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Francesco REYES

Ricercatore t.d. art. 24 c. 3 lett. B
Dipartimento di Scienze della Vita sede ex-Agraria

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Pubblicazioni

2023 - A hierarchical dataset of vegetative and reproductive growth in apple tree organs under conventional and non-limited carbon resources [Articolo su rivista]
Reyes, F; Tagliavini, M; Gianelle, D
abstract

A monitoring of apple fruit, shoot and trunk growth was per-formed on 15 trees, equally split according to three treat-ments, which determined heavily contrasting carbon assim-ilate availability: unmanipulated trees (FRU), thinned trees (THI) and defruited trees (DEF). Several variables describe the vegetative growth on FRU and DEF trees (shoot length, base diameter, number of fruits on shoot, and height, diameter, pruning intensity and number of fruits of the branch carrying the shoot; trunk circumfer-ence), as well as the fruit growth on FRU and THI trees (3 fruit diameters). Additional measurements from ancillary shoots (apical diameter, number of leaves, leaf dry weight, stem dry weight, fresh mass, volume) and fruits (3 diameters, dry weight) from trees undergoing the same treatments, pro-vide a more complete (destructive) characterization of organs growth, thanks to several measurements performed across the growing season. Organs are provided with categorical variables indicating the treatment, tree, canopy height, orien-tation (for both shoots and fruit), as well as branch and shoot identifiers, so that hierarchical modeling of the dataset can be performed. The dataset is completed with dates and day of the year of the measurements and the accumulated grow-ing degree days from full bloom. Data can be used to calcu-late apple tree absolute and relative growth rates, maximum potential growth rates, as well as shoot growth responses to thinning and pruning. The dataset can also be used to cali-brate allometric relationships, estimate structural apple tree growth parameters and their variability.(c) 2023 Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

2023 - Composts from Grapevine and Hazelnut By-Products: A Sustainable Peat Partial Replacement for the Growth of Micropropagated Hazelnut and Raspberry in Containers [Articolo su rivista]
Bignami, Cristina; Reyes, Francesco; Saccaggi, Mario; Pane, Catello; Zaccardelli, Massimo; Ronga, Domenico
abstract

2023 - Earthworm-Driven Changes in Soil Chemico-Physical Properties, Soil Bacterial Microbiota, Tree/Tea Litter Decomposition, and Plant Growth in a Mesocosm Experiment with Two Plant Species [Articolo su rivista]
Sofo, Adriano; Khanghahi, Mohammad Yaghoubi; Curci, Maddalena; Reyes, Francesco; Briones, Maria J I; Sarneel, Judith M; Cardinale, Domenico; Crecchio, Carmine
abstract

: Earthworms and soil microorganisms contribute to soil health, quality, and fertility, but their importance in agricultural soils is often underestimated. This study aims at examining whether and to what extent the presence of earthworms (Eisenia sp.) affected the (a) soil bacterial community composition, (b) litter decomposition, and (c) plant growth (Brassica oleracea L., broccoli; Vicia faba L., faba bean). We performed a mesocosm experiment in which plants were grown outdoors for four months with or without earthworms. Soil bacterial community structure was evaluated by a 16S rRNA-based metabarcoding approach. Litter decomposition rates were determined by using the tea bag index (TBI) and litter bags (olive residues). Earthworm numbers almost doubled throughout the experimental period. Independently of the plant species, earthworm presence had a significant impact on the structure of soil bacterial community, in terms of enhanced α- and β-diversity (especially that of Proteobacteria, Bacteroidota, Myxococcota, and Verrucomicrobia) and increased 16S rRNA gene abundance (+89% in broccoli and +223% in faba bean). Microbial decomposition (TBI) was enhanced in the treatments with earthworms, and showed a significantly higher decomposition rate constant (kTBI) and a lower stabilization factor (STBI), whereas decomposition in the litter bags (dlitter) increased by about 6% in broccoli and 5% in faba bean. Earthworms significantly enhanced root growth (in terms of total length and fresh weight) of both plant species. Our results show the strong influence of earthworms and crop identity in shaping soil chemico-physical properties, soil bacterial community, litter decomposition and plant growth. These findings could be used for developing nature-based solutions that ensure the long-term biological sustainability of soil agro- and natural ecosystems.

