Poorter Lourens, Kitajima Kaoru
Forest Ecology and Forest Management Group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
Ecology. 2007 Apr;88(4):1000-11. doi: 10.1890/06-0984.
In many plant communities, there is a negative interspecific correlation between relative growth rates and survival of juveniles. This negative correlation is most likely caused by a trade-off between carbon allocation to growth vs. allocation to defense and storage. Nonstructural carbohydrates (NSC) stored in stems allow plants to overcome periods of stress and should enhance survival. In order to assess how species differ in carbohydrate storage in relation to juvenile light requirements, growth, and survival, we quantified NSC concentrations and pool sizes in sapling stems of 85 woody species in moist semi-evergreen and dry deciduous tropical forests in the rainy season in Bolivia. Moist forest species averaged higher NSC concentrations than dry forest species. Carbohydrate concentrations and pool sizes decreased with the light requirements of juveniles of the species in the moist forest but not in the dry forest. Combined, these results suggest that storage is especially important for species that regenerate in persistently shady habitats, as in the understory of moist evergreen forests. For moist forest species, sapling survival rates increased with NSC concentrations and pool sizes while growth rates declined with the NSC concentrations and pool sizes. No relationships were found for dry forest species. Carbon allocation to storage contributes to the growth-survival trade-off through its positive effect on survival. And, a continuum in carbon storage strategies contributes to a continuum in light requirements among species. The link between storage and light requirements is especially strong in moist evergreen forest where species sort out along a light gradient, but disappears in dry deciduous forest where light is a less limiting resource and species sort out along drought and fire gradients.
在许多植物群落中，幼体的相对生长速率与存活率之间存在种间负相关。这种负相关很可能是由于碳分配到生长与分配到防御和储存之间的权衡所致。茎中储存的非结构性碳水化合物（NSC）能使植物克服压力期，并应能提高存活率。为了评估物种在碳水化合物储存方面如何因幼体对光照的需求、生长和存活而有所不同，我们在玻利维亚雨季的湿润半常绿和干燥落叶热带森林中，对85种木本植物幼树茎中的NSC浓度和储量进行了量化。湿润森林物种的NSC平均浓度高于干燥森林物种。在湿润森林中，碳水化合物浓度和储量随物种幼体对光照的需求而降低，但在干燥森林中并非如此。综合来看，这些结果表明，储存对于在持续阴暗生境中再生的物种尤为重要，比如在湿润常绿森林的林下。对于湿润森林物种，幼树存活率随NSC浓度和储量的增加而提高，而生长速率则随NSC浓度和储量的增加而下降。干燥森林物种未发现这种关系。碳分配到储存通过其对存活的积极作用，促成了生长 - 存活的权衡。而且，碳储存策略的连续性促成了物种间光照需求的连续性。储存与光照需求之间的联系在湿润常绿森林中尤为强烈，在那里物种沿光照梯度分布，但在干燥落叶森林中则消失了，在干燥落叶森林中光照是一种限制较小的资源，物种沿干旱和火灾梯度分布。
