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Today, native vegetation in the Valdivian Coastal Range (VCR) is restricted to areas where small-scale land use dominates resulting in a vegetation mosaic. This study (1) provides a description of the vegetation types (VT) within the vegetation mosaic, (2) identifies land use drivers that lead to either degradation or recovery processes and, (3) attempts to provide an explanation for the vegetation mosaic with a conceptual model. In two regions of the VCR we sampled 102 plots for composition of vegetation and indicators of livestock browsing, timber cutting and coppice forestry. We classified the vegetation using a flexible beta method and Bray-Curtis distance. Diagnostic species were identified by an extended indicator species analysis. The clustering results were visualized in NMDS and recursive partitioning was used to explain variations in the VTs as a function of the land use variables. Differentiating effects were tested using PERMANOVA and a conceptual model for the vegetation dynamics was developed from the results. Four VTs such as (1) extensively grazed non-native grasslands (EGN); (2), closed and semi-closed grazed Ugni and Berberis shrublands; (3) severely impacted evergreen forests; and (4) sparsely disturbed evergreen forests were recognized. The browsing indicators were important for differentiating the VTs. The EGN grasslands were differentiated by having more than 0.075 dung piles/m2. Areas with fewer dung piles but direct browsing effects had the greatest impact on vegetation. Forests were preserved when the mean browsing index was equal to or lower than 0.5. The cutting frequency was significant in determining overall floristic composition. We showed that shrublands and evergreen forests within the vegetation mosaic and the result of small-scale farming led to high native forest species richness. This makes the vegetation mosaic especially valuable in a landscape dominated by exotic tree monocultures.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
R. Suzuki
,
T. Ohdaira
,
K. Yamada
,
T. Yamazaki
,
N. Sei
,
T. Mikado
,
T. Noguchi
,
H. Ohgaki
,
S. Sugiyama
,
M. Chiwaki
,
T. Shimizu
,
M. Kawai
,
M. Yokoyama
,
S. Hamada
,
K. Saeki
,
N. Nishimura
, and
T. Tomimasu

Abstract  

A positron lifetime study has been done on dielectric multilayer cavity mirrors for free-electron-laser experiments by the use of a variable-energy pulsed positron beam. A long-lived ortho-positronium component has been observed at low positron energy region, corresponding to the depth of the top amorphous SiO2 layer. The intensity of the positronium component correlates with the degradation and restoration of the mirrors. We discuss the relation between the positronium intensity and degradation mechanism of the mirrors. The present studies revealed that the slow positron lifetime technique is highly sensitive to the properties of the mirrors and is useful for the evaluation of the mirrors.

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