Search

Large-scale afforestation is a key measure to mitigate global warming, however, implementation may result in land-use competition with agriculture. To avoid such competition, carbon mitigation methods using arid and semi-arid areas have been proposed, but to our knowledge there is no report of rates of sequestration based on long-term observations from actual experimentation. In this study (1999–2015), in an arid area near Leonora, Western Australia (annual rainfall: 220 mm year−1; pan evaporation: 3400 mm year−1), carbon sequestration was assessed in above and below ground biomass in Eucalyptus camaldulensis under ambient conditions and with active site amelioration (combination of water harvesting with large mounds and hardpan blasting). The carbon sequestration rate was estimated at 7.92 Mg-CO2-e ha−1 year−1 for a total carbon sink of 230 Mg-CO2-e ha−1. Carbon mitigation may thus be a viable option in arid regions, not only in Western Australia but globally, and can be enhanced with active site engineering.

We have developed prototype resistive plate chambers (RPCs) for the LEPS2 experiment at SPring-8 in Japan. At LEPS2, RPCs will be used as time-of-flight detectors. The goal is to achieve a time resolution of 50 ps with a readout cell as large as possible. We made several types of RPCs and examined the dependence of time resolution with the size and the shape of the readout cell. We found that the time resolution and the efficiency largely depend on the shape of the readout cell and the position where it is excited. We confirmed that two-ends strip-shaped readout cells performed better than one-end readout cells, and a promising time resolution of 60 ps was obtained with a 2.5 cm (wide) × 108 cm (long) readout.

Long-term changes in the precipitation data at Sturt Meadows were analyzed by the Mann-Kendall statistics and the Lepage test. Yearly and spring precipitation increased significantly from 1910 to 2008, and the significance levels were p < 0.10 and 0.01, respectively. The data of daily precipitation were classified into two groups (class 1-4 and 5) separated by the distribution of the data, and class 1-4 precipitation increased significantly. There were 4 significant-climatic jumps (1925-27, 1963, 1979-1982 and 1993) by results of the Lepage test. The averages of yearly precipitation during whole years and the latest period are 215.0 and 280.9 mm/year, respectively. The averages of monthly precipitation in February, October and November during the latest period (1993-2008) is higher than those in the previous periods. That in February during the latest period was especially heavy, when the mean precipitation in February was six times higher than that in the previous period. This change was attributed to the increase in the frequency of storm events in February during the latest period. Monthly precipitation exceeding 100 mm/month in February was recorded three times (1995, 2001 and 2006), and this occurred only 2 times in previous periods (1925 and 1975).

Carbon fixation by afforestation in semi-arid land has been proposed as one of the most promising countermeasures against the global warming issue. Our demonstration area for carbon fixation suffered some serious problems, such as salinization and water logging, which we attempted to solve. We tried to reduce the groundwater level by taking advantage of the transpiration of planted trees. The two sites used were identified as D-low and D-high. In this study, the transpiration of planted trees, soil water change, and groundwater level were measured. E. sargentii and E. occidentalis were considered to be optimum. From the analyses of the groundwater and soil water contents, water was found to gather at the D-low site. However, analysis of the Neutron Moisture Meter (NMM) data indicated that the volumetric water content did not rise. Through the transpiration of planted trees, groundwater was absorbed via tree roots located in deep soil. Thus, the groundwater level was expected to decrease, but this decrease was prevented by the collected water. On the other hand, due to afforestation at the D-high site, where it was difficult for water to gather, a decreasing tendency in the amount of groundwater was clearly shown by the volumetric water content. Furthermore, the precipitation water trickled down through the soil surface layer, which was expected to mitigate the salt accumulation in topsoil. Soil improvement effects by afforestation, i.e., desalination and the prevention of water logging through the transpiration of planted trees, were confirmed in our research area.

The definitive version is available at www.blackwell-synergy.com.