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Author Aubry-Kientz, Mélaine ; Laybros, Anthony ; Weinstein, Ben ; Ball, James G. C. ; Jackson, Toby ; Coomes, David ; Vincent, Grégoire
Title Multisensor data fusion for improved segmentation of individual tree crowns in dense tropical forests Type Journal Article
Year 2021 Publication IEEE Journal of Selected topics in Applied Earth Observations and Remote Sensing Abbreviated Journal
Volume (up) 14 Issue Pages 3927-3936
Keywords
Abstract Automatic tree crown segmentation from remote sensing data is especially challenging in dense, diverse, and multilayered tropical forest canopies, and tracking mortality by this approach is even more difficult. Here, we examine the potential for combining airborne laser scanning (ALS) with multispectral and hyperspectral data to improve the accuracy of tree crown segmentation at a study site in French Guiana. We combined an ALS point cloud clustering method with a spectral deep learning model to achieve 83% accuracy at recognizing manually segmented reference crowns (with congruence >0.5). This method outperformed a two-step process that involved clustering the ALS point cloud and then using the logistic regression of hyperspectral distances to correct oversegmentation. We used this approach to map tree mortality from repeat surveys and show that the number of crowns identified in the first that intersected with height loss clusters was a good estimator of the number of dead trees in these areas. Our results demonstrate that multisensor data fusion improves the automatic segmentation of individual tree crowns and presents a promising avenue to study forest demography with repeated remote sensing acquisitions.
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Publisher IEEE Place of Publication Editor
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Call Number EcoFoG @ webmaster @ Serial 1008
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Author Leponce, Maurice ; Dejean, Alain ; Mottl, Ondrej ; Klimes, Petr
Title Rapid assessment of the three-dimensional distribution of dominant arboreal ants in tropical forests Type Journal Article
Year 2021 Publication Insect Conservation and Diversity Abbreviated Journal
Volume (up) 14 Issue 4 Pages 426-438
Keywords
Abstract Ants are omnipresent in tropical forests, especially territorially dominant arboreal ants whose territories are spatially segregated forming ‘ant mosaics’. These ecologically important species are rarely used in conservation monitoring because of the difficulty in collecting them. We developed a standardised baitline protocol to study the distribution of dominant ants on canopy trees and also a procedure to objectively define species dominance, even in unknown ant assemblages.
Besides eliminating the need to climb trees, this protocol allows live arboreal ant specimens to be sampled at different heights. Behavioural aggressiveness assays between the collected workers provide data on the three-dimensional distribution of colonies and on interactions between species. We compared the results of the behavioural tests to those from null models.
In the New Guinean lowland forest studied, we show that the canopy was either shared by multiple territorial species or inhabited by a single species with a large territory. The baitline protocol collected up to half of the arboreal ant species found in a felling census. However, the proportion of species collected at baits decreased with the increasing spatial dominance of single territorial species.
Behavioural observations used in the protocol allowed a more efficient detection of ant mosaics than null models. Territorially dominant ants were active on both understorey and canopy trees.
The protocol is fast and easy to replicate. It is a potential tool for understanding and monitoring the spatiotemporal dynamics of arboreal ant assemblages and can detect populous colonies, including those of invasive species
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Corporate Author Thesis
Publisher Royal Entomological Society Place of Publication Editor
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Call Number EcoFoG @ webmaster @ Serial 1047
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Author Harper, Anna B. ; Williams, Karina E. ; McGuire, Patrick ; Duran Rojas, Maria Carolina ; Hemming, Debbie ; Verhoef, Anne ; Huntingford, Chris ; Rowland, Lucy ; Marthews, Toby ; Breder Eller, Cleiton ; Mathison, Camilla ; Nobrega, Rodolfo L.B. ; Gedney, Nicola ; Vidale, Pier Luigi ; Otu-Larbi, Fred ; Pandey, Divya
Title Improvement of modeling plant responses to low soil moisture in JULESvn4.9 and evaluation against flux tower measurements Type Journal Article
Year 2021 Publication Geoscientific Model Development Abbreviated Journal
Volume (up) 14 Issue 6 Pages 3269-3294
Keywords
