The olive grove belt of Chania (Crete) has been selected as pilot area by the Greek Committee for Combating Desertification Local Focal Point. The work was conducted in co-operation with the EU Research Project OLIVERO (The Future of Olive Plantation Systems on Sloping and Mountainous Land; Scenarios for Production and Natural Resource Conservation. Quality of Life and Management of Living Resources, Key Actions n0: 5.1 and 5.5, Project No: QLK5-CT-2002-01841). All the necessary data for the application of the DIS4ME were collected by the Agricultural University of Athens in collaboration with the Institute of Subtropical Plants and Olive Trees of Chania. The work was partially funded by both OLIVERO and DESERTLINKS projects.

	g	Pilot area and methodology
	g	Socio-economic relevance and policy implications
	g	Discussion and conclusions

g Pilot area and methodology

The area is located in western Crete, in the south western part of Chania prefecture, covering an area of 60,657 hectares. It is characterized by a variety of landscapes, lithological units and climatic conditions.

• The pilot area is primarily covered by olive groves, but also by vines, citrus, annual crops, nut trees, and natural vegetation (shrubs, pine forest, oak forest).
• Soils are formed on a variety of parent materials such as limestone, shale, marl, conglomerates and alluvial deposits.
• Slope gradient ranges from gently sloping (slope 2-6%) to very steep (slope >35%) with dominant classes greater than 18%.
• Soil depth ranges from shallow (depth <30 cm) to very deep (depth >150 cm). Soils formed on marl, conglomerates, and alluvial deposits are relatively deep (soil depth >75 cm), while soils formed on shale and limestone are shallow to moderately deep (depth 15-120 cm).
• A gradient in rainfall occurs across the area with the average annual rainfall ranging from 665 mm in the lowland (northern part) to 1100 mm in the upper mountainous area (southern part). The average air temperature is 18.9°C.

Mapping vegetation. Vegetation was mapped on the basis of the dominant species such as olives, vines, citrus, annuals, shrubs (e.g. Quercus sp, Erica sp, Pistacia sp.), pines, deciduous oak, chestnuts (Castanea sativa), and bare land. The percentage cover by each type of vegetation was defined in classes by aerial ortho-photo-interpretation and field survey at a scale of 1:30,000. The following classes of plant cover were used: <25%, 25-50%, 50-75% and >75%. In each mapping unit there was usually more than one of the dominant species mentioned above. Therefore, vegetation type and percentage cover was included in the vegetation map.

The boundaries of each mapping unit were drawn on an aerial photograph and the type of vegetation and the percentage cover was identified by (a) using the ERDAS image analysis software and (b) ground data collected on a field survey in which 335 sites were described. Then the data were introduced into ArcGIS (edition 8.3) for further analysis of the various mapping units of the area and compilation of the final vegetation map.

Vegetation of the study area in Chania, Crete

Mapping soils. The soil parameters used for applying DIS4ME were mapped in a scale 1:50.000:

• soil texture of the surface horizon,
• drainage conditions,
• presence of rock fragments,
• depth to bedrock,
• degree and direction of soil development,
• slope gradient,
• slope aspect,
• erosion of the soil surface,
• and parent material.

These land parameters were studied in a dense network of 1811 field observations and were recorded on each mapping unit. The boundaries of the mapping units were drawn on aerial photographs supplied by the Geographical Service of the Greek Army.

Part of the soil map of the area showing the mapping units with the corresponding mapping symbols (colors corresponds to the same parent material).

The soil textural classes were defined according the USDA system (Soil Survey Staff, 1975), and were grouped into the following textural classes: very coarse (S, LS), coarse (SL), medium (L, SiL, Si), moderately fine (SCL, CL, SiCL) and fine (SC, C, SiC). The parent material was defined according to the geological map of the area (scale 1:50,000) supplied by the Greek National Institute of Geology and Mineral Exploitation (IGME). The main parent materials mapped in the study area were marl, shale, limestone, conglomerates, and alluvial deposits. Soil depth to unconsolidated bedrock was measured in auger holes or in cuts. The following classes were used: very shallow (depth 0-15 cm), shallow (15-30 cm), moderately shallow (30-60 cm), moderately deep (60-100 cm), deep (100-150 cm) and very deep (>150 cm). Slope gradient was described using the topographic maps. The soils were classified according to the Soil Taxonomy (Soil Survey Staff, 1975) into three broad categories (Soil Orders), viz. Entisols, Inceptisols, and Alfisols.

The degree of erosion was assessed qualitatively and semi-quantitatively during the soil survey. In all mapping units, the present situation of erosion was characterized, according to: (a) the presence or absence of the A-horizon; (b) to the existence and percentage of eroded spots; (c) to the degree of exposure of the parent material on the soil surface; and (d) to the presence of erosional gullies as follows:

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g Socio-economic relevance and policy implication

Olive groves cover extensive areas along the Mediterranean Europe. According to the Greek National Action Plan, the olive belt is highly sensitive to desertification. Olives groves have been widely extended in hilly areas in the last decades. Olive trees are considered as a type of Mediterranean vegetation with high resistance to drought, low fire risk, high erosion protection of the soils from raindrop impacts due to high plant cover existing during the whole year. Olive trees can survive under adverse climatic and soil conditions protecting the land from desertification and providing a significant income to the farmers. Of course if land is intensively cultivated, especially in hilly areas, erosion rates due to surface water runoff and tillage are high, affecting desertification.

