Current-year shoot based approach for annual variation in the reproductive output in Siberian alder (Alnus hirsuta var. sibirica)

Abstract

Siberian alder (Alnus hirsuta var. sibirica) shows annual variation in reproductive output. However, this phenomenon has not been explained by hypotheses proposed in previous studies. In this study, we constructed a matrix model of current-year shoot dynamics to estimate and compare the reproductive output of current-year shoot population with or without annual variation, and explained the annual variation of reproductive output in terms of a reproductive strategy of the current-year shoot population of Siberian alder. The current-year shoot population of Siberian alder was divided into three functional groups: reproductive, maintenance, and explorative shoot sub-populations. A transition matrix was calculated from the relationships between 1-year-old shoots and the current-year shoots on them. The dynamics of the current-year shoot population was simulated using the estimated matrix on the patterns with or without annual variation in reproductive output. The pattern with annual variation in reproductive output yielded more reproductive current-year shoots than the pattern with high reproductive output every year. The annual variation of reproductive output may well be regarded as a reproductive strategy of current-year shoots to increase lifetime fecundity.