Understanding the relationship between masting and stored carbohydrate resources in trees by a radioactive carbon analysis method

许多树种每年的种子产量都有很大的波动，这种现象被称为桅杆。资源收支模型是解释主伐机制的一个关键假设，它基于主伐年的大量播种取决于多年储存的大量资源这一假设。但是，桅杆物种真的需要这样一个长期的存储，以产生一个大的种子作物？为了验证这一假设，我们研究了碳积累期的种子生产，估计放射性碳（^<14>C）分析，和繁殖间隔之间的关系，在10个冠层树种在温带落叶林和17个龙脑香属物种在热带雨林。这些物种的生殖间隔差异很大。在所研究的所有物种中，种子成熟的积累期小于1.4年。此外，无论是物种还是繁殖间隔，碳积累期与年种子产量波动之间均无显著相关性。我们的研究结果表明，温带和热带树冠树木使用的光合产物在当前和/或前一年的种子生产，无论生殖间隔。因此，可能有必要重新考虑储存碳水化合物资源对桅杆的重要性。

Many tree species undergo a large fluctuation from year to year in seed production, a phenomenon known as masting. The resource budget model, based on the assumption that abundant seeding in a masting year depends on abundant resources stored over several years, is a key hypothesis in explaining the mechanism of masting. But do masting species really need such a long-term storage in order to produce a large seed crop? To test this hypothesis, we studied relation between carbon accumulation periods for seed production, estimated by radiocarbon (^<14>C) analyses, and reproductive intervals in 10 canopy-tree species in a temperate deciduous forest and 17 dipterocarp species in a tropical rain forest. These species differ widely in their reproductive intervals. In all the species studied, the accumulation period toward seed maturation was less than 1.4 years. Moreover, regardless of species or reproductive intervals, there was no significant correlation between the carbon accumulation period and the fluctuation of annual seed production. Our results suggest that temperate and tropical canopy trees used the photosynthates produced in the current and/or the previous year for seed production regardless of reproductive intervals. It might therefore be necessary to reconsider the importance of stored carbohydrate resources for masting.