The properties of any soil are dependent on its constituents, their proportions, and their flows and fluctuations both in space and in time. The soil is an interlinked system where all constituents influence each other through a myriad of interactions, making it nearly impossible to separate, describe and study individual physical, chemical and biological processes. This chapter describes the scientific underpinnings of soil science; it then defines the basic soil properties, the methods used to measure them and their relevance to the forest ecosystem and its functioning.

Any soil typically consists of three phases: solid, liquid and gaseous. The solid phase is represented by mineral or organic particles of various shapes and sizes, the liquid phase by water with varying concentrations of soluble compounds and the gaseous phase by soil air. All are essential parts of soil formation and functioning; however, we can imagine a soil without its liquid or gas constituent. A temporarily dried out or completely flooded soil would still be considered a soil, but we would not define a material as soil if it was lacking the solid phase. We therefore start the description of soil properties by discussing the solid phase and its most important property: texture.

Physical properties

Texture

Texture describes the relative proportion of solid soil constituents according to their size. The term mineral texture refers to the size distribution of mineral particles, which can be determined by a simple granulometric analysis.