Abstract Drought is predicted to increase in the future due to climate change, bringing with it myriad impacts on ecosystems. Plants respond to drier soils by reducing stomatal conductance in order to conserve water and avoid hydraulic damage. Despite the importance of plant drought responses for the global carbon cycle and local and regional climate feedbacks, land surface models are unable to capture observed plant responses to soil moisture stress. We assessed the impact of soil moisture stress on simulated gross primary productivity (GPP) and latent energy flux (LE) in the Joint UK Land Environment Simulator (JULES) vn4.9 on seasonal and annual timescales and evaluated 10 different representations of soil moisture stress in the model. For the default configuration, GPP was more realistic in temperate biome sites than in the tropics or high-latitude (cold-region) sites, while LE was best simulated in temperate and high-latitude (cold) sites. Errors that were not due to soil moisture stress, possibly linked to phenology, contributed to model biases for GPP in tropical savanna and deciduous forest sites. We found that three alternative approaches to calculating soil moisture stress produced more realistic results than the default parameterization for most biomes and climates. All of these involved increasing the number of soil layers from 4 to 14 and the soil depth from 3.0 to 10.8 m. In addition, we found improvements when soil matric potential replaced volumetric water content in the stress equation (the “soil14psi” experiments), when the critical threshold value for inducing soil moisture stress was reduced (“soil14p0”), and when plants were able to access soil moisture in deeper soil layers (“soil14_dr*2”). For LE, the biases were highest in the default configuration in temperate mixed forests, with overestimation occurring during most of the year. At these sites, reducing soil moisture stress (with the new parameterizations mentioned above) increased LE and increased model biases but improved the simulated seasonal cycle and brought the monthly variance closer to the measured variance of LE. Further evaluation of the reason for the high bias in LE at many of the sites would enable improvements in both carbon and energy fluxes with new parameterizations for soil moisture stress. Increasing the soil depth and plant access to deep soil moisture improved many aspects of the simulations, and we recommend these settings in future work using JULES or as a general way to improve land surface carbon and water fluxes in other models. In addition, using soil matric potential presents the opportunity to include plant functional type-specific parameters to further improve modeled fluxes.
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Publisher European Geosciences Union Place of Publication Editor
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Call Number EcoFoG @ webmaster @ Serial 1057
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Author Fisher, J.B.; Malhi, Y.; Bonal, D.; Da Rocha, H.R.; De Araujo, A.C.; Gamo, M.; Goulden, M.L.; Hirano, T.; Huete, A.R.; Kondo, H.; Kumagai, T.; Loescher, H.W.; Miller, S.; Nobre, A.D.; Nouvellon, Y.; Oberbauer, S.F.; Panuthai, S.; Roupsard, O.; Saleska, S.; Tanaka, K.; Tanaka, N.; Tu, K.P.; Von Randow, C.
Title The land-atmosphere water flux in the tropics Type Journal Article
Year 2009 Publication Global Change Biology Abbreviated Journal Glob. Change Biol.
Volume (up) 15 Issue 11 Pages 2694-2714
Keywords Amazon; eddy covariance; evaporation; evapotranspiration; ISLSCP-II; LBA; model; remote sensing; tropical
Abstract Tropical vegetation is a major source of global land surface evapotranspiration, and can thus play a major role in global hydrological cycles and global atmospheric circulation. Accurate prediction of tropical evapotranspiration is critical to our understanding of these processes under changing climate. We examined the controls on evapotranspiration in tropical vegetation at 21 pan-tropical eddy covariance sites, conducted a comprehensive and systematic evaluation of 13 evapotranspiration models at these sites, and assessed the ability to scale up model estimates of evapotranspiration for the test region of Amazonia. Net radiation was the strongest determinant of evapotranspiration (mean evaporative fraction was 0.72) and explained 87% of the variance in monthly evapotranspiration across the sites. Vapor pressure deficit was the strongest residual predictor (14%), followed by normalized difference vegetation index (9%), precipitation (6%) and wind speed (4%). The radiation-based evapotranspiration models performed best overall for three reasons: (1) the vegetation was largely decoupled from atmospheric turbulent transfer (calculated from X decoupling factor), especially at the wetter sites; (2) the resistance-based models were hindered by difficulty in consistently characterizing canopy (and stomatal) resistance in the highly diverse vegetation; (3) the temperature-based models inadequately captured the variability in tropical evapotranspiration. We evaluated the potential to predict regional evapotranspiration for one test region: Amazonia. We estimated an Amazonia-wide evapotranspiration of 1370 mm yr(-1), but this value is dependent on assumptions about energy balance closure for the tropical eddy covariance sites; a lower value (1096 mm yr(-1)) is considered in discussion on the use of flux data to validate and interpolate models.
