|
1. Definition
| Name |
AIR
TEMPERATURE |
| Brief
definition |
Air temperature is an
important climatic factor affecting atmospheric drought, rate
of soil water evaporation and plant growth.
 |
Automatic
meteorological station for recording data such as open
pan evaporation, air temperature, wind speed, etc. (photo
by C. Kosmas). |
|
| Unit of measure |
Degree Celsius
(°C) |
| Spatial scale |
regional, local |
| Temporal scale |
annual |
2. Position
within the logical framework DPSIR
3. Target and
political pertinence
| Objective |
Contribution
to the definition of environmentally sensitive areas to desertification
and a climatic factor affecting land use change decision-making. |
| Importance
with respect to desertification |
Air temperature
(along with other climatic parameters such as rainfall) affects
the xerothermic index of an area. It is a critical environmental
factor in determining water stress which affects the evolution
of natural vegetation and may cause reduced vegetation cover.
Also air temperature in semi-arid and arid climates affects
water evaporation from the soil surface and plant transpiration.
Furthermore, soil salinity or alkalinity is affected under adverse
drainage conditions and poor quality of ground water. |
| International
Conventions and agreements |
The UNCCD emphasizes
that in order to combat desertification, it must be tackled
within the general framework of actions that promote sustainable
development. |
| Secondary objectives
of the indicator |
Selection of
appropriate vegetation type and management practices in combating
desertification. |
4. Methodological
description and basic definitions
| Definitions
and basic concepts |
The aridity of the Mediterranean
climate, combining high temperatures and frequent droughts,
is considered as the most important factor affecting the evolution
of plant communities. The various ecosystems present in the
Mediterranean region have a great capacity for adaptation
and resistance to high air temperatures and prolonged drought.
Extreme conditions of high temperatures and either atmospheric
or soil drought cause plant stress. The severity and the duration
of the stress determine the extent of the resulting plant
damage. Short periods of stress damage the plants and reduce
their potential for growth but do not kill them. Prolonged
stress increases the damage and eventually kills the plants.
Air temperature, in combination
with other climate and soil factors, affects the formation
of salt-affected soils in arid and semi-arid regions. Salts
are accumulated in the soils because more salts move into
the plant rooting zone than move out. Water evaporation from
the soil surface and transpiration from the crops (both affected
by temperature) remove water but leaves salts in the soil.
The presence of even a small concentration of salts in good
quality of irrigation water leads to salt accumulation unless
leached away by rain or irrigation water. In areas with high
evaporation rates, capillary rise is accelerated and salts
accumulate residually, where drainage is more or less absent.
The extent to which this will happen at a local scale will
depend on various factors controlled by the water balance,
soil type, and by the total salt and sodium input. The increasing
concentrations of salts result in radical changes in the water
economy of the soil, creating a potentially adverse ecological
environment for native vegetation or agricultural crops leading
to desertification.
|
| Benchmarks
Indication of the values/ranges of value |
- <12,
- 12-15,
- 15-19,
- 18-21,
- >21 °C for desertification
due to salinization effect
|
| Methods of
measurement |
Air temperature
is measured by a digital or other type of thermometer. |
| Limits of the
indicator |
This indicator
can be assessed quantitatively without subjecting to personal
judgment. |
| Linkages with
other indicators |
Aridity
index (1), Land use type,
Vegetation cover, Water
availability, Drought resistance,
Fire risk, Fire
frequency |
5. Evaluation
of data needs and availability
| Data required
to calculate the indicator |
Mean annual
air temperature. |
| 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 institutions or local stations
involved in collecting and elaborating meteorological 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
|
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 p. |
| Other references |
Troeh, H.R., Hobbs, J.
A., and Donahue, R. L. 1980. Soil and water conservation for
productivity and environmental protection. Prentice-Hall,
Inc., Emglewood Cliffs, New Jersey, 454-570 pp.
Rowell, D. L. 1994. Soil
Science, Methods & Applications. Longman Scientific &
Technical, Essex, England, 277-302 pp.
|
| Contacts Name
and address |
Agricultural
University of Athens
Dr Constantinos Kosmas
email: lsos2kok@aua.gr |
|
