Centre d'Ecologie Fonctionnelle et Evolutive, Centre National de la Recherche Scientifique (CNRS), 1919 Route de Mende, 34293 Montpellier 5, France.
Ecology. 2010 Oct;91(10):3057-68. doi: 10.1890/09-2313.1.
Mast seeding, the synchronous, highly variable seed production among years, is very common in tree species, but there is no consensus about its main causes and the main environmental factors affecting it. In this study, we first analyze a long-term data set on reproductive and vegetative growth of Quercus ilex in a mediterranean woodland in order to identify the main environmental drivers of interannual variation in flower and seed production and contrast the impact of climate vs. adaptive factors as main causes of masting. Second, we conducted an experiment of rainfall exclusion to evaluate the effects of an increasing drought (simulating predictions of global change models) on both reproductive processes. The annual seed crop was always affected by environmental factors related to the precipitation pattern, these abiotic factors disrupting the fruiting process at different periods of time. Seed production was strongly dependent upon water availability for the plant at initial (spring) and advanced (summer) stages of the acorn maturation cycle, whereas the final step of seed development was negatively affected by the frequency of torrential-rain events. We also found clear evidence that seed masting in the study species is not only regulated by selective endogenous rhythms, but is mainly a physiological response to the variable environment. Our results from the rainfall exclusion experiment corroborated the conclusions obtained from the 26-year fruiting record and demonstrated that the high interannual variation in seed crop was mainly determined by the success in seed development rather than by the flowering effort. Under a global change scenario, it could be expected that the drier conditions predicted by climate models reinforce the negative effects of summer drought on seed production, leading to negative consequences for tree recruitment and forest dynamics.
结实高峰期，即树木在同步的、高度多变的年份间产生大量种子的现象，在树种中十分常见，但关于其主要成因以及影响主要环境因素，目前尚未达成共识。在本研究中，我们首先分析了地中海林地中一种常绿栎树（Quercus ilex）在长期的繁殖和营养生长数据，以确定影响结实高峰期的年际变化的主要环境驱动因素，并对比气候和适应因素对结实高峰期的影响，以确定它们是否为主要成因。其次，我们进行了降雨排除实验，以评估在模拟全球变化模型预测的干旱加剧的情况下，对繁殖过程的影响。年种子产量始终受到与降水模式相关的环境因素的影响，这些生物因素在不同时期扰乱了结实过程。种子产量强烈依赖于植物在橡子成熟周期的初始（春季）和后期（夏季）阶段的水分供应，而种子发育的最后一步则受到暴雨频率的负面影响。我们还发现了明确的证据表明，研究物种的结实高峰期不仅受到选择性内源节律的调控，还是植物对环境变化的生理响应。我们的降雨排除实验结果与 26 年结实记录的结论相符，表明年际间种子产量的高度变化主要取决于种子发育的成功与否，而不是开花的努力程度。在全球变化情景下，可以预计气候模型预测的干燥条件会加强夏季干旱对种子产量的负面影响，从而对树木繁殖和森林动态产生负面影响。
