AOBPreview originally published online on January 22, 2007
Annals of Botany 2007 99(3):537-544; doi:10.1093/aob/mcl283
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Trade-offs Between Seedling Growth and Survival in Deciduous Broadleaved Trees in a Temperate Forest
Laboratory of Forest Ecology, Graduate School of Agricultural Science, Tohoku University, Naruko-onsen, Osaki, Miyagi 989-6711, Japan
* E-mail seiwa{at}bios.tohoku.ac.jp
Received: 16 August 2006 Returned for revision: 23 October 2006 Accepted: 16 November 2006 Published electronically: 22 January 2007
Background and Aims: In spatially heterogeneous environments, a trade-off between seedling survival and relative growth rate may promote the coexistence of plant species. In temperate forests, however, little support for this hypothesis has been found under field conditions, as compared with shade-house experiments. Performance trade-offs were examined over a large resource gradient in a temperate hardwood forest.
Methods: The relationship between seedling survival and seedling relative growth rate in mass (RGRM) or height (RGRH) was examined at three levels of canopy cover (forest understorey, FU; small gap, SG; and large gap, LG) and at two microsites within each level of canopy cover (presence or absence of leaf litter) for five deciduous broad-leaved tree species with different seed sizes.
Key Results: Within each species, both RGRM and RGRH usually increased with increasing light levels (in the order FU < SG < LG), whereas little difference was observed based on the presence or absence of litter. Seedling survival in FU was negatively correlated with both RGRM and RGRH in both LG and SG. The trade-off between high-light growth and low-light survival was more evident in the relationship with LG as compared with SG. An intraspecific trade-off between survival and RGR was observed along environmental gradients in Acer mono, whereas seedlings of Betula platyphylla var. japonica survived and grew better in LG.
Conclusions: The results presented here strongly support the idea of light gradient partitioning (i.e. species coexistence) in spatially heterogeneous light environments in temperate forests, and that further species diversity would be promoted by increased spatial heterogeneity. The intraspecific trade-off between survival and RGR in Acer suggests that it has broad habitat requirements, whereas Betula has narrow habitat requirements and specializes in high-light environments.
Key words: Coexistence, gap, gap size, habitat selection, habitat width, light, niche partitioning, relative growth rate, seed size, successional status