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Titre : Climatic drivers of greening trends in the Alps Type de document : Imprimé Auteurs : Gianluca Filippa ; Edoardo Cremonese ; Marta Galvagno ; Michel Isabellon ; Arthur Bayle ; Philippe Choler ; Bradley Z. Carlson ; Simone Gabellani ; Umberto Morra di Cella ; Mirco Migliavacca Année de publication : 2019 Article en page(s) : 1-15 Catégories : [CBNPMP-Géographique] Alpes
[CBNPMP-Thématique] Relations climat-végétation
[LOTERRE-Biodiversité] Changement climatiqueRésumé : Since the 1980s, vegetated lands have experienced widespread greening at the global scale. Numerous studies have focused on spatial patterns and mechanisms of this phenomenon, especially in the Arctic and sub-Arctic regions. Greening trends in the European Alps have received less attention, although this region has experienced strong climate and land-use changes during recent decades. We studied the rates and spatial patterns of greening in an inner-alpine region of the Western Alps. We used MODIS-derived normalized difference vegetation index (NDVI) at 8-day temporal and 250 m spatial resolution, for the period 2000–2018, and removed areas with disturbances in order to consider the trends of undisturbed vegetation. The objectives of this study were to (i) quantify trends of greening in a representative area of the Western Alps; and (ii) examine mechanisms and causes of spatial patterns of greening across different plant types. We show that 63% of vegetated areas experienced significant trends during the 2000–2018 period, of which only 8% were negative. We identify (i) a climatic control on spring and autumn phenology with contrasting effects depending on plant type and elevation, and (ii) land-use change dynamics, such as shrub encroachment on abandoned pastures and colonization of new surfaces at high elevation. Below 1500 m, warming temperatures promote incremental greening in the transition from spring to summer, but not in fall, suggesting either photoperiod or water limitation. In the alpine and sub-alpine belts (>1800 m asl), snow prevents vegetation development until late spring, despite favorable temperatures. Instead, at high elevation greening acts both in summer and autumn. However, photoperiod limitation likely prevents forested ecosystems from fully exploiting warmer autumn conditions. We furthermore illustrate two emblematic cases of prominent greening: recent colonization of previously glaciated/non vegetated areas, as well as shrub/tree encroachment due to the abandonment of agricultural practices. Our results demonstrate the interplay of climate and land-use change in controlling greening dynamics in the Western Alps. Lien pérenne : DOI : 10.3390/rs11212527 Permalink : https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=148069
in Remote sensing > 11 (2019) . - 1-15Filippa, Gianluca, Cremonese, Edoardo, Galvagno, Marta, Isabellon, Michel, Bayle, Arthur, Choler, Philippe, Carlson, Bradley Z., Gabellani, Simone, Morra di Cella, Umberto, Migliavacca, Mirco 2019 Climatic drivers of greening trends in the Alps. Remote sensing, 11: 1-15.Documents numériques
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Article (2019)URLApplication of UAV-based methodology for census of an endangered plant species in a fragile habitat / Kody Rominger in Remote sensing, 11 (2019)
Titre : Application of UAV-based methodology for census of an endangered plant species in a fragile habitat Type de document : Imprimé Auteurs : Kody Rominger ; Susan E. Meyer Année de publication : 2019 Article en page(s) : 719 Catégories : [CBNPMP-Thématique] Télédétection Résumé : Accurate census is essential for endangered plant management, yet lack of resources may make complete on-the-ground census difficult to achieve. Accessibility, especially for species in fragile habitats, is an added constraint. We examined the feasibility of using UAV (unmanned aerial vehicle, drone)-based imagery for census of an endangered plant species, Arctomecon humilis (dwarf bear-poppy), an herbaceous perennial gypsophile endemic of the Mojave Desert, USA. Using UAV technology, we captured imagery at both 50-m altitude (census) and 15-m altitude (validation) at two populations, White Dome (325 ha) and Red Bluffs (166 ha). The imagery was processed into orthomosaics that averaged 2.32 cm ground sampling distance (GSD) for 50-m imagery and 0.73 cm GSD for 15-m imagery. Putative poppy plants were marked in the 50-m imagery according to predefined criteria. We then used the 15-m imagery from each area to verify the identification accuracy of marked plants. Visual evaluation of the 50-m imagery resulted in errors of both commission and omission, mainly caused by failure to accurately identify or detect small poppies (<10 cm diameter). Higher-resolution 30-m altitude imagery (1.19 cm GSD) greatly reduced errors of commission. Habitat classification demonstrated that poppy density variation was closely tied to soil surface color. This study showed that drone imagery can potentially be used to census rare plant species with distinctive morphology in open habitats and understand their spatial distribution. Lien pérenne : DOI : 10.3390/rs11060719 Permalink : https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=151549
in Remote sensing > 11 (2019) . - 719Rominger, Kody, Meyer, Susan E. 2019 Application of UAV-based methodology for census of an endangered plant species in a fragile habitat. Remote sensing, 11: 719.Documents numériques
Article (2019)URL
Titre : Estimating rangeland forage production using remote sensing data from a small unmanned aerial system (sUAS) and planetscope satellite Type de document : Imprimé Auteurs : Han Liu ; Randy A. Dahlgren ; Royce E. Larsen ; Scott M. Devine ; Leslie M. Roche ; Anthony T. O'Geen ; Andy J. Y. Wong ; Sarah Covello ; Yufang Jin Année de publication : 2019 Article en page(s) : 595 Catégories : [CBNPMP-Thématique] Télédétection Résumé : Rangelands cover ~23 million hectares and support a $3.4 billion annual cattle industry in California. Large variations in forage production from year to year and across the landscape make grazing management difficult. We here developed optimized methods to map high-resolution forage production using multispectral remote sensing imagery. We conducted monthly flights using a Small Unmanned Aerial System (sUAS) in 2017 and 2018 over a 10-ha deferred grazing rangeland. Daily maps of NDVI at 30-cm resolution were first derived by fusing monthly 30-cm sUAS imagery and more frequent 3-m PlanetScope satellite observations. We estimated aboveground net primary production as a product of absorbed photosynthetically active radiation (APAR) derived from NDVI and light use efficiency (LUE), optimized as a function of topography and climate stressors. The estimated forage production agreed well with field measurements having a R2 of 0.80 and RMSE of 542 kg/ha. Cumulative NDVI and APAR were less correlated with measured biomass (????2 = 0.68). Daily forage production maps captured similar seasonal and spatial patterns compared to field-based biomass measurements. Our study demonstrated the utility of aerial and satellite remote sensing technology in supporting adaptive rangeland management, especially during an era of climatic extremes, by providing spatially explicit and near-real-time forage production estimates. Lien pérenne : DOI : 10.3390/rs11050595 Permalink : https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=151703
in Remote sensing > 11 (2019) . - 595Liu, Han, Dahlgren, Randy A., Larsen, Royce E., Devine, Scott M., Roche, Leslie M., O'Geen, Anthony T., Wong, Andy J. Y., Covello, Sarah, Jin, Yufang 2019 Estimating rangeland forage production using remote sensing data from a small unmanned aerial system (sUAS) and planetscope satellite. Remote sensing, 11: 595.Documents numériques
Article (2019)URL
