气候变化领域集成服务门户(CCPortal): Phenology of short vegetation cycles in a Kenyan rangeland from PlanetScope and Sentinel-2

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DOI	10.1016/j.rse.2020.112004
	Phenology of short vegetation cycles in a Kenyan rangeland from PlanetScope and Sentinel-2
	Cheng Y.; Vrieling A.; Fava F.; Meroni M.; Marshall M.; Gachoki S.
发表日期	2020
ISSN	00344257
卷号	248
英文摘要	The short revisit times afforded by recently-deployed optical satellite sensors that acquire 3–30 m resolution imagery provide new opportunities to study seasonal vegetation dynamics. Previous studies demonstrated a successful retrieval of phenology with Sentinel-2 for relatively stable annual growing seasons. In semi-arid East Africa however, vegetation responds rapidly to a concentration of rainfall over short periods and consequently is subject to strong interannual variability. Obtaining a sufficient density of cloud-free acquisitions to accurately describe these short vegetation cycles is therefore challenging. The objective of this study is to evaluate if data from two satellite constellations, i.e., PlanetScope (3 m resolution) and Sentinel-2 (10 m resolution), each independently allow for accurate mapping of vegetation phenology under these challenging conditions. The study area is a rangeland with bimodal seasonality located at the 128-km2 Kapiti Farm in Machakos County, Kenya. Using all the available PlanetScope and Sentinel-2 imagery between March 2017 and February 2019, we derived temporal NDVI profiles and fitted double hyperbolic tangent models (equivalent to commonly-used logistic functions), separately for the two rainy seasons locally referred to as the short and long rains. We estimated start- and end-of-season for the series using a 50% threshold between minimum and maximum levels of the modelled time series (SOS50/EOS50). We compared our estimates against those obtained from vegetation index series from two alternative sources, i.e. a) greenness chromatic coordinate (GCC) series obtained from digital repeat photography, and b) MODIS NDVI. We found that both PlanetScope and Sentinel-2 series resulted in acceptable retrievals of phenology (RMSD of ~8 days for SOS50 and ~15 days for EOS50 when compared against GCC series) suggesting that the sensors individually provide sufficient temporal detail. However, when applying the model to the entire study area, fewer spatial artefacts occurred in the PlanetScope results. This could be explained by the higher observation frequency of PlanetScope, which becomes critical during periods of persistent cloud cover. We further illustrated that PlanetScope series could differentiate the phenology of individual trees from grassland surroundings, whereby tree green-up was found to be both earlier and later than for grass, depending on location. The spatially-detailed phenology retrievals, as achieved in this study, are expected to help in better understanding climate and degradation impacts on rangeland vegetation, particularly for heterogeneous rangeland systems with large interannual variability in phenology and productivity. © 2020 The Author(s)
英文关键词	Digital repeat photography; Landscape variability; Multi-temporal analysis; NDVI time series; Phenology; PlanetScope; Semi-arid rangelands; Sentinel-2; Spatial resolution
语种	英语
scopus关键词	Hyperbolic functions; Rain; Satellite imagery; Vegetation; Chromatic coordinate; Hyperbolic tangent models; Interannual variability; Observation frequencies; Repeat photographies; Satellite constellations; Vegetation dynamics; Vegetation phenology; Forestry; annual variation; growing season; mapping method; MODIS; NDVI; phenology; rangeland; satellite constellation; satellite imagery; Sentinel; spectral resolution; vegetation dynamics; Kenya; Machakos
来源期刊	Remote Sensing of Environment
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/179186
作者单位	University of Twente, Faculty of Geo-information Science and Earth Observation, P.O. Box 217, Enschede, 7500 AE, Netherlands; International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, 00100, Kenya; European Commission, Joint Research Centre (JRC), Via E. Fermi 2749, Ispra, VA I-21027, Italy; International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, 00100, Kenya
推荐引用方式 GB/T 7714	Cheng Y.,Vrieling A.,Fava F.,et al. Phenology of short vegetation cycles in a Kenyan rangeland from PlanetScope and Sentinel-2[J],2020,248.
APA	Cheng Y.,Vrieling A.,Fava F.,Meroni M.,Marshall M.,&Gachoki S..(2020).Phenology of short vegetation cycles in a Kenyan rangeland from PlanetScope and Sentinel-2.Remote Sensing of Environment,248.
MLA	Cheng Y.,et al."Phenology of short vegetation cycles in a Kenyan rangeland from PlanetScope and Sentinel-2".Remote Sensing of Environment 248(2020).