Miscanthus condensatus is the most important pioneer species in volcanically devastated site formed by the 2000-year eruption in Miyake-jima Island. The soils coursed by volcanic activities have extremely low nitrogen content. MultispeQ a non-invasive portable device was used to conducted field experiments to demonstrate photosynthetic properties of M. condensatus. Relative chlorophyll (RC), photosynthetically active radiation (PAR), and photochemistry of Photosystem II (Phi2) were obtained by MultispeQ, and soil nitrogen content (SN) were also obtained.
About RC in response to SN, it was found that RC increased with SN in low soil N sites (0 - 0.2% dry soil weight) but tend to be constant in relative high soil N sites (above 0.2% dry soil weight). In addition, the effects of SN on Phi2 controlling for PAR only on extremely low soil N sites (0 - 0.1% dry soil weight), but no not differ among other soil N sites (above 0.1% dry soil weight). These results indicate that PSII activity of M. condensatus seems to reach a certain level at low soil N sites except for extremely low soil N sites. Except for extremely low soil N sites, M. condensatus may achieve normal photosynthetic activity.