CAREER: Functional Bases for the Trade-Off Between Growth and Survival of Tree Seedlings

职业：树苗生长和生存之间权衡的功能基础

• 批准号: 0093303
• 负责人: Kaoru Kitajima
• 金额: $ 38.65万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-05-01 至 2006-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0093303&HistoricalAwards=false
• 关键词: CAREER; Functional; Bases; Trade; Off

How limited resources are allocated to different functions has strong consequences to growth rates and survival of organisms at both individual and population levels. Fast growth is inherently incompatible with high survival potential, a trade-off strongly suggested in recent studies of regeneration of trees in tropical and temperate forests. Shade tolerant species recruit saplings through maintenance of slow-growing seedlings that tolerate various biotic and abiotic stresses in the understory. In contrast, light-gap dependent species colonize with abundant and well-dispersed seeds and fast-growing seedlings having low tolerance of biotic and abiotic stress. The simplest yet most general hypothesis for such a trade-off relationship is that species allocating more resources to storage and defense survive better, but exhibit slower growth (at least in a short term). In plants, higher allocation of carbon (i.e., photosynthetically captured energy) to construction of new leaves leads to a compound return of carbon income and fast growth rates. However, this allocation pattern must come at the cost of relatively less carbon allocated to storage (i.e., energy savings as non-structural carbohydrates) and defense (e.g., tough support tissue, and chemical toxins that resist against herbivory and disease). Consequently, species that employ allocation strategies for fast growth should suffer from high mortality rates because these species are more vulnerable to herbivory, pathogen attack and physical disturbance. Kitajima will test this overall hypothesis through a series of comparative studies of carbon storage and carbon-based defenses in seedlings of tropical tree species in Panama. Seven family pairs of species exhibiting contrasting growth rates and survival will be raised under standardized conditions in a greenhouse for comparison of allocation to energy storage in stems and roots, and carbon-based defenses (lignin and other phenolic compounds). In a second experiment, this researcher will test the ecological role of storage allocation in the field by examining growth and survival of seedlings of species displaying contrasting degrees of storage allocation as they respond to shading and simulated herbivory treatments. In the third study, patterns of allocation to storage and defense will be examined to elucidate their relationship to longer-term growth and survival in naturally recruited seedlings in the forest understory. Whole-plant carbon budgets (total gross and net carbon gain, proportion of carbon gain to respiration, tissue construction, storage, and root exudate) will be quantified for two species of plants in the wild-coffee genus (Psychotria) in the final study. This research will be integrated with educational activities. The philosophical implications of the physiological constraints in ecological interactions go beyond purely biological interactions. Ecological models based on allocation-based trade-offs are important in training not only those students anticipating professional careers as ecologists, but also for those students pursuing studies in non-scientific disciplines that affect the societal responses to ecological and environmental issues. Allocation trade-offs, thus, will be emphasized in Kitajima's teaching in both undergraduate- and graduate-level courses. Her research and teaching will be most directly integrated in the course "Summer Research Experience in Tropical Ecology," in which undergraduate students will have an outstanding educational experience as hands-on participants in this research in Panama.

如何将有限的资源分配给不同的功能，对生物体在个体和种群水平上的生长率和生存有着强烈的影响。 快速生长与高生存潜力本质上是不相容的，最近对热带和温带森林树木再生的研究强烈建议了这种权衡。耐荫物种通过维持生长缓慢的幼苗来招募树苗，这些幼苗能够承受林下各种生物和非生物压力。与此相反，光隙依赖的物种殖民与丰富的和良好的分散的种子和快速生长的幼苗具有较低的生物和非生物胁迫的耐受性。对于这种权衡关系，最简单但最普遍的假设是，分配更多资源用于储存和防御的物种生存得更好，但增长较慢（至少在短期内）。在植物中，更高的碳分配（即，光合作用捕获的能量）到新叶的构建导致碳收入和快速生长率的复合回报。然而，这种分配模式必须以分配给储存的碳相对较少为代价（即，作为非结构性碳水化合物的能量节省）和防御（例如，坚韧的支持组织和抵抗食草动物和疾病的化学毒素）。因此，采用快速增长的分配策略的物种应该遭受高死亡率，因为这些物种更容易受到草食动物，病原体攻击和物理干扰。Kitajima将通过一系列对巴拿马热带树种幼苗的碳储存和碳基防御的比较研究来验证这一总体假设。七个家庭对表现出不同的生长速度和生存将提高标准化条件下，在温室中的能量储存分配在茎和根，和碳基防御（木质素和其他酚类化合物）的比较。 在第二个实验中，本研究人员将测试存储分配在该领域的生态作用，通过检查幼苗的生长和生存的物种显示对比度的存储分配，因为他们响应遮光和模拟草食动物治疗。 在第三项研究中，分配到存储和防御的模式将被检查，以阐明它们的关系，以长期的生长和生存在森林林下自然招募的幼苗。在最终研究中，将对野生咖啡属（九节属）的两种植物的全植物碳预算（总碳增益和净碳增益，碳增益与呼吸的比例，组织结构，储存和根分泌物）进行量化。这项研究将与教育活动相结合。生态相互作用中生理约束的哲学含义超出了纯粹的生物相互作用。生态模型的基础上分配为基础的权衡是重要的，不仅在培训那些学生预期的职业生涯作为生态学家，但也为那些学生追求的非科学学科的研究，影响社会对生态和环境问题的反应。分配权衡，因此，将强调北岛的教学在本科和研究生课程。她的研究和教学将最直接地融入课程“热带生态学夏季研究经验”，其中本科生将在巴拿马的这项研究中作为实践参与者获得出色的教育经验。