To survive and thrive in nature, plants respond to climate changes across seasonal cycles, which is also known as phenological sensitivity. If documented and analyzed, phenological data can provide valuable insights concerning the impact of climate change on terrestrial ecosystems.

  

Although the impact of a warming climate on phenological trends in vegetation has been widely investigated, it has long been debated whether precipitation or temperature is the main contributor to spring vegetation green-up (SVG) in alpine dry ecosystems on the Third Pole.

  

Researchers from the Institute of Tibetan Plateau Research, Chinese Academy of Sciences, have now provided an answer. LI Xiang, ZHANG Lin and LUO Tianxiang proposed and confirmed the hypothesis that precipitation—specifically, monsoon rainfall onset (RSO)—rather than temperature is the main driver of SVG spatiotemporal variability across alpine dry ecosystems on the Third Pole. Their findings were recently published in the 10th volume of Scientific Reports under the title “Rainy season onset mainly drives the spatiotemporal variability of spring vegetation green-up across alpine dry ecosystems on the Third Pole.”

 Image by Alicja

 

To test their hypothesis, Li and Luo calculated the dates of rainy season onset (RSO) and spring vegetation green-up (SVG) across 67 target areas near 67 weather stations on the Third Pole. They based their calculations on time-series data for daily mean temperature and precipitation (1974-2013), and of the Normalized Difference Vegetation Index from the Moderate Resolution Imaging Spectroradiometer (2001-2013), respectively.

  

The satellite-derived SVG data was validated by 7-year observations (2007-2013) for leaf emergence of dominant species in alpine meadows along elevations isolines in the Damxung area of Tibet. According to Luo, they found that SVG generally synchronized with or lagged behind RSO, even when seasonal air temperatures were above 0°C for a month before SVG. 

 

Based on their observed data of a Kobresia meadow in Damxung, Tibet, Li and Luo suggested that while plants tend to avoid drought and frost damage, they are more phenologically sensitive to precipitation or RSO.

  

“Phenological responses to climate change may be involved in complicated evolutionary adaptions to environmental stresses,” Li said. “The knowledge of the plant’s phenological responses to environmental changes can help in analyzing the effects of climate change on individual plant species, and the ecosystems they are in.”

 

Editor's note: the study was supported by STEP,a TPE related science project.