Collaborative Research: Asynchrony in the timing of goose-vegetation interactions: implications for biogeochemical cycling in wet sedge tundra

陆地高纬度生态系统正经历着温度的急剧上升、降水的变化和生长季节的提前，这对营养相互作用具有重要意义。这些变化的最明显的后果之一是，迁徙动物与它们所依赖的能量、营养和哺育幼仔的牧草物候之间的时间关系不耦合。此外，高纬度地区的食草动物可能会调节生物地球化学对气候变化的响应，从而大大改变生态系统的功能。然而，草食-植被相互作用的同步性变化对生物地球化学循环的影响尚不清楚。该项目将在阿拉斯加西部的育空-库斯科维姆（Y-K）三角洲进行，那里有强有力的证据表明，气候变化正在推动植物物候与鹅迁徙时间之间进化联系的时间脱钩。研究的紧迫性在于：阿拉斯加正在发生世界上最迅速的气候变化，使候鸟及其影响的生态系统过程容易受到新条件的影响，并且随着生长季节的快速推进，候鸟喂养生态严重滞后，威胁到当地社区不可替代的生存资源。总体研究目标是量化生长季节的推进和植被-鹅相互作用同步性的变化如何改变Y- K三角洲C和N循环的大小和模式。两个具体问题将通过实验解决：植物生长时间如何与鹅到达时间相互作用，从而改变植物产量、叶面化学和氮有效性；植物生长的时间如何与鹅的到达时间相互作用，从而改变整个夏季生态系统的净二氧化碳交换量、生态系统光合作用总量和生态系统呼吸量？SAVANNA-YK是一个生物地球化学模型，认为放牧是对Y-K三角洲植被和微量气体过程的关键控制，将用于预测这些生态系统过程和植物-食草动物相互作用将如何继续变化，改变生态系统过程的性质和景观动态。本研究的学术价值体现在三个方面：第一，研究候鸟及其主要饵料在生态系统生物地球化学循环中的物候解耦，这是同类研究中的首次。更具体地说，与其他专注于草食动物存在与否和/或草食动物密度对这些循环的影响的项目相比，该研究首次调查了食草动物的时间如何与植物物候相互作用，从而影响生物地球化学循环；这项研究首次采用实验方法来解决阿拉斯加西部亚北极地区的营养不匹配问题，同时将这些发现与针对北部湿莎草系统量身定制的预测生态系统模型相结合。这种结合使得研究气候变化对草食-植被相互作用的影响在未来几年将如何影响大的空间尺度；该研究侧重于对候鸟至关重要的植物物种，而其他关注气候变化影响的北方研究则侧重于对候鸟觅食生态不重要的苔原植物物种。研究的更广泛影响将通过若干活动来实现。首先，将利用国家物候网络的协议建立一个公民科学观测站。整个Y-K三角洲的学生将记录鹅的到达时间和草和木本植物的主要物候事件。其次，将招募来自伯特利地区高中的学生协助进行实地研究，并有机会开发小型项目。每年春天，研究人员将访问乡村教室，介绍该项目、气候变化和动植物相互作用；分享研究领域以前和正在进行的研究结果；招募有兴趣的学生。第三，通过阿拉斯加本土科学与工程项目（ANSEP）的阿拉斯加本土本科生将被招聘为现场和实验室技术人员；这些学生也可以开发自己的项目。第四，虚拟科学将与当地教师一起开发博客、播客和教学视频，这些视频可以分发到阿拉斯加西部和其他地区的远程教室。第五，目标和结果将传达给当地的组织机构，这些组织机构有来自每个大村庄的代表，以便为研究建立知识和支持，并为依靠鹅为生的家庭提供教育渠道。最后，一名博士后研究员、一名研究生和几名本科生将获得新的培训、指导，并有机会在项目活动中进行合作，并在科学会议上展示他们的发现。

Terrestrial high-latitude ecosystems are experiencing dramatic increases in temperature, changes in precipitation, and advancement of the growing season with important implications for trophic interactions. Uncoupling of the temporal relationships between migratory animals and the phenology of the forage they rely on for energy, nutrition, and rearing of young is one of the most glaring consequences of these changes. Furthermore, herbivores in high latitudes are likely to mediate biogeochemical responses to climate change substantially altering ecosystem function. However, little is known about how changes in the synchrony of herbivore-vegetation interactions will influence biogeochemical cycles.This project will be conducted on the Yukon-Kuskokwim (Y-K) Delta in western Alaska, where there is strong evidence that climate change is driving temporal decoupling of the evolved linkage between the phenology of plants and the timing of goose migration. There is an urgency to the research because: some of the most rapid climate changes in the world are underway in Alaska, leaving migratory geese and the ecosystem processes they influence vulnerable to new conditions, and with the rapid advancement of the growing season, migratory goose feeding ecology is lagging substantially, threatening an irreplaceable subsistence resource for Native communities.The overall research objective is to quantify how an advancing growing season and changes in the synchrony of vegetation-goose interactions alter the magnitudes and patterns of C and N cycling in the Y- K Delta. Two specific questions will be addressed with an experiment: How does the timing of plant growth interact with goose arrival time to alter summer-long magnitudes of plant production, foliar chemistry, and N availability; and, How does the timing of plant growth interact with goose arrival time to alter summer-long magnitudes of net ecosystem CO2 exchange, gross ecosystem photosynthesis, and ecosystem respiration? SAVANNA-YK, a biogeochemical model that considers grazing a critical control on vegetation and trace gas processes in the Y-K Delta, will be used to predict how these ecosystem processes and plant-herbivore interactions will continue to change, altering the nature of ecosystem processes and landscape dynamics in years to come.The intellectual merit of the research is three-fold: The focus on phenologic decoupling of migratory birds and their primary forage on ecosystem biogeochemical cycles is the first of its kind. More specifically, the research is the first to investigate how the timing of herbivory interacts with plant phenology to affect biogeochemical cycles compared to other programs that have focused on the presence or absence of herbivores and/or on herbivore density effects on these cycles; The research is the first to take an experimental approach to the issue of trophic mismatch in the western Alaskan sub-Arctic while integrating these findings with forecasting ecosystem models tailored to wet sedge systems of the north. This combination allows investigation into how climate change effects on herbivore-vegetation interactions will influence large spatial scales in years to come; and The research focuses on plant species that are critical to migratory geese, while other northern studies focusing on climate change effects have focused on tundra plant species that are not critical to migratory bird foraging ecology.The broader impacts of the research will be realized throughh several activities. First, a citizen- science observatory will be established using protocols of the National Phenology Network. Students throughout the Y-K delta will record goose arrival times and key phenological events in grasses and woody plants. Second, students from Bethel Regional High School will be recruited to assist in the field research and be given the opportunity to develop small projects. Researchers will visit village classrooms each spring to introduce the project, climate change, and plant-animal interactions; share results of previous and ongoing research in the study area; and recruit interested students. Third, Native Alaskan undergraduate students through the Alaska Native Science and Engineering Program (ANSEP) will be recruited as field and laboratory technicians; these students may also develop their own projects. Fourth, Virtual Science will be used with local teachers to develop blogs, pod-casts, and instructional videos that can be distributed to remote classrooms throughout western Alaska and beyond. Fifth, objectives and results will be communicated to Native organizational bodies, which have representatives from each major village, to build knowledge and support for the research, and provide educational outlets for families who rely on geese for subsistence. Finally, one post-doctoral researcher, one graduate student, and several undergraduates will be provided new training, mentoring, and an opportunity to collaborate on project activities and present their findings at scientific meetings.