Pubblicazioni Scientifiche

Filtri di ricerca 9 risultati
Reset
Pubblicazioni per anno
Above ground biomass and tree species richness estimation with airborne lidar in tropical Ghana forests
Vaglio Laurin , Gaia , Puletti , Nicola , Chen , Qi , Corona , P. , Papale , Dario , Valentini , Riccardo
lidar biomass species richness carbon monitoring tropical forests west africa
Mostra abstract
Estimates of forest aboveground biomass are fundamental for carbon monitoring and accounting; delivering information at very high spatial resolution is especially valuable for local management, conservation and selective logging purposes. In tropical areas, hosting large biomass and biodiversity resources which are often threatened by unsustainable anthropogenic pressures, frequent forest resources monitoring is needed. Lidar is a powerful tool to estimate aboveground biomass at fine resolution; however its application in tropical forests has been limited, with high variability in the accuracy of results. Lidar pulses scan the forest vertical profile, and can provide structure information which is also linked to biodiversity. In the last decade the remote sensing of biodiversity has received great attention, but few studies focused on the use of lidar for assessing tree species richness in tropical forests. This research aims at estimating aboveground biomass and tree species richness using discrete return airborne lidar in Ghana forests. We tested an advanced statistical technique, Multivariate Adaptive Regression Splines (MARS), which does not require assumptions on data distribution or on the relationships between variables, being suitable for studying ecological variables. We compared the MARS regression results with those obtained by multilinear regression and found that both algorithms were effective, but MARS provided higher accuracy either for biomass (R<sup>2</sup> = 0.72) and species richness (R<sup>2</sup> = 0.64). We also noted strong correlation between biodiversity and biomass field values. Even if the forest areas under analysis are limited in extent and represent peculiar ecosystems, the preliminary indications produced by our study suggest that instrument such as lidar, specifically useful for pinpointing forest structure, can also be exploited as a support for tree species richness assessment. © 2016 Elsevier B.V.
🔗 Vai alla pubblicazione
2016
Rivista
International Journal of Applied Earth Observation and Geoinformation
Dettagli
Vol. 52 pp. 371 - 379
DOI
Discrimination of tropical forest types, dominant species, and mapping of functional guilds by hyperspectral and simulated multispectral Sentinel-2 data
Vaglio Laurin , Gaia , Puletti , Nicola , Hawthorne , William D. , Liesenberg , Veraldo , Corona , P. , Papale , Dario , Chen , Qi , Valentini , Riccardo
forest sentinel-2 dominant species forest type functional composition guilds hyperspectral tropical
Mostra abstract
To answer new scientific and ecological questions and monitor multiple forest changes, a fine scale characterization of these ecosystems is needed, and could imply the mapping of specific species, of detailed forest types, and of functional composition. This characterization can be now provided by the novel Earth Observation tools. This study aims to contribute to understanding the innovation in forest and ecological research that can be brought in by advanced remote sensing instruments, and proposes the guild mapping approach as a tool to efficiently monitor the varied tropical forest resources. We evaluated, in tropical Ghanaian forests, the ability of airborne hyperspectral and simulated multispectral Sentinel-2 data, and derived vegetation indices and textures, to: distinguish between two different forest types; to discriminate among selected dominant species; and to separate trees species grouped according to their functional guilds: Pioneer, Non Pioneer Light Demanding, and Shade Bearer. We then produced guild classification maps for each area using hyperspectral data. Our results showed that with both hyperspectral and simulated Sentinel-2 data these discrimination tasks can be successfully accomplished. Results also stressed the importance of texture features, especially if using the lower spectral and spatial Sentinel-2 resolution data, and highlighted the important role of the new Sentinel-2 data for ecological monitoring. Classification results showed a statistically significant improvement in overall accuracy using Support Vector Machine, over Maximum Likelihood approach. We proposed the functional guilds mapping as an innovative approach to: (i) monitor compositional changes, especially with respect to the effects of global climate change on forests, and particularly in the tropical biome where the occurrence of hundreds of species prevents mapping activities at species level; (ii) support large-scale forest inventories. The imminent Sentinel-2 data could serve to open the road for the development of new concepts and methods in forestry and ecological research. © 2016 Elsevier Inc.
