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

人类依靠正常运作的淡水生态系统(如溪流、湖泊、湿地)提供食物、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将如何改变以应对环境破坏。然而，过去在大空间尺度上衡量这种变化的努力至少因两个挑战而变得复杂：1)不同地区有不同的物种，这使得在涉及生态系统功能时很难跨物种进行比较；2)收集生态信息是极其劳动密集型的，这使得研究生态群落在空间和时间上都很困难。该项目使用尖端的生态方法解决了这些问题。首先，为了克服物种周转的限制，该项目将使用被称为大小谱(例如，大到小生物的相对丰度)的动物身体大小分布来衡量生态系统的结构和功能，这种分布被认为是跨生态系统的，无论物种组成如何。大小光谱是食物链中能量从一个有机体转移到另一个有机体的效率的指标。其次，该项目利用已经从国家生态观测网络(NEON)收集和整理的数据，克服了后勤方面的限制。利用霓虹灯数据，研究人员将分析各种环境条件下溪流的大量粒度谱，以确定溪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，因为它对淡水生态系统可能如何在宏观生态范围内应对未来的温度情景进行了关键测试。研究人员还将开发软件，使公众可以免费获得人体尺寸分布的分析，并使生态学家更容易在未来进行研究。50多年的研究揭示了整个生态系统的一个共同模式，即丰度(N)随着体重(M)的增加而下降。这种关系的形状由一个被称为丰度尺寸谱的幂定律N~M(Exp B)来描述，指数b随着通过食物链的能量流动的变化而变化。B的值几乎总是负值，这表明生态模式非常一致。然而，气候变化预计会改变体型光谱，这在一定程度上是基于体型随温度的变化。尽管体型和体温之间的关系看起来很简单，但实验和野外研究证明了体型光谱-温度关系的不同结果，发现体型光谱在不同的温度范围内有正、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，这使得很难预测尺寸光谱如何在较大尺度上(如大陆)随温度变化。此外，与b温度关系理论预测的偏差可以通过考虑资源供应的变化来解决，但大范围的资源供应的影响也是未知的。这个项目使用统计模型来确定河流温度和资源供应对由国家监测网络代表的广泛环境梯度上的河流大小谱指数的影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为是值得支持的。

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.