupted in 2000, deposition of volcanic ash and poisonous gas caused a severe damage to vegetation and soil in limited area around the crater of Mt. Oyama. So, we can see various ecosystems from bareland to matured forest in the small island. These various ecosystems provide suitable situation for research on nitrogen mineralization and its relationship with vegetation and microbe communities. The present study aims to estimate nitrogen mineralization rate (NMR) in soil and the relationship between NMR and microbial community functional diversity (MFD). We measured the NNM rate in field by using resin core method in various 11 sites during the growing season, 2013. By using sub-samples from incubated soil, we also investigated soil microbial functional diversity (MFD) by means of BIOLOG plates technique. In addition, we monitored the moisture, the temperature, and we also analyzed organic matter content, total carbon and nitrogen concentration of surface soil. Results showed that NNM rate range were -0.1 to 1.1 mg N_kg-1 soil_d-1 and higher in sites colonized by N2-fixing trees. Soil MFD were different among sites, and tend lower in the bare land or grass sites. There was no significant link between NMR and MFD in soil at the Miyakejima island.

keywords:nitrogen mineralization,vegetation gradient,soil microbial functional diversity