2023 - Plant Growth and Root Morphology Are Affected by Earthworm-Driven (Eisenia sp.) Changes in Soil Chemico-Physical Properties: a Mesocosm Experiment with Broccoli and Faba Bean [Articolo su rivista]
Reyes, Francesco; Sorgonà, Agostino; Briones, Maria J. I.; Crecchio, Carmine; Sofo, Adriano
abstract

2023 - Protection net and the canopy layer decouple gas exchanges, affecting carbon and water fluxes: the case of a kiwi orchard in a Mediterranean environment [Articolo su rivista]
Reyes, Francesco; Vendrame, Nadia; Dichio, Bartolomeo; Xiloyannis, Cristos; Andrea, Pitacco
abstract

2023 - Reduction of copper inputs in the management of key diseases of grapevine, olive and tomato by an innovative Zeo-biopesticide [Abstract in Atti di Convegno]
Modica, F.; Fagioli, L.; Cortiello, M.; Giovanardi, D.; Reyes, F.; Stefani, E.
abstract

2023 - The ESSU concept for designing, modeling, and auditing ecosystem service provision in intercropping and agroforestry systems. A review [Articolo su rivista]
Rafflegeau, Sylvain; Gosme, Marie; Barkaoui, Karim; Garcia, Léo; Allinne, Clémentine; Deheuvels, Olivier; Grimaldi, Juliette; Jagoret, Patrick; Lauri, Pierre‑éric; Merot, Anne; Metay, Aurélie; Reyes, Francesco; Saj, Stéphane; Nicolas Curry, George; Justes, Eric
abstract

2022 - Protection net and the canopy layer decouple gas exchanges, affecting carbon and water net fluxes: the case of a kiwi orchard in a Mediterranean environment [Poster]
Reyes, F.; Dichio, B.; Xiloyannis, C.; Pitacco, A.
abstract

2022 - Subtoxic levels of some heavy metals cause differential root-shoot structure, morphology and auxins levels in Arabidopsis thaliana [Articolo su rivista]
Sofo, A.; Khan, N. A.; D'Ippolito, I.; Reyes, F.
abstract

Contamination of soil by heavy metals severely affects plant growth and causes soil pollution. While effects on plant growth have been investigated for metals taken individually or in groups, less is known about their comparative effects. In this study Arabidopsis thaliana seedlings were grown for 14 days in Petri dishes containing medium contaminated by six common heavy metals (Hg, Cd, Pb, Cu, Ni and Zn), at the minimum concentrations defined as toxic by the most recent EU legislation on contamination of agricultural soils. (a) Root structure and morphology, (b) metal composition and translocation, and (c) the levels of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) were analyzed. Metals accumulated more in roots than in shoots, with concentrations that differed by several orders of magnitude depending on the metal: Cd (ca. 700 × and ca. 450 × in roots and shoots, respectively), Hg (150 ×, 80 × ), Ni (50 ×, 20 × ), Cu (48 ×, 20 × ), Zn (23 ×, 6 × ), and Pb (9 ×, 4 × ). Responses were significant for at least nine of the ten root parameters (with the exception of Hg), and five of the six shoot parameters (with the exception of Zn). Cu and Zn induced respectively the strongest responses in root hormonal (up to ca. 240% the control values for IBA, 190% for IAA) and structural parameters (up to 210% for main root length, 330% for total lateral root length, 220% for number of root tips, 600% for total root surface, and from 2.5° to 26.0° of root growth angle). Regarding the shoots, the largest changes occurred for shoot height (down to 60% for Ni), rosette diameter (down to 45% for Hg), leaf number (up to 230% for Zn) and IBA (up to 240% for Pb and Cu). A microscope analysis revealed that shape and conformation of root hairs were strongly inhibited after Cd exposure, and enhanced under Hg and Pb. The results could have positive applications such as for defining toxicity thresholds (in phytoremediation) and acceptable concentration levels (for policies) for some of the most common heavy metals in agricultural soils.

