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Canopy soils on large trees are important for supporting the lives of many canopy plants, and thereby increasing regional biodiversity. However, because of the less accessibility to canopy soils, there is insufficient knowledge on how canopy soils produce available nitrogen (N) for canopy plants through the activity of canopy soil microbes. Canopy soils usually have different soil properties from ground soils, so we hypothesized that canopy soils would have unique microbial communities compared to ground soils, but still provide available N for canopy plants. Here, we compared soil N availability, including net N mineralization and nitrification rate, and microbial communities between canopy soils (organic soils) collected at various heights of a large Cercidiphyllum japonicum tree and ground soils (organic and mineral soils) in a cool-temperate old-growth forest of Japan. The canopy soils had significantly different N availability (mass-based higher but volume-based lower) and microbial communities from the ground mineral soils. Among organic soils, the height of the soil had an impact on the microbial communities but not on the N availability, which agreed with our hypothesis. Despite the decrease in fungal abundance in the higher soils, the increase in certain components of the cellulose-decomposing fungi and oligotrophic bacteria may contribute to the available N production. Also, the abundance of ammonia-oxidizers did not change with the height, which would be important for the nitrification rate. Our study implied canopy soils could provide N to canopy plants partly through the functional redundancy within different microbial communities and constant population of ammonia-oxidizers. [ABSTRACT FROM AUTHOR]

Huge groundwater reserves are under the foot of Mt. Fuji, the tallest volcanic mountain in Japan, and the residence time of the groundwater as estimated from the36Cl/Cl isotope ratio is in the range of 20–35 years. All springwater samples contain nearly saturated concentrations of oxygen. The groundwater field was separated into four areas based on regional slopes of the groundwater table and estimated groundwater flow directions. Springwater samples showed that physicochemical characteristics of the groundwater in the region are relatively constant; Ion concentrations were characterized as the Ca-HCO3type, irrespective of location at the foot of the mountain. The density of prokaryotes in the springwater, which was in the range of 102–104cells mL−1, was low compared with any other groundwater so far reported. Although the density of prokaryotes was low, retrieved clones show that the prokaryotes belonged to eight bacterial and two archaeal phyla, and included both aerobic and obligate anaerobic prokaryotes. Some retrieved clones were related to thermophilic prokaryotes, which are optimally adapted to temperatures greater than 40°C. This finding suggests that at least some of the source of the groundwater was located at a depth of 600 m or greater, based on a temperature gradient of 4°C/100 m. This depth is far below the lava layer which was taken to be a substantial pool of groundwater. Microbiological information may provide insight into the transport route of groundwater until it emerges. [ABSTRACT FROM AUTHOR]