The impacts of climate change and human activities on alpine vegetation and permafrost in the Qinghai-Tibet Engineering Corridor

Abstract

The Qinghai-Tibet Engineering Corridor (QTEC) in China may reflect the changes in the alpine ecosystem of the Qinghai–Tibet Plateau (QTP) that are driven by global climate change combined with intensive human activities. We used the normalized difference vegetation index (NDVI) as an indicator of alpine vegetation activity and the permafrost active layer thickness (ALT) as an indicator of permafrost dynamics to understand the impacts of climate change, human activity, or their combination on the alpine ecosystem in the QTEC. Based on the types of frozen ground, we separated the QTEC into northern, permafrost, and southern zones. The surface air temperature increased by 0.28 °C per decade from 1982 to 2010, and the rising trend of air temperature was most prominent in the permafrost zone (P < 0.05); the total precipitation exhibited a significant increase of 15 mm per decade (P < 0.05). The level of human activity in the QTEC rose slowly before 2000 and rapidly after 2000. The NDVI trends over the QTEC increased over the past thirty years, but the NDVI declined in some areas from 2001 to 2010, especially in the southern QTEC. The permafrost in the QTEC continued to thaw, and the ALT increased. Our results indicated that the QTEC experienced a significant warming and wetting trend. The increased precipitation improved the alpine vegetation activity across much of the QTEC, and the increased air temperature accelerated the thawing of permafrost. However, the construction and operation of the Qinghai–Tibet Railway since 2001 and 2006 promoted an influx of residents and tourists, boosted the local economy, and resulted in the deterioration of the alpine vegetation, particularly in the southern QTEC. Moreover, our results suggested that improvement of alpine vegetation cannot necessarily prevent permafrost degradation caused by warming.