Soil and the Environment - Soils for Fine Wines - page 5

Deciduous

Lichens, mosses, Sedges, grasses, forest

liverworts shrubs

Thin litter Thick litter Deep,

layer, poorly layer over a dark-brown,

decomposed, thin, organic organic

over shallow A horizon horizon

depth of grading into

weathering
rock

merging

weathering very

1 m

parent gradually

material into lighter-

colored
mineral soil

Unaltered Unaltered

parent

over altered

parent parent

material material material

INITIAL STAGE LITHOSOL BROWN FOREST SOIL

Figure 1.1 Stages in soil profile formation on calcareous parent material in a humid temperate climate

(White 1997). Reproduced with permission of Blackwell Science Ltd.

more than a thin layer of weathered material stabilized by primitive plants, such
as lichens, mosses, and liverworts. The lichen is able to fix N 2 gas from the air
(section 4.2.2.1) and to extract other essential elements for growth from the weath-
ering rock surface. Within a century or so, as the organomineral material accu-
mulates, more advanced species of sedge and grass, which are adapted to the harsh
habitat, become established. The developing soil is sometimes called a Lithosol .
Colonizing microorganisms and animals feed on the dead plant remains and grad-
ually increase in number and variety. Leaf litter deposited on the surface is mixed
into the soil by burrowing animals and insects, where its decomposition is has-
tened by microorganisms. Thus, the remnants of each generation of plants and
animals provide the diet of carbon compounds, or substrate, for their successors.
The eventual appearance of shrubs and trees, with their deeper roots, pushes the
zone of rock weathering farther below the soil surface. After a few hundred years
more, a Brown Forest Soil emerges.
The names Lithosol and Brown Forest Soil are examples of soil names that have
a broad connotation. Because of the complexity of soil formation, many different
soil types occur in the landscape, which inevitably leads to many soil names. Soil
variability and the naming of soils are discussed in box 1.3.

1.2.2 The Soil Profile

The diagrams of figure 1.1 introduce the concept of a soil profile . This is the ver-
tical development of the soil from the surface to the weathering rock below (fig.
1.2). The weathering rock is called parent material . Within the soil profile, hori-
zontal zones of different color, stoniness, hardness, texture, and other visible or
tangible properties are often visible. These are called soil horizons . The upper hori-
zon, from which materials are generally washed downward, is described as eluvial ;