Abstract:

In this paper, the principles and methodologies for developing data set of land cover characteristics for the Northeast China transect (NECT) are discussed. Data set was developed using multi-temporal NOAA/AVHRR NDVI images with 1-km spatial resolution. Elevation, climate, soil, vegetation, land use, land resource, ecoregions, political boundaries, economic data, and social data were included as data layers, and all data layers were standardized and then integrated by digitization, spatial interpolation, geometrical registration, and projection transformation. Using this data set, several land use characteristics were mapped and analyzed. 1) Land cover mapping: multi-temporal NOAA/AVHRR NDVI images with 1-km spatial resolution were adopted to classify the land cover map of NECT. The first classification included 8 land cover types, forest, grassland, desert, shrub, cropland, mixed type, building area and water bodies. There were 12 land cover types in the second classification. Classification accuracy was 81.61% determined by ground truthing. The land cover patterns reflected the integrated physical geographical characteristics of NECT. 2) Land cover parameters were calculated using multi-temporal remotely sensed reflectance data that included annual NDVI maximum (NDVI max ), seasonal NDVI amplitude (x am ) and annual NDVI standard deviation (x′ s). Strong inter-annual and seasonal changes in vegetation growth for different land cover types were apparent. NDVI max, x am and x′ s showed an increasing trend with an increase in annual average temperatures for meadow steppe, typical steppe and desert steppe. 3) Two methods were used to evaluate seasonal changes in the length of the growing seasons over time. The length of the growing seasons of the meadow steppe and typical steppe lengthened by (9±2) days and (11±3) days, respectively, from 1983 to 1999. Similar change was not detected for the desert steppe. These results are in accordance with field records. This data set is a foundation for future research on land cover characteristics and their changes along the NECT. It also is an important contribution to international research on large-scale gradients as well as to global change research based upon the NECT.

Key words: NECT, Land cover, Multi-temporal NOAA/AVHRR NDVI images