Linking CZO, LTER, and NEON- Putting Biology into the Critical Zone

Abstract:

With the advent of the Critical Zone Observatory Network, new opportunities are emerging to link the geological and ecological aspects of environmental science. Interactions between the CZO Network and the 30-year old Long-Term Ecological Research (LTER) Network can provide the opportunity to interpret long-term ecological research in the context of the geologic forces that have shaped both the form and function of the landscape. Using four examples from the Luquillo Mountains in tropical Puerto Rico, I highlight the ways in which ecological patterns and processes are driven by the underlying geologic template. The distribution of stream biota in the Luquillo Mountains is striking, with predatory fish below large geomorphic breaks; above these waterfalls, fish are absent, and shrimp dominate the biota. The critical zone thus structures aquatic communities. A second example is provided by the role of soil texture and structure in driving rates of greenhouse gas production. In the moderately well drained soils of the Luquillo Mountains, water-filled pore space is a key driver of methane production. Critical zone characteristics thus shape biotic function and ecosystem carbon balance. A third example is the effect of riparian zone structure on watershed-scale nitrogen losses. Due to differences in the geomorphology of the riparian zone on volcaniclastic and intrusive bedrock, adjacent watersheds have remarkably different patterns in stream nitrate following hurricanes. Nitrogen losses from these watersheds are driven by interactions between biology and lithology that affect riparian zone function. Finally, in the deep critical zone (5 m) bacterial growth is dominated by autotrophic iron-oxidizing bacteria, with implications for weathering, the development of flow pathways, and solute transport. In this case, biota may be driving the formation of the critical zone through biotic effects on weathering. In each example, our ability to understand the importance of critical zone processes is enhanced by the broad ecological context provided by LTER research. With the anticipated inauguration of NEON observatories in the next several years, a whole new set of opportunities will arise to establish links between the critical zone and ecological processes across North America.