🔗 Vai alla pubblicazione
2016
Rivista
Remote Sensing of Environment
Dettagli
Vol. 176 pp. 163 - 176
DOI
Continental Contrasts in Climate Extremes That Control Tree Fecundity
Clark , James S. , Andrus , Robert A. , Arianoutsou , Margarita , Ascoli , Davide , Bergeron , Yves , Bogdziewicz , Michał , Boivin , Thomas , Bonal , Raúl , Caignard , Thomas , Cailleret , Maxime , Calama , Rafael A. , Camarero , Jesús Julio , Chianucci , Francesco , Cienciala , Emil , Courbaud , Benoít , Delzon , Sylvain , Dietze , Michael C. , Espelta , Josep Maria , Fady , Bruno , Fyllas , Nikolaos M. , Gilbert , Gregory S. , Gratzer , Georg , Guignabert , Arthur , Hacket-Pain , Andrew J. , Hampe , Arndt , Hanley , Mick E. , Hille Ris Lambers , Janneke , Holik , Jan , Hoshizaki , K. , Hu , Miao , Ibáñez , Inés , Işık , Fatih , Jenkins , Lauren , Johnstone , Jill F. , Journé , Valentin , Kadioglu , Alper Kaan , Kızılaslan , İrem Sena , Knops , Johannes Michael Hubertus , Kobe , Richard K. , Köse , Nesibe , Külah , Eylül U. , Kunstler , Georges , LaMontagne , Jalene M. , Ledwoń , Mateusz , Lehtonen , Aleksi , Loewe-Muñoz , Verónica F. , Lutz , James A. , Mårell , Anders , Meyer , Kira , Moran , Emily V. , Motta , Renzo , Myers , Jonathan A. , Nagel , Thomas A. , Pérez-Ramos , Ignacio M. , Piechnik , Łukasz , Podgórski , Tomasz , Poulton-Kamakura , Renata , Qiu , Tong , Redmond , Miranda D. , Reid , Chantal D. , Rodman , Kyle C. , Rodríguez-Sánchez , Francisco , Šamonil , Pavel , Šebeň , Vladimír , Seget , Barbara , Sharma , Shubhi , Socha , Jarosław Ł. , Steele , Michael A. , Straub , Jacob N. , Sutton , Samantha , Thomas , Peter A. , Vacchiano , Giorgio , Venner , Marie Claude , Venner , Samuel , Zavala , Miguel A. , Zheng , Shiqi , Żywiec , Magdalena
drought climate extremes forest recovery late freeze
Mostra abstract
In 2023, more than half of olive harvests (Olea europaea) across Spain, Greece, and Türkiye were lost to drought. The same year late freeze destroyed 90% of the peach crop (Prunus persica) on the Georgia Piedmont and the apple crop (Malus domestica) in central New York, Vermont, and southern Quebec. Climate extremes now rank with the costliest threats to agriculture, but their role in forest recovery from diebacks that are happening globally is unknown for lack of tree fecundity estimates in forests. Tolerance of climate extremes could depend on past exposure but constrained by phylogenetic conservatism. We report a continental scale analysis of climate extremes and forest fecundity across North America and Europe showing that responses to late freeze and drought are happening now. Species differences are not explained by the traits typically included in ecological studies and they are weakly associated with phylogeny. Late freeze, that is, freezing temperatures that follow the onset of flower development in spring, is shown to be “normal” in North America, but not Europe, potentially explaining failed seed production due to delayed onset and the resultant shorter growing period by North American transplants dating back at least to the 18th century. Drought has thus far had the greatest impacts in dry forested regions, but here too, species differences are not explained by traditional trait values. If responses have been buffered from drought and late freeze by past exposure, acclimation and local adaptation prove inadequate as extremes intensify. © 2026 John Wiley & Sons Ltd.
