Variations in the foliar δ¹³C and C₃/C₄ species richness in the Japanese flora of Poaceae among climates and habitat types under human activity

Abstract

For 383 Poaceae species harvested over the Japanese islands and stored as herbarium specimens along several decades, we determined C 3 and C 4 types of photosynthesis from leaf stable carbon isotope ratio (d 13 C). Then, we sought the relationships between C 4 species richness and climatic factors or habitat types. Except for the two Panicum species (P. lanuginosum and P. scoparium) having the possibility of C 3 -C 4 intermediate, 227 and 154 species were classified into C 3 and C 4 . The C 4 species richness increased from northern to southern islands in Japan, positively correlated with mean annual air temperature. Greater C 4 species richness in the seashore habitats, and smaller C 4 species richness in the shaded, wet and highland habitats would be related to the photosynthetic responses to local environmental factors such as irradiance level and temperature regime. No difference of leaf d-value of C 3 Poaceae was obtained between the habitats with different soil water availability, suggesting the less importance of soil water availability on leaf water-use efficiency in C 3 Poaceae species in Japan having humid climate. Additionally, possible effects of human activity around the harvested time or site on leaf d-value were estimated, because the habitat includes the sites with high human activity. Leaf d-value was decreased with sampling year, and it was higher in the densely inhabited district for both C 3 and C 4 . They are probably due to a historical decrease in the atmospheric d-value via increasing human activity, and high gas emission at the districts of high human density.

Urban warming favours C4 plants in temperate European cities

“…Nevertheless, species‐richness contributions of C 4 plants in urban assemblages remained lower than those reported from naturally C 4 ‐domi nated assemblages, such as Australian grasses where C 4 plants contribute towards approximately 60% of total plant richness on average (Hattersley ). Coastal regions of the UK also show increased proportions of C 4 plants, in agreement with findings from other temperate regions such as Japan, which were attributed to the saline soils and increased irradiance generally found in coastal regions (Hanba, Kobayashi & Enomoto ). Furthermore, coastal areas are less likely to experience winter temperatures below freezing (Fig.…”

“…() noted that biomass of C 4 plants increased substantially in heated plots, demonstrating that increased yield of C 4 photosynthesis under warmer conditions is translated into gains in plant growth. These mechanisms provide a compelling explanation for why ambient temperature has been identified as a key determinant of patterns of C 3 and C 4 plant distributions and relative abundances (Hattersley ; Ueno & Takeda ; Ehleringer, Cerling & Helliker ; Hanba, Kobayashi & Enomoto ; Pyankov et al . ; Pau, Edwards & Still ; Angelo & Daehler ).…”

“…Similar geographic patterns have been identified in European (Pyankov et al . ) and Japanese (Ueno & Takeda ; Hanba, Kobayashi & Enomoto ) plant assemblages, and elevation gradients of C 3 and C 4 grasses in Hawai'i have also been attributed to environmental temperature (Angelo & Daehler ).…”

Stable carbon isotope characteristics of desert plants in the Junggar Basin, China

“…The leaf d 13 C values in C 3 plants ranged from À23.3 ± 0.2 to À30.1 ± 0.3& with the average value of À26.8&. The averaged leaf d 13 C values in C 3 plants in the Junggar Basin is somewhat greater than the previously reported values, such as À27& by Smith and Epstein (1971), À27& by O'Leary (1981), À27.1& by Zheng and Shangguan (2007), and À29.2& by Hanba et al (2010). This may attribute primarily to the fact that lower water availability induced less photosynthetic discrimination.…”

“…Within-species variation in leaf d 13 C is observed in several species Ma et al 2008;Hanba et al 2010). The observed isotopic difference for a given species growing in contrasting environmental conditions is attributed either to water availability-related difference in stomatal openness or nutrient-associated difference in photosynthetic capacity as photosynthetic discrimination against 13 CO 2 is determined by both CO 2 supply rate, which is regulated by stomatal openness, and CO 2 consuming rate, which is related to photosynthetic capacity (Hamerlynck et al 2004).…”