Dynamic Pedogenesis: New Views on Some Key Soil Concepts, and a Model for Interpreting Quaternary Soils

Abstract

Inasmuch as soils are open systems and rarely, if ever, achieve equilibrium with their environments, it is philosophically sound to view all soils as expressing varying levels of polygenesis as that term has been redefined. Soil genesis and resultant morphology may then be viewed in a comprehensive framework of soil evolution that consists of two linked pathways, one developmental and the other regressive, that reflect interactions of both exogenous and endogenous vectors (vectors are factors, processes, and conditions of pedogenesis). Following this philosophy, a model of pedogenesis is framed in an evolutional paradigm that emphasizes the integrated effects of dynamic and passive pedogenic vectors in directing pathways and in controlling rates of soil genesis through time. The dynamic vectors include energy and mass fluxes, frequencies of soil wetting and drying, water table dynamics, organisms, feedback processes, and pedoturbation. The passive vectors include parent materials, soil chemical environment, stability of geomorphic surfaces, and various evolved soil properties and conditions (accessions). Both sets of vectors vary spatially, and the dynamic vectors, more so than passive vectors, fluctuate through time. The model is expressed as S=f(D,P,dD/dt,dD/dt) where S is the state of the soil or degree of profile evolution, D is the set of dynamic vectors, P is the set of passive vectors, and dD/dt and dP/dt denote change through time t. The model helps explain the apparent minimal development and regressed character of some old soils and the rapid and strong development of some young ones.

The effect of a dynamic soil scheme on the climate of the mid-Holocene and the Last Glacial Maximum

“…Future transient GCM studies may utilise more sophisticated soil schemes, which should have the aim of deriving time-dependent variables in terms of nonlinear progressive and regressive soil development, acting on different timescales (Johnson et al, 1990;Hoosbeek and Bryant, 1992).…”

Three Principles of Soil Change and Pedogenesis in Time and Space

“…Hence, this challenges Jenny's assumption of independence among the soil-forming factors. In fact, soil environments change continuously through time, a point stressed by Dokuchaev and others (e.g., Rode, 1947;Johnson et al, 1990). …”

“…However, the net result of these complex sets of processes are either (i) the formation of smaller units toward soil solid residuals or matrix (dissipative processes), or (ii) the formation of larger units toward soil structure (organizing processes, involving various fl uxes that lead to net entropy export from the soil to the surrounding). Simultaneous occurrence of dissipating and organizing processes during pedogenesis has long been recognized (e.g., Hole, 1961;Smeck et al, 1983;Johnson and Watson-Stegner, 1987;Johnson et al, 1990;Addiscott, 1995;Rasmussen et al, 2005;Lin, 2010aLin, , 2010b. Th erefore, we may approximate the net result of total entropy change in a soil system (ΔS total ) over a pedogenic time period as (Fig.…”

“…Space-for-time substitution has been commonly used in soil chronosequence studies, which unquestionably has improved our knowledge of soil development. However, it also has encountered criticisms from the beginning (e.g., Nikiforoff, 1949;Stevens and Walker, 1970;Fitzpatrick, 1971;Chesworth, 1973aChesworth, , 1973bBockheim, 1980;Huggett, 1998;Richter and Markewitz, 2001;Buol et al, 2003;Sommer et al, 2008;Johnson and Miyanishi, 2008 …”

Evolução De Paleocabeceira De Drenagem Do Rio Chopinzinho (Sul Do Brasil) Durante O Quaternário Superior

“…No caso desta última, difi cilmente há canais de drenagem e o fl uxo de água ocorre de forma hipodérmica diante de baixo gradiente hidráulico . Já o horizonte 19Ab chama a atenção por mostrar-se, em seu topo, ressecado e fragmentado em blocos subangulares rígidos (Tabela 1), fenômeno de pedogênese regressiva (JOHNSON et al, 1990). Partes desses fragmentos foram incorporadas nos horizontes alóctones sobrejacentes na forma de pedorrelíquias.…”