Abstract:

To clarify the spatial-temporal variation characteristics of vegetation covers in the Changtang National Nature Reserve during the growing season and their responses to climate change, based on the MODIS NDVI and the meteorological data of the same period, the variation trend and stability of NDVI and their response to climate factors during vegetation growing season from 2000 to 2020 in the Changtang National Nature Reserve were caculated. The results showed that: (1) the average NDVI in the growing season of vegetation in the Changtang National Nature Reserve was 0.02-0.55, and the average value was 0.138, which showed a spatial distribution characteristic that gradually decreased from southeast to northwest; (2) in 86.39% of the Changtang National Nature Reserve, the NDVI in the vegetation growing season (June to September) showed a slow upward trend, and reached a significant level in most areas (P<0.05), while the remaining 13.61% of the area showed a declining trend, and there was a significant trend in only a few areas (P<0.05); the overall vegetation status showed an improving trend with time; (3) since 2000, the stability of NDVI in the growing season of the Changtang National Nature Reserve was relatively poor, most of the areas with NDVI≤0.1 were in low stability, the low and medium stability areas were the main type, which accounted for 86.66% of the Changtang National Nature Reserve; (4) the climate in the Changtang National Nature Reserve was getting warmer and wetter during the vegetation growing season; NDVI was positively correlated with temperature and precipitation as a whole during the growing season. The research conclusions could provide a scientific basis for the ecological protection of vegetation in this region under the background of climate change.

Key words: Changtang National Nature Reserve, NDVI (normalized differential vergetation index), spatial-temporal characteristics, temperature, precipitation