Retrieval of Sun-Induced Chlorophyll Fluorescence (F) spectrum is one of the challenging perspectives for further advancing F studies towards a better characterization of vegetation structure and functioning. In this study, a simplified Spectral Fitting retrieval algorithm suitable for retrieving the F spectrum with a limited number of parameters is proposed (two parameters for F). The novel algorithm is developed and tested on a set of radiative transfer simulations obtained by coupling SCOPE and MODTRAN5 codes, considering different chlorophyll content, leaf area index and noise levels to produce a large variability in fluorescence and reflectance spectra. The retrieval accuracy is quantified based on several metrics derived from the F spectrum (i.e., red and far-red peaks, O2 bands and spectrally-integrated values). Further, the algorithm is employed to process experimental field spectroscopy measurements collected over different crops during a long-lasting field campaign. The reliability of the retrieval algorithm on experimental measurements is evaluated by cross-comparison with F values computed by an independent retrieval method (i.e., SFM at O2 bands). For the first time, the evolution of the F spectrum along the entire growing season for a forage crop is analyzed and three diverse F spectra are identified at different growing stages. The results show that red F is larger for young canopy; while red and far-red F have similar intensity in an intermediate stage; finally, far-red F is significantly larger for the rest of the season.
Human societies face challenges in transitioning towards low-carbon economies and sustainable management of land use and natural resources. Documenting and learning from past transitions helps policy-makers cope with such challenges. The agricultural revolution in Cantabrian Spain (ca. 7000 cal a BP) was one major adaptation of hunter-gatherers to a changing environment that started with the Last Glacial Maximum (ca. 24 000 cal a BP) and lasted until the Mid-Holocene (ca. 5300 cal a BP). Classic approaches to documenting prehistoric cultural timelines are based on manufacturing and technology, thus limited in their ability to describe the sustainability of past societies. Energy regimes, a functional societal approach independent from time, investigate and consider patterns of resource and energy use in various cohabiting and cooperating cultural phases. To examine past energy regimes, a database of archaeological remains was compiled to document four indicators: mobility, economy, overexploitation and societal complexity. Statistical analyses were conducted to elucidate trends, changes and continuity in subsistence strategies by hunter-gatherers and sedentary societies. Results show that energy regimes act as a complement to cultural phases, adding novel functional analyses of past societies to cultural stratigraphy units common in archaeology, shedding light on the sustainability of past societal transitions.
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