In the Amazon estuary, the açaí palm (Euterpe oleracea) grows on the tidal floodplain. The fruit of this plant is a regional staple food. Owing to the selective removal of other tree species, intensive açaí-growing regions are rapidly expanding. At present, the effects of water level fluctuations, topography, and intensive cultivation on açaí growth are poorly understood. In the present study, we investigated the effects of water level fluctuations with different topography and plant species mixtures on açaí growth, by surveying trees in six study plots on Cação Island, five plots on Murutizal Island, and two plots each on Juruateua and Juba islands, Pará State, Brazil. Elevation and above- and underground water levels were measured to assess submergence conditions in the plots on Cação Island. Açaí exhibited better growth on higher ground at 5 m, non-reducing surface soil, shorter durations of submergence (110-120 h month ^－1), more consecutive days of non-submergence (6 d month ^－1), and in the presence of mututi (Pterocarpus sp.), miriti (Mauritia flexuosa), and ucuúba (Virola surinamensis). The results for most of the study sites suggest that >6 consecutive days of non-submergence per month resulted in land characteristics that were suitable for sustainable açaí production and simultaneous ecosystem conservation. The results also suggested a combination of other tree species (>20% of total), and density of approximately 1,000 açaí ha^－1 was appropriate for efficient açaí production.

To elucidate uptake via the roots and the dynamics of cesium (Cs) in Japanese cedar (Cryptomeria japonica D. Don), we measured the stable cesium (¹³³Cs), rubidium (Rb), and potassium (K) content in the needles and wood of Japanese cedar harvested from four sites: 1) Kawauchi; 2) Kamikawauchi; 3) Otama; and 4) Tadami in Fukushima Prefecture, Japan. The levels of deposition of radiocesium were different among sites. The contents of ¹³³Cs, Rb, and K were higher in current needles and heartwood than in old needles and sapwood, respectively. In addition, ¹³³Cs, Rb, and K content tended to be lower in the small than in the large trees. This result suggests that Cs would be accumulated in heartwood, particularly in mature trees. Proportional relationships were observed between ¹³³Cs in old needles and heartwoods as well as sapwoods. Therefore, ¹³³Cs in wood may be estimated from ¹³³Cs in needles. ¹³³Cs in needles and wood varied among sites, with higher levels observed in Tadami and Kamikawauchi. Exchangeable K in surface soil was slightly lower in Tadami and Kamikawauchi than in Kawauchi and Otama. Soil exchangeable ¹³³Cs was the highest in Tadami. The ¹³³Cs uptake via roots and the dynamics of ¹³³Cs in Japanese cedar may be affected by soil exchangeable K and ¹³³Cs.

To clarify the impact of harvesting logging residues at thinning on the soil properties and stand growth on plots of 45- year-old Japanese cedar (Cryptomeria japonica), we investigated the tree census and carried out a soil survey three years after thinning at whole-tree harvesting, short wood logging, and no harvesting (no thinning) plots in Kamaishi, Iwate Prefecture, Japan. The results for the chemical and physical soil analysis showed low porosity in the whole-tree harvesting plot, while no significant differences were found in the chemical properties of the soil among the plots. The low percentage of vegetation cover by the forest floor vegetation in the whole-tree harvesting plot resulted in heavy soil movement and caused the reduction in soil porosity. The impact of harvesting logging residues on the stand growth was inconclusive, although the stand growth at the whole-tree harvesting plot tended to be lower than that at the other plots studied. These results indicate that harvesting logging residues at thinning on steep slopes may influence soil physical properties.