滇青冈种子产量与锥象甲种群动态的相关性及其对不同尺度气候变化的响应

Large-scale climatic events such as the El Ni?o-Southern Oscillation (ENSO) associated with local weather conditions can influence community structure and dynamics, through their impact on seed production. Consequently, variation in seed production can influence species interactions and population dynamics.A primary objective of this research is to investigate these ecological processes in a subtropical evergreen broad-leaved forest community dominated by Quercus schottkyana. Seeds of Q.schottkyana will be collected throughout the production season, specimens of weevils (Curculio spp.) (the major seed predator) will be regularly collected during seed dispersal, and infestation rates by weevils will be estimated. Based on long-term seed production records and seed infestation rates, we will test the hypothesis that climatic indices at different scales influence seed production and consequently weevil population dynamics. Seed traits such as dry mass and germination percentage will also be measured, and seedling establishment will be recorded. From these data we can model how variation in large-scale climatic indices influence local weather which in turn leads to a cascade of interactions involving timing of seed production, seed number and size, germinability, weevil infestations, and probability of seedling establishment.Based on these data, interactions between Q.schottkyana and weevil populations and their responses to climatic variations at different scales will be discussed. This project is significant because it adds to the understanding of the factors that influence the maintenance of Asian subtropical evergreen broad-leaved forest ecosystems which is one of the world's biodiversity hotspots and currently under severe anthropogenic threat.Understanding these linkages is critical to applying proper scientifically-based management principles to conserve the biodiversity of forests in SW China in the context of global climate change.

大尺度气候事件如厄尔尼诺-南方涛动等能与当地气候条件结合，影响植物种子的生产和种群间的相互关系，进而影响整个群落的结构和动态。本项目将以滇青冈为优势种的亚热带常绿阔叶林为研究对象来探究这一系统过程：通过对滇青冈种子常年的收集，分析不同尺度气候要素对种子产量年际变化的影响；通过对种子主要捕食者锥象甲标本的定期采集和鉴定和对滇青冈种子侵染率的测定，分析多种锥象甲种群动态与种子产量和气候要素的关系；通过研究滇青冈种子干重、萌发率、含水量的周际和年际差异和记录滇青冈幼苗的建立情况，分析种子生理属性和幼苗建立与种子产量和气候要素的关系；根据以上研究结果，探讨滇青冈和锥象甲种群的动态关系及其对不同尺度气候变化的响应。这项研究，对深入理解亚洲亚热带常绿阔叶林生态系统的维持机制和大尺度气候变化对群落动态的影响，对在全球气候变化的背景下，探索如何有效维持我国西南地区的生物多样性，都有着重要的科学意义。

滇青冈是亚热带常绿阔叶林的主要建群种和优势种之一，对西南地区生态平衡和生物多样性的保持有着重要的作用。本课题试图通过对滇青冈种子产量、锥象甲种群动态 10年的观测，通过对滇青冈种子在散播后的命运和幼苗建立的观察，通过对滇青冈周际和年际种子生理学属性的研究，分析不同尺度的气候变化对滇青冈种子产量、对种子产量与锥象甲种群的关系和对滇青冈种群动态的影响。滇青冈种子的产量有着显著的年际差异。种子的产量不受种子干重的影响。但随着种子散播的持续，后期的种子比散播前期的种子重且有更高的活力。在通常情况下，锥象甲种群和种子产量形成密度制约关系（随着种子产量的增加，虫蛀率增加）；滇青冈种子散播的高峰期、锥象甲侵害种子的高峰期和高活力种子散播的高峰期三者相错。滇青冈通过产生大量的种子，“用”种子散播前期的低质量种子“满足”锥象甲种群，而保留下散播后期的高活力种子。当厄尔尼诺-南方涛动加剧，干旱发生时，滇青冈种群响应气候变化而种子产量降低。散播期前期的种子无法满足锥象甲种群，锥象甲对滇青冈种子的侵染期延长，滇青冈种群能保留下的活种子数量减少。锥象甲对滇青冈种子的侵染率平均为34%。滇青冈种子对脱水敏感。尽管其果皮能有效地保持水分，使得部分种子能够抵御散播后半年的干旱，在春季（4月）成苗。但干燥造成约72%的健康（未虫蛀）种子死亡，仍是健康种子死亡的主要原因。土壤能够较好地保持滇青冈种子的水分及活力。但次年5-7月，成年的椰小蠹（鞘翅目，象甲科）入侵所有滇青冈种子，造成无论地面还是地下健康种子的普遍死亡，仅有土壤中已萌发或成苗（占土壤中健康种子20%）的滇青冈种子可能成为幼苗。在啮齿类动物和干燥的影响下，仅37%的幼苗能够在样地存活一年半以上。滇青冈种群的补充是非常有限的。大尺度气候（即厄尔尼诺现象）所造成的干旱不仅影响了滇青冈种子的产量，使得滇青冈和和锥象甲种群的协同关系的破裂，从而导致能有效补充滇青冈种群的种子数量减少，还可能增加了滇青冈种子在散播后和成苗后死亡的概率。