Treeline advances in a changing climate: understanding how climate affects reproduction and early life stages in Black spruce

气候变化中的林线进展：了解气候如何影响黑云杉的繁殖和早期生命阶段

• 批准号: NE/V021397/1
• 负责人: Andrew Hacket Pain
• 金额: $ 1.62万
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV021397%2F1
• 关键词: Treeline; advances; changing; climate; understanding

NERC : Jessie Foest : NE/S00713X/1Northern high-latitude ecosystems are warming faster than any other ecosystem on Earth. Such warming strongly affects the vegetation in previously temperature-limited systems such as the sub-arctic tundra. Treelines, the ecotones between forests and the tree-less tundra, are expected to respond by shifting northwards. However, a meta-analysis on treeline advances found that only half of the examined treelines had advanced since 1900. Why warming is associated with treeline advances in some but not other populations remains unresolved.It is crucial to understand how treeline ecosystems will respond to climate change. Firstly, the soils in tree-less tundra regions store a third of the Earth's soil carbon. When trees encroach on these areas, they change soil conditions (e.g. drying, aerating soils) and facilitate further vegetation shifts. This may release the stored carbon from the soil. Additionally, climate feedback loops may arise because of changes in the system's albedo, where an increase in tree cover may drive further warming.Tree reproduction may help explain why treelines show lagged responses to warming. A recent global synthesis of reproductive behaviour across 13 sub-arctic treeline ecotones reported that low numbers of viable seeds were produced in these populations. In plants, the early life stages that occur after seeds fall to the forest floor (i.e. germination and seedling establishment) are characterised by high mortality rates. Low levels of seed production may thus result in complete failure of seedling recruitment. Consequently, some populations might be unable to advance poleward with climate warming. However, we have a poor understanding of how seed production and seed viability vary in sub-arctic forests. In this project we will investigate how climate controls seed production and viability in black spruce (Picea mariana), the dominant treeline-forming species in the north-west sub-arctic. Moreover, the proposed research will be used to establish a longer-term experiment to test our hypothesis that the capacity for black spruce treeline advance is determined by their ability to produce sufficient viable seeds.Snapshot data collected by the hosting group and their network between 2006-2011 revealed that the amount of spring-time growing degree days (days with daily mean temperatures >5 degree C), higher levels of summer precipitation and higher conspecific densities of trees increase seed production in a variety of treeline-forming species. Consecutive years with more growing degree days and low precipitation levels, variables linked to moisture stress, were associated with low seed production. Seed viability was affected by climatic conditions during flowering, as well as by stand and seed characteristics. Continuing and expanding data collection in these quickly changing ecosystems will help determine if the drivers of seed production are changing. Such an evolving understanding is required to accurately model and predict future seed availability in forest tundra systems.

NERC：Jessie Foest：NE/S00713X/1 Northern高纬度生态系统的变暖速度比地球上任何其他生态系统都快。这种变暖强烈影响先前温度有限的系统（例如亚北极苔原）中的植被。绿线（森林和无育树的苔原之间的ecotones）有望通过向北转移来做出回应。然而，一项对绿琳进展的荟萃分析发现，自1900年以来，只有一半的绿线线已经进步了。为什么在某些但没有其他人群中，温暖与绿氧化和绿线疗法有关。首先，无树苔原地区的土壤存储了地球土壤碳的三分之一。当树木侵占这些区域时，它们会改变土壤状况（例如干燥，充气土壤），并促进植被转移。这可能会从土壤中释放储存的碳。此外，由于系统反照率的变化，气候反馈回路可能会出现，因为树覆盖物的增加可能会推动进一步的变暖。树繁殖可能有助于解释为什么树木对温暖的响应滞后响应。最近在13个亚北极线丝烯元素中，全球综合了生殖行为，报告说，在这些人群中产生了少量的可行种子。在植物中，种子后发生的早期生命阶段掉落到森林地面（即发芽和幼苗建立）的特征是高死亡率。因此，低水平的种子产量可能导致幼苗募集的完全失败。因此，一些人口可能无法通过气候变暖前进。但是，我们对种子生产和种子生存能力在亚北极森林中的不同程度不足。在该项目中，我们将研究气候如何控制黑云杉（Picea Mariana）的种子生产和生存能力，这是西北亚北极地区的主要树木形成物种。此外，拟议的研究将用于建立长期实验，以测试我们的假设，即黑云杉的能力是由它们产生足够可行种子的能力确定的。宿主组收集的数据及2006年至2011年之间的网络收集的数据，在2006年至2011年之间的网络收集了较高的春季增长量（较高的夏季范围，较高的夏季繁殖水平），并且越来越高的夏季种子的水平增加了种子的较高水平。树形成物种。连续年增长的天数和低降水水平，与水分应力相关的变量与种子产量低有关。种子活力受到开花期间气候条件的影响，以及林分和种子特征。在这些快速变化的生态系统中，继续和扩展数据收集将有助于确定种子生产的驱动因素是否在变化。需要这种不断发展的理解才能准确地建模并预测森林苔原系统中未来的种子可用性。