Predicting Physical Disturbance in a Changing Environment: The Effect of Spatial and Temporal Scale

目前关于竞争、捕食、补充、演替和干扰在群落生态学中的作用的想法部分是基于在被海浪席卷的岩石海岸的潮间带进行的实验，这些研究作为生态学理论对现实世界进行预测的能力的基准。海岸的试验性效用在很大程度上是由于社区中个人的快速流动。在暴露的海岸上，周转主要是由于环境影响，预测生物分布和丰度的最终能力取决于我们在所有相关空间和时间尺度上预测物理环境的近距离能力，以及我们对环境压力的生物后果的解释能力。现场试验表明，从离岸波高预测岸上给定位置施加的最大波浪力是可行的。然而，这些力(一种重要的环境压力)在空间和时间上都有很大的不同，这种模式被称为1/f噪声：检查海岸的空间或时间尺度越大，测量到的变化就越大。因此，很难明确规定一个网站的波曝光量。由于潮间带群落动力学的许多方面与波浪暴露密切相关，当试图推广(“放大”)小规模实验的结果时，海岸的1/f噪声特性可能会成为问题。然而，物种多样性的初步测量表明，即使在物理1/f噪声存在的情况下，植物和动物也可能以一种产生明确空间结构的方式与物理环境相互作用。这个项目以这些结果为基础，研究了几个基本的生态过程(例如，补充、生长和捕食强度)如何在空间和时间尺度上变化，以及这些尺度如何对群落动态的整体格局做出贡献。野外实验将沿着潮间带的一个水平样带进行，以前的工作描述了最大波浪诱导力和最高温度的空间变化。将在200米的横断面上以2米的间隔同时测量：贻贝和藤壶的补充速率，贻贝和藤壶的生长速度，腹足类对藤壶的捕食强度，贻贝底床的扰动，以及先前未被占用的底质的演替过程。每季度将对每个位置的物种丰度进行测量，并根据这些物种多样性计算样带上100个点的物种多样性。由于这些测量是在等间距的点上进行的，因此可以使用光谱分析来检查每个生态过程或生物属性的变化与物理环境(波浪力和温度)的共同变化之间的特定尺度的相互关系。结合捕食强度实验，将对藤壶类主要腹足类捕食者(Nucella和Acansina)的黏附强度和觅食速度进行测量。这些现场实验将直接衡量生态过程是否存在定义的尺度，以及(如果有)生物如何与环境1/f噪声相互作用产生相应的群落动力学尺度(S)。除了探索波浪力的空间和时间变化外，以前的工作还表明，岸上的最大波浪诱导力对应的水速大约是标准波浪破碎理论预测的两倍。这些极端速度(高达25m/S)的原因被认为与破碎波与复杂的岩石海岸地形的相互作用有关。例如，当破碎的波被折射，使两个波面相撞时，就会产生一股水的喷射，其速度远远大于任何一种波的速度。实验将在实验室波浪水池中进行，以表征波浪在各种模型岸上破裂时产生的流动，从而描绘出可以预期提高速度的情况。结合这些实验，将对固定在底物上的物体施加的力进行测量。这些测量(除了在现场进行的类似测量之外)将用于测试从力测量计算的表面极端水速是否实际上是波浪前沿撞击岸上动植物的人工产物。这项工作将使人们能够第一次量化控制被海浪席卷的海岸上的群落动态的内在空间和时间尺度的过程，从而在波浪“天气”、海岸线地形和补充、生长、捕食和演替过程之间建立机械联系。这些机制的阐明代表着朝着能够根据小规模相互作用进行大规模机械性预测迈出了重要的第一步，这些预测可能是对沿海海洋保护区的适当设计的重要投入。

Current ideas regarding the roles of competition, predation, recruitment, succession, and disturbance in community ecology are based in part on experiments in the intertidal zone of wave-swept rocky shores, and these studies serve as benchmarks for the ability of ecological theory to make predictions about the real world. Much of the experimental utility of the shore is due to the rapid turnover of individuals in the community. On exposed shores where turnover is due primarily to environmental effects, the ultimate ability to predict the distribution and abundance of organisms rests on our proximal ability to predict the physical environment at all relevant spatial and temporal scales, and on our ability to account for the biological consequences of environmental stress.Field experiments have shown that it is feasible to predict from offshore wave height the maximum wave forces imposed at a given location on the shore. However, these forces (an important environmental stress) vary substantially through both space and time in a pattern known as 1/f-noise: the larger the spatial or temporal scale at which the shore is examined, the larger the variation measured. As a result, it is difficult to specify unambiguously the wave exposure of a site. Because many aspects of intertidal community dynamics are closely tied to wave exposure, the 1/f-noise characteristic of the shore becomes potentially problematic when an attempt is made to generalize ("scale up") the results of small-scale experiments. Preliminary measurements of species diversity suggest, however, that it is possible for plants and animals to interact with the physical environment in a fashion that produces well-defined spatial structure even in the presence of physical 1/f-noise. This project builds on these results by examining how several basic ecological processes (e.g., recruitment, growth, and predation intensity) vary across spatial and temporal scales, and how these scales contribute to the overall pattern in community dynamics.Field experiments will be conducted along a horizontal transect in the intertidal zone for which previous work has characterized the spatial variation in maximum wave-induced force and maximum temperature. Simultaneous measurements will be made at 2-m intervals along a 200-m transect of: the rate of recruitment of mussels and barnacles, the rate of growth of mussels and barnacles, the intensity of gastropod predation on barnacles, disturbance in the mussel bed, and the course of succession on previously unoccupied substratum. Quarterly measurements will be made of species abundances at each location, and from these species diversity is calculated at each of the 100 points on the transect. Because these measurements are made at equally spaced points, it is possible to use spectral analysis to examine the scale-specific cross-correlation between the variation in each ecological process or biological attribute and the co-occurring variation of the physical environment (wave force and temperature). In conjunction with the experiment on predation intensity, measurements will be made of the adhesive tenacity and foraging speed of the primary gastropod predators of barnacles (Nucella and Acanthina). These field experiments will provide a direct measure of whether there are defined scales for ecological processes, and (if so) how biology interacts with environmental 1/f-noise to yield the relevant scale(s) of community dynamics.In addition to exploring the spatial and temporal variation in wave forces, previous work has shown that maximum wave-induced forces on the shore correspond to water velocities that are approximately twice those predicted by standard theories of wave breaking. The cause of these extreme velocities (up to 25 m/s) is thought to be tied to the interaction of breaking waves with the complex topography of the rocky shore. For example, when breaking waves are refracted so that two wave fronts collide, a jet of water is produced the velocity of which is substantially greater than that of either wave. Experiments will be conducted in a laboratory wave tank to characterize the flows resulting when waves break on a variety of model shores, thereby to delineate the circumstances under which enhanced velocities can be expected. In conjunction with these experiments measurements will be made of the force exerted on objects held fixed to the substratum. These measurements (in addition to similar measurements conducted in the field) will be used to test the possibility that the apparently extreme water velocities calculated from force measurements are in fact an artifact of the manner in which the leading edge of a wave impacts plants and animals on the shore. This work will allow one to quantify for the first time the inherent spatial and temporal scales of processes that govern community dynamics on wave-swept shores, and thereby to forge mechanistic links among the wave "weather," the shoreline topography, and the processes of recruitment, growth, predation, and succession. The elucidation of these mechanisms represents an important first step toward an ability to make large-scale mechanistic predictions from small-scale interactions, predictions that may be important inputs into the appropriate design of coastal marine protected areas.