Abstract

The great intellectual fascination of pedology derives from its comparative study of the
diversity of Earth’s soil, its interdisciplinarity required to understand even a single soil, and the
many ways in which soil interacts with the natural and cultural environment (Richter and
Yaalon, 2012).

Not surprisingly, pedologists have been instrumental to the development of the
interdisciplinary Earth science of the critical zone (Jordan et al. 2001; Lin and Wilding, 2005),
the critical zone being defined as the life-supporting system of Earth’s surficial terrestrial
processes. As an integrated body, the Earth’s critical zone (“a thing” in the words of W.E.
Dietrich, personal communication) extends the conventional definition of ecosystem to include
not only the atmosphere, climate, and foliar boundary layer down through the soil to the
deepest zone of mineral weathering. Defined by its fluids, the critical zone spans the
atmosphere to the deepest aquifers; defined by time, the critical zone spans all biological and
geological time scales and history; defined by its slogan, the critical zone extends “from
treetop to bedrock”. Jordan et al. (2001) when coining the critical zone used the word “critical”
for good reason to emphasize the growing concern about human influence on this lifesupporting
system (Latour 2014). It is no coincidence that at the same moment that a
congruence exists in the core concepts of ecology’s ecosystem and Earth sciences’ critical zone
(Richter and Billings 2015), our geological epoch may be renamed the Anthropocene (Waters
et al., 2015).

We propose that a paradigm of Earth’s critical zones is that of soil production (Figure 1), a
brilliant but underutilized framework first proposed by Gilbert (1877). (Note that what Gilbert
called “soil” was later called “regolith” (Merrill 1897), although in this piece and others (Richter
and Markewitz, 1995), we follow the Gilbert tradition). Here, we suggest that the soilproduction
paradigm can provide new perspectives of Earth’s systems for ecosystem
ecologists, critical zone scientists, and pedologists alike. We describe two examples of soil
production at the Calhoun Critical Zone Observatory, a 70-year old research station in the
Southern Piedmont of North America, a site that provides special insights into these critical
zone issues, both over geologic history and during the Anthropocene itself. The first example is
a residual soil and weathering profile produced directly from granitic gneiss below, a profile
that includes fractured bedrock, saprolite, and argillic Bt horizons; the second example is a
profile derived from transported paleo- colluvium from materials previously weathered in
place. The comparison of residual and transported materials helps us understand how all soil
state factors of climate, biota, geologic substrate, and geomorphology are dynamic over a
soil’s lifetime. We conclude by considering the role of human forcings as a dynamic and
overwhelming new state factor in the Anthropocene (Dudal, 2001, Richter and Yaalon, 2012).

Citation

Richter, D. (2017): Soil production, Earth’s critical zone, and the Anthropocene (Keynote talk for Theme 2: Climate Change). Wageningen Soil Conference 2017, 'Soil Science in a Changing World', 27-31 August 2017, Wageningen, The Netherlands.

This Paper/Book acknowledges NSF CZO grant support.