Agricultural Landscape Dynamics and Its Response in Seasonal Vegetation Activities in the Loess Plateau, Northern Shaanxi, China

摘要

The ecological and environmental conditions in semiarid areas are closely linked to landscape dynamics. This study examined the seasonal vegetation activities of landscape classes and dynamics in the Loess Plateau in North Shaanxi Province, China. Landscape dynamics were studied by comparing Landsat images in 1987 and 2007, and classified as landscape transitions, landscape variations and unchanged landscape. The characteristics of seasonal vegetation activities, such as dates for onset-of-greenness, peaks, and onset-of-senescence for landscapes were determined using Moderate Resolution Imaging Spectroradiometer (MODIS) 10-day vegetation index composite products (2002-2009). The landscape dynamics showed that some sloping croplands were converted to woodlands and grasslands. Vegetation activities responded diversely and seasonally to landscape classes and dynamics. Temporal analysis of the Normalized Difference Vegetation Index (NDVI) showed that the time of onset-of-greenness and onset-of-senescence were similar for all major landscape classes, while the time of peak vegetation activity was longer for tree than grass species. The analysis of seasonal vegetation activities and landscape dynamics indicated that seasonal vegetation activities were not only relative to landscape classes, but also affected by landscape dynamics.