Characterising the spring and autumn land surface phenology of Macaronesian species using Sentinel-2 data: the case of Canary Islands

Abstract

Land surface phenology (LSP), the study of seasonal dynamics of vegetation analysing phenological metrics -phenometrics- derived from vegetation indices time series (VI), has emerged as an important research focus in recent decades as LSP patterns have been considered as an important ecological indicator for understanding the functioning of terrestrial ecosystems. LSP from high-spatial-resolution satellite imagery in ecosystems with significant heterogeneity of plant species, such as Macaronesian ecosystems, are needed for a better understanding on how these ecosystems function. The objective of this study was to monitor LSP dynamics of representative species of the Canary Islands: Olea Cerasiformis, Pistacia atlantica, Juniperus turbinata, Pinus canariensis, Myrica Faya and Erica arborea. NDVI (Normalised Difference Vegetation Index) Sentinel-2 time series at a spatial and temporal resolution of 10 meters and 5 days were generated for the 2018-2020 period. Atmospheric disturbances and noise were reduced using a double-logistic function. SOS (start of the growing season), EOS (end of the growing season) and LOS (length of the growing season) were extracted using a threshold-based method. Thermophilus species, such as Olea Cerasiformis and Pistacia atlantica had the SOS in October-November and the EOS between June and July. Juniperus turbinata showed double seasonality in La Palma, being the first growing season between November-December and April-May and the second growing season between May-June and September-October. Growing season of Pinus canariensis started in September-October and ended in April-June, nevertheless a double seasonality was observed in some locations of Pinus canariensis, probably associated to the understory. Subtropical laurel forest composed by different plant species, such as Myrica Faya and Erica arborea, did not show a clear seasonality. The species-specific LSP patterns for the Canary Islands can contribute to stablishing a baseline to monitor future impacts of climate change in Macaronesian biogeographical region.