Izuki ENDO

The long-term behaviour of radiocaesium (Cs-137) activity concentrations in forest ecosystems and their downstream impacts remain important issues in the deciduous broadleaf forests of Fukushima, Japan following the Fukushima Daiichi Nuclear Power Plant accident. To predict Cs-137 cycling and discharge in the forest ecosystem, it is important to understand the spatial dynamics of the Cs-137 inventory and transport along hillslopes. Therefore, we observed the spatial distribution of the Cs-137 inventory and Cs-137 transport via sediment and litter of a deciduous forest hillslope in Fukushima, Japan in 2016 and 2017 and examined how the spatial distribution of Cs-137 inventory was formed using a mass balance model. In 2017, the Cs-137 activity concentration was significantly greater in the downslope riparian area (455 kBq/m(2)) than in the upslope ridge area (179 kBq/m(2)). Annual Cs-137 transport within litter and sediment contributed <0.5% to the current Cs-137 inventory and cannot explain the current spatial variation of Cs-137 inventory on the hillslope. The mass balance model results showed that if the initial Cs-137 deposition was distributed uniformly in 2011, the spatial distribution of the hillslope Cs-137 inventory was influenced mainly by the movement of leaf litter with a high Cs-137 activity concentration.

Abstract The diverse socio-cultural conditions in Indonesia can make it difficult to develop sustainable micro-hydro power (MHP) generation in rural areas. However, the existing framework of sustainable development indicators to assess MHP sustainability does not include indicators for locations with traditional characteristics. This study aimed to develop indicators related to the specific cultural features for evaluating the sustainability of MHP generation. The identification of indicators was accomplished through field investigations and literature studies. Thirty-one experts in the Delphi method validated the indicators. The results revealed three indicators related to specific traditional characteristics and importance to the sustainability of MHP generation, i.e., electricity-supported cultural activities, customary rules of environmental protection, and directive of a traditional leader. These indicators can be elaborated with the existing framework and expected to increase sustainability assessment efforts for MHP generation in remote locations.

Litter usually drops to the ground, but some is retained within the canopy. Mass and CO2 efflux from retained litter may play a significant role in carbon cycling in tropical rainforests where emergent trees with complicated canopy structures are observed. This study aimed to show vertical variation in the mass and CO2 efflux (R-litter) of the retained litter and examined its contribution to carbon cycling in a Bornean tropical rainforest. The retained litter was collected from six 40 m tall columns with a radius of 1.6 m using an 85 m tall crane at six subplots. Dry mass and R-litter were measured in the laboratory. The mass of the retained litter from the sampling points ranged from 0.35 g to 187.0 g, and R-litter of the retained litter (42.4 +/- 43.4 mg CO2 kg(-1) h(-1)) was significantly lower than that of the soil surface litter (85.9 +/- 39.2 mg CO2 kg(-1)h(-1)) because of the lower water content in the retained litter. The mean mass of the retained litter measured from the ground to the canopy was 40.6 +/- 22.2 g m(-2). The greatest mass was observed at a height of 0-2 m. The ratio of the retained litter mass to the soil surface litter mass ranged from 1.0% to 11.5% with a mean of 5.2%, suggesting that litter retained within the canopy can contribute to carbon storage in this forest. On the other hand, R-litter did not differ with height, and the ratio of R-litter to aboveground autotrophic respiration was less than 1%. This study is the first to show that the litter retained within the canopy can sporadically be a moderate hot spot for C storage, but it is not a significant source of released CO2.