LTREB Renewal: Experimental tests of alternative states on rocky intertidal shores.

将生态系统从一种类型的社区转变为另一种类型的意外事件，人们对此知之甚少，但往往会产生严重的生态和经济影响，美国西南部多产草原突然崩溃为沙漠就是一个例子。这个项目将调查在缅因湾有遮挡的岩石海岸上以海藻或贻贝为主的替代群落之间转换的根本原因。一项独特的长期实验将促进人们对自然群落对不同规模生态扰动的适应能力、环境条件恢复时生态转型的可逆程度以及生态群落受到扰动时的可预测性的总体理解。研究团队包括一名来自缅因州的高中教师，他与这个项目有很长的联系。她的学生每年将有6到8人参加实地研究，老师将开发适合高中生和K-12教师的课堂活动。原始数据、实验区全景照片和教育活动将以电子方式提供，调查人员将在YouTube上发布一段关于数据归档和管理的视频。研究人员将测试以下假设：(1)在冬季罕见的大规模冰冲发生时，会发生贻贝床和杂草林替代群落状态的转换，(2)在冰冲形成的大片空地上建立的群落是不可预测的，(3)重建期间物种到达的顺序推动群落发展，(4)替代群落是稳定的。这些假设将使用控制后影响前(BACI)设计进行验证，该设计包括不同大小的试验性清理、1996-97年创建的未清理对照和2010-11年度再次清理的一半这些对照。除了收集描述这些发展中群落演替模式的数据外，研究人员还将分析对贻贝的捕食率、不同大小斑块中贻贝的死亡率，以及每年招募四个关键物种的幼体。数据分析将比较第一次实验(1997-2008年)和第二次实验(2011-2021年)的结果，以测试社区发展是否可预测。重复实验以测试自然生态系统中替代群落状态的方法是独一无二的，并对其他生态系统中替代群落状态的研究具有广泛的影响。

Unexpected events that tip an ecosystem from one type of community to another are poorly understood yet often have serious ecological and economic effects, exemplified by the sudden collapse of productive grasslands into desert in the southwestern US. This project will investigate the underlying causes of the switch between alternative communities, dominated by either seaweeds or mussels, on sheltered rocky shores in the Gulf of Maine. A unique long-term experiment will advance general understanding of the resilience of natural communities to ecological perturbations of different sizes, the extent to which ecological transitions are reversible when environmental conditions are restored, and the predictability of ecological communities when perturbed. The research team includes a high school teacher from Maine who has a long association with this project. Six to eight of her students will participate in the field research each year, and the teacher will develop classroom activities appropriate for high school students and K-12 teachers. Primary data, panoramic photographs of the experimental plots, and educational activities will be available electronically, and the investigators will post a YouTube video on data archiving and management. The researchers will test hypotheses that (1) switches between alternative community states of mussel beds and rockweed stands occur in response to infrequent, large-scale occurrences of ice scour during winter, (2) the community that becomes established in large clearings made by ice scour is not predictable, (3) the order of species arrival during re-establishment drives community development and (4) the alternative communities are stable. These hypotheses will be tested using a Before-After-Control-Impact (BACI) design consisting of experimental clearings of different sizes, uncleared controls that were created in 1996-97, and half of these controls that were cleared again in 2010-11. In addition to collecting data characterizing patterns of succession in these developing communities, the researchers will assay rates of predation on mussels, mortality rates of mussels in patches of different sizes, and recruitment of juveniles of four key species annually. Analyses of data will compare outcomes from the first run of the experiment (1997-2008) with those from the second run (2011-2021) to test if community development is predictable. The approach of repeating an experiment to test for alternative community states in a natural ecosystem is unique and has broad implications for studies of alternative states in other ecosystems.