@Article{BontempoDalaPonzVale:2020:AdSiAi,
author = "Bontempo, Edgard and Dalagnol da Silva, Ricardo and Ponzoni,
Fl{\'a}vio Jorge and Valeriano, Dalton de Morisson",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto
Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)} and {Instituto Nacional de Pesquisas
Espaciais (INPE)}",
title = "Adjustments to sif aid the interpretation of drought responses at
the caatinga of Northeast Brazil",
journal = "Remote Sensing",
year = "2020",
volume = "12",
number = "19",
pages = "1--29",
month = "Oct",
keywords = "chlorophyll fluorescence, SIF, drought, spectral vegetation
indices, Caatinga, GOME-2, abiotic stress.",
abstract = "Sun-Induced chlorophyll Fluorescence (SIF) relates directly to
photosynthesis yield and stress but there are still uncertainties
in its interpretation. Most of these uncertainties concern the
influences of the emitting vegetations structure (e.g., leaf
angles, leaf clumping) and biochemistry (e.g., chlorophyll
content, other pigments) on the radiative transfer of fluorescent
photons. The Caatinga is a large region in northeast Brazil of
semiarid climate and heterogeneous vegetation, where such
biochemical and structural characteristics can vary greatly even
within a single hectare. With this study we aimed to characterize
eleven years of SIF seasonal variation from Caatinga vegetation
(2007 to 2017) and to study its responses to a major drought in
2012. Orbital SIF data from the instrument GOME-2 was used along
with MODIS MAIAC EVI and NDVI. Environmental data included
precipitation rate (TRMM), surface temperature (MODIS) and soil
moisture (ESA CCI). To support the interpretation of SIF responses
we used red and far-red SIF adjusted by the Suns zenith angle
(SIF-SZA) and by daily Photosynthetically Active Radiation (dSIF).
Furthermore, we also adjusted SIF through two contrasting
formulations using NDVI data as proxy for structure and
biochemistry, based on previous leaf-level and landscape level
studies: SIF-Yield and SIF-Prod. Data was tested with time-series
decomposition, rank correlation, spatial correlation and Linear
Mixed Models (LMM). Results show that GOME-2 SIF and adjusted SIF
formulations responded consistently to the observed environmental
variation and showed a marked decrease in SIF emissions in
response to a 2012 drought that was generally larger than the
corresponding NDVI and EVI decreases. Drought sensitivity of SIF,
as inferred from LMM slopes, was correlated to land cover at
different regions of the Caatinga. This is the first study to show
correlation between landscape-level SIF and an emergent property
of ecosystems (i.e., resilience), showcasing the value of remotely
sensed fluorescence for ecological studies.",
doi = "10.3390/rs12193264",
url = "http://dx.doi.org/10.3390/rs12193264",
issn = "2072-4292",
language = "en",
targetfile = "bontempo2020.pdf",
urlaccessdate = "21 maio 2024"
}