从种子到幼苗的物种生活史策略和密度制约与古田山亚热带森林幼苗更新的关系

Understanding the factors influencing seedling dynamics is critical to understanding forest community dynamics because the seedling stage suffers high mortality and, therefore, represents a significant bottleneck in the life cycle of trees. Nowadays numerous cases have verified the role of density dependence in regulating seedling dynamics and recently studies showed that it can promote species coexistence by the variation of its strength among species. Plants endure long-term interactions with ambient environment and each species has special life-history strategy for survival at evolution level. Seedlings of species with differing life-history strategies are expected to respond differently to neighbourhood interactions. Seed size varies strikingly among plant species, even within the same community in natural forests. We expect that the variation of seed size related with species life strategies can explain well seedling performance and the variation of density dependence among species together with seedling relative growth rate. However, ecologists know less about the separated and combined contribution of density dependence and life strategies to seedling dynamics and diverse-species coexistence. So here we ask four questions: 1) do species life-history strategies from seeds to seedlings have close connection? Such as, species with big seeds have low seedling growth rate; furthermore, do species life-history strategies determine the differentiation of seedling dynamics among species? 2) does the difference of species life-history strategies among species determine the differentiation of strength of density dependence among species? 3) which is the best model to predict seedling dynamics combined neighborhood density and life-history strategies? 4) what is the relationship of density dependence and life-history strategies with species coexistence in forest plot? We plan to conduct the study of seed-seedling transition in 24 ha Gutianshan subtropical forest. First we will measure seed size using seed mass of 159 species and conduct seed germination experiment to get seed germination rates and germination capacities. Then we will calculate the ratio of seed productive and seedling recruitment through seed traps and seedling observing. These all together, we will furthermore evaluate species life strategies. Meanwhile, we will conduct two seedling experiments in natural drought seasons. One is seedling field observing experiment in the 24 ha forest plot. Another is seedling monitoring experiment near the forest plot. In the seedling field observing experiment, we will calculate the ratio of seed production and seedling recruitment, observe the dynamics of seedling growth and mortality in two natural drought seasons of Gutianshan and analyze the relationship of seedling dynamics with species life strategies and density dependence. Furthermore, we test whether species life strategies determine the variation of density dependence among species or not. In the seedling monitoring experiment, we will monitor the seedling dynamic changes of 10 species belonging to Fagaceae in two density levels enduring two natural drought seasons. At the same way, we will test the influence of neighborhood density on seedling growth and mortality and conduct the relationship of life history strategies from seeds to seedlings and density dependence. These will enhance to evaluate tolerance–fecundity trade-off among species in the same forest. Our study will contribute to comprehensively understanding the role of density dependence and species inherent life strategies in seedling dynamics and diverse-species coexistence. Meanwhile, our findings will give advices for biodiversity conservation and forest restoration.

幼苗阶段是种群建植成功的关键时期，幼苗对密度制约响应的种间差异促进物种共存已被证实。然而，密度制约种间差异是不是其内在的生活史策略决定的呢？综合密度制约和物种生活史策略来研究幼苗动态变化来解释物种共存鲜有报道。因此，本研究计划基于古田山亚热带常绿阔叶林24公顷森林样地为研究平台，测定其159个物种的种子性状，开展种子萌发实验；野外种子雨和幼苗观测和幼苗控制实验结合，在群落尺度上，自然干旱胁迫下，主要研究：1）从种子到幼苗各种生活史策略指标之间的关联，验证忍耐力-繁殖权衡等假说，及生活史策略与幼苗动态变化的关系；2）幼苗对密度制约响应的种间差异与种子-幼苗生活史策略种间差异的关系，理解密度制约发生的内在驱动力；3）生活史策略和邻居效应建立预测幼苗动态的最优模型；4）综合生活史策略和密度制约理解古田山常绿阔叶林多物种共存。本研究结果将促进对局域群落物种共存的理解，为生物多样性保护提供指导。

亚热带天然林因其生态和经济功能而具有独特性。然而，这些森林中的大多数已经高度退化，削弱了提供生态和经济效益的能力。富集种植是恢复自然退化的重要途径森林。物种配置对丰富种植具有重要意义。物种关联是指占据一个栖息地的不同物种之间的相互关系，是对物种相互作用形成的有机联系的静态描述。因此，物种关联为富集种植的物种安排提供了科学依据。在这项研究中，在中国亚热带浙江省乌田山国家级自然保护区的原始森林中调查了优势树种（包括幼树和成年树）之间的物种关联。 该研究的目的是为丰富种植的物种安排提供信息。结果表明，整体物种关联表现出显着的净正关联，表明原始森林中稳定结构和物种组成的动态平衡。根据树种的树种关联和对光的需求，确定了最佳树种安排，以支持丰富种植以恢复自然退化的森林。预计该研究成果将有助于中国亚热带地区天然退化林的恢复。..此外，物种丰富度和多样性极大地影响着森林的结构和功能，是可持续森林管理的关键指标。 抽样调查广泛应用于森林清单，因为它们可以有效地评估森林特征。但是，需要适当的样本图设计。在温带森林中建立了一个 20 公顷的普查样地，以获得物种丰富度和物种多样性的真实值。 评估了一个单一地块设计和九个集群地块设计。 结果表明，不同地块设计的森林物种丰富度和物种多样性存在显着差异。 具有正方形子地块配置 (SCONFIG) 和 500 平方米的地块覆盖范围 (EGROUND) 的地块地块设计在估计森林物种丰富度方面表现出最佳性能（准确度、精确度）。 相比之下，EGROUND 为 1000 m2 的矩形聚类图更适合评估物种多样性。 这项研究表明，在评估温带森林的物种丰富度和物种多样性方面，聚类图优于单个图。