The start and end of the growing season in Pakistan during 1982-2015

Phenology plays an important role in plant productivity and ecosystem function. Long-term observations of crop phenology are being used to track crop responses to climate change. In this paper, a dataset of 34years (1982-2015) of biweekly advanced very high-resolution radiometer (AVHRR) normalized difference vegetation index, third generation (NDVI3g), measurements was used to examine the spatial and temporal patterns of crops. Phenological aspects such as the start of the season (SOS), the end of the season (EOS), and their variability were investigated using the NDVI time series for Pakistan. The quantitative effects of climate variables, namely, temperature and precipitation, were analyzed to determine the seasonal variability in crop phenology. The study indicates a large spatial and temporal variation in the different phenological characteristics of crops within the country throughout the study period. The length of the growing season coincides well with the onset and withdrawal of monsoons; a high positive correlation in the moist northern part of the study area was observed, whereas the semiarid areas in the south exhibited a small positive correlation. The temperature in the spring primarily controlled early SOS, and warmer autumn temperature delayed EOS. The results indicate that the crops were influenced by climate. Crop monitoring on a spatial scale is essential to developing outcomes and reducing exposure risks in the future.