Remote sensing-based quantification of spatial variation in canopy phenology of four dominant tree species in Europe

Qifei Han

doi:10.1117/1.jrs.7.073485

Abstract

Spatial variation of phenology is a central feature of global change research. Satellite remote sensing is used for continental to global monitoring due to the limitations of long-term field observations of plant phenology. A threshold method was used to estimate the start of the season, length of the season, maximum normalized difference vegetation index (NDVI), and integral NDVI for selected tree species using remote sensing based NDVI data acquired by the VEGETATION instrument on board Satellite Pour l’Observation de la Terre (SPOT VGT NDVI). Afterward, the spatial patterns in the satellite-derived phenological metrics for four dominant tree species (i.e., beech, birch, pine, and spruce) across Europe were characterized. The results indicate that: (1) The SOS occurs 1.6–2.9 days later and the average LOS is 2.7–3 days shorter per 1 deg of latitude increase from south to north. (3) The SOS occurs 0.7–1.8 days later and the LOS was 0.6–2 days shorter per 100-m increase in altitude for the four species. (4) The SOS and LOS across Europe are well correlated with the mean annual air temperature (1°C correlates with a 4.5-day advance in the SOS and a 7-day extension in the LOS). Our research is the first one to characterize the spatial and temporal variations of phenology for different tree species across Europe using remote sensing.

Highlights

Phenology includes the study of annual rhythms of biological phenomena mainly in relation to climatic parameters.[1]
Pixels that correspond to water surfaces, rock, deserts, or other surface features with insufficient normalized difference vegetation index (NDVI) dynamics, where phenological metrics could not be calculated, are shown in white
Our results suggested that the phenology corresponds well with changes in air temperature associated with the onset of spring, especially with the mean temperature during the month of the start of the season

Summary

Introduction

Phenology includes the study of annual rhythms of biological phenomena mainly in relation to climatic parameters.[1]. The research on plant phenology has improved the understanding of the variations in lifecycle events in the past centuries[2,3,4,5,6] using site- and species-specific phenological measurements.[7,8] phenological data from many parts of the world are comparatively scarce. Ecological models relating to climate-change studies require phenological information at large spatial scales rather than inventory data that focus mostly on specific plant species and are mostly point observations. The use of remote sensing data for inferring the phenological characteristics of vegetation is increasingly regarded as a key to understanding large-area seasonal phenomena.[9] Among all remote-sensing indices, the normalized difference vegetation index (NDVI) is the index most often used in studying seasonal variations, in growing vegetation, and the shifts between vegetation covers.[10,11,12]

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