Address [Fisher, Joshua B.; Malhi, Yadvinder] Univ Oxford, Environm Change Inst, Sch Geog & Environm, Oxford OX1 3QY, England, Email: joshbfisher@gmail.com
Corporate Author Thesis
Publisher WILEY-BLACKWELL PUBLISHING, INC Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1354-1013 ISBN Medium
Area Expedition Conference
Notes ISI:000270662000011 Approved no
Call Number EcoFoG @ eric.marcon @ Serial 101
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Author Malhi, Y.; Aragao, L.E.O.C.; Metcalfe, D.B.; Paiva, R.; Quesada, C.A.; Almeida, S.; Anderson, L.; Brando, P.; Chambers, J.Q.; da Costa, A.C.L.; Hutyra, L.R.; Oliveira, P.; Patino, S.; Pyle, E.H.; Robertson, A.L.; Teixeira, L.M.
Title Comprehensive assessment of carbon productivity, allocation and storage in three Amazonian forests Type Journal Article
Year 2009 Publication Global Change Biology Abbreviated Journal Glob. Change Biol.
Volume (up) 15 Issue 5 Pages 1255-1274
Keywords allocation; Amazonia; carbon; growth; litterfall; productivity; respiration; roots; soil; tropical forest
Abstract The allocation and cycling of carbon (C) within forests is an important component of the biospheric C cycle, but is particularly understudied within tropical forests. We synthesise reported and unpublished results from three lowland rainforest sites in Amazonia (in the regions of Manaus, Tapajos and Caxiuana), all major sites of the Large-Scale Biosphere-Atmosphere Programme (LBA). We attempt a comprehensive synthesis of the C stocks, nutrient status and, particularly, the allocation and internal C dynamics of all three sites. The calculated net primary productivities (NPP) are 10.1 +/- 1.4 Mg C ha(-1) yr(-1) (Manaus), 14.4 +/- 1.3 Mg C ha(-1) yr(-1) (Tapajos) and 10.0 +/- 1.2 Mg C ha(-1) yr(-1) (Caxiuana). All errors bars report standard errors. Soil and leaf nutrient analyses indicate that Tapajos has significantly more plant-available phosphorus and calcium. Autotrophic respiration at all three sites (14.9-21.4 Mg C ha yr(-1)) is more challenging to measure, with the largest component and greatest source of uncertainty being leaf dark respiration. Comparison of measured soil respiration with that predicted from C cycling measurements provides an independent constraint. It shows general good agreement at all three sites, with perhaps some evidence for measured soil respiration being less than expected. Twenty to thirty percent of fixed C is allocated belowground. Comparison of gross primary productivity (GPP), derived from ecosystem flux measurements with that derived from component studies (NPP plus autotrophic respiration) provides an additional crosscheck. The two approaches are in good agreement, giving increased confidence in both approaches to estimating GPP. The ecosystem carbon-use efficiency (CUEs), the ratio of NPP to GPP, is similar at Manaus (0.34 +/- 0.10) and Caxiuana (0.32 +/- 0.07), but may be higher at Tapajos (0.49 +/- 0.16), although the difference is not significant. Old growth or infertile tropical forests may have low CUE compared with recently disturbed and/or fertile forests.
Address [Malhi, Yadvinder; Aragao, Luiz Eduardo O. C.; Metcalfe, Daniel B.; Anderson, Liana] Sch Geog & Environm, Environm Change Inst, Oxford OX1 3QY, England, Email: yadvinder.malhi@ouce.ox.ac.uk
Corporate Author Thesis
Publisher WILEY-BLACKWELL PUBLISHING, INC Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1354-1013 ISBN Medium
Area Expedition Conference
Notes ISI:000265033700015 Approved no
Call Number EcoFoG @ eric.marcon @ Serial 117
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Author Duminil, J.; Caron, H.; Scotti, I.; Cazal, S.O.; Petit, R.J.
Title Blind population genetics survey of tropical rainforest trees Type Journal Article
Year 2006 Publication Molecular Ecology Abbreviated Journal Mol. Ecol.
Volume (up) 15 Issue 12 Pages 3505-3513
Keywords Bayesian assignment tests; genetic diversity; geographical structure; South America; species delimitation
Abstract Rainforest tree species can be difficult to identify outside of their period of reproduction. Vascular tissues from Carapa spp. individuals were collected during a short field trip in French Guiana and analysed in the laboratory with nuclear and chloroplast markers. Using a Bayesian approach, > 90% of the samples could be assigned to one of two distinct clusters corresponding to previously described species, making it possible to estimate the genetic structure of each species and to identify cases of introgression. We argue that this blind procedure represents a first-choice rather than a fallback option whenever related taxa are investigated.