🔗 Vai alla pubblicazione
2026
Rivista
Global Change Biology
Dettagli
Vol. 32 (2)
DOI
The Relationship Between Maturation Size and Maximum Tree Size From Tropical to Boreal Climates
Journé , Valentin , Bogdziewicz , Michał , Courbaud , Benoít , Kunstler , Georges , Qiu , Tong , Aravena Acuña , Marie Claire , Ascoli , Davide , Bergeron , Yves , Berveiller , Daniel , Boivin , Thomas , Bonal , Raúl , Caignard , Thomas , Cailleret , Maxime , Calama , Rafael A. , Camarero , Jesús Julio , Chang-Yang , Chia Hao , Chave , Jérôme , Chianucci , Francesco , Curt , Thomas , Cutini , Andrea , Das , Adrian J. , Daskalakou , Evangelia N. , Davi , Hendrik , Delpierre , Nicolas , Delzon , Sylvain , Dietze , Michael C. , Calderon , Sergio Donoso , Dormont , Laurent , Espelta , Josep Maria , Farfan-Rios , William R. , Fenner , Michael , Franklin , Jerry F. , Gehring , Catherine A. , Gilbert , Gregory S. , Gratzer , Georg , Greenberg , Cathryn H. , Guignabert , Arthur , Guo , Qinfeng , Hacket-Pain , Andrew J. , Hampe , Arndt , Han , Qingmin , Hanley , Mick E. , Hille Ris Lambers , Janneke , Holik , Jan , Hoshizaki , K. , Ibáñez , Inés , Johnstone , Jill F. , Knops , Johannes Michael Hubertus , Kobe , Richard K. , Kurokawa , Hiroko , Lageard , Jonathan G.A. , LaMontagne , Jalene M. , Ledwoń , Mateusz , Lefèvre , François , Leininger , Theodor D. , Limousin , Jean Marc , Lutz , James A. , Macias , Diana S. , Mårell , Anders , McIntire , Eliot J.B. , Moran , Emily V. , Motta , Renzo , Myers , Jonathan A. , Nagel , Thomas A. , Naoe , Shoji , Noguchi , Mahoko , Norghauer , Julian M. , Oguro , Michio , Ourcival , Jean Marc , Parmenter , Robert R. , Pearse , Ian S. , Pérez-Ramos , Ignacio M. , Piechnik , Łukasz , Podgórski , Tomasz , Poulsen , John R. , Redmond , Miranda D. , Reid , Chantal D. , Šamonil , Pavel , Scher , C. Lane , Schlesinger , William H. , Seget , Barbara , Sharma , Shubhi , Shibata , Mitsue , Silman , Miles R. , Steele , Michael A. , Stephenson , Nathan L. , Straub , Jacob N. , Sutton , Samantha , Swenson , Jennifer J. , Swift , Margaret , Thomas , Peter A. , Uríarte , María , Vacchiano , Giorgio , Whipple , Amy Vaughn , Whitham , Thomas G. , Wright , Stuart Joseph , Zhu , Kai , Zimmerman , Jess K. , Żywiec , Magdalena , Clark , James S.
seed production allometry life history size tree fecundity tree maturation
Mostra abstract
The fundamental trade-off between current and future reproduction has long been considered to result in a tendency for species that can grow large to begin reproduction at a larger size. Due to the prolonged time required to reach maturity, estimates of tree maturation size remain very rare and we lack a global view on the generality and the shape of this trade-off. Using seed production from five continents, we estimate tree maturation sizes for 486 tree species spanning tropical to boreal climates. Results show that a species' maturation size increases with maximum size, but in a non-proportional way: the largest species begin reproduction at smaller sizes than would be expected if maturation were simply proportional to maximum size. Furthermore, the decrease in relative maturation size is steepest in cold climates. These findings on maturation size drivers are key to accurately represent forests' responses to disturbance and climate change. © 2024 John Wiley & Sons Ltd.
