Abstract:

In this paper， low mountain meadow in Tacheng， Xinjiang， China， is taken as the research object. Combined with the monthly Normalized Difference Vegetation Index （NDVI） data， meteorological data （including annual mean temperature and precipitation） and socio-economic development data （including annual average livestock carrying capacity， total meat production and per capita net income of farmers and herdsmen） from 2001 to 2020， using correlation analysis and trend analysis by means of ArcGIS 10.2.2 software， the temporal and spatial variation characteristics of NDVI， meteorological factors and socio-economic development data in study area were studied in the 20 years. From the point of view of climate change and human activities， the driving forces affecting NDVI change of low mountain meadow were discussed， and the effectiveness and timeliness of grassland restoration measures taken in the past were revealed. The results showed that： （1） In the past 20 years， NDVI in the vegetation growing season generally showed a slight upward trend. However， there was a reversal around 2008， mainly in the form of a significant downward trend from 2001 to 2008 and an upward trend from 2009 to 2020 . These trends indicate that the vegetation index of lowland meadow shows a trend of first decreasing and then increasing， and the vegetation shows a smaller greening trend after 2009. From 2001 to 2008， low mountain meadow was in the greening state， the greening phenomenon was mainly distributed in the southwest， South and east of the study area， but there was a browning trend， and the decrease of NDVI was the biggest in summer， and it was in the browning state from 2009 to 2020， the greening phenomenon is mainly distributed in the southwest of the study area， but there is a weak greening trend， and the increase of NDVI is the biggest in summer. （2） The general change of the growing season from 2001 to 2020 is a “warm and dry” trend， but the “warm and dry” trend has slowed down since 2009， the southern part of the meadow experienced a warming process of decreasing precipitation， while the northwest and northeast parts showed a cooling process of increasing precipitation in the past 20 years. （3） The number of livestock and total meat production both showed a trend of rapid increase， then a gradual increase and a sharp decrease， and the per capita net income showed an increasing trend. The reduction in the number of livestock and meat production is related to local measures such as banning grazing， closing down grazing， returning farmland to grassland， returning grazing to grassland， etc. （4） There was significantly positive correlation between NDVI and precipitation， but not for temperature and livestock production. （5） The measures implemented in the past， such as returning farmland to grassland， returning grazing to grassland and so on， had produced short-term effects. Even though the meadow vegetation showed a weak greening trend after 2009， it is still difficult to reverse the state of vegetation degradation. In the future， new measures or projects should be proposed in order to fundamentally realize the restoration and long-term sustainable development of grassland.

Key words: low mountain meadow, normalized difference vegetation index （NDVI）, climate change, driving forces, Tacheng Region