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Çankırı Karatekin Üniversitesi (2015)

Making desertification risk map in semi-arid field : Sample of Çankırı- Sarıkaya

GÜL Ebru

Titre : Making desertification risk map in semi-arid field : Sample of Çankırı- Sarıkaya

Yarı-kurak alanlarda çölleşme risk haritasının oluşturulması : Çankırı- Sarıkaya örneği

Auteur : GÜL Ebru

Université de soutenance : Çankırı Karatekin Üniversitesi

Grade : Doktora Tezi 2015

Résumé
In recent years, land degradation and decrease in biological production due to climate change and human impact have made it necessary combat desertification, which has become a major environmental problem on a global scale. This study was carried out in Sarıkaya region of Yapraklı district, a semi-arid region, approximately 45 km North-East from the center of Çankırı province, to evaluate desertification risk across various land use types. The study area is approximately 1000 ha and is under land uses of forest and agriculture. Desertification Indicator System for Mediterranean Europe (DIS4ME), developed for the Mediterranean countries, was used for calculating desertification risk. Soil samples were taken at 632 predefined sites (252 from agricultural areas, 122 from oak forests and 258 from pine forests). A desertification survey form was filled at each sampling site. Desertification risk and environmental sensitivity index were calculated with the DIS4ME. DIS4ME-calculated and field-observed desertification risk values were compared to evaluate successes of DIS4ME. DIS4ME-calculated desertification risk values were interpolated with kriging. Desertification risk and ESA type sensitivity score surface maps were built for the entire study area and the corresponding sub-regions (land uses). Of the study area, 349,12 ha (34,91%) occurred in no risk class, 322,89 ha (32,29%) in low risk class, 70,21 ha (7,02%) in medium risk class, and 258,78 ha (25,88%) in high risk class. DIS4ME-caluculated ESA type sensitivity score values varied from 1,18 to 1,61, while field calculated values based on the expert opinion varied from 1,19 to 1,60. A large part of the study area (597,29 ha) was in fragile and 370,61 in critical sensitivity class. Results from correlation analysis between observed and DIS4ME-calculated ESA type sensitivity scores (r =0.876 ; p<0.01) showed that the DIS4ME system can be used to evaluate desertification in the study area. Geostatistical analysis showed that the desertification risk and ESA scores strongly spatially dependent in the study area and that kriging predicted both parameters successfully at unsampled locations in the study area. Land use type and land use change appeared the most important factors aggrevating desertification risk. Desertification criteria and indicators should be considered in land use planning to avoid further land degradation in the study area. Similar studies should be conducted in different land uses, geographic regions, climates, and topographic conditions for developing to generalize procedures in nationwide evaluations of desertification.

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Page publiée le 9 janvier 2023