Pedological concepts to be considered in soil chronosequence studies

Soil chronosequence data may easily be interpreted in a too straightforward and simple a way if some relevant theoretical background is not kept in mind. This paper discusses pedological concepts that are considered relevant for soil chronosequence studies and may provide some guidance for establishing soil chronosequences and interpreting obtained data. Concepts related to the soil system, soil body, and soil-forming factors are introduced, and advantages and disadvantages of different types of soil chronosequences are pointed out. The question of whether soil formation reaches steady-state is raised, leading to the conclusion that some soil properties achieve steady-state whereas others do not, and that soil formation as a whole may only rarely reach a kind of near steady-state. The influence of climate and relief, and associated three-dimensional water and material fluxes in landscapes, are addressed, and concepts related to pedogenic processes, soil properties, and energy and matter transfers as drivers of soil formation are discussed. Feedback systems and thresholds in soil development are highlighted, the concept of progressive vs regressive pedogenesis is introduced, and potential shortcomings of soil chronosequence studies are addressed. Implications of each of the mentioned concepts for soil chronosequence studies are pointed out.