Desertification in the south Junggar Basin, 2000-2009: Part I. Spatial analysis and indicator retrieval

Desertification is a serious environmental problem that threatens ecological balance and society sustainability, and pursuit of efficient techniques for its monitoring is always highlighted. Compared to in-situ investigation, remote sensing (RS) has proved to be an efficient solution plan, particularly for large covers, whereas previous RS-based studies mostly focused on proposal and validation of various indicators for different scenarios. To comprehensively reflect desertification and project its trend, this study attempted to develop a new comprehensive RS information model, with the scenario for test deployed at the south Junggar Basin, China in the last decade (2000-2009). The premise of establishing such a model, however, is not simple, involving selection of RS images with appropriate spatial resolutions and uniform retrievals of indicators with high accuracies. To handle these fundamental problems, this Part I compared the merits and faults of MODIS and TM images in desertification characterization, by making spatial analyses including land cover patch- and pixel-scale analyses and land attribute semi-variance and scale-agreement analyses. After the MODIS images with the resolution of 250 m were identified to be the appropriate choice, multiple representative indicators including NDVI, fraction of vegetation cover, land surface temperature, albedo and soil moisture that relate to different aspects of desertification processes were uniformly retrieved by using their individual effective algorithms and downscaling. Tests showed the spatial analyses did help in ensuring the premise of the whole study and the retrievals of indicators were reliable. The contributions are of fundamental implications for improving RS-based desertification analysis and have created a firm foundation for developing a RS information model in Part II.