Our synthesis proposes that there are three key propositions of ecosystem ecology. In these, we seek to integrate ecosystem ecology and biogeochemistry, evolutionary ecology of organisms, and human impacts on ecosystems.
Results/Conclusions
First, ecosystems are constrained by the laws of thermodynamics, but because they are open to energy through photosynthesis, they may store energy in carbon-carbon bonds against the pull of entropy. The spatial and temporal patterns of net storage of energy in C-C bonds (net ecosystem production) are the most fundamental attributes of ecosystems and the globe, driving trophic dynamics and element cycling. The key components of NEP, autotrophy and heterotrophy, are each controlled to a different degree by the physical environment (water, temperature, oxygen, other nutrients, gravity, etc), and thus, interesting and important patterns of NEP exist through space and time. In return, rates of NEP and its distribution control oxidation, temperature, and UV, ultimately constraining the evolution of metabolic pathways through the millennia.
Second, as noted by many key authors, the stoichiometry of organisms determines nutrient distribution within and among ecosystems. The distribution of all biologically active elements can be explained by the fact that they are hooked onto carbon skeletons and travel through the biota together. The main differences among biologically active element cycles occur when elements are in their inorganic phase. Elements that are highly soluble, tightly captured by soils, or have gaseous phases may be lost from ecosystems such that their availability constrains the C cycle. Elements that can serve as electron acceptors allow heterotrophy to occur in important places, frequently resulting in the production of greenhouse gases. And elements that, in their reduced form, can serve as energy sources play important roles feeding back to the C cycle.
Third, the effects of humans on ecosystem matter and energy dynamics may be predicted by two fundamental characteristics: the turnover time of the compartments, and by the evolutionary history of the dominant organisms. Compartments characterized by rapid turnover are likely to be resilient, while those characterized by very slow turnover can be resistant to change. However, when such slow-turnover, resistant compartments are altered (such as very old soils), recovery may be impossible over human time scales. Ecosystems subjected to perturbations that fall within the evolutionary history of the dominant organisms are characterized by resistance to change; those subjected to perturbations outside the evolutionary history of the dominant organisms respond with either altered steady states or instability.