2022 - Water use of yellow-fleshed kiwifruit during an annual cycle [Articolo su rivista]
Green, S.; Reyes, F.; Dichio, B.; Mastroleo, M.; Xylogiannis, E.
abstract

Irrigation is particularly important in Italian kiwifruit orchards because of high summer evapotranspiration demand and very low rainfall totals. To date, very little research has been done to define the water needs of kiwifruit (Actinidia chinensis var. chinensis 'Zesy002' commonly known as Gold3) vines. In this project, we are studying the water balance of a kiwifruit orchard during an annual cycle in Italy using a measurement and modelling approach. Field experiments were carried out in an orchard of 6-year-old vines planted in 5.0-m wide rows at a trunk spacing of 2.0 m. Trunk sap flow (T) was measured using the heat-pulse method and soil moisture was measured using time domain reflectometry (TDR). T peaked at 5.5 L h-1during the middle of the day. Corresponding values of the daily sap flow peaked at almost 60 L d-1, on average. The equivalent rate of vine transpiration, ETC, equalled 6.0 mm d-1. Mid-summer values of the reference evapotranspiration, ETO, were up to 8 mm d-1during June and July and they dropped back to about 2 mm d-1during late autumn (October). Results from this study are contributing to the development of guidelines for growers on irrigation best practice that will help overcome reduced productivity resulting from poor orchard irrigation practices.

2021 - Alley cropping mitigates the impacts of climate change on a wheat crop in a mediterranean environment: A biophysical model-based assessment [Articolo su rivista]
Reyes, F.; Gosme, M.; Wolz, K. J.; Lecomte, I.; Dupraz, C.
abstract

Introduction: Climate change (CC) and the increased occurrence of extreme climatic events pose a serious threat to crop yields and their stability worldwide. This study analyzed the CC mitigation potential of an alley cropping system on crop physiological stresses and growth as compared to a monoculture system. Materials and Methods: Growth of winter durum wheat, cultivated alone (agriculture) and in combination with hybrid walnut (agroforestry), was simulated with the Hi-sAFe agrofo2restry model, as driven by business-as-usual Intergovernmental Panel on Climate Change (IPCC) projections, split into three scenarios, representing Past (1951-1990), Present (1991-2030), and Future (2031-2070) climatic conditions. Crop growth and the occurrence of thermal, nitrogen, and water stresses were analyzed. Results: Cold-related stresses were modest in Past and almost disappeared over time. Heat, drought, and nitrogen stresses increased about twofold from Past to Future, but were reduced by 20-35% in agroforestry, already with medium-sized trees (diameter at breast height (DBH) of about 10-15 cm). Crop yields in agriculture increased from Past to the end of Present and then remained stable. This moderately decreased with tree age in agroforestry (especially in Future). Discussion: The impact of CC on the crop was buffered in agroforestry, especially for the most extreme climatic events. The mitigation of crop microclimate and the increased stability of crop yields highlight the potential of agroforestry as a CC adaptation strategy.

2021 - Moria del kiwi: alterazione della struttura anatomica e morfologica delle radici di actinidia sottoposte a condizioni di asfissia del suolo [Abstract in Atti di Convegno]
D’Ippolito, Ilaria; Mininni, An; Dichio, B; Reyes, F; Xylogiannis, E; Mastroleo, M; Sofo, A
abstract

produzione negli ultimi anni a causa della diffusione della sindrome del declino dell’actinidia (KVDS/moria). Sintomi simili al KVDS sono stati osservati in diversi ambienti e vengono spesso associati a ristagno idrico e asfissia radicale, con conseguente marciume radicale. Nell'ambito del progetto Zespri “Water and soil management of G3 in Italy”, nel 2020 è stata avviata la sperimentazione in actinidieti colpiti da moria a Latina (Lazio, - ET0 732 mm) al fine di indagare sulle possibili cause e suggerire delle soluzioni per contrastare questa fisiopatia. Sono stati raccolti campioni di radici da piante sane e confrontati con campioni raccolti da piante affette da KVDS. Per l’analisi microscopica, le radici sono state fissate in formalina al 10%, disidratate e incluse in paraffina. Ogni singolo campione è stato sezionato in sezioni dello spessore di 5 μm e colorate con diverse metodiche. Macroscopicamente, le radici affette da KVDS sono risultate marcescenti, mostrando una perdita di rizoderma e parenchima corticale. L’analisi microscopica ha rilevato danneggiamenti del sistema radicale con rottura e decomposizione tissutale, sfaldamento di rizoderma, area corticale con evidente perdita di turgore cellulare, disfacimento iniziale della stele ed evidente distacco della corteccia dai tessuti conduttori centrali. Nel campione di controllo, le radici hanno presentato un rizoderma con spessore di 13 μm e una dimensione media di cellule del parenchima di 44,5 μm, a differenza del campione KVDS, in cui lo spessore del rizoderma, quasi assente, è stato di 8,3 μm e la dimensione media delle cellule di 34,7 μm. Dall’analisi dei gas tellurici è emerso che, conseguentemente all'insorgenza del ristagno idrico nel suolo, nei suoli attorno alle piante colpite da KVDS, il potenziale redox, parametro inversamente correlato alla concentrazione di ossigeno, è risultato essere significativamente più basso (+331 vs. +368 mV; media 0-90 cm di profondità), mentre sono state riscontrate concentrazioni più elevate di CO2 (7467 vs. 5870 ppm; media 0-90 cm di profondità), un indicatore di condizioni anossiche del suolo. Per migliorare le qualità fisica del suolo e assicurare una crescita ottimale delle radici di actinidia, sarà applicata una gestione innovativa del suolo volta ad aumentarne la sostanza organica e ridurre la compattazione, facilitando il movimento orizzontale e verticale dell'acqua nel terreno per fornire alle radici di actinidia l'ossigeno necessario per mitigare gli effetti di microrganismi potenzialmente patogeni, molti dei quali proliferano in ambienti anaerobi. Sarà, infine, ottimizzata la gestione della chioma e dell’apparato radicale per bilanciare il rapporto tra radici e foglie e migliorare la capacità delle piante di riprendersi da questo declino fisiologico.