🔗 Vai alla pubblicazione
2024
Rivista
Ecology Letters
Dettagli
Vol. 27 (9)
DOI
Evolutionary ecology of masting: mechanisms, models, and climate change
Bogdziewicz , Michał , Kelly , Dave J. , Ascoli , Davide , Caignard , Thomas , Chianucci , Francesco , Crone , Elizabeth E. , Fleurot , Emilie , Foest , Jessie J. , Gratzer , Georg , Hagiwara , Tomika , Han , Qingmin , Journé , Valentin , Keurinck , Léa , Kondrat , Katarzyna , McClory , Ryan W. , LaMontagne , Jalene M. , Mundo , Ignacio A. , Nussbaumer , Anita , Oberklammer , Iris , Ohno , Misuzu , Pearse , Ian S. , Pesendorfer , Mario B. , Resente , Giulia , Satake , Akiko , Shibata , Mitsue , Snell , Rebecca S. , Szymkowiak , Jakub , Touzot , Laura , Zwolak , Rafał , Żywiec , Magdalena , Hacket-Pain , Andrew J.
climate change economies of scale environmental prediction plant demography plant reproduction
Mostra abstract
Many perennial plants show mast seeding, characterized by synchronous and highly variable reproduction across years. We propose a general model of masting, integrating proximate factors (environmental variation, weather cues, and resource budgets) with ultimate drivers (predator satiation and pollination efficiency). This general model shows how the relationships between masting and weather shape the diverse responses of species to climate warming, ranging from no change to lower interannual variation or reproductive failure. The role of environmental prediction as a masting driver is being reassessed; future studies need to estimate prediction accuracy and the benefits acquired. Since reproduction is central to plant adaptation to climate change, understanding how masting adapts to shifting environmental conditions is now a central question. © 2024 The Authors
🔗 Vai alla pubblicazione
2024
Rivista
Trends in Ecology and Evolution
Dettagli
Vol. 39 (9) pp. 851 - 862
DOI
Masting is uncommon in trees that depend on mutualist dispersers in the context of global climate and fertility gradients
Qiu , Tong , Aravena Acuña , Marie Claire , Ascoli , Davide , Bergeron , Yves , Bogdziewicz , Michał , Boivin , Thomas , Bonal , Raúl , Caignard , Thomas , Cailleret , Maxime , Calama , Rafael A. , Calderon , Sergio Donoso , Camarero , Jesús Julio , Chang-Yang , Chia Hao , Chave , Jérôme , Chianucci , Francesco , Courbaud , Benoít , Cutini , Andrea , Das , Adrian J. , Delpierre , Nicolas , Delzon , Sylvain , Dietze , Michael C. , Dormont , Laurent , Espelta , Josep Maria , Fahey , Timothy J. , Farfan-Rios , William R. , Franklin , Jerry F. , Gehring , Catherine A. , Gilbert , Gregory S. , Gratzer , Georg , Greenberg , Cathryn H. , Guignabert , Arthur , Guo , Qinfeng , Hacket-Pain , Andrew J. , Hampe , Arndt , Han , Qingmin , Holik , Jan , Hoshizaki , K. , Ibáñez , Inés , Johnstone , Jill F. , Journé , Valentin , Kitzberger , Thomas A. , Knops , Johannes Michael Hubertus , Kunstler , Georges , Kurokawa , Hiroko , Lageard , Jonathan G.A. , LaMontagne , Jalene M. , Lefèvre , François , Leininger , Theodor D. , Limousin , Jean Marc , Lutz , James A. , Macias , Diana S. , Mårell , Anders , McIntire , Eliot J.B. , Moore , Christopher M. , Moran , Emily V. , Motta , Renzo , Myers , Jonathan A. , Nagel , Thomas A. , Naoe , Shoji , Noguchi , Mahoko , Oguro , Michio , Parmenter , Robert R. , Pearse , Ian S. , Pérez-Ramos , Ignacio M. , Piechnik , Łukasz , Podgórski , Tomasz , Poulsen , John R. , Redmond , Miranda D. , Reid , Chantal D. , Rodman , Kyle C. , Rodríguez-Sánchez , Francisco , Šamonil , Pavel , Sanguinetti , Javier D. , Scher , C. Lane , Seget , Barbara , Sharma , Shubhi , Shibata , Mitsue , Silman , Miles R. , Steele , Michael A. , Stephenson , Nathan L. , Straub , Jacob N. , Sutton , Samantha , Swenson , Jennifer J. , Swift , Margaret , Thomas , Peter A. , Uríarte , María , Vacchiano , Giorgio , Whipple , Amy Vaughn , Whitham , Thomas G. , Wion , Andreas P. , Wright , Stuart Joseph , Zhu , Kai , Zimmerman , Jess K. , Żywiec , Magdalena , Clark , James S.