Address INRA, UMR Biodivers Genes & Ecosyst, F-33612 Cestas, France, Email: caron@pierroton.inra.fr
Corporate Author Thesis
Publisher BLACKWELL PUBLISHING Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0962-1083 ISBN Medium
Area Expedition Conference
Notes ISI:000241157400002 Approved no
Call Number EcoFoG @ eric.marcon @ Serial 175
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Author Hardy, O.J.; Maggia, L.; Bandou, E.; Breyne, P.; Caron, H.; Chevallier, M.H.; Doligez, A.; Dutech, C.; Kremer, A.; Latouche-Halle, C.; Troispoux, V.; Veron, V.; Degen, B.
Title Fine-scale genetic structure and gene dispersal inferences in 10 Neotropical tree species Type Journal Article
Year 2006 Publication Molecular Ecology Abbreviated Journal Mol. Ecol.
Volume (up) 15 Issue 2 Pages 559-571
Keywords French Guiana; gene dispersal; seed dispersal; spatial genetic structure; tropical trees
Abstract The extent of gene dispersal is a fundamental factor of the population and evolutionary dynamics of tropical tree species, but directly monitoring seed and pollen movement is a difficult task. However, indirect estimates of historical gene dispersal can be obtained from the fine-scale spatial genetic structure of populations at drift-dispersal equilibrium. Using an approach that is based on the slope of the regression of pairwise kinship coefficients on spatial distance and estimates of the effective population density, we compare indirect gene dispersal estimates of sympatric populations of 10 tropical tree species. We re-analysed 26 data sets consisting of mapped allozyme, SSR (simple sequence repeat), RAPD (random amplified polymorphic DNA) or AFLP (amplified fragment length polymorphism) genotypes from two rainforest sites in French Guiana. Gene dispersal estimates were obtained for at least one marker in each species, although the estimation procedure failed under insufficient marker polymorphism, limited sample size, or inappropriate sampling area. Estimates generally suffered low precision and were affected by assumptions regarding the effective population density. Averaging estimates over data sets, the extent of gene dispersal ranged from 150 m to 1200 m according to species. Smaller gene dispersal estimates were obtained in species with heavy diaspores, which are presumably not well dispersed, and in populations with high local adult density. We suggest that limited seed dispersal could indirectly limit effective pollen dispersal by creating higher local tree densities, thereby increasing the positive correlation between pollen and seed dispersal distances. We discuss the potential and limitations of our indirect estimation procedure and suggest guidelines for future studies.
Address Univ Libre Bruxelles, Serv Ecoethol Evolut, B-1050 Brussels, Belgium, Email: ohardy@ulb.ac.be
Corporate Author Thesis
Publisher BLACKWELL PUBLISHING Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0962-1083 ISBN Medium
Area Expedition Conference
Notes ISI:000235045500021 Approved no
Call Number EcoFoG @ eric.marcon @ Serial 183
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Author Gloor, M.; Phillips, O.L.; Lloyd, J.J.; Lewis, S.L.; Malhi, Y.; Baker, T.R.; Lopez-Gonzalez, G.; Peacock, J.; Almeida, S.; de Oliveira, A.C.A.; Alvarez, E.; Amaral, I.; Arroyo, L.; Aymard, G.; Banki, O.; Blanc, L.; Bonal, D.; Brando, P.; Chao, K.J.; Chave, J.; Davila, N.; Erwin, T.; Silva, J.; Di Fiore, A.; Feldpausch, T.R.; Freitas, A.; Herrera, R.; Higuchi, N.; Honorio, E.; Jimenez, E.; Killeen, T.; Laurance, W.; Mendoza, C.; Monteagudo, A.; Andrade, A.; Neill, D.; Nepstad, D.; Vargas, P.N.; Penuela, M.C.; Cruz, A.P.; Prieto, A.; Pitman, N.; Quesada, C.; Salomao, R.; Silveira, M.; Schwarz, M.; Stropp, J.; Ramirez, F.; Ramirez, H.; Rudas, A.; ter Steege, H.; Silva, N.; Torres, A.; Terborgh, J.; Vasquez, R.; van der Heijden, G.
Title Does the disturbance hypothesis explain the biomass increase in basin-wide Amazon forest plot data? Type Journal Article
Year 2009 Publication Global Change Biology Abbreviated Journal Glob. Change Biol.