2021 - Working together for the better - An integrated approach to KVDS [Altro]
Xylogiannis, E; Mastroleo, M; D’Ippolito, I; Mininni, An; Reyes, F; Laterza, D; Tuzio, Ac; Sofo, A; Dichio, B; Green, S; Marocchi, F
abstract

Italy; the second-largest kiwifruit producing country in the world, has lost 10 percent of its production in recent years to Kiwifruit Vine Decline Syndrome (KVDS). Now a comprehensive examination of environmental factors, soil quality; fertility issues and kiwifruit crop management techniques could help the industry to better understand the phenomena involved and find solutions.

2020 - MuSCA: A multi-scale source-sink carbon allocation model to explore carbon allocation in plants. An application to static apple tree structures [Articolo su rivista]
Reyes, F.; Pallas, B.; Pradal, C.; Vaggi, F.; Zanotelli, D.; Tagliavini, M.; Gianelle, D.; Costes, E.
abstract

Background and aims: Carbon allocation in plants is usually represented at a topological scale, specific to each model. This makes the results obtained with different models, and the impact of their scales of representation, difficult to compare. In this study, we developed a multi-scale carbon allocation model (MuSCA) that allows the use of different, user-defined, topological scales of a plant, and assessment of the impact of each spatial scale on simulated results and computation time. Methods: Model multi-scale consistency and behaviour were tested on three realistic apple tree structures. Carbon allocation was computed at five scales, spanning from the metamer (the finest scale, used as a reference) up to first-order branches, and for different values of a sap friction coefficient. Fruit dry mass increments were compared across spatial scales and with field data. Key Results: The model was able to represent effects of competition for carbon assimilates on fruit growth. Intermediate friction parameter values provided results that best fitted field data. Fruit growth simulated at the metamer scale differed of ~1 % in respect to results obtained at growth unit scale and up to 60 % in respect to first order branch and fruiting unit scales. Generally, the coarser the spatial scale the more predicted fruit growth diverged from the reference. Coherence in fruit growth across scales was also differentially impacted, depending on the tree structure considered. Decreasing the topological resolution reduced computation time by up to four orders of magnitude. Conclusions: MuSCA revealed that the topological scale has a major influence on the simulation of carbon allocation. This suggests that the scale should be a factor that is carefully evaluated when using a carbon allocation model, or when comparing results produced by different models. Finally, with MuSCA, trade-off between computation time and prediction accuracy can be evaluated by changing topological scales.

