| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2002: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2001: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
We analyzed the popular dynamics of Trillium apetalon and T. camschatcense under varying environment, using the census data during about 15 years. Moreover, we developed a method to check the reliability of elasticity matrix, which is an index of population dynamics, in density-dependent matrix model.
As for the former, we estimated the mean and variance of important life-history parameters (survival rate and fecundity etc.) and examined the effect of temporal variation of those parameters on the expectation of population growth rate. As the result, we obtained the probabilities of increase and decrease of the population and clarified several points; (1) The probability that the population of Trillium apetalon decreases under 30% after 50 years is 75.6%, while the probability that the population of Trillium camschatcense decreases under 30% after 50 years is 0%. (2) In both species, elements with high sensitivity are different from elements that contribute more to the decrease of the population size.
As for the latter, we obtained the theoretical elasticity matrix at equilibrium and the elasticity matrix under actually varying dynamics, and compared them. We found that the discrepancy between them depend largely on the life history pattern and the pattern of density-dependence. In the case of Beverton-Holt-type density dependent function, the discrepancy is relatively small, while in the case of Ricker-type density dependent function, the discrepancy is large. The reliability of elasticity matrix is becoming low when the species in question is monocarpic and delayed growth.
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