The contribution of germination functional traits to population dynamics of a desert plant community

Zhenying Huang, Shuangshuang Liu, Kent J. Bradford, Travis E. Huxman and D. Lawrence Venable


一个荒漠植物群落中萌发功能性状对种群动态的贡献
生活史早期事件决定着植物种群和群落的动态。种子生态和萌发格局可决定物种对环境变化的适应范围,从而决定物种多样性和群落动态。理解这些性状的适应后果和环境过滤作用将可对生态系统的过程进行解释和预测。我们对荒漠一年生植物的萌发生理及其与已有的功能生态学框架的关系进行了研究,以解释13种植物的长期种群动态。我们的目标是测定何种萌发功能性状可以在野外决定长期的种群动态过程。一些物种在萌发的最低温、最适温和最高温、萌发热时间、萌发最低水势与20年平均萌发数量、25年平均萌发日期、种子大小和长期种群统计变化间有显著的相关关系。萌发率、存活率和结实率在种群大小的年际变化中具有显著作用,但在不同物种间所占的百分比不同。物种萌发生理和萌发率间的关系在年际间变化,在温暖的年份萌发季节中降雨对快速萌发的物种有利。萌发率低和种群统计变化大的物种水分利用效率低、营养生长快、结出的种子小且萌发慢。我们确定了一些与在种群动态中起重要作用的萌发生物学相关的功能性状。


Abstract
Early life-cycle events play critical roles in determining the population and community dynamics of plants. The ecology of seeds and their germination patterns can determine range limits, adaptation to environmental variation, species diversity and community responses to climate change. Understanding the adaptive consequences and environmental filtering of such functional traits will allow us to explain and predict ecological dynamics. Here we quantify key functional aspects of germination physiology and relate them to an existing functional ecology framework to explain long-term population dynamics for 13 species of desert annuals. Our goal was to assess the extent to which germination functional biology contributes to long-term population processes in nature. Some of the species differences in base, optimum and maximum temperatures for germination, thermal times to germination, and base water potentials for germination were strongly related to 20-year mean germination fractions, 25-year average germination dates, seed size, and long-term demographic variation. Comparisons of germination fraction, survival and fecundity versus yearly changes in population size found significant roles for all three factors, though in varying proportions for different species. Relationships between species’ germination physiologies and relative germination fractions varied across years, with fast-germinating species being favored in years with warm temperatures during rainfall events in the germination season. Species with low germination fractions and high demographic variance have low integrated water-use efficiency, higher vegetative growth rates and smaller, slower19 germinating seeds. We have identified and quantified a number of functional traits associated with germination biology that play critical roles in ecological population dynamics.