2019 - An Enhanced Field-based Yield Potential Spatial Clustering Method based on Seasonality, Climate Variability and Plot Topography [Relazione in Atti di Convegno]
Reyes, F.; Mzid, N.; Casa, R.; Pascucci, S.; Pignatti, S.
abstract

2019 - An Enhanced Yield Potential Spatial Clustering Method, accounting for Seasonality, Heterogeneous Morphology and Climate Variability. An application in the Umbria Region (Central Italy) for the SMARTAGRI PROJECT [Poster]
Reyes, F.; Mzid, N.; Casa, R.; Pascucci, S.; Pignatti, S.; Chiodini, G.
abstract

2019 - Calibration of the 3D Hi-sAFe agroforestry model for hybrid walnut [Abstract in Atti di Convegno]
Wolz, K; Dupraz, C; Lecomte, I; Gosme, M; Reyes, F
abstract

Hi-sAFe is a 3D biophysical model designed to explore the interactions between tres and crops in agroforestry systems. Utilization of any tree species within Hi-sAFe requires parame- terization and calibration of the model for that tree species. We carried out these three steps for hybrid walnut (Juglans regia x nigra). Data used for parameterization and calibration came from the literature and long-term experimental plots at the Restinclières Estate near Montpel- lier in Southern France (Inurreta-Aguirre et al. 2018). The three plots included two alley crop- ping systems of hybrid walnut and durum wheat (Triticum durum) and a pure forestry system of hybrid walnut with a natural ground cover. A total of 21 Hi-sAFe tree inputs were unable to be parameterized directly and were included in the model calibration. Optimal parameter values were searched for using a multi-objective evolutionary algorithm (MOEA) similar to the NSGA-II algorithm (Deb et al. 2002). The root mean square errors of the measured vs. modeled diameter at breast height (DBH) in each plot were used as objective functions to minimize. The final Pareto optimal front of the MOEA contained a diversity of tree parameter sets. Accuracy of modeled crop relative yield in the A2 plot was used as a final criterion to select the best pa- rameter set. These calibrated Hi-sAFe parameters for hybrid walnut can be used to confidently explore hybrid walnut agroforestry systems across pedoclimatic and management conditions.

2019 - Crop microclimate: can alleycropping alleviate climate change effects on durum wheat? [Abstract in Atti di Convegno]
Reyes, F; Gosme, M; Wolz, K; Lecomte, I; Dupraz, C
abstract

2019 - Hi-sAFe: A 3D agroforestry model for integrating dynamic tree-crop interactions [Articolo su rivista]
Dupraz, C.; Wolz, K. J.; Lecomte, I.; Talbot, G.; Vincent, G.; Mulia, R.; Bussiere, F.; Ozier-Lafontaine, H.; Andrianarisoa, S.; Jackson, N.; Lawson, G.; Dones, N.; Sinoquet, H.; Lusiana, B.; Harja, D.; Domenicano, S.; Reyes, F.; Gosme, M.; Van Noordwijk, M.
abstract

Agroforestry, the intentional integration of trees with crops and/or livestock, can lead to multiple economic and ecological benefits compared to trees and crops/livestock grown separately. Field experimentation has been the primary approach to understanding the tree-crop interactions inherent in agroforestry. However, the number of field experiments has been limited by slow tree maturation and difficulty in obtaining consistent funding. Models have the potential to overcome these hurdles and rapidly advance understanding of agroforestry systems. Hi-sAFe is a mechanistic, biophysical model designed to explore the interactions within agroforestry systems that mix trees with crops. The model couples the pre-existing STICS crop model to a new tree model that includes several plasticity mechanisms responsive to tree-tree and tree-crop competition for light, water, and nitrogen. Monoculture crop and tree systems can also be simulated, enabling calculation of the land equivalent ratio. The model's 3D and spatially explicit form is key for accurately representing many competition and facilitation processes. Hi-sAFe is a novel tool for exploring agroforestry designs (e.g., tree spacing, crop type, tree row orientation), management strategies (e.g., thinning, branch pruning, root pruning, fertilization, irrigation), and responses to environmental variation (e.g., latitude, climate change, soil depth, soil structure and fertility, fluctuating water table). By improving our understanding of the complex interactions within agroforestry systems, Hi-sAFe can ultimately facilitate adoption of agroforestry as a sustainable land-use practice.