plant seed seeds tree trees reproduction fertility satiety satiation
Mostra abstract
The benefits of masting (volatile, quasi-synchronous seed production at lagged intervals) include satiation of seed predators, but these benefits come with a cost to mutualist pollen and seed dispersers. If the evolution of masting represents a balance between these benefits and costs, we expect mast avoidance in species that are heavily reliant on mutualist dispersers. These effects play out in the context of variable climate and site fertility among species that vary widely in nutrient demand. Meta-analyses of published data have focused on variation at the population scale, thus omitting periodicity within trees and synchronicity between trees. From raw data on 12 million tree-years worldwide, we quantified three components of masting that have not previously been analysed together: (i) volatility, defined as the frequency-weighted year-to-year variation; (ii) periodicity, representing the lag between high-seed years; and (iii) synchronicity, indicating the tree-to-tree correlation. Results show that mast avoidance (low volatility and low synchronicity) by species dependent on mutualist dispersers explains more variation than any other effect. Nutrient-demanding species have low volatility, and species that are most common on nutrient-rich and warm/wet sites exhibit short periods. The prevalence of masting in cold/dry sites coincides with climatic conditions where dependence on vertebrate dispersers is less common than in the wet tropics. Mutualist dispersers neutralize the benefits of masting for predator satiation, further balancing the effects of climate, site fertility and nutrient demands. © 2023, The Author(s), under exclusive licence to Springer Nature Limited.
🔗 Vai alla pubblicazione
2023
Rivista
Nature Plants
Dettagli
Vol. 9 (7) pp. 1044 - 1056
DOI
Review of ground and aerial methods for vegetation cover fraction (fCover) and related quantities estimation: definitions, advances, challenges, and future perspectives
Li , Linyuan , Mu , Xihan , Jiang , Hailan , Chianucci , Francesco , Hu , Ronghai , Song , Wanjuan , Qi , Jianbo , Liu , Shouyang , Zhou , Jiaxin , Chen , Ling , Huang , Huaguo , Yan , Guangjian
airborne remote sensing fcover ground measurements image and lidar unmanned aerial vehicle (uav) “cover” attribute
Mostra abstract
Vegetation cover fraction (fCover) and related quantities are basic yet critical vegetation structure variables in various disciplines and applications. Ground- and aerial-based proximal and remote sensing techniques have been widely adapted across multiple spatial extents. However, the definitions of fCover-related nomenclatures have not yet been fully standardized, leading to confusing terms and making comparing historic measures difficult. With the issues potentially arising from an increasing diversity of fCover and related quantities estimation methods and corresponding uncertainties, there is also a growing need to spread knowledge on the current advances, challenges, and perspectives, especially in the context of no such existing review for ground- and aerial- based estimation. This paper provides the current knowledge mainly concerning passive image-based methods and active light detection and ranging (LiDAR) -based methods. We first harmonized the definitions of fCover and its related quantities (e.g., effective