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Article Dans Une Revue CATENA Année : 2003

Geomorphic responses to long-term land use changes in Eastern Macedonia (Greece)

Résumé

Distinct phases of stream aggradation, soil erosion and landscape stability in the basin of Drama (Eastern Macedonia, Greece) over the past 7000 years can be tied directly to long term land use changes. During the Middle and Late Holocene, 1-4 m of alluvial fill accumulated in the centre of the basin and along the Angithis valley. Low levels of alluvial aggradation were recorded during the Late Neolithic and the Early Bronze Age (7400-4000 cal. BP). In the centre of the basin, along the lower course of the Xeropotamos, the rate of aggradation has doubled since the Late Bronze Age (0.5 to 0.6 mm/yr) compared to the Holocene as a whole (0.25 mm/yr). Moderate rates of alluvial fill were experienced during the Late Bronze Age (3600-3000 cal. BP) but the most significant destabilisation of the soils occurred later than in many regions of Greece. Two historical phases of alluvial aggradation and soil erosion are identified, in the Antique and the Early Byzantine Era (third century BC-seventh century AD) and more significantly in the Ottoman period (beginning of the fifteenth to the twentieth century AD). In the latter period, the rate of accumulation was three to five times greater than in the Late Holocene. A lag-time of almost three millennia is noted between the arrival of the first farmers and the onset of erosion. This is mainly explained by the settlement pattern during the Neolithic and the Early Bronze Age. It appears that the early farmers preferred to cultivate the more stable soils on the gentle slopes at the centre of the basin, while the glades that opened onto the regional forest were too scarce and discontinuous. During the Late Bronze Age, the land use pattern changed. The soils then under cultivation, located on the foothills, were less stable and occur on steeper slope that are more susceptible to erosion. This contributed also to the difficulty of forest restoration after the first noticeable land clearance, and probably explains the appearance of the first traces of soil erosion and alluvial aggradation. Since the Antique Era, the intensity of land use has increased. The two phases of accelerated alluviation in historical times are clearly linked to land use changes, particularly with the upstream progression of cropping and grazing. The high sensitivity of the new land under cultivation or grazing in foothills and mountainous areas was crucial for accelerating alluvial aggradation, though this was also influenced by climatic fluctuations. The major period of aggradation in the Ottoman period is clearly associated with both climatic and anthropogenic factors. It appears that the early historic deforestation and agricultural activities rendered river systems more sensitive to relatively modest changes in climate.
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Dates et versions

hal-00292297 , version 1 (01-07-2008)

Identifiants

  • HAL Id : hal-00292297 , version 1

Citer

Laurent Lespez. Geomorphic responses to long-term land use changes in Eastern Macedonia (Greece). CATENA, 2003, 51 (3-4), pp.181-208. ⟨hal-00292297⟩
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