Collaborative Research: MSA: The influence of temperature and resource supply on community size spectra in streams

人类依靠功能正常的淡水生态系统（如溪流、湖泊、湿地）来获取食物、娱乐和饮用水。生态学的一个主要挑战是了解淡水生态系统如何响应环境破坏而发生变化。然而，过去在大空间尺度上测量这种变化的努力因至少两个挑战而变得复杂：1)不同的地方有不同的物种，这使得在涉及生态系统功能时难以进行跨物种比较；2)收集生态信息极其劳动密集型，这使得难以研究空间和时间上的生态群落。这个项目用前沿的生态方法解决了这些问题。首先，为了克服物种更替的局限性，该项目将使用被称为尺寸光谱的动物身体大小分布（例如，大型生物与小型生物的相对丰度）来测量生态系统的结构和功能，这些分布被认为在整个生态系统中都是保守的，无论物种组成如何。尺寸谱是食物链中能量从一种生物转移到另一种生物的效率的指标。其次，该项目通过使用已经从国家生态观测站网络（NEON）收集和整理的数据，克服了后勤限制。利用NEON数据，研究人员将分析各种环境条件下河流中的大量尺寸光谱，以确定河流温度和营养物质如何影响淡水生态系统。这个项目符合国家利益，因为它为淡水生态系统如何在宏观生态尺度上对未来的温度情景作出反应提供了一个关键的测试。研究人员还将开发软件，使公众可以免费获得体型分布的分析，并使生态学家在未来更容易进行研究。50多年来的研究揭示了生态系统中一个共同的模式，即丰度(N)随着体重(M)的增加而下降。这种关系的形状用幂律N ~ M（exp b）来描述，称为丰度大小谱，指数b随食物网能量流的变化而变化。b的值几乎总是负的，这表明一个非常一致的生态模式。然而，气候变化预计会改变体型光谱，这部分是基于体型随温度的变化。尽管身体尺寸和温度之间的关系看似简单，但实验和实地研究表明，尺寸光谱温度关系的结果截然不同，在不同的温度状态下，尺寸光谱会出现正、负和中性的变化。这些研究在很大程度上是由相对较小的空间尺度上的有限样本组成的，因此很难预测在大陆等更大尺度上尺寸光谱如何随温度变化。此外，对b-温度关系的理论预测的偏差可以通过考虑资源供应的变化来解决，但大尺度上资源供应的影响也是未知的。该项目利用统计建模来确定河流温度和资源供应对河流大小光谱指数的影响，这些指数跨越一个国家监测网络所代表的广泛环境梯度。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Humans rely on properly functioning freshwater ecosystems (e.g., streams, lakes, wetlands) for food, recreation, and drinking water. A major challenge in ecology is to understand how freshwater ecosystems will change in response to environmental disruptions. However, past efforts at measuring this change across large spatial scales are complicated by at least two challenges: 1) different places have different species, which makes it hard to compare across species when it comes to ecosystem function, and 2) collecting ecological information is extremely labor intensive, which makes it difficult to study ecological communities over space and time. This project solves those problems using cutting-edge ecological approaches. First, to overcome the limitations of species turnover, this project will measure ecosystem structure and function using animal body size distributions known as size-spectra (e.g., the relative abundance of large to small organisms), which are thought to be conserved across ecosystems regardless of species composition. Size spectra are an indicator of how efficiently energy is transferred from one organism to another in a food chain. Second, this project overcomes logistical limitations by using data already collected and curated from the National Ecological Observatory Network (NEON). Using NEON data, the researchers will analyze a large collection of size-spectra in streams over a wide range of environmental conditions to determine how stream temperature and nutrients influence freshwater ecosystems. This project is in the national interest because it provides a critical test of how freshwater ecosystems might respond to future temperature scenarios at macroecological scales. The researchers will also develop software that makes analysis of body size distributions freely available to the public and easier for ecologists to study in the future. Over 50 years of research reveals a common pattern across ecosystems in which abundance (N) declines with increasing body mass (M). The shape of this relationship is described by a power law, N ~ M(exp b), known as the abundance size-spectrum, and the exponent b varies in relation to changes in energy flow through the food web. The value of b is almost always negative, suggesting a remarkably consistent ecological pattern. However, climate change is expected to alter size-spectra, based in part on shifts in body size with temperature. Despite a seemingly simple relationship of body size and temperature, experimental and field studies demonstrate disparate results for size spectra-temperature relationships, finding positive, negative, and neutral shifts in size-spectra across temperature regimes. These studies largely consist of limited samples across relatively small spatial scales, making it difficult to predict how size-spectra varies with temperature at larger scales such as continents. In addition, deviations from theoretical predictions of the b-temperature relationship may be resolved by accounting for variation in resource supply, but the effect of resource supply at large scales is also unknown. This project uses statistical modeling to determine the influence of stream temperature and resource supply on stream size spectra exponents across a broad environmental gradient represented by a national monitoring network.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.