Hydrogeology, Chemical Weathering, and Soil Formation. Allen Hunt

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1 Soil as a System: A History

       Richard J. Huggett

       School of Environment, Education, and Development, University of Manchester, Manchester, UK

      ABSTRACT

      The idea of soil as a system is not yet a hundred years old. Its origins lie in Dokuchaev’s view of soil as an independent object, an idea promoted so successfully and eloquently by Hans Jenny. It was Jenny who first thought of soil as a system. His CLORPT equation focused on state factors (external drivers) of the soil system and, later, ecosystems. His approach was largely statistical and empirical. Later, a few researchers investigated energy as a soil‐system driver. A different line of investigation, spurred by Milne’s catena concept, saw soil as a spatial system. Research in this field began in earnest with Simonson’s concept of soil as an open system, which at first involved one‐dimensional soil profiles but was later extended to catenas and three‐dimensional soil landscapes, all researched using a rich variety of statistical and deterministic models. Last came the recognition that soil is part of an interdependent system. This line of enquiry began with conceptual models of the ecosphere. Since the millennium it has made big advances from cross‐disciplinary enquiries focusing on the Earth’s critical zone and interactions between soils and geomorphology, soils and hydrology, soils and life, and soils and humans.

1.1. INTRODUCTION

      Ideas about soil have a long and rich history. It is perhaps easy to dismiss older notions as outmoded, but the foundations of soil science laid down by the creators of the subject still have currency, even though later thinkers have refined them and added new elements. Expanding a metaphor, if Isaac Newton could see further by standing on the shoulders of giants, then modern soil scientists can see further by standing in the soil pits of their predecessors. This chapter will explore the view taken by Hans Jenny, a veritable giant among soil scientists, that soil may be regarded as a system. Jenny mooted this idea in 1930, but soil concepts developed in the five decades before that date provide an essential background and they will be discussed first, before considering soil as a system, soil as a spatial system, and soil as an interdependent system. The chapter will end with a brief look at prospects for the systems approach in pedology.

In developing ideas about soil and soil formation, Jenny, his predecessors, and later researchers have put forward various models that attempt to explain the structure and function of soil systems and their component parts. Table 1.1 summarizes some of these models and serves as a guide for the discussion that follows.

1.2. SOIL AS AN INDEPENDENT BODY

As a discipline in its own right, soil science emerged and flowered during the second half of the nineteenth century when a few researchers proposed the idea of soil as an independent entity (Brevik & Cerdà, 2016). This radical idea was presaged by Friedrich Albert Fallou (1862), who argued that soil was distinct from the underlying geology, and who also coined the term pedology. Arguably, Eugene Woldemar Hilgard recognized the independent nature of soil in his Report on the Geology and Agriculture of Mississippi published in 1860 (Jenny, 1961b). But it is undeniably the case that modern soil science was born in the early 1880s when Dokuchaev published his Russian Chernozem in 1883.

Table 1.1 Soil models with selected examples.

      Source. Partly inspired by discussion in Hoosbeek and Bryant (1992) and discussion and tables in Minasny et al. (2008).