Fresh litter acts as a substantial phosphorus source of plant species appearing in primary succession on volcanic ash soil

Plants have difficulty absorbing phosphorus from volcanic ash soils owing to the adsorption of phosphorus by aluminum and iron in the soils. Thus, on volcanic ash soils, the phosphorus source for natural vegetation is expected to be organic matter, however, there is a lack of experimental evidence regarding this occurrence. Here, we studied the effect of organic matter on plant growth of some species that occur in primary successions of volcanic ash soil ecosystems, based on growth experiments and chemical analyses. We found that a large amount of inorganic phosphorus (but only a limited amount of inorganic nitrogen) is leached from fresh leaf litter of the pioneer spices Fallopia japonica at the initial stage of litter decomposition. Phosphorus from the fresh litter specifically activated the growth of subsequently invading nitrogen-fixing alder when immature volcanic soil was used for cultivation. In contrast, old organic matter in mature soil was merely a minor source of phosphorus. These results suggest that fresh litter of F. japonica is essential for growth of nitrogen-fixing alder because the litter supplies phosphorus. We consider that rapid phosphorus cycles in fresh litter-plant systems underlie the productivity of natural vegetation even in mature ecosystems established on volcanic ash soils.

Pinhole Multistep Centrifuge Outflow Method for Estimating Unsaturated Hydraulic Properties with Small Volume Soil Samples

If soil hydraulic conductivity or water holding capacity could be measured with a small volume of samples, it would benefit international fields where researchers can only carry a limited amount of soils out of particular regions. We performed a pinhole multistep centrifuge outflow method on three types of soil, which included granite decomposed soil (Masa soil), volcanic ash soil (Andisol soil), and alluvial clayey soil (paddy soil). The experiment was conducted using 2 mL and 15 mL centrifuge tubes in which pinholes were created on the top and bottom for air intrusion and outflow, respectively. Water content was measured at 5, 15, and 30 min after applying the centrifuge to examine the equilibrium time. The results showed that pinhole drainage worked well for outflow, and 15 or 30 min was sufficient to obtain data for each step. Compared with equilibrium data, the retention curve was successfully optimized. Although the curve shape was similar, unsaturated hydraulic conductivities deviated largely, which implied that Ks caused convergence issues. When Ks was set as a measured constant, the unsaturated hydraulic properties converged well and gave excellent results. This method can provide soil hydraulic properties of regions where soil sampling is limited and lacks soil data.

Effect of Alkaline Concentrations on the Synthesis of Volcanic Soil-Based Zeolite for Methylene Blue Removal by Fenton-Like Oxidation Process

This study demonstrates the potential use of volcanic ash soil (VAS) as raw materials for preparing zeolite without adding any templates or seeds. Here we investigated the effect of alkaline concentrations on the synthesis of VAS-based zeolite and enhanced its ability for methylene blue (MB) removal by Fenton-like process. Zeolite materials were directly synthesized by mixing the amount of VAS within alkaline concentrations of 0.5 (P1), 1.5 (P2), and 3.0 mol/L (P3), respectively, followed by a simple hydrothermal procedure at 100 oC for 24 h. The prepared sample characteristics were obtained from the Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analysis, which confirmed the formation of zeolite A and some mineral phases in P2 and P3 samples. The mentioned samples reached equilibrium state at MB concentration of 200 mg/L with high adsorption capacity values compared to VAS. The adsorption showed a better fit to the Langmuir isotherm model (R2]0.99), in which the maximum uptake capacities were found to be 24.03 mg/g for P2 and 14.30 mg/g for P3. Interestingly, the percentage of MB removal using P2 and P3 increased greatly from 52.81% and 32.26% to 98.92% and 98.85% by Fenton-like process, respectively.

2-dimensional effective stress analysis for a damaged bridge located in the caldera of Mount Aso in 2016 Kumamoto earthquake

<p>In this paper, we conducted a two-dimensional effective stress analysis in consideration of the interaction between the ground and the structure for the Kurumakaeri Bridge which is located in the caldera of Mount Aso. From the results of the analyses, it is confirmed that the ground around the abutment subsided by about 26 cm due to the deformation of the soft volcanic ash soil. Furthermore, it is confirmed that the collision between the superstructure and the abutment happened because the abutment moved to the front side. Due to this movement, the deformation of about 34 cm occurred at the rubber bearing after the earthquake ended.</p>