Plant species in extreme habitat condition will exhibit physiological responses to extreme habitats environment. In Miyake-jima volcano, three dominant pioneer species, Miscanthus condensatus， Alnus sieboldiana and Fallopia japonica successfully colonized the volcanically devastated site. To understand the successional mechanism and physiological responses of pioneer species to extreme habitats, comparison of photosynthetic traits among multi-pioneer species in volcanically devastated site is effective.
Methods
Study sites are located in volcanically devastated area formed by the 2000-year eruption. The three pioneer species (M. condensatus，A. sieboldiana and F. japonica) are growing there. Eight well-growing plants of each species were selected to demonstrate photosynthetic traits, such as Saturated photosynthetic rate (Amax). Leaf mass per area (LMA) and Leaf nitrogen (Leaf N) was calculated from sampled leaves. Photosynthetic nitrogen use efficiency (PNUE) was determined by the ratio Amax and the leaf N.
Result and discussion
About the leaf N content, there were the following trends: A. sieboldiana> F. japonica> M. condensatus(P<0.05). As for the value of LMA and Amax, the maximun appears on F. japonica and M. condensatus, respectively. About the PNUE value, M. condensatus was significantly higher than A. sieboldiana and F. japonica (P<0.01).
Here, we considered that due to high PNUE value, M. condensatus can be adaptive to the extremely low soil N conditions in Miyake-jima volcanically devastated area in contrast to A. sieboldiana which has N fixing ability.