关键词: CO₂浓度升高, 水溶性有机碳, 氮素添加, 根际, 水溶性有机氮

Abstract: Based on remote sensing (RS) and geographic information system (GIS) technology, and using the normalized difference vegetation index (NDVI) of different resolution in the Loess Plateau from 1982 to 2011, the multi-scale change characteristics of different periods of the Loess Plateau vegetation landscape in relation to the terrain were analyzed by multi-scale spatial statistics method of wavelet analysis. The results indicated that the vegetation landscape of Loess Plateau exhibited periodic changes from 1982 to 2011, mainly including three phases, namely the vegetation restoration phase before 1990, the vegetation degradation phase from 1990-2001 and vegetation recovery phase after 2001. Furthermore, the spatial heterogeneity, data acquisition time, data resolution and spatial position of vegetation landscape had good correlations with topography in the Loess Plateau. On one hand, higher vegetation index and data resolution caused greater spatial heterogeneity of vegetation landscape, and the spatial heterogeneity of vegetation landscape along the longitude direction was greater than that along the latitude direction. On the other hand, the multi-scale NDVI variation was correlated to topographical factors, and the correlation coefficients ranked as follows: DEM > CTI > slope > aspect. These results will be of great significance for vegetation landscape rational adjustments, biodiversity enhancement, soil erosion control, and landscape continuity enhancement, and provide important basis for ecological environment construction in the Loess Plateau.

Key words: dissolved organic nitrogen, rhizosphere, dissolved organic carbon, nitrogen addition, elevated CO₂ concentration