2019 - Theory and description of the 3D Hi-sAFe agroforestry model [Abstract in Atti di Convegno]
Dupraz, C; Wolz, K; Lecomte, I; Talbot, G; Vincent, G; Mulia, R; Reyes, F; Gosme, M; Van Noordwijk, M
abstract

2018 - How important is adapting regional climatic projections to the local environment? A procedure for microclimatic corrections makes the difference for crop growth in a virtual experiment [Relazione in Atti di Convegno]
Reyes, F.; Gosme, M.; Blanchet, G.; Dupraz, C.
abstract

Climatic conditions drive plant metabolism and growth and their projections are used as drivers in modelling experiments for the prediction of crop yields. However, these are generally issued at regional scale, and do not consider microclimatic variations. In this study we question the impact of taking into account microclimate adjustments on simulated crop yield. A procedure for the correction of temperature and humidity to the local microclimate is proposed and applied on climatic predictions for a site, resulting in modifications of about 2% in mean daily relative humidity and 2.5°C in mean daily maximum temperature. Crop yield is predicted with a processbased agroforestry model, for the pure crop and in the alley-cropping system, using both climatic series. Predicted crop yield differed by up to 58% in individual years and overall by 22% (CV RMSE) across climatic series. A significant trend in crop yield disappeared after corrections. This study highlights the importance of taking into account microclimatic corrections when using climatic projections to predict crop growth on realistic sites.

2018 - Influence of latitude on the light availability for intercrops in an agroforestry alley-cropping system [Articolo su rivista]
Dupraz, C.; Blitz-Frayret, C.; Lecomte, I.; Molto, Q.; Reyes, F.; Gosme, M.
abstract

Light competition by trees is often regarded as a major limiting factor for crops in alley-cropping agroforestry. Northern latitude farmers are usually reluctant to adopt agroforestry as they fear that light competition will be fiercer in their conditions. We questioned the light availability for crops in alley-cropping at different latitudes from the tropic circle to the polar circle with a process-based 3D model of alley-cropping agroforestry. Two tree densities and two tree line orientations were considered. The effect of the latitude was evaluated with same-sized trees. The relative irradiance of the crops was computed for the whole year or at specific times of the year when crops need more light. The heterogeneity of crop irradiance across the alley was also computed. Surprisingly, crop relative irradiance of summer crops at high latitudes is high, at odds with farmers’ fears. Best designs were highlighted for improving the crop irradiance: North–South tree lines are recommended at high latitudes and East–West tree lines at low latitudes. At medium latitudes, North–South tree lines should be preferred to achieve an homogeneous irradiance of the crop in the alley. If we assume that trees at northern latitudes grow slower when compared to southern latitudes, then alley-cropping agroforestry is highly advisable even at high latitudes with summer crops.

2017 - A multi-scale model to explore carbon allocation in plants [Articolo su rivista]
Reyes, F.; Gianelle, D.; Pallas, B.; Costes, E.; Pradal, C.; Tagliavini, M.; Zanotelli, D.
abstract

Understanding and simulating carbon allocation in plants is necessary to predict carbohydrates allocation among growing and competing organs and, plant growth and structure development in relation to climatic conditions. In this context, several carbon allocation models have been developed but no clear consensus exists on (i) the most appropriate topological scale (organ, metamer, compartment...) to represent this process on complex plant structures and (ii) the importance of distances between organs in carbon transport. Multi-scale tree graph (MTG) is a formalism allowing the representation of geometry and topology of a tree structure at different scales. In this study, a multi-scale model was built to compute carbon allocation at different and user-defined spatial scales, using the MTG formalism. The implementation takes into account the distances between sources and sinks, the strength of the sinks and the available carbohydrates, following the equations of two previously developed models: SIMWAL and QualiTree. This allows multiple scales (e.g., metamer, growing unit, branch) to be combined during the computation of carbon allocation. For instance, allocation could be computed alternatively among plant components represented at metamer scale, or among growing units and then redistributed from each growing unit to its component metamers. Simulations on simple shoots, represented at different scales, showed how the scales chosen to represent the system influence the results of the predicted carbon allocation. This modelling approach was first applied to apple tree to analyze the impact of the scale of representation (growth unit, metamer) on the predicted organ growth variability. The present work will be available through the OpenAlea platform and will provide existing Functional Structural Plant Models with a new generic model to simulate carbon allocation in plants, depending on user-defined biological hypotheses, such as the choice of the scale of representation or the effect of distance.

