1998 Volume 43 Issue 4 Pages 357-367
Calamagrostis longiseta, C. langsdorffii and C. hakonensis are perennial C_3 grasses and usually occur in cool habitats. In the Kirigamine grassland of central Japan, the distribution of these three species is limited to altitudes higher than 1,650m a.s.l.. The objective of the present study was to clarify the temperature optima and the upper temperature limits for vegetative and reproductive growth of these species, and to examine whether these species are physiologically restricted to higher altitudes. We chose four sites with altitudes of 14,600, 1,342 and 1,712 m a.s.l. to provide an altitudinal gradient, collected these Calamagrostis species from subalpine grasslands, and grew them at sites on the gradient. Pot experiments conducted from 1993 to 1995 showed similar patterns of growth response to the gradient in the three species, although the dry matter yield was different. These species possess a certain degree of acclimation capacity to higher temperatures. Overall, however, the results showed clearly that the three species preferred medium altitudes (600 to 1,342m), where the plants could attain higher total biomass, height and total number of tillers, leading to success in reproductive growth. Plants could succeed in vegetative and reproductive growth at high altitude (1,712m), but total biomass was least here due to the short growing period. Vegetative growth of plants at low altitude (14m) could take place during the relatively cool period from spring to early summer, but marked declines occurred in net photosynthesis and aboveground green biomass during the following hot summer. In addition, the plants grown at low altitude appeared unable to flower, and the results suggest that the warm winter combined with the subsequent rapid rise in temperature may limit the reproductive growth of these Calamagrostis species. These results suggest that the optimal temperature for the growth of these three grasses may occur at medium altitudes within the selected gradient, and range between 6.8℃ and 10.4℃ if it is described by the annual mean temperature of the three experimental years. Moreover, if there is a lack of competition from neighbors, and temperature is the only important factor determining growth, then these three species prefer medium altitudes for their growth rather than high altitude where temperature conditions are mostly similar to the Kirigamine grassland, and the upper temperature limits for their growth occur only at extremely low altitudes. We therefore suggest that the growth of these Calamagrostis species is probably not physiologically limited by warmer temperatures at lower altitudes (1,500-1,650m) in the Kirigamine grassland.
