|
1. Definition
| Name |
PARENT
MATERIAL |
| Brief
definition |
The unconsolidated more
or less chemically weathered mineral from which the soil is
formed by pedogenic processes.
 |
Residual
soil formed by pedogenic processes on a consolidated parent
material of volcanic lava (photo by C. Kosmas) |
|
| Unit of measure |
None |
2. Position
within the logical framework DPSIR
3. Target and
political pertinence
| Objective |
Contribution
to the definition and mapping of ESAs and evaluation of the
desertification risk of an area. |
| Importance
with respect to desertification |
Areas with
soils formed on different types of parent materials exhibit
various degrees of sensitivity to land degradation and desertification.
For example, limestone produces shallow soils with a relatively
dry moisture regime characterized by high erodibility and slow
vegetation recovery. Many Mediterranean landscapes on limestone
are desertified with the soil mantle eroded and the vegetation
completely removed. Similarly, acid igneous materials produce
shallow coarse-textured soils with high erodibility and desertification
risk. Stony soils formed on conglomerates and shale-sandstones,
despite their normally low productivity, may supply appreciable
amounts of previously stored water to the stressed plants and
secure a non-negligible biomass production even in extremely
dry years. On the other hand, soils formed on marl, despite
their considerable depth and high productivity in normal and
wet years, they are very susceptible to desertification, unable
to support any annual vegetation in particularly dry years due
to adverse soil physical properties and the absence of gravel
and stone mulching. |
| International
Conventions and agreements |
The CCD emphasizes
that combating desertification must be tackled within the general
framework of actions to promote sustainable development.
|
| Secondary objectives
of the indicator |
Within the
ESA model for investigation of the individual processes linked
to plant productivity, land degradation and desertification.
|
4. Methodological
description and basic definitions
| Definitions
and basic concepts |
Parent material is considered
as a soil-forming factor affecting soil properties, plant
growth, soil erosion and ecosystem resilience. When parent
material is exposed on or near the soil surface, it is subjected
to genetic and environmental factors such as climate (including
water and temperature effects), macro and micro organisms
acting for over a period of time and soil is formed. The derived
soils have specific physical, chemical, and morphological
properties closely related to the parent material. For example
soils formed on limestone are usually moderately fine- to
fine-textured, slow permeable, with high pH, high base saturation
and high nutrient status, in the opposite soils formed on
sandstones are usually coarse-textured, highly permeable,
low pH, low base saturation, and low nutrient status.
Studies conducted in hilly
areas of the island of Lesvos have shown that parent material
greatly affects the degree of soil erosion. Areas with soils
formed on pyroclastics showed the highest degree of erosion.
In the opposite, areas with soils formed on vytrophiric lava
were well vegetated and protected from erosion (see figure).
The following type of parent material, after pyroclastics,
with soils vulnerable to erosion was volcanic lava. Soils
formed on shale, schist and basic igneous rocks had about
the same proportion of severely eroded area but lower than
those in pyroclastics and volcanic lava. Based on the degree
of erosion measured in the island of Lesvos, the various parent
materials can be classified in the following order with respect
to decreasing vulnerability to soil erosion:
Pyroclastics>volcanic
lava>marble, limestone>shale, schist, basic igneous>vytrophiric
lava.
Of course, other parameters
such as type of vegetation, topography, intensity of land
use, etc., can affect soil erosion, differentiating the above
order of parent material classification.
 |
Distribution
of the various degrees of erosion measured in soils formed
in different parent materials in the island of Lesvos
(Kosmas et al., 2000). |
The presence of cracks
or fractures and faults into the bedrock favours the soil
formation by weathering or the removal of soil aggregates
into the cracks by gravity. The formed 'tube' type soils are
well protected from erosion and the percolating water can
be stored within them and protected from evaporation. The
presence of deep soils in cracks and faults is of great ecological
importance, supporting relatively well the natural vegetation
under Mediterranean climatic conditions, and avoiding desertification
over wide-ranging hilly areas.
|
| Benchmarks
Indication of the values/ranges of value |
Parent material types
are grouped thus
- alluvium, colluvium,
lake deposits, eolian deposits
- shale, schist
- clay deposits, conglomerate
- sandstone
- marl
- plysch
- basic igneous
- metamorphic rocks
- acid igneous
- other
|
| Methods
of measurement |
Parent
material is easy to identify in the field or can be defined
by using the geological map of the area (scale 1:50,000). |
| Limits
of the indicator |
In
case that parent material consists of various types of geological
formations then the dominant type is selected for defining ESAs.
|
| Linkages with
other indicators |
Soil
depth, Soil texture, Slope
gradient, Vegetation cover,
Rock fragments, Soil
erosion, Infiltration
capacity
|
5. Evaluation
of data needs and availability
| Data required
to calculate the indicator |
Identification
of the type of parent material of the specific area.
|
| Data
sources |
Necessary
data are usually available and accessible and the cost/benefit
ratio is reasonable. |
| Availability
of data from national and international sources |
Data can be
obtained from various regional, national or international institutions
involved in the collection and the analysis of geological data.
|
6. Institutions
that have participated in developing the indicator
| Main institutions
responsible |
Agricultural
University of Athens
|
| Other contributing
organizations |
Universities
of Lisbon, Murcia, Basilicata, Amsterdam, Leeds
|
7. Additional
information
| Bibliography
|
Kosmas,
C., Kirkby, M. and Geeson, N. 1999. Manual on: Key indicators
of desertification and mapping environmentally sensitive areas
to desertification. European Commission, Energy, Environment
and Sustainable Development, EUR 18882, 87 |
| Other
references |
Kosmas, C., Danalatos,
N., Moustakas, N., Tsatiris B., Kallianou, Ch. and Yassoglou,
N., 1993. The impacts of parent material and landscape position
on drought and biomass production of wheat under semi-arid
conditions. Soil Technology, 6: 337- 349.
Kosmas, C., Gerontidis,
St., and Marathainou, M. 2000. The effect of land use change
on soil and vegetation over various lithological formations
on Lesvos (Greece). Catena, 40:51-68.
Kosmas, C., Danalatos,
N. and Gerontidis, S. 2000. The effect of land parameters
on vegetation performance and degree of erosion under Mediterranean
conditions. Catena, 40:3-17
Ruiz-Flano, P., Garcia-Ruiz,
J.M. and Ortigosa, L., 1992. Geomorphological evolution of
abandoned fields. A case study in the Central Pyrenees. Catena,
19:301-308.
|
| Contacts
Name and address |
Agricultural University
of Athens, Laboratory of Soils and Agricultural Chemistry,
Iera Odos 75, Athens 11855, Greece
Dr Constantinos Kosmas
email: lsos2kok@aua.gr
|
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