Effects of vegetation phenology on vegetation productivity in the Qinghai Lake Basin of the Northeastern Qinghai–Tibet Plateau

Investigating the impacts of vegetation phenology on vegetation productivity is of great significance to understand the adaptation of terrestrial ecosystems to climate change. This research explored the impact of phenological variations on vegetation productivity using the MODIS remote sensing data sets in the Qinghai Lake basin. Our findings showed (1) that the mean vegetative SOS (start of the growing season), LOS (Length of the growing season), and DOS (Dormancy of growing season) during 2001–2015 range from April 6th to June 19th, 91d to186d and August 11th to November 6th, respectively. The regional mean SOS showed an advance trend from 2001 to 2015 in the Qinghai Lake Basin, with an advance rate of about 2 d/a; LOS tended to shorten, and the shortening rate was about 1.06 d/a; DOS had a clear advancement trend with a rate of about 1 d/a. (2) The annual average NPP and GPP in Qinghai Lake basin from 2001 to 2015 were between 0 to 542.86 gC·m-2·a-1 and 0 to 815.48 gC·m-2·a-1; the slopes of NPP and GPP in the Qinghai Lake basin were between -18.96 to 30.83 and -26.83 to 45.18, respectively. (3) Through correlation analysis of vegetation phenology and vegetation productivity, On the spatial scale, it can be seen that the advance of SOS and DOS in the Qinghai Lake basin will reduce NPP and GPP, and the extension of LOS will increase NPP and GPP significantly. In the direction of the altitude gradient (the altitude was from 3200 m to 4400 m), when the SOS was delayed by 1 day, NPP and GPP will decrease by 12.31 gC·m-2 and 18.69 gC·m-2 respectively; when DOS was delayed by 1 day, NPP and GPP will increase by 8.55 gC·m-2 and 12.89 gC·m-2, respectively; when LOS was increased by 1 day, NPP and GPP will increase by 5.08 gC·m-2 and 7.68 gC·m-2, respectively. (4) In the direction of the altitude gradient, the order of influence of vegetation phenology on vegetation productivity was: SOS> DOS> LOS. On the spatial scale, there were spatial differences in the effects of SOS and DOS on vegetation productivity. The results showed that vegetation phenology had a significant effect on productivity in the Qinghai Lake basin, which had important reference significance for regional ecosystem management and ecological construction. © 2021, Saudi Society for Geosciences.