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Accueil du site → Doctorat → Allemagne → 2010 → Photogrammetric techniques for the functional assessment of tree and forest resources in Khorezm, Uzbekistan

Rheinischen Friedrich-Wilhelms-Universität Bonn (2010)

Photogrammetric techniques for the functional assessment of tree and forest resources in Khorezm, Uzbekistan

Tupitsa Alexander

Titre : Photogrammetric techniques for the functional assessment of tree and forest resources in Khorezm, Uzbekistan

Photogrammetrische Techniken zur funktionellen Beurteilung von Baum- und Waldressourcen in Khorezm, Usbekistan

Auteur : Tupitsa Alexander

Université de soutenance : Rheinischen Friedrich-Wilhelms-Universität Bonn

Grade : Doctoral Thesis 2010

A system for inventorying and monitoring forests and tree plantings is indispensable for a proper management of this perennial vegetation. In the mid 1990s, the Government of Uzbekistan (GoU) launched various nationwide tree growing programs. Owing to limited funds and lack of a suitable methodology, the Main Forestry Department (MFD) has not been able to conduct a reliable and comprehensive forest inventory since 1991. On the other hand, photogrammetry combined with GIS-based tools has shown its value and accuracy for assisting in forest inventories worldwide. Given that aerial photographs 1:20,000 are taken in the leafless season every five years by the Land and Geodesy Cadastre Center of Uzbekistan for actualizing topographic maps, the intention of this study is (i) to examine to what extent these photographs can be used for the inventory of forests and tree plantations, and develop a standard methodology with photogrammetry for the MFD, and (ii) to map and perform a functional assessment of tree plantings and forests (e.g., the windbreak function of hedgerows or the spatial extent of tree plantations) and forests (the spatial extent and condition of natural floodplain forests (tugai) in the region of Khorezm in Uzbekistan. The selected study area in two transects (NS and WE) covers virtually all typical land uses and vegetation formations in an area comprising about 10% of the Khorezm region. An analytical stereo plotter and GIS-based tools were applied. The key results of interpretation and measurements of the aerial photographs are summarized as follows. First, detailed and accurate information on the extent of tree plantations and forests in developed thematic classes could be extracted. Also, windbreak design criteria, such as orientation to the prevailing winds, mean stand height, length (reaching the edges of the related field) and crown closure (as a proxy of porosity) could be determined. Second, species composition, vitality and age classes of tree plantations and forests, as well width (number of rows) of hedgerows/windbreaks could not be extracted with photogrammetry and would require field surveys. The inventory shows that most of the hedgerows in Khorezm did not meet principal windbreak design criteria and, consequently, are not effective for reducing soil erosion or improving microclimatic conditions. In particular, this is due to the small extent (<1.5%) in irrigated fields, low height (<5 m) and insufficient length (in ca. 50% of the hedgerows) of dominating single species such as white mulberry, willows and hybrid poplars, which were all concurrently used for production purposes. In contrast, orientation to the prevailing winds, crown closure, width and vitality were fair. The area of other tree plantations was ca. 1% of the agricultural land in Khorezm and was dominated by apple and apricot. The vitality of these plantations was satisfactory. Substantiated by the generally young age, it seems that the tree plantation programs of the GoU have been successful to a certain degree with respect to orchards, while hedgerows and wood plantations need to be extended. In this respect, photogrammetry would allow the GoU to closely monitor the implementation dynamics of the programs. Finally, the findings indicate a low forest cover (<1%) in Khorezm and reduction by 60% of the tugai forests in 1990-2003, of which ca. 40% could be reversed into forests. With the applied methodology, the MFD should be able to develop better site-specific recommendations for protecting and improving the tugai forest ecosystem


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