• Non-Icimod Publication

Land use change effects on soil degradation, carbon and nutrient stocks and greenhouse gas emission in mountain watersheds

  • Awasthi, K. D.

This thesis is based on five papers (1 submitted, 1 published, 1 accepted and 2 revised and resubmitted for publication), which are included. The objectives of this thesis are to: (i) assess the magnitude of soil erosion under different land use systems, organic carbon and nutrient losses in Bari (upland maize and millet cropping system) land and prepare erosion risk map for Mardi watershed using predictive models (Revised Universal Soil Loss Equation combined with geographical information system); (ii) determined organic carbon and nutrient distribution and stock at different depth under different land uses and their stock at 0-15 cm depth along the elevation gradient; (iii) assess greenhouse gases (CH4 and CO2) emission from different land uses and along the altitudinal gradient in Mardi watershed; and (iv) quantify land use changes, landscape fragmentation and geomorphometric parameters in relation to land degradation in Mardi and Fewa watersheds of Nepal. Five land uses, Bari , irrigated rice ( Khet ), managed forest, grazing and unmanaged forest with free grazing, were selected for monitoring the soil erosion rates, while the four dominant land uses ( Bari , Khet , managed forest and grazing), were selected for collecting the gas samples. Results showed that an initial and final infiltration rate of Bari land were higher compared to other land uses. Khet land showed lowest infiltration rate. The measured mean annual loss varied from 1.3-34.4 t/ha. The Khet land experienced the minimum soil loss compared to other land uses, whereas heavily grazed and degraded grazing land experienced the highest soil loss. Soil organic carbon and nitrogen stocks increased with increase in elevation up to 2600 m asl. Khet land was source of CH4 emission to the atmosphere in the rainy and autumn seasons, whereas Bari and grazing were sources of CH4 only during the rainy season. The net forest cover in Mardi watershed increased by more than two-fold (2.4%) compared to that of Fewa watershed (1.1%). The magnitude of abandoned land was found to be four-fold higher in the Mardi watershed than that in Fewa. The applicability of the land use metrics for detecting the land use change was also investigated. Landscape metrics, which are based on the number, size, shape and arrangement of patches of different land uses, are used together with areal statistics to quantify the landscape structure and composition.

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    Agricultural Univ. of Norway, Oslo