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g Discussion and conclusions

Olive grove distribution. Systematic olive groves or mixed olive groves with agricultural crops or natural vegetation cover 81.8% (49,617 hectares) of the pilot area. 17% of the total area (10,311 ha) is covered with spare trees or systematic olive groves in combination with natural vegetation or agricultural crops. The percentage cover with olive groves in these mapping units is less than 25% of area. The majority of these mapping units are found on the upper mountainous areas in combination with natural vegetation. In some cases, such mapping units are found in lower elevations, on steep hillslopes or in valleys in combination with natural vegetation or agricultural crops.

Table: Distribution of the olive groves based on the percentage of plant cover in the research area of Chania, Crete.

The most widespread mapping units (35% of the total area) are those in which olive groves covers 25-50% of the land. The rest of the land is covered with natural vegetation or agricultural crops or remains bare. Mapping units with olive plant cover ranging from 50-75%, or >75% occupy 19.2% and 10.6% of the total area, respectively. These are the systematic olive groves found mainly in the lower landscape positions of the pilot area. Hilly areas with only natural vegetation are included in the pilot area, covering 17.5% of the landscape.

Main soil characteristics. The soils are characterized by a wide range properties since they have been formed in a variety of parent materials and various topographic, vegetation and climatic conditions. The main parent materials are marl, schist, conglomerates, limestone and alluvial or colluvial deposits.

Table: Distribution of the various parent materials in the study area of Chania

Shale is the main parent material covering 56.3% of the study area. It is considered as one of the better parent materials for growing olives since the rock is easily weathered (allowing plant nutrients to become available and rain water to be stored in and adsorbed by the roots during the dry period). Limestone extends mainly in the central and south part and covers 14.9% of the area. The majority of the soils existing on limestone are highly degraded and mainly covered with natural vegetation of shrubs. Marl and conglomerates cover about the same area (12.1% and 11.7%, respectively) and they are located mainly in the northern region. Conglomerates are usually found in higher elevations than marls. Two categories of marl can be distinguished: (a) those containing inter-bedded sandy layers partially consolidated with calcium carbonates and silicates restricting root penetration and (b) marls containing clay unconsolidated materials in deep layers allowing better plant growth. Conglomerates usually contain high amounts of rock fragments restricting effective root depth. Finally alluvial deposits cover 5% of the area and are located in valleys along main rivers in the northern part of region.

Map of parent materials in the Chania DIS4ME pilot area

The soils are usually well drained, medium (27.7% of the area) to moderately fine (89.1%) or fine-textured (3.2%). Soils formed on shale are usually medium to moderately fine, while soils formed on marl, limestone and conglomerates are moderately fine to fine textured. Soils formed on conglomerates and shale usually contain high amounts of rock fragments. Soils in about half of the pilot area (53.2%) contain more than 60% rock fragments in the soil surface. Studies in similar areas have been shown that rock fragments in the soil reduce soil erosion and soil water loss from evaporation.

Table: Distribution of soil depth

Soil depth depends on the type of parent material, slope gradient, and degree of erosion. 28.5% of the area is covered by moderately deep (30-60 cm) soils. Soils 60-100 cm and 100-150 cm deep cover 23.7% and 16.1% of the total area, respectively. Very deep soils (>150 cm) cover 14.8% and are mainly located in northern part of the study area formed in marl, conglomerates, or alluvial deposits. Relatively extensive areas are highly degraded with soils less than 30 cm deep (16.9% of the area) indicating a higher sensitivity to desertification.

Map of soil depth in the Chania DIS4ME pilot area

Table: Distribution of slope gradient classes

The study area is rather hilly with a highest peak at 1320 meters ASL. Slopes are usually steeper in the southern region. Here very steep slopes (>35%) prevail throughout, covering 42.4% of the area. Moderately steep (18-25%) to steep (25-35%) slopes occupy 17.0% and 22.4% of the area, respectively. Moderately steep (18-25%) to strongly sloping soils (12-18%) cover 8.9% and 17.0% of the area, respectively. Nearly flat (<2%), gently sloping (2-6%) and moderately sloping (6-12%) soils cover a relatively small proportion of the area (1.2%, 4.4%, and 3.4%, respectively). The physiographic configuration of terrain with steep slopes and landscapes highly dissected by channels and rivers favours high erosion rates and occurrence of landslides in some cases.

Map of slope gradients in the Chania DIS4ME pilot area

Table: Distribution of degree of soil erosion

Most of the soils in the area are moderately eroded. Such soils are found in hilly areas with olive groves which are ploughed or in overgrazed pastures with frequent burning of natural vegetation and cover 48% of the total area. Slightly eroded soils cover 28.1% of the area and they are mainly located in areas with olive groves under no tillage management practices or in areas with natural vegetation protected from overgrazing and fires. Severely eroded soils cover 17.8% of the area and they are mainly found in intensively cultivated olive groves or overgrazed pastures. Soils without erosion cover 5.1% of the area and they are located in the valleys.

Map of soil erosion in the Chania DIS4ME pilot area

Environmentally sensitive areas to desertification. Based on the stage of land degradation and the sensitivity to desertification four categories of environmentally sensitive areas (ESAs) were found in the Chania pilot area. The most widely extended ESAs areas are fragile (78% of the total area) followed by critical (14%), potential (4%) and non-threatened areas (4%).

	Map of environmentally sensitive areas to desertification under the existing land use and management practices (N=non-threatened, P=potential, F1, F2, F3=fragile, and C1, C2, C3=critical areas to desertification)
	Distribution of the various types of ESAs under the existing land use and management characteristics

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