Abstract
Abstract. Global environmental change is rapidly altering the dynamics of terrestrial vegetation, and phenology is a classic proxy to detect the response of vegetation to the changes. On the Tibetan Plateau, the earlier spring and delayed autumn vegetation phenology is widely reported. Remotely sensed NDVI can serve as a good data source for vegetation phenology study. Here GIMMS NDVI3g data was used to detect vegetation phenology status on the Tibetan Plateau. The spatial and temporal gradients are combined to depict the velocity of vegetation expanding process. This velocity index represents the instantaneous local velocity along the Earth’s surface needed to maintain constant vegetation condition. This study found that NDVI velocity show a complex spatial pattern. A considerable number of regions display a later starting of growing season (SOS) and earlier end of growing season (EOS) reflected by the velocity change, particularly in the central part of the plateau. Nearly 74 % vegetation experienced a shortened growing season length. Totally, the magnitude of the phenology velocity is at a small level that reveals there is not a significant variation of vegetation phenology under the climate change context.
Highlights
1.1 BackgroundUnder the global change context, how the spatial displacement of vegetation phenology changes correspond has attracted lots of attentions from the study filed (Elmore, 2016; Zhu, 2016)
The remotely sensed NDVI3g data used in this study was derived from NOAA’s Advanced Very High Resolution Radiometer (AVHRR) sensor, which was produced in the framework of the Global Inventory Monitoring and Modeling System (GIMMS) project
In this study we have applied the concept of velocity to remotely sensed vegetation phenology fields which combines spatial and temporal gradients information to detect the vegetation phenology dynamic on the Tibetan Plateau
Summary
Under the global change context, how the spatial displacement of vegetation phenology changes correspond has attracted lots of attentions from the study filed (Elmore, 2016; Zhu, 2016). The current vegetation extent will be rearranged over the compact districts with climate change and human activities. As the third polar on the earth, Tibetan Plateau is sensitive to climate changes and human activities. Studies using satellite-derived data or experiment data, have pointed out it has experienced a continuous greening trend (Zhang, 2013; Shen, 2015). These research commonly applied spatial or temporal pattern analysis on the vegetation or NDVI-derived phenology. The concept of the velocity of change offers the opportunity to directly compare the ongoing change in the spatial patterns of vegetation phenology (Loarie, 2009). We mapped the velocity of change in vegetation phenology, which was calculated using the satellite-derived long-term NDVI
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