MCA: Ontogenetic constraints to climate change resilience – Investigating consequences of heteroblasty under increasing aridity in New Zealand forests

MCA：气候变化恢复力的个体发育限制 — 调查新西兰森林日益干旱的情况下异质发育的后果

• 批准号: 2218916
• 负责人: Kasey Barton
• 金额: $ 28.71万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-01-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2218916&HistoricalAwards=false
• 关键词: MCA; Ontogenetic; constraints; climate; change

Forest trees are experiencing increased physiological stress due to rising temperatures, less predictable rainfall, and more extreme events such as extreme heatwaves, storms, and floods. Because plants change considerably in form and function as they grow from seedlings to juveniles to adults, the effects of climate change on plant survival and growth are expected to change with plant age. This could have large consequences for the persistence of species on the landscape. For example, an unusually hot or arid climate period after a disturbance that kills adult trees (like a hurricane or a forest fire), could cause high mortality of regenerating tree seedlings thereby limiting forest recovery. Additionally, unusual climate stressors such as prolonged drought, could lead to dieback of adult trees with consequences for watershed functioning, carbon storage and wildlife habitat. At the individual plant species scale, we do not understand how plants will tolerate climate change as they grow from juveniles to adults, particularly for long-lived plants that experience changing climates within their lifetimes. This project investigates climate change effects on several forest tree species by comparing the performance of distinct juvenile forms versus adult stage trees of several species in New Zealand forests in response to simulated droughts of two different kinds. These forests have been reduced in area by land use change and introduced animals, and their unique biodiversity is now being threatened by climate change. Island plants may be particularly vulnerable to climate change due to their limited distributions and potentially limited overall flexibility in growth traits compared to mainland forest tree species. This work will evaluate existing variability within each species across a natural climate gradient and evaluate how different populations respond to drought in a controlled greenhouse setting. The study will improve our understanding of drought tolerance in different life stages of these forest trees, help to identify the climate conditions that might be refugia where these species can continue to exist as both seedlings and adults as climate warms and dries, and also areas on the landscape where populations are likely to be highly susceptible to mortality because of juvenile sensitivity to climate change or adult tree death. This information will contribute to the conservation of native island species while engaging native Pacific Island students, and Indigenous forest managers in the research process.Plants change considerably in form and function as they grow, with the result that seedlings and juvenile trees usually differ from adult trees in leaf shape, rates of photosynthesis and water use, and in the production of spines and toxins as defense against herbivores. Such ontogenetic changes are thought to help plants survive and grow through environments that also shift as plants mature. For example, seedlings grow near the ground where it is colder, drier, shadier, and less windy than the environment adult plants experience, and they may experience different types and intensities of herbivory. For many plant species, the shifts in environmental conditions as plants pass through developmental phases are predictable, leading to the evolution of fixed developmental changes in plant form and function, a life history known as heteroblasty. Climate change is introducing new variability within short time scales, including more consecutive days without rain, more extreme rainfall events, and directional changes in mean annual rainfall. How these climatic changes will affect plants throughout their lifetimes, especially those with fixed ontogenetic shifts in form and function, is unclear. This project investigates how species with fixed (homoblastic) versus flexible (heteroblastic) ontogenetic shifts in form and function perform under climate change using a combination of approaches, including field studies to measure morphological and physiological traits in seedlings and adults across different climates, and greenhouse experiments to test the degree to which plant traits are plastic under simulated climate change conditions. Many species with fixed developmental patterns occur on islands where species are particularly vulnerable to environmental change because they have limited ranges that have been reduced by historic land use change. Hence, this project will be carried out in New Zealand where heteroblasty is common. This work will improve our understanding of climate change effects on plants as they grow up, and contribute to the conservation of native island species under the threat of global change. It will engage native Pacific Island students in research, and will work with Indigenous forest knowledge holders to exchange information on important island tree species and their potential responses to climate change.This project is jointly funded by the Population and Community Ecology program and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

由于气温上升，降雨量难以预测，以及极端热浪、风暴和洪水等更极端的事件，林木正经历着越来越大的生理压力。由于植物从幼苗到幼体再到成体在形态和功能上都发生了很大的变化，因此气候变化对植物生存和生长的影响预计会随着植物的年龄而变化。这可能会对物种在该地貌上的持久性产生重大影响。例如，在导致成年树木死亡的干扰(如飓风或森林火灾)之后的异常炎热或干旱的气候时期，可能会导致再生树苗的高死亡率，从而限制森林恢复。此外，长期干旱等不寻常的气候压力可能会导致成年树木死亡，从而对流域功能、碳储存和野生动物栖息地造成影响。在单个植物物种的尺度上，我们不知道植物如何在从幼年到成年的过程中忍受气候变化，特别是对于在其有生之年经历气候变化的长期植物。该项目通过比较新西兰森林中几种不同树种的幼树和成年树在应对两种不同类型的模拟干旱时的表现，调查了气候变化对几种森林树种的影响。由于土地利用的变化和引入的动物，这些森林的面积已经减少，它们独特的生物多样性现在正受到气候变化的威胁。海岛植物可能特别容易受到气候变化的影响，因为它们的分布有限，与大陆森林树种相比，其生长特征的总体灵活性可能也有限。这项工作将评估每个物种在自然气候梯度上的现有变异性，并评估不同种群在受控温室环境下如何应对干旱。这项研究将提高我们对这些林木不同生活期的耐旱性的理解，有助于确定这些物种在气候变暖和干燥时可以作为苗木和成虫继续存在的气候条件，以及由于幼树对气候变化的敏感性或成年树木死亡而导致种群高度容易死亡的地区。这些信息将有助于保护当地的岛屿物种，同时让当地的太平洋岛屿学生和当地的森林管理者参与到研究过程中。植物在生长过程中在形式和功能上发生了很大的变化，结果是苗木和幼树在叶子形状、光合作用速率和水分利用方面通常与成年树不同，并在产生刺和毒素以防御食草动物方面有所不同。这种个体发育变化被认为有助于植物在随着植物成熟而变化的环境中生存和生长。例如，幼苗生长在地面附近，那里比成年植物所经历的环境更冷、更干燥、更阴凉、风更少，它们可能会经历不同类型和强度的食草动物。对于许多植物物种来说，随着植物经历发育阶段，环境条件的变化是可以预测的，导致植物形态和功能的固定发育变化的进化，这一生活史被称为异种成体。气候变化在短时间尺度内带来了新的变异性，包括更多的连续无雨日，更多的极端降雨事件，以及年平均降雨量的方向性变化。这些气候变化将如何影响植物的整个生命周期，特别是那些在形式和功能上具有固定个体发育变化的植物，目前尚不清楚。该项目使用多种方法研究在形式和功能上具有固定(同质)和灵活(异质)个体发育变化的物种在气候变化下的表现，包括实地研究以测量不同气候下苗木和成虫的形态和生理特征，以及温室实验以测试植物特征在模拟气候变化条件下的可塑性程度。许多具有固定发展模式的物种出现在岛屿上，在这些岛屿上，物种特别容易受到环境变化的影响，因为它们的活动范围有限，但由于历史上土地利用的变化而减少了。因此，这个项目将在新西兰进行，那里的异种成骨很常见。这项工作将提高我们对气候变化对植物生长影响的理解，并有助于在全球变化威胁下保护本土岛屿物种。这个项目由种群和社区生态计划和既定的激励竞争研究计划(EPSCoR)共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。