Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA.
Department of Ecology and Evolutionary Biology and Kansas Biological Survey, University of Kansas, Lawrence, KS, 66047, USA.
New Phytol. 2015 May;206(3):900-912. doi: 10.1111/nph.13338. Epub 2015 Mar 2.
Integrative concepts of the biosphere, ecosystem, biogeocenosis and, recently, Earth's critical zone embrace scientific disciplines that link matter, energy and organisms in a systems-level understanding of our remarkable planet. Here, we assert the congruence of Tansley's (1935) venerable ecosystem concept of 'one physical system' with Earth science's critical zone. Ecosystems and critical zones are congruent across spatial-temporal scales from vegetation-clad weathering profiles and hillslopes, small catchments, landscapes, river basins, continents, to Earth's whole terrestrial surface. What may be less obvious is congruence in the vertical dimension. We use ecosystem metabolism to argue that full accounting of photosynthetically fixed carbon includes respiratory CO₂ and carbonic acid that propagate to the base of the critical zone itself. Although a small fraction of respiration, the downward diffusion of CO₂ helps determine rates of soil formation and, ultimately, ecosystem evolution and resilience. Because life in the upper portions of terrestrial ecosystems significantly affects biogeochemistry throughout weathering profiles, the lower boundaries of most terrestrial ecosystems have been demarcated at depths too shallow to permit a complete understanding of ecosystem structure and function. Opportunities abound to explore connections between upper and lower components of critical-zone ecosystems, between soils and streams in watersheds, and between plant-derived CO₂ and deep microbial communities and mineral weathering.
生物圈、生态系统、生物地理群落以及最近的地球关键带的综合概念包含了将物质、能量和生物体联系在一起的科学学科，从系统层面理解我们这个非凡的星球。在这里，我们断言坦斯利（Tansley）（1935）关于“一个物理系统”的古老生态系统概念与地球科学关键带的一致性。从植被覆盖的风化剖面和山坡、小流域、景观、流域、大陆到地球整个陆地表面，生态系统和关键带在时空尺度上是一致的。不太明显的是在垂直维度上的一致性。我们利用生态系统代谢来论证，对光合作用固定的碳的充分核算包括传播到关键带本身底部的呼吸 CO₂和碳酸。虽然呼吸作用的一小部分，但 CO₂的向下扩散有助于确定土壤形成的速率，最终影响生态系统的演化和恢复力。由于陆地生态系统上部的生命显著影响整个风化剖面的生物地球化学，因此大多数陆地生态系统的下部边界划定在太浅的深度，无法完全理解生态系统的结构和功能。有很多机会可以探索关键带生态系统的上部和下部组成部分、流域中的土壤和溪流以及植物衍生的 CO₂与深层微生物群落和矿物风化之间的联系。
