Schramski John R, Dell Anthony I, Grady John M, Sibly Richard M, Brown James H
College of Engineering, University of Georgia, Athens, GA 30602;
Systemic Conservation Biology, Department of Biology, Georg August University, Göttingen 37073, Germany; National Great Rivers Research and Education Center, Alton, IL 62024;
Proc Natl Acad Sci U S A. 2015 Feb 24;112(8):2617-22. doi: 10.1073/pnas.1423502112. Epub 2015 Jan 26.
Understanding the effects of individual organisms on material cycles and energy fluxes within ecosystems is central to predicting the impacts of human-caused changes on climate, land use, and biodiversity. Here we present a theory that integrates metabolic (organism-based bottom-up) and systems (ecosystem-based top-down) approaches to characterize how the metabolism of individuals affects the flows and stores of materials and energy in ecosystems. The theory predicts how the average residence time of carbon molecules, total system throughflow (TST), and amount of recycling vary with the body size and temperature of the organisms and with trophic organization. We evaluate the theory by comparing theoretical predictions with outputs of numerical models designed to simulate diverse ecosystem types and with empirical data for real ecosystems. Although residence times within different ecosystems vary by orders of magnitude-from weeks in warm pelagic oceans with minute phytoplankton producers to centuries in cold forests with large tree producers-as predicted, all ecosystems fall along a single line: residence time increases linearly with slope = 1.0 with the ratio of whole-ecosystem biomass to primary productivity (B/P). TST was affected predominantly by primary productivity and recycling by the transfer of energy from microbial decomposers to animal consumers. The theory provides a robust basis for estimating the flux and storage of energy, carbon, and other materials in terrestrial, marine, and freshwater ecosystems and for quantifying the roles of different kinds of organisms and environments at scales from local ecosystems to the biosphere.
了解个体生物对生态系统内物质循环和能量通量的影响，对于预测人为变化对气候、土地利用和生物多样性的影响至关重要。在此，我们提出一种理论，该理论整合了代谢（基于生物体的自下而上）和系统（基于生态系统的自上而下）方法，以描述个体的新陈代谢如何影响生态系统中物质和能量的流动与存储。该理论预测了碳分子的平均停留时间、系统总通量（TST）以及再循环量如何随生物体的体型、温度以及营养组织而变化。我们通过将理论预测与旨在模拟不同生态系统类型的数值模型输出以及真实生态系统的实证数据进行比较，来评估该理论。尽管不同生态系统中的停留时间相差几个数量级——从浮游植物生产者微小的温暖海洋中的数周，到树木生产者庞大的寒冷森林中的数百年——但正如预测的那样，所有生态系统都落在同一条线上：停留时间与整个生态系统生物量与初级生产力的比率（B/P）呈斜率为1.0的线性增加。TST主要受初级生产力的影响，而再循环则受从微生物分解者到动物消费者的能量转移的影响。该理论为估计陆地、海洋和淡水生态系统中能量、碳和其他物质的通量与存储，以及量化从局部生态系统到生物圈尺度上不同种类生物和环境的作用，提供了一个坚实的基础。
