**1. Introduction**

#### **1.1. Dwarf bamboo in Japan**

Dwarf bamboo is a small size bamboo species that distributes in Eastern Asia. On the classification of bamboo in Japan, dwarf bamboo is separated from the other bamboos. For dwarf bamboo, the sheath of culm remains until its death, whereas other bamboo species are

removed their sheath during the process of culm growth. Six genera and 72 species of dwarf bamboo are grown in Japan (**Table 1**) [1]. Moreover, the genera of *Sasa* and *Pleioblastus* are divided into several sections by their morphological characteristics [1]. The northern limit of distribution area of dwarf bamboo is considered at the middle part of Sakhalin where the genus *Sasa* distributes [3].

widely [1, 8]. In Hokkaido Island, which is located in the most northern part of Japan, the distribution of these three species is separated (**Figure 1**, [8]). These species are separated by the snow depth. The main distribution area of *S. nipponica* is the eastern part of Hokkaido, which faces the coast of the Pacific Ocean. Snow depth of this area is lower than other areas (below 75 cm of maximum snow depth) [4]. The distribution of *S. kurilensis* is the mountain area with heavy snow (over 150 cm of maximum snow depth). The distribution of *S. senanensis* is at the middle range of maximum snow depth between *S. nipponica* and *S. kurilensis* (75−150 cm). Also, the three *Sasa* species have different freezing tolerance. The climate in the area of the coast of Pacific Ocean the minimum temperature is lower than −10°C, and soil freezing occurs due to low snow depth [5]. The freezing tolerance for the bud of *S. nipponica* (−10 to −15°C) is higher than *S. kurilensis* and *S. senanensis* (−5 to −10°C) [9]. As a result, bud of *S. nipponica* can survive soil freezing. On the other hand, the distribution area of *S. kurilensis* and *S. senanensis* is covered with deep snow during the winter [1, 4]. The culms of *S. kurilensis* and *S. senanensis* are laid on the ground by the weight of snow cover. Snow has low thermal conductivity [10], and low air temperature is not easily conducted to the soil; as a result, soil can escape freezing [11]. Thus, *S. kurilensis* and *S. senanensis* can survive under the snow cover in winter. When the leaf and culm of *S. kurilensis* and *S. senanensis* are exposed above the snow depth, these organs cannot survive [12, 13]. The three *Sasa* species have different morphology types (**Figure 2**, [4]). The culm height of *S. kulinensis* reaches 3 m, and its longevity is estimated to be over 10 years. The upper part

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**Figure 1.** The distribution of the three *Sasa* species in Hokkaido Island located in Northern Japan (modification from

Toyooka et al. [8]).

The habitats of dwarf bamboo in Japan are restricted by climate, especially winter [4]. The climate in Japan is divided by the coasts of the Sea of Japan and Pacific Ocean [5], and the coast of the Sea of Japan area is considered as the snowy area. The presence of snow is an important factor to restrict the distribution of dwarf bamboo, and the main genus to distribute in the snowy area is *Sasa* [1]. Among the five sections of *Sasa* genus, *Macrochlamys* and *Sasa* can distribute in snowy area, since they are adapted to the snowy environment [1]. In this article, we introduce the ecological characteristics of the three species in genus *Sasa* that grow in the northern part of Japan. We also focus on growth characteristics of the three dominant species of genus *Sasa* with an ecophysiological method.

#### **1.2. Ecological characteristics of three** *Sasa* **species in Northern Japan**

In Northern Japan, the dwarf bamboo is a typical and essential component of the forest floor [6, 7]. In this region, *Sasa kurilensis*, *Sasa senanensis*, and *Sasa nipponica* distributed


**Table 1.** Genera of dwarf bamboo distributed in Japan [1, 2].

widely [1, 8]. In Hokkaido Island, which is located in the most northern part of Japan, the distribution of these three species is separated (**Figure 1**, [8]). These species are separated by the snow depth. The main distribution area of *S. nipponica* is the eastern part of Hokkaido, which faces the coast of the Pacific Ocean. Snow depth of this area is lower than other areas (below 75 cm of maximum snow depth) [4]. The distribution of *S. kurilensis* is the mountain area with heavy snow (over 150 cm of maximum snow depth). The distribution of *S. senanensis* is at the middle range of maximum snow depth between *S. nipponica* and *S. kurilensis* (75−150 cm). Also, the three *Sasa* species have different freezing tolerance. The climate in the area of the coast of Pacific Ocean the minimum temperature is lower than −10°C, and soil freezing occurs due to low snow depth [5]. The freezing tolerance for the bud of *S. nipponica* (−10 to −15°C) is higher than *S. kurilensis* and *S. senanensis* (−5 to −10°C) [9]. As a result, bud of *S. nipponica* can survive soil freezing. On the other hand, the distribution area of *S. kurilensis* and *S. senanensis* is covered with deep snow during the winter [1, 4]. The culms of *S. kurilensis* and *S. senanensis* are laid on the ground by the weight of snow cover. Snow has low thermal conductivity [10], and low air temperature is not easily conducted to the soil; as a result, soil can escape freezing [11]. Thus, *S. kurilensis* and *S. senanensis* can survive under the snow cover in winter. When the leaf and culm of *S. kurilensis* and *S. senanensis* are exposed above the snow depth, these organs cannot survive [12, 13].