canopy cover, crown cover, stratified vegetation cover, and canopy fraction). Secondly, the typical applications of fCover and related quantities over a range of scales, fields, and ecosystems were summarized. Thirdly yet importantly, we offered a comprehensive review of traditional non-imaging methods, image-based methods (e.g., segmentation, unmixing, and spectral retrieval), point cloud-based methods (e.g., rasterization), and LiDAR return-based methods (e.g., return number index and return intensity retrieval) across different platforms (i.e., ground, unmanned aerial vehicle (UAV) and airplane). Our investigation of fCover and related quantities estimation touches upon various vegetation ecosystems, including agriculture cropland, grassland, wetland, and forest. Finally, the current challenges and future directions were discussed, such as image signal processing under complex heterogeneous surfaces and stratified cover and non-photosynthesis cover retrieval. We, therefore, expect that this review may offer an insight into fCover and related quantities estimation and serve as a reference for remote sensing scientists, agronomists, silviculturists, and ecologists. © 2023 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS)
🔗 Vai alla pubblicazione
2023
Rivista
ISPRS Journal of Photogrammetry and Remote Sensing
Dettagli
Vol. 199 pp. 133 - 156
DOI
Linking seed size and number to trait syndromes in trees
Bogdziewicz , Michał , Aravena Acuña , Marie Claire , Andrus , Robert A. , Ascoli , Davide , Bergeron , Yves , Brveiller , Daniel , Boivin , Thomas , Bonal , Raúl , Caignard , Thomas , Cailleret , Maxime , Calama , Rafael A. , Calderon , Sergio Donoso , Camarero , Jesús Julio , Chang-Yang , Chia Hao , Chave , Jérôme , Chianucci , Francesco , Cleavitt , Natalie L. , Courbaud , Benoít , Cutini , Andrea , Curt , Thomas , Das , Adrian J. , Davi , Hendrik , Delpierre , Nicolas , Delzon , Sylvain , Dietze , Michael C. , Dormont , Laurent , Farfan-Rios , William R. , Gehring , Catherine A. , Gilbert , Gregory S. , Gratzer , Georg , Greenberg , Cathryn H. , Guignabert , Arthur , Guo , Qinfeng , Hacket-Pain , Andrew J. , Hampe , Arndt , Han , Qingmin , Hoshizaki , K. , Ibáñez , Inés , Johnstone , Jill F. , Journé , Valentin , Kitzberger , Thomas A. , Knops , Johannes Michael Hubertus , Kunstler , Georges , Kobe , Richard K. , Lageard , Jonathan G.A. , LaMontagne , Jalene M. , Ledwoń , Mateusz , Leininger , Theodor D. , Limousin , Jean Marc , Lutz , James A. , Macias , Diana S. , Mårell , Anders , McIntire , Eliot J.B. , Moran , Emily V. , Motta , Renzo , Myers , Jonathan A. , Nagel , Thomas A. , Naoe , Shoji , Noguchi , Mahoko , Oguro , Michio , Kurokawa , Hiroko , Ourcival , Jean Marc , Parmenter , Robert R. , Pérez-Ramos , Ignacio M. , Piechnik , Łukasz , Podgórski , Tomasz , Poulsen , John R. , Qiu , Tong , Redmond , Miranda D. , Reid , Chantal D. , Rodman , Kyle C. , Šamonil , Pavel , Holik , Jan , Scher , C. Lane , van Marle , Harald Schmidt , Seget , Barbara , Shibata , Mitsue , Sharma , Shubhi , Silman , Miles R. , Steele , Michael A. , Straub , Jacob N. , Sun , I. Fang , Sutton , Samantha , Swenson , Jennifer J. , Thomas , Peter A. , Uríarte , María , Vacchiano , Giorgio , Veblen , Thomas Thorstein , Wright , Boyd R. , Wright , Stuart Joseph , Whitham , Thomas G. , Zhu , Kai , Zimmerman , Jess K. , Żywiec , Magdalena , Clark , James S.
