The alien woody legume, black locust （Robinia pseudoaca-cia）, has invaded Japanese black pine （Pinus thunbergii） forests located in Japan’s coastal plain and hill regions where gaps are formed in pine forests aft...The alien woody legume, black locust （Robinia pseudoaca-cia）, has invaded Japanese black pine （Pinus thunbergii） forests located in Japan’s coastal plain and hill regions where gaps are formed in pine forests after nematode infestation. Nitrogen fixation by legumes acceler-ates N cycling in forest ecosystems. We studied temporal change in the annual tree-ring resolution N stable isotope composition （δ15N, a per mil deviation of δ15N/14N ratio, relative to atmospheric N2δ15N=0‰） at two natural locations of Japanese black pine forest with black locust that differed in the time since black locust establishment （Shohnai in north-east and Kita-Kyushu in southwest Japan）. Analyzed tree-rings covered the period from 1990/1992 to 2009. N acquisition by Japanese black pine from black locust N input to the soil was evidenced by temporal shifting of N stable isotope composition on the annual pine tree rings. With pro-gressive development of the forest stand,δ15N values of earlier tree-ringsδ15N of -5‰） from black pine associated with black locust shifted to-wards values similar to those of black locustδ15N values nearly to-1‰）, which suggests acquisition of N by N2 fixation （Shohnai site）. In con-trast, in a forest where black locust had settled for two or three genera-tions, in a black pine stand （Kita-Kyushu site）, longer periods of N en-richment in the soil were reflected in the elevated tree-ringδ15N values of newly established black pine trees. Based on tree-ringδ15N data from the Shohnai site, we determined that about 10 years after black locust establishment, soil N had already been enriched by black locust N, this, in turn, contributed to N fertilization of surrounding trees in mixed stands.展开更多
We made comparison of magnetic property between two loess/paleosol sediments from theBeiyuan section, Linxia and the Shajinping section, Lanzhou. The two sections apart only 100 km inNE-SW direction. At the Beiyuan se...We made comparison of magnetic property between two loess/paleosol sediments from theBeiyuan section, Linxia and the Shajinping section, Lanzhou. The two sections apart only 100 km inNE-SW direction. At the Beiyuan section, enhancement of the low-field magnetic susceptibility, ARMsusceptibility and SIRM are observed in paleosols. The positive correlations among these threeparameters suggest the presence of two magnetic components, i.e. the background component and theenhanced component. The unblocking curves of low-temperature IRM give strong evidence for the ideaof the two components. On the contrary, the magnetic parameters are almost constant throughout theShajinping section. The enhanced component is not found in the Shajinping section. The magneticproperties of the background component are indistinguishable between the two sections. Contrastingmagnetic properties imply the difference of soil formation process between the two sections.展开更多
Differential and total cross sections of the γp→π0p and the γd→π0pn reaction were measured for photon energies between 640 and 1 150 MeV. The data have been compared with SAID and MAID model calculations. π0 ph...Differential and total cross sections of the γp→π0p and the γd→π0pn reaction were measured for photon energies between 640 and 1 150 MeV. The data have been compared with SAID and MAID model calculations. π0 photoproduction on the deuteron shows a strong suppression of the 2nd resonance which is clearly seen in the γp→π0p reaction.展开更多
文摘The alien woody legume, black locust （Robinia pseudoaca-cia）, has invaded Japanese black pine （Pinus thunbergii） forests located in Japan’s coastal plain and hill regions where gaps are formed in pine forests after nematode infestation. Nitrogen fixation by legumes acceler-ates N cycling in forest ecosystems. We studied temporal change in the annual tree-ring resolution N stable isotope composition （δ15N, a per mil deviation of δ15N/14N ratio, relative to atmospheric N2δ15N=0‰） at two natural locations of Japanese black pine forest with black locust that differed in the time since black locust establishment （Shohnai in north-east and Kita-Kyushu in southwest Japan）. Analyzed tree-rings covered the period from 1990/1992 to 2009. N acquisition by Japanese black pine from black locust N input to the soil was evidenced by temporal shifting of N stable isotope composition on the annual pine tree rings. With pro-gressive development of the forest stand,δ15N values of earlier tree-ringsδ15N of -5‰） from black pine associated with black locust shifted to-wards values similar to those of black locustδ15N values nearly to-1‰）, which suggests acquisition of N by N2 fixation （Shohnai site）. In con-trast, in a forest where black locust had settled for two or three genera-tions, in a black pine stand （Kita-Kyushu site）, longer periods of N en-richment in the soil were reflected in the elevated tree-ringδ15N values of newly established black pine trees. Based on tree-ringδ15N data from the Shohnai site, we determined that about 10 years after black locust establishment, soil N had already been enriched by black locust N, this, in turn, contributed to N fertilization of surrounding trees in mixed stands.
文摘We made comparison of magnetic property between two loess/paleosol sediments from theBeiyuan section, Linxia and the Shajinping section, Lanzhou. The two sections apart only 100 km inNE-SW direction. At the Beiyuan section, enhancement of the low-field magnetic susceptibility, ARMsusceptibility and SIRM are observed in paleosols. The positive correlations among these threeparameters suggest the presence of two magnetic components, i.e. the background component and theenhanced component. The unblocking curves of low-temperature IRM give strong evidence for the ideaof the two components. On the contrary, the magnetic parameters are almost constant throughout theShajinping section. The enhanced component is not found in the Shajinping section. The magneticproperties of the background component are indistinguishable between the two sections. Contrastingmagnetic properties imply the difference of soil formation process between the two sections.
文摘Differential and total cross sections of the γp→π0p and the γd→π0pn reaction were measured for photon energies between 640 and 1 150 MeV. The data have been compared with SAID and MAID model calculations. π0 photoproduction on the deuteron shows a strong suppression of the 2nd resonance which is clearly seen in the γp→π0p reaction.
