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1. Definition
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Name
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DROUGHT
RESISTANCE
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Brief
definition
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Resistance
to aridity is determined by the capacity of vegetation
species to resist serious or moderate water stress
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Unit
of measure
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A
relative value assigned to different classes of vegetation
cover. (This indicator cannot be quantified in a simple
manner but can be estimated on the basis of the properties
of the single species to resist conditions of water
scarcity even for prolonged periods.)
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2.
Position within the logical framework DPSIR
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Type of indicator
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State.
As a vegetation property linked to desertification,
it has an influence on the capacity of the vegetation
component to oppose the action of erosive agents.
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3.
Target and political pertinence
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Objective
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Contribution
to the definition and mapping of ESAs (Kosmas et al.,
1999) through the definition of a Vegetation Quality
Index.
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Importance
with respect to desertification
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This
indicator is part of a set of tools to identify and
mitigate land degradation developed in the MEDALUS
project target areas. Together with other vegetation
vulnerability indicators, it contributes to producing
a scale of vegetation quality and consequently to
the elaboration of development strategies compatible
with the resources available in the given area.
Resistance to aridity is combined with vegetation
cover, erosion protection and fire risk to form a
Vegetation Quality Index.
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International
Conventions and agreements
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The
UNCCD emphasizes the fact that combating desertification
must be tackled within the general framework of actions
to promote sustainable development.
Within
Agenda 21 drought resistance has relevance to Chapter
12 - Management of fragile ecosystems: combating desertification
and drought.
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Secondary objectives
of the indicator
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Within the ESAs model
objectives include: a) Investigation of the individual
processes linked to land degradation and desertification;
b) development of countermeasures and strategies to
protect land from desertification and to promote sustainable
development; c) comparison with the physical-environmental
characteristics of other target areas.
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4.
Methodological description and basic definitions
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Definitions
and basic concepts
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Resistance
to aridity is defined as the capacity of individual plant
species or plant communities to resist moisture stress, which
is typical feature in arid and semi-arid environments. Since
the response to a reduction in water availability leads to
a reduction in the above-ground surface of the plant and consequently
to the leaf coverage index, the presence of species with a
reduced capacity to tolerate water scarcity (or the absence
of tolerant species) increases the probability of major erosion
occurring with the arrival of the rainy season. However, the
presence of species highly resistant to long periods of drought
ensures an adequate ground cover.
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Benchmarks
Indication of the values/ranges of value
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5
different classes have been defined corresponding
to the differing resistance capacities of the different
classes:
- very high (mixed
Mediterranean maquis/evergreen forests, Mediterranean
maquis;
- high (conifers,
deciduous forest species, olive trees);
- moderate (poliannual
tree crops such as vine, almond, fruit trees);
- low (polyannual
meadows);
- very low (annual
crops, annual meadows).
A
score is attributed to each of the 5 classes: the
scores are multiplied with the scores of fire risk;
erosion protection and vegetation cover indicators
to form the Vegetation Quality Index.
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Methods
of measurement
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The
vegetation has to be classified on the basis of the
aridity-resistance characteristics of individual species,
of the plant communities, and of the crops present,
by means of field surveys or remote sensing.
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Limits
of the indicator
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Limits
are associated with the high level of simplification
of the proposed classification.
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Linkages with other
indicators
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Fire
risk, Erosion
protection, Vegetation
cover
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5.
Evaluation of data needs and availability
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Data
required to calculate the indicator
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Information
has to be obtained on the type of vegetation, defined
on the basis of structure and dominant species of:
1) mixed Mediterranean maquis/evergreen forests; 2)Mediterranean
maquis; 3) permanent meadows; 4) annual meadows; 5)deciduous
forests; 6) pine forests; 7) evergreen forests with
the exception of pine forests; 8) polyannual evergreen
crops; 9) polyannual deciduous crops 10) winter annual
crops; 11) summer annual crops; 12) bare land.
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Data
sources
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Land
cover maps with vegetation classes of the physionomical-structural
type. Aerial photographs taken from private and public
agencies (ex. IGMI). LANDSAT, SPOT, NOAA satellite
images.
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Availability
of data from national and international sources
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If
data results from field surveys their cost is high.
If it derives from the interpretation of aerial photographs
the cost is much more reasonable. If remotely sensed
data from satellites is to be resorted to, their cost
at present is quite high, but it will drop quite considerably
in the near future.
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6.
Institutions that have participated in developing the indicator
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Main
institutions responsible
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Agricultural
University of Athens
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Other
contributing organizations
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Universities
of: Lisbon, Murcia, Basilicata, Amsterdam, Leeds
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7.
Additional information
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Bibliography
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Kosmas C. Ferrara A.,
Briassouli H., Imeson I., 1999 Methodology for mapping
ESAs to desertification. The Medalus Project, Mediterranean
desertification and land use. Manual on key indicators
of desertification and mapping environmentally sensitive
areas to desertification. Edited by Kosmas C., M.,
Geeson N. EUR 18882. pp. 31-47
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Other
references
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Kosmas C., 1998. Qualitative
indicators of desertification. Proceedings of the
International Seminar held in Porto Torres, Italy
18-20 September, 1998: pp. 81-100.
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Contacts Name and address
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Agricultural University
of Athens
Scientific responsibility: Dr Constantinos Kosmas
Address: Laboratory of Soils and Agricultural Chemistry,
Iera Odos 75, Botanikos 11855, Athens GR
Telephone/fax: (30) 1 529 4097
Email Isos2kok@aua.gr
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