**2. Ecophysiological characteristics of three** *Sasa* **species**

#### **2.1. Background**

In the previous chapter, we summarized the ecological characteristics of the three dominant *Sasa* sp. in Northern Japan: *S. kurilensis*, *S. senanensis*, and *S. nipponica.* We showed specific traits of leaves and culm longevity of the three species. To survive and grow under different growth conditions, the *Sasa* species have adapted to each habitat through morphological and physiological adaptation. For example, leaf and stem longevities of *S. nipponica* are 1 year, and so its leaf has to obtain large amount of photosynthetic productivity during the one growing period. In contrast, leaves and culms of *S. kurilensis* can survive for a long period. Therefore, it also may be possible for *S. kurilensis* to obtain photosynthetic productivity for a long period. In general, plant growth form can be evaluated through ecophysiological characteristics [20, 21]. Photosynthetic characteristics of three *Sasa* species have been measured by previous research [22–24]. However, characteristics cannot be compared because the measurement was done under different conditions.

There are contrasting growth characteristics, namely fast and slow [25]. Fast-growing species have short-lived leaves with a high photosynthetic capacity, whereas slow-growing species have long lived leaves with a low photosynthetic capacity that can maintain its function over long periods. The differences of photosynthetic capacity between fast- and slow-growing species are related to foliar nitrogen concentration, which is usually higher in fast-growing than in slow-growing species [25]. In contrast, photosynthetic nitrogen use efficiency is an indicator for allocation of nitrogen to photosynthetic apparatus; slow-growing species shows a high value [25]. The nitrogen use characteristic is predicted to be different according to life form. For example, the photosynthetic rate and concentration of nitrogen may be high for *S. nipponica,* since it has a short leaf longevity. We predicted, in contrary, that leaves of *S. kurilensis* may have a low photosynthetic rate and low nitrogen concentration. The long longevity of *S. kurilensis* may be compensated with low photosynthetic productivity as found in several kinds of evergreen spruce [21].

The aim of this chapter is to show ecophysiological characteristics of the three *Sasa* species in relation to their different life forms, such as leaf longevity, culm height, etc. We measured the seasonal change of photosynthetic rates, concentrations of nitrogen and chlorophyll, and leaf thickness of different aged leaves of the three *Sasa* species planted in a common garden.
