| Summary: | How photosynthetic-related leaf traits of non-nitrogen (N)-fixing pioneer species respond to extreme habitat conditions of primary succession is still not well-elucidated, especially in volcanically N-deplete habitats. The effect of N-deplete soil on photosynthetic-related leaf traits can provide a basis for predicting how plants adjust their strategies to adapt to such habitats. To examine the responses of leaf traits to extreme conditions, we investigated <i>Miscanthus condensatus</i> (a non-N-fixing C<sub>4</sub> pioneer grass) which grows on a volcanically devastated area on Miyake-jima Island, Japan, in which the volcanic ash has been deposited for 17–18 years since the 2000-year eruption. Leaf N content (N<sub>area</sub>), light-saturated photosynthetic rate (A<sub>max</sub>), and photosynthetic N use efficiency (PNUE) in three contrasting study sites: bare land (BL), shrub land gap (SLG), and shrub land under canopy (SLUC) were determined. Results indicated that compared to previous studies and internal comparison of Miyake Island, <i>M. condensatus</i> in BL was able to maintain a relatively high A<sub>max</sub>, N<sub>area</sub> and PNUE. The higher A<sub>max</sub> was in part a result of the higher PNUE. This is a characteristic necessary for its successful growth in N-deplete soils. These results suggest that <i>M. condensatus</i> has photosynthetic-related advantages for adaptation to volcanically N-deplete habitats.
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