fecundity functional traits leaf economics life history strategies size syndrome tree recruitment
Mostra abstract
Aim: Our understanding of the mechanisms that maintain forest diversity under changing climate can benefit from knowledge about traits that are closely linked to fitness. We tested whether the link between traits and seed number and seed size is consistent with two hypotheses, termed the leaf economics spectrum and the plant size syndrome, or whether reproduction represents an independent dimension related to a seed size–seed number trade-off. Location: Most of the data come from Europe, North and Central America and East Asia. A minority of the data come from South America, Africa and Australia. Time period: 1960–2022. Major taxa studied: Trees. Methods: We gathered 12 million observations of the number of seeds produced in 784 tree species. We estimated the number of seeds produced by individual trees and scaled it up to the species level. Next, we used principal components analysis and generalized joint attribute modelling (GJAM) to map seed number and size on the tree traits spectrum. Results: Incorporating seed size and number into trait analysis while controlling for environment and phylogeny with GJAM exposes relationships in trees that might otherwise remain hidden. Production of the large total biomass of seeds [product of seed number and seed size; hereafter, species seed productivity (SSP)] is associated with high leaf area, low foliar nitrogen, low specific leaf area (SLA) and dense wood. Production of high seed numbers is associated with small seeds produced by nutrient-demanding species with softwood, small leaves and high SLA. Trait covariation is consistent with opposing strategies: one fast-growing, early successional, with high dispersal, and the other slow-growing, stress-tolerant, that recruit in shaded conditions. Main conclusions: Earth system models currently assume that reproductive allocation is indifferent among plant functional types. Easily measurable seed size is a strong predictor of the seed number and species seed productivity. The connection of SSP with the functional traits can form the first basis of improved fecundity prediction across global forests. © 2023 John Wiley & Sons Ltd.
🔗 Vai alla pubblicazione
2023
Rivista
Global Ecology and Biogeography
Dettagli
Vol. 32 (5) pp. 683 - 694
DOI
Ultrahigh-resolution boreal forest canopy mapping: Combining UAV imagery and photogrammetric point clouds in a deep-learning-based approach
Li , Linyuan , Mu , Xihan , Chianucci , Francesco , Qi , Jianbo , Jiang , Jingyi , Zhou , Jiaxin , Chen , Ling , Huang , Huaguo , Yan , Guangjian , Liu , Shouyang
crown cover canopy mapping image overlap self-supervised deep learning sfm point cloud uav imagery
Mostra abstract
Accurate wall-to-wall estimation of forest crown cover is critical for a wide range of ecological studies. Notwithstanding the increasing use of UAVs in forest canopy mapping, the ultrahigh-resolution UAV imagery requires an appropriate procedure to separate the contribution of understorey from overstorey vegetation, which is complicated by the spectral similarity between the two forest components and the illumination environment. In this study, we investigated the integration of deep learning and the combined data of imagery and photogrammetric point clouds for boreal forest canopy mapping. The procedure enables the automatic creation of training sets of tree crown (overstorey) and background (understorey) data via the combination of UAV images and their associated photogrammetric point clouds and expands the applicability of deep learning models with self-supervision. Based on the UAV images with different overlap levels of 12 conifer forest plots that are categorized into “I”, “II” and “III” complexity levels according to illumination environment, we compared the self-supervised deep learning-predicted canopy maps from original images with manual delineation data and found an average intersection of union (IoU) larger than 0.9 for “complexity I” and “complexity II” plots and larger than 0.75 for “complexity III” plots. The proposed method was then compared with three classical image segmentation methods (i.e., maximum likelihood, Kmeans, and Otsu) in the plot-level crown cover estimation, showing outperformance in overstorey canopy extraction against other methods. The proposed method was also validated against wall-to-wall and pointwise crown cover estimates using UAV LiDAR and in situ digital cover photography (DCP) benchmarking methods. The results showed that the model-predicted crown cover was in line with the UAV LiDAR method (RMSE of 0.06) and deviate from the DCP method (RMSE of 0.18). We subsequently compared the new method and the commonly used UAV structure-from-motion (SfM) method at varying forward and lateral overlaps over all plots and a rugged terrain region, yielding results showing that the method-predicted crown cover was relatively insensitive to varying overlap (largest bias of less than 0.15), whereas the UAV SfM-estimated crown cover was seriously affected by overlap and decreased with decreasing overlap. In addition, canopy mapping over rugged terrain verified the merits of the new method, with no need for a detailed digital terrain model (DTM). The new method is recommended to be used in various image overlaps, illuminations, and terrains due to its robustness and high accuracy. This study offers opportunities to promote forest ecological applications (e.g., leaf area index estimation) and sustainable management (e.g., deforestation). © 2022 The Author(s)
🔗 Vai alla pubblicazione
2022
Rivista
International Journal of Applied Earth Observation and Geoinformation
Dettagli
Vol. 107
DOI