POPULATION MAINTENANCE OF THE SHORT-LIVED SHRUBSAMBUCUSIN A DECIDUOUS FOREST

Abstract

This study quantitatively clarifies the life history of a shrub, Sambucus racemosa ssp. sieboldiana, in an old-growth forest, the Ogawa Forest Reserve, Japan, by a demographic approach using a projection matrix model that incorporates interactions between demographic parameters and canopy height dynamics. S. racemosa is a common deciduous shrub in central Japan and is known to grow predominantly at forest edges or roadsides. This indicates that it is a highly light-demanding species, and occurrence in gaps in old-growth stands suggests its "fugitive," gap-dependent life history in old-growth forests. We found that one distinctive feature of this species was that its seedlings can survive well in shaded conditions by alternating stems every year like perennial herb species. Matrix model analyses demonstrated that S. racemosa can continuously regenerate under the present disturbance regime of this forest and is highly adaptable to the structural dynamics of the old-growth forest. The maturity of S. racemosa shrubs depends on their size, and nearly all (>90%) of the mature (reproducing) individuals were found in gaps or near gaps. But wide seed dispersal by birds and the ability to form both seed banks and seedling banks, the latter of which has been regarded as a common characteristic of shade-tolerant climax species, probably increase the species' chances to encounter canopy gaps. Dynamic-canopied matrix models showed that the greatest elasticity is with shaded seedling survival. The frequent stem alternation of shaded seedlings often makes the growth rate negative, but the survival rate of seedlings in low light awaiting new gap creation is remarkably high (0.93 yr(-1)). The lower survival rate of the larger individuals and smaller minimum size to start reproduction than other canopy or subcanopy shade-tolerant species indicate that S. racemosa has the potential to reproduce before the closure of the encountered gaps and to complete its life history rapidly.

Reproductive phenology of Sambucus nigra subsp. canadensis in the Abies religiosa temperate forest of the Magdalena river basin, Mexico City

“…For example, in Sambucus nigra subsp. nigra and Sambucus racemosa, it has been reported that their establishment and fruit production increases in sites with the highest light availability (Atkinson & Atkinson 2002, Abe et al 2008, Schaefer & Braun 2009). These results coincide with what we found in this study, since in micro-environment one, which showed the highest canopy openness as well as light amount, the individuals of S. nigra subsp.…”

Comparative Population Dynamics of Two Closely Related Species Differing in Ploidy Level

“…Most studies addressing the population biology of various plant species investigate specific life-cycle stages or single traits, such as seed production, seedling survival or population size (e.g., [4], [5], [6], [7], [8], [9], [10], [11]). However, to understand the causes of changes in population size, it is necessary to investigate the complete life cycle of a species, as it is only by putting the various life-cycle transitions into the context of the whole life cycle that we can understand the consequences of the differences in single life history traits for the dynamics of a population (e.g., [12], [13], [14], [15], [16], [17], [18], [19]). …”

Spatial distribution pattern of soil seed bank in canopy gaps of various sizes in temperate secondary forests, Northeast China

“…Biotic characteristics of species (e.g., seed dispersal, germination/dormancy, seed size) also have great effects on the spatial distribution of soil seed bank, consequently on the distribution of aboveground vegetation and the relationship between seed bank and vegetation in forest ecosystems (Thompson et al 1998;Abe et al 2008;Pazos and Bertiller 2008;Stromberg et al 2008). Under the gap forming disturbance, the correlation between extant and potential (seed bank) vegetation may change.…”