Volume (up) 15 Issue 10 Pages 2418-2430
Keywords Amazon rainforest; carbon sink; disturbance; mortality; power law
Abstract Positive aboveground biomass trends have been reported from old-growth forests across the Amazon basin and hypothesized to reflect a large-scale response to exterior forcing. The result could, however, be an artefact due to a sampling bias induced by the nature of forest growth dynamics. Here, we characterize statistically the disturbance process in Amazon old-growth forests as recorded in 135 forest plots of the RAINFOR network up to 2006, and other independent research programmes, and explore the consequences of sampling artefacts using a data-based stochastic simulator. Over the observed range of annual aboveground biomass losses, standard statistical tests show that the distribution of biomass losses through mortality follow an exponential or near-identical Weibull probability distribution and not a power law as assumed by others. The simulator was parameterized using both an exponential disturbance probability distribution as well as a mixed exponential-power law distribution to account for potential large-scale blowdown events. In both cases, sampling biases turn out to be too small to explain the gains detected by the extended RAINFOR plot network. This result lends further support to the notion that currently observed biomass gains for intact forests across the Amazon are actually occurring over large scales at the current time, presumably as a response to climate change.
Address [Gloor, M.; Phillips, O. L.; Lloyd, J. J.; Lewis, S. L.; Baker, T. R.; Lopez-Gonzalez, G.; Peacock, J.; Feldpausch, T. R.] Univ Leeds, Sch Geog, Leeds LS2 9JT, W Yorkshire, England, Email: eugloor@googlemail.com
Corporate Author Thesis
Publisher WILEY-BLACKWELL PUBLISHING, INC Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1354-1013 ISBN Medium
Area Expedition Conference
Notes ISI:000269577800006 Approved no
Call Number EcoFoG @ eric.marcon @ Serial 196
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Author Marti, G.; Eparvier, V.; Litaudon, M.; Grellier, P.; Gueritte, F.
Title A New Xanthone from the Bark Extract of Rheedia acuminata and Antiplasmodial Activity of Its Major Compounds Type Journal Article
Year 2010 Publication Molecules Abbreviated Journal Molecules
Volume (up) 15 Issue 10 Pages 7106-7114
Keywords Rheedia acuminata, Clusiaceae; xanthones; antiplasmodial activity; cytotoxicity
Abstract Bioassay-guided fractionation of the ethyl acetate bark extract of Rheedia acuminata led to the isolation of the new compound 1,5,6-trihydroxy-3-methoxy-7-geranyl-xanthone (1), together with four known compounds 2-5. These compounds were tested in vitro for their antiplasmodial activity on a chloroquine-resistant strain of Plasmodium falciparum (FcB1) and for their cytotoxicity against the human diploid embryonic lung cell line MRC-5.
Address [Eparvier, Veronique] CNRS, UPS2561, F-97300 Cayenne, France, Email: guillaume.marti@icsn.cnrs-gif.fr
Corporate Author Thesis
Publisher MDPI AG Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1420-3049 ISBN Medium
Area Expedition Conference
Notes ISI:000283587400030 Approved no
Call Number EcoFoG @ webmaster @ Serial 282
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Author Paine, C.E.T.; Norden, N.; Chave, J.; Forget, P.-M.; Fortunel, C.; Dexter, K.G.; Baraloto, C.
Title Phylogenetic density dependence and environmental filtering predict seedling mortality in a tropical forest Type Journal Article
Year 2012 Publication Ecology Letters Abbreviated Journal Ecol. Lett.
Volume (up) 15 Issue 1 Pages 34-41
Keywords Community assembly; Density dependence; French Guiana; Generalised linear mixed models; Janzen-Connell hypothesis; Seedling recruitment; Species coexistence; Survival
Abstract Negative density dependence (NDD) and environmental filtering (EF) shape community assembly, but their relative importance is poorly understood. Recent studies have shown that seedling's mortality risk is positively related to the phylogenetic relatedness of neighbours. However, natural enemies, whose depredations often cause NDD, respond to functional traits of hosts rather than phylogenetic relatedness per se. To understand the roles of NDD and EF in community assembly, we assessed the effects on seedling mortality of functional similarity, phylogenetic relatedness and stem density of neighbouring seedlings and adults in a species-rich tropical forest. Mortality risks increased for common species when their functional traits departed substantially from the neighbourhood mean, and for all species when surrounded by close relatives. This indicates that NDD affects community assembly more broadly than does EF, and leads to the tentative conclusion that natural enemies respond to phylogenetically correlated traits. Our results affirm the prominence of NDD in structuring species-rich communities. © 2011 Blackwell Publishing Ltd/CNRS.
Address Department of Biology, University of Florida, Gainesville, FL 32611, United States
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ISSN 1461023x (Issn) ISBN Medium
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Notes Export Date: 13 December 2011; Source: Scopus; Coden: Eclef; doi: 10.1111/j.1461-0248.2011.01705.x; Language of Original Document: English; Correspondence Address: Paine, C.E.T.; Institut für Evolutionsbiologie und Umweltwissenschaften, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland; email: timothy.paine@ieu.uzh.ch Approved no
Call Number EcoFoG @ webmaster @ Serial 373
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