2016 - Maximum growth potential and periods of resource limitation in apple tree [Articolo su rivista]
Reyes, Francesco; Dejong, T.; Franceschi, Pietro; Tagliavini, M.; Gianelle, Damiano
abstract

Knowledge of seasonal maximum potential growth rates are important for assessing periods of resource limitations in fruit tree species. In this study we assessed the periods of resource limitation for vegetative (current year stems, and woody biomass) and reproductive (fruit) organs of a major agricultural crop: the apple tree. This was done by comparing relative growth rates of individual organs in trees with reduced competition for resources to trees grown under standard field conditions. Special attention was dedicated to disentangling patterns and values of maximum potential growth for each organ type. The period of resource limitation for vegetative growth was much longer than in another fruit tree species (peach): from late May until harvest. Two periods of resource limitation were highlighted for fruit: from the beginning of the season until mid-June, and about one month prior to harvest. By investigating the variability in individual organs growth we identified substantial differences in relative growth rates among different shoot categories (proleptic and epicormic) and within each group of monitored organs. Qualitatively different and more accurate values of growth rates for vegetative organs, compared to the use of the simple compartmental means, were estimated. Detailed, source-sink based tree growth models, commonly in need of fine parameter tuning, are expected to benefit from the results produced by these analyses.

2015 - Delineation of individual tree crowns from ALS and hyperspectral data: a comparison among four methods [Articolo su rivista]
Dalponte, Michele; Reyes, Francesco; Kandare, Kaja; Gianelle, Damiano
abstract

In this paper four different delineation methods based on airborne laser scanning (ALS) and hyperspectral data are compared over a forest area in the Italian Alps. The comparison was carried out in terms of detected trees, while the ALS based methods are compared also in terms of attributes estimated (e.g. height). From the experimental results emerged that ALS methods outperformed hyperspectral one in terms of tree detection rate in two of three cases. The best results were achieved with a method based on region growing on an ALS image, and by one based on clustering of raw ALS point cloud. Regarding the estimates of the tree attributes all the ALS methods provided good results with very high accuracies when considering only big trees.

2014 - Delineation of Individual Tree Crowns from ALS and Hyperspectral data: a comparison among four methods [Poster]
Reyes, Francesco; Kandare, Kaja; Frizzera, Lorenzo; Gianelle, Damiano; Dalponte, Michele
abstract

Forest structural properties are traditionally acquired during extensive fieldwork campaigns. A great potential for time saving is given by remote sensing assisted inventories. Recently great attention has been devoted to individual tree crowns (ITC) level forest inventories. In ITC inventories a key step is the delineation of the tree crowns. Thus, in this study we will compare four methods for the identification of individual tree crowns (ITC) based on high density airborne laser scanning (ALS) and hyperspectral data. The study area is an alpine forest located in Lavarone at 1400 m (Trento Province, Italy) above sea level. 600 trees were inventoried in a plot of 4800 m2, of which 58% Silver Fir (total basal area: 37 m2/ha), 23% European beech (total basal area: 2 m2/ha), 19% Norway Spruce (total basal area: 22 m2/ha). ALS data were acquired by an Optech ALTM 3100EA sensor, with a mean density of 8.6 points/m2 for the first return (laser pulse wavelength 1064 nm, laser repetition rate 100 kHz) and with up to four recorded returns for each laser pulse. Methods 1 and 2 exploit both a CHM in raster and point cloud formats. The main difference among them is that method 1 uses a watershed segmentation to delineate the ITC, while method 2 uses a region growing algorithm. In greater detail the two methods can be summarized as follows: i) a raster CHM is created from point cloud; ii) the CHM is properly filtered to avoid inclusion of non-vegetated objects; iii) a watershed segmentation (method 1) or a region growing (method 2) is applied; iv) ITCs are reshaped using a morphological filter and their raw ALS point cloud distribution. Method 3 is based on raw ALS cloud and focuses on the delineation of intermediate and suppressed trees. In greater detail the method can be summarized as follows: i) the point cloud is divided into horizontal layers to which a 3D K-means clustering is applied; ii) K-means clusters are grouped using a prolate ellipsoid shape along all the layers; iii) the distribution of points in the clusters is estimated along x and y axes and the uneven distributed clusters are separated into two new 3D clusters; iv) clusters are eventually merged along all layers, in 2D space, and grouped into final 3D clusters representing ITCs. Method 4 is based on hyperspectral data. ITCs are delineated on a single raster band (band at 810 nm). In greater detail the method can be summarized as follows: i) the raster image is filtered with a low pass filter, and with a thresholding filter in order to highlight only the tree crowns; ii) a watershed segmentation algorithm is applied; iii) a morphological filter is used in order to reshape the final ITCs. The above described methods will be compared with the field inventory data for the identification of individual trees and their canopy sizes.