Satellite-Based Observations Reveal the Altitude-Dependent Patterns of SIFyield and Its Sensitivity to Ambient Temperature in Tibetan Meadows

Ruonan Chen,Xinjie Liu,Liangyun Liu

doi:10.3390/rs13071400

Abstract

Photosynthesis and its sensitivity to the changing environment in alpine regions are of great significance to the understanding of vegetation–environment interactions and other global ecological processes in the context of global change, while their variations along the elevation gradient remain unclear. Using solar-induced chlorophyll fluorescence (SIF) derived from satellite observations, we discovered an increase in solar-induced fluorescence yield (SIFyield) with rising elevation in Tibetan meadows in the summer, related to the altitudinal variation in temperature sensitivity at both seasonal and interannual scales. Results of the altitudinal patterns of SIFyield demonstrated higher temperature sensitivity at high altitudes, and the sensitivity at the interannual scale even exceeds that at seasonal scale when the elevation reaches above 4700 m. This high-temperature sensitivity of SIFyield at high altitudes implies potential adaptation of alpine plants and also indicates that changes in photosynthesis-related physiological functions at high altitudes should receive more attention in climate change research. The altitudinal SIFyield patterns revealed in this study also highlight that variations in temperature sensitivity should be considered in models, otherwise the increasing trend of SIFyield observations can never be discovered in empirical simulations.

Highlights

The photosynthesis activity of alpine vegetation and its response to the changing environment has been an attractive topic for centuries [1,2] due to its unparalleled scientific and social significance
The SIFyield changes along the elevation gradient shows an increase in values at higher elevation on summer days in the Tibetan Plateau
From DOY 173 (21 or 22 June) to DOY 245 (1 or 2 September), 8 out of 10 records support the increase in SIFyield at high altitudes in summer, and the increase trend is apparent on DOYs

Summary

Introduction

The photosynthesis activity of alpine vegetation and its response to the changing environment has been an attractive topic for centuries [1,2] due to its unparalleled scientific and social significance. Plants along the altitudinal gradient usually habituate themselves well to local environmental conditions, their physiological traits vary over relatively short horizontal distances [1,3]. Due to the unique combination of extreme environmental stresses along the altitude gradient, such as low temperature and high light intensity, large amounts of special materials for evolutionary studies on adaptation strategies can be found in alpine regions, which appeals to numerous ecologists and evolutionists [1,3,4,5,6]. The special combination of environmental stresses makes the alpine area a natural laboratory for vegetation–climate interaction research. Understanding the altitudinal variations in unique traits of alpine plants and their environmental sensitivity will help in revealing their adaptation mechanism in mountain areas, describing the impact of climate change on vegetation, and predicting the

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