removed their sheath during the process of culm growth. Six genera and 72 species of dwarf bamboo are grown in Japan (**Table 1**) [1]. Moreover, the genera of *Sasa* and *Pleioblastus* are divided into several sections by their morphological characteristics [1]. The northern limit of distribution area of dwarf bamboo is considered at the middle part of Sakhalin where the

The habitats of dwarf bamboo in Japan are restricted by climate, especially winter [4]. The climate in Japan is divided by the coasts of the Sea of Japan and Pacific Ocean [5], and the coast of the Sea of Japan area is considered as the snowy area. The presence of snow is an important factor to restrict the distribution of dwarf bamboo, and the main genus to distribute in the snowy area is *Sasa* [1]. Among the five sections of *Sasa* genus, *Macrochlamys* and *Sasa* can distribute in snowy area, since they are adapted to the snowy environment [1]. In this article, we introduce the ecological characteristics of the three species in genus *Sasa* that grow in the northern part of Japan. We also focus on growth characteristics of the three dominant species

In Northern Japan, the dwarf bamboo is a typical and essential component of the forest floor [6, 7]. In this region, *Sasa kurilensis*, *Sasa senanensis*, and *Sasa nipponica* distributed

genus *Sasa* distributes [3].

186 Bamboo - Current and Future Prospects

*Sasa*

*Pleioblastus*

Subgen. Nipponocalamus

of genus *Sasa* with an ecophysiological method.

**1.2. Ecological characteristics of three** *Sasa* **species in Northern Japan**

Section *Macrochlamys* 6 *Sasa kurilensis* Makino et Shibata

Section *Crassinodi* 8 *Sasa nipponica* Makino et Shibata

*Sasamorpha* 2 *Sasamorpha purpurascens* (Hechel) Makino

*Chimonobambusa* 1 *Chimonobambusa marmoreal* (Mitford) Makino

Section *Lasioderma* 9 *Sasa shimidzuana* Makino Section *Monilicladae* 4 *Sasa tsuboiana* Makino Section *Sasa* 9 *Sasa senanensis* Rehder

*Sasaella* 10 *Sasaella ramosa* Makino

*Pseudosasa* 2 *Pseudosasa japonica* Makino

Subgen. Pleioblastus 4 *Pleioblastus linearis* Nakai

Section *Medakea* 6 *Pleioblastus simonii* Nakai Section *Nezasa* 11 *Pleioblastus chino* Makino

**Table 1.** Genera of dwarf bamboo distributed in Japan [1, 2].

**Genera and section Number of species Typical species**

The three *Sasa* species have different morphology types (**Figure 2**, [4]). The culm height of *S. kulinensis* reaches 3 m, and its longevity is estimated to be over 10 years. The upper part

**Figure 1.** The distribution of the three *Sasa* species in Hokkaido Island located in Northern Japan (modification from Toyooka et al. [8]).

of the culm of *S. kulinensis* has buds on nodes and continues to bifurcate. In contrast, there are no buds at lower part of the culm of *S. kulinensis*. The leaves of *S. kulinensis* can survive for relatively longer time, and its longevity ranges from 3 to 5 years. The culm height of *S. senanensis* is about 2 m, and its longevity is 5 years. The culm of *S. senanensis* has buds on every node. The leaf longevity of *S. senanensis* is about 2 years. In contrast, the culm height of *S. nipponica* is less than 1 m, and its longevity is also about 1 year. The buds of *S. nipponica* exist at the underground of the culm. The leaf longevity of *S. nipponica* is less than 1 year.

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

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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

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.

This research was conducted in an arboretum of the Hokkaido Research Center, Forestry and Forest products Research Institute (43°00′N, 141°23′E, 141 m a.s.l.) located in Sapporo City, Hokkaido, Japan. The annual mean, maximum, and minimum temperatures at the metrological station of this centre were 7.3, 35.7, and −22.8°C, respectively, from 1975 to 2003 [26]. The range of annual precipitation was from 581 to 1490 mm year−1 during 1975–2003 [26]. The maximum snow depth in winter was 130 cm [26]. In this arboretum, the subterranean stem of *S. kurilensis*, *S. senanensis*, and *S. nipponica* was planted in 1982. The size of planting area was 5 × 10 m for each *Sasa* species. Plantations of *Sasa* species were exposed to full sunlight the

We measured the photosynthetic rate at light saturation (*Psat*, μmol m−2 s−1) from May to October 2004. The measurements were carried out at 10:00–15:00 each month. Second leaves counted from the top of culm of each *Sasa* species were used for the measurement of *Psat*. We

whole day because there were no surrounding trees around the plantation.

done under different conditions.

kinds of evergreen spruce [21].

**2.2. Materials and methods**

The three *Sasa* species have well-developed rhizome systems and are dominant at the forest floor in general forests of this region [14, 15]. As a result, the light environment under the *Sasa* species is quite dark, and regeneration of other species is suppressed [16]. Moreover, the *Sasa* species has high regeneration ability after disturbances. When forests suffer from forest fires, forest cannot restore; however, dwarf bamboo is able to regenerate as ground vegetation [17, 18]. The flowering period of the *Sasa* species is estimated to be 60–100 years [4]; however, information of flowering is still limited. Based on previous information, flowering of *Sasa* species occurs synchronously and often expands over 1000 ha in area [4, 19]. After flowering, numerous seeds are produced, and all culms of the *Sasa* species dies [4, 19], as does a monocarpic plant.

**Figure 2.** Morphological characteristics of the three *Sasa* species (modification from Makita [4]).
