Spatio-Temporal Variation of Vegetation Phenology on Loess Plateau in Shaanxi-Gansu- Ningxia Region in Recent 12 Years

Based on a ten-year (1999-2010) SPOT VEGETATION dataset, spatio-temporal vegetation phonological phenological features on the Shaan-Gan-Ning Loess Plateau were studied. The method of harmonic analysis of time series (HANTS) was adopted to pre-process the raw data, the fourier interpolation method to turn NDVI ten-day data into daily data, and the threshold value method and the maximum ratio method to specify vegetation phonological phenological phases. Results show that the multi-year average of vegetation phenology space distribution in the Shanxi-Gansu-Ningxia Region varied with the latitude, that is to say, the lower the latitude, the relatively earlier the growth season started (SOG) and ended (EOG)and the shorter the growth season (LOG). Moreover, it started 3 days earlier (P<0.01), ended two days earlier (P<0.01), and lasted one day longer (P>0.05) with the attitude rising every 100 m. During the ten ten-year period (1999 – 2010), the annual rate of change in vegetation phenology, SOG, EOGand LOG in that region, was -0.02, 0.003 and 0.02 d?a^-1, respectively. The vegetation phenology in most part of the Loess Plateau tended to have SOG advanced, EOG postponed and LOG extended, which were supposed to be related to variation of precipitation and the river net system. In high latitude regions, arid and low in temperature, vegetation growth started stagnation earlier and shortened in life cycle.