Shoot growth dynamics and size-dependent shoot fate of a clonal plant,Festuca rubra, in a mountain grassland |
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Authors: | Toshihiko Hara and Tomas Herben |
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Institution: | (1) The Institute of Low Temperature Science, Hokkaido University, Sapporo 060, Japan;(2) Academy of Sciences of the Czech Republic, Institute of Botany, CZ-252 43 Průhonice, Czech Republic |
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Abstract: | The relation of the within-season and between-season patterns of shoot growth were compared in a clonal grass with long-lived
shoots,Festuca rubra, in a mown mountain grassland. The growth rate of shoot length from spring to summer in a year was almost constant for each
shoot irrespective of spring shoot length each year. The annual shoot growth rate from spring to spring was negatively correlated
with the shoot length in the first spring. Shoots of different length and age therefore tended to converge over time to a
population of identical shoot size, suggesting an equalizing effect of growth pattern on size structure. Shoot size (shoot
length and number of leaves) influenced the fates of shoots. Larger shoots showed an increased incidence of both flowering
and formation of intravaginal daughter shoots and a decreased incidence of death in the subsequent time period. The fates
of shoots were independent of their age. Although the negatively size-dependent springto-spring annual shoot growth rate acted
to decrease shoot size variation, the remaining variation within the shoot population was still sufficient to generate different
fates of shoots. These fates were not related to the previous life history of individual shoots. There was a significantly
positive effect of the shoot size at initiation on its life expectancy. This was mainly attributable to the positively size-dependent
survival rate of shoots in the early stage (<1 year old) of shoot life history. Later on (> 1 year old), shoot size had little
effect on the survival rate of shoots. Once small young shoots have survived this early stage (< 1 year old) in life history,
they can grow vigorously, little affected by competition regardless of shoot size, and converge to a stable size structure
of shoots of similar size. Only shoot size in the early stage ( < 1 year old) of life history is important for the persistence
of a shoot population. |
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Keywords: | daughter shoot formation flowering shoot demography shoot survival diffusion model stability of shoot population |
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