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DOI	10.1016/j.rse.2020.112042
	Does ASCAT observe the spring reactivation in temperate deciduous broadleaf forests?
	Pfeil I.; Wagner W.; Forkel M.; Dorigo W.; Vreugdenhil M.
发表日期	2020
ISSN	00344257
卷号	250
英文摘要	Scatterometer observations over land are sensitive to the water content in soil and vegetation, but have been rarely used to study seasonal changes in the plant water status and seasonal development of deciduous trees. Here we use Advanced Scatterometer (ASCAT) observations to investigate the sensitivity of C-band backscatter to spring phenology of temperate deciduous broadleaf forests in Austria. ASCAT's multi-angle looking capability enables the observation of backscatter over a large range of incidence angles. The vegetation status affects the slope of the backscatter-incidence angle relationship. We discovered a maximum in the slope around the month April, hereafter referred to as spring peak, predominantly in regions covered by deciduous broadleaf forest. We hypothesized that the spring peak indicates the average timing of leaf emergence in the deciduous trees in the sensor footprint. The hypothesis was tested by comparing the timing of the spring peak to leaf unfolding observations from the PEP725 phenology database, to the increase of leaf area index (LAI) during spring, and to temperature. Our results demonstrate a good agreement between the ASCAT spring peaks, phenology observations and temperature conditions. The steepest increase in LAI however lags behind the ASCAT peak by several days to a few weeks, suggesting that the spring peak in fact marks the timing of maximum woody water content, which occurs right before leaf emergence. Based on these observations, we conclude that the ASCAT signal has a high sensitivity to spring reactivation and in particular water uptake of bare deciduous broadleaf trees. Our findings might provide the basis for novel developments to estimate eco-physiological changes of forests during spring at large scales. © 2020 The Authors
英文关键词	Active microwave remote sensing; Advanced Scatterometer (ASCAT); Deciduous broadleaf forest; Functional phenology; Slope; Vegetation
语种	英语
scopus关键词	Backscattering; Meteorological instruments; Vegetation; Broadleaf forest; C-band backscatters; Incidence angles; Plant water status; Seasonal changes; Sensor footprints; Temperature conditions; Water content in soil; Forestry; ASCAT; backscatter; broad-leaved forest; deciduous forest; deciduous tree; hypothesis testing; leaf area index; physiological response; water content; water uptake; Austria
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/179143
作者单位	Department of Geodesy and Geoinformation, Research Unit Remote Sensing, TU Wien, Vienna, Austria; Centre for Water Resource Systems, TU Wien, Vienna, Austria; Faculty of Environmental Sciences, Institute for Photogrammetry and Remote Sensing, TU Dresden, Dresden, Germany
推荐引用方式 GB/T 7714	Pfeil I.,Wagner W.,Forkel M.,et al. Does ASCAT observe the spring reactivation in temperate deciduous broadleaf forests?[J],2020,250.
APA	Pfeil I.,Wagner W.,Forkel M.,Dorigo W.,&Vreugdenhil M..(2020).Does ASCAT observe the spring reactivation in temperate deciduous broadleaf forests?.Remote Sensing of Environment,250.
MLA	Pfeil I.,et al."Does ASCAT observe the spring reactivation in temperate deciduous broadleaf forests?".Remote Sensing of Environment 250(2020).