Aliena Var Research Articles

Reserves and species diversity of soil seed banks in four types of forest on Mt. Taibai, Qinling Mountains

The soil seed bank represents the pool of potential species for a plant community. It plays a critical role in community succession and maintenance of the community structures and functions. We analyzed the distribution of soil seed banks and their characteristics in four forest types: Larix chinensis forest, Betula utilis forest, Quercus aliena var. acuteserrata forest, and Abies fargesii forest based on 240 samples collected on the southern slope of Mt. Taibai, Qinling Mountains, Central China. The results are summarized as follows: (1) the soil seed bank reserve of B. utilis forest was the largest one (1.7677×104 ind./m2), while L. chinensis forest the smallest (1.742×103 ind./m2). Seed characteristics influenced soil seed bank reserves. (2) the seed bank of Q. aliena var. acuteserrata forest contained 50 species, which was the highest of the four forest types. The seed reserves were highest in litter layer, followed by that in humus layer and subsurface soil layer. The seed banks of deciduous broad-leaved forests exhibited higher dominance and lower evenness than those of coniferous forests. The seed bank evenness index was highest in A. fargesii forest. (3) the reserves and density of seed banks showed similar patterns along the altitudinal gradient and in the four forest types. In this study, the soil samples were divided into three layers: litter layer, humus layer and subsurface soil layer. This sampling method improved on previous methods, which sampled soil at a fixed soil depth. Having taken the characteristics of soils into account, seed density was a better indicator of the soil seed bank characteristics than the seed reserve.

Different responses to shade of evergreen and deciduous oak seedlings and the effect of acorn size

An evergreen oak species, Cyclobalanopsis multinervis , and a deciduous oak species, Quercus aliena var. acuteserrata were grown from acorns under two light levels (full sunlight and shade at about 18 % of full sunlight, simulating the light intensities in forest clearings and gaps, respectively) for one growing season. Three hypotheses were tested: (i) the deciduous species grows faster than the evergreen species in forest gaps and clearings; (ii) the deciduous species responds more strongly in terms of growth and morphology to variation in light climate than the evergreen species; and (iii) seedling size is positively correlated to acorn size. The results showed: (i) at both light levels, the deciduous seedlings gained significantly more growth in biomass and height than the evergreen seedlings; (ii) both species produced significantly more biomass in full sunlight than in shade, without showing any significant difference in height between treatments. Increase in light intensity improved the growth of the deciduous seedlings more strongly; (iii) at a similar age, the deciduous seedlings showed a greater response in leaf morphology and biomass allocation to variation in light levels, but when compared at a similar size, biomass allocation patterns did not differ significantly between species; (iv) bigger acorns tended to produce larger seedlings, larger leaf sizes and more leaf area, between and within species. These differences demonstrate that the deciduous species is gap-dependent and has the advantage over the evergreen species in forest gaps and clearings.