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Walnut tree species (Juglans spp.) are commonly used for high-quality wood production in plantation forestry. In this paper, the most relevant walnut plantations in Italy and Spain have been reviewed and analysed under a geographic and technician management point of view. Between 2016 and 2019 a total of 96 plantations (15 - 25 years old) were visited distributed in the North-western part of the Mediterranean basin. A statistical analysis (linear model no interaction and PCA) was then performed to evaluate the relative importance of some environmental and management variables for walnut trees in analysed plantations. Results highlighted a variable situation with many different adopted planting schemes across the regions as well as a not standardised spatial layout and management type (thinning). Lower densities and smaller trees were adopted in Italy with about 200 trees ha-1 versus 330 trees ha-1 in Spain. In addition to the age of the plantation as one of the most influencing parameters also the plantation density and the average crown diameter were highly statistically significant. Overall, the interesting potentiality of walnut for timber production with active management in suitable areas was detected as the focal point for a successful timber production from walnut trees.

Within the activity of the H2020 'WOODnat' project ("Second generation of planted hardwood forests in the European Union") the growth parameters, yield and sanitary conditions of the most important walnut (Juglans spp.) plantations, established in Italy in the 1990s and in Spain starting from 1996, were recorded. One of the objectives of the project was to evaluate tree growth and stem quality to derive insight on the main environmental factors affecting the production of this valuable specie. An inventory of walnut plantations in the area of interest was necessary due to the relevance of this tree species in the EU timber market. In this paper the final dataset is presented and available with DOI: 10.5281/zenodo.3769940. The database is finalized to narrow the knowledge gap between growers and processing industry with the aim to relaunching the market for this valuable species. Data were collected in the spring 2017 and winter 2017-2018 on 27 stands established in Northern Italy (Piemonte and Lombardia), on 51 stands in Central Italy (Toscana and Marche) and on 17 stands in Spain for a total of 95 plantations. In each plantation, general information was collected such as the planting layout, spacing, age, environment conditions as well as tree-level dendrometric data and phytosanitary information. The sampled stands have been georeferenced in WGS84 reference system (EPSG 4326). These data can be exploited to assess potential wood volume obtainable and quality of raw material, and to identify the weaknesses and errors, strengths and opportunities of the experiences conducted to plan future plantings with greater awareness.

In the past centuries a notable reduction of lowland forests in Italy was detected as a result of the spreading of intensive agriculture and deforestation activities. According to the national forest inventory (INFC 2005) the English oak (Quercus robur L.) is mainly a scattered species and is distributed across 146,000 hectares of mixed forests. However this species has often been used in many national programs to recreate new woodlands in the lowlands as well as tree farming plantations. In the '80s, during the restoration program of the Santa Barbara mining area in the Municipality of Cavriglia (Valdarno, Tuscany), about 172 hectares of tree farming plantations were created with English oak. Due to the lack of a specific volume equation for Italian plantations a sampling campaign was carried out. The volume of 299 sample trees was measured using the Heyer formula and a volume equation was studied as a polynomial function of DBH and total height of trees. The final equation demonstrated to be quite robust with a RMSE of 0.0176 m3 corresponding to a relative RMSE of 10%.

Questa pubblicazione è stata realizzata nell’ambito delle attività previste dal Piano della Rete Rurale Nazionale (RRN) 2014-2020. L’obiettivo della RRN è favorire lo sviluppo rurale attraverso azioni volte a: i. incentivare la partecipazione del partenariato, delle organizzazioni e delle amministrazioni all’attuazione dello sviluppo rurale, ii. informare il pubblico e i potenziali beneficiari sulla politica di sviluppo rurale e su eventuali possibilità di finanziamento; iii. promuovere l’innovazione nel settore agricolo, nella produzione alimentare, nella silvicoltura e nelle zone rurali. In tale contesto il Piano RRN ha previsto anche una “scheda attività” interamente dedicata alla materia forestale (Scheda n. 22 - Foreste); nello specifico con la sotto scheda Foreste 22.2.1 - Miglioramento sostenibile delle produzioni forestali nazionali sono state realizzate, nel biennio di attività 2014-2016, azioni di confronto tra i principali portatori di interesse (attraverso Focus Group e Workshop tematici) e di trasferimento della conoscenza e dell’innovazione. Questo opuscolo si inserisce in questo contesto e fornisce linee guida, prevalentemente di natura tecnica applicativa, di rapida e semplice consultazione, rivolte a tutti coloro che operano nel settore selvicolturale e dello sviluppo rurale con particolare attenzione ai principali portatori di interesse del settore e della filiera. Nell’ambito delle attività di approfondimento, confronto e divulgazione sui cedui di castagno (sotto scheda 22.2.1.C), il presente documento si propone, di definire e proporre anche nell’attuazione delle misure forestale previste nei PSR regionali dalla politica di sviluppo rurale, approcci selvicolturali idonei ad aumentare e diversificare la produzione legnosa, migliorare la stabilità e la funzionalità ecologica dei popolamenti, ridurre i costi ambientali e sociali derivati dall’importazione di legname, promuovere un’azione importante di stoccaggio del carbonio.

Coppice management in Italy has traditionally focused on a single or few dominating tree species. Tree-oriented silviculture can represent an alternative management system to get high value timber production in mixed coppice forests. This study illustrates an application of the tree-oriented silvicultural approach in Turkey oak (Quercus cerris L.) coppice forests. The rationale behind the proposed silvicultural approach is to combine traditional coppicing and localized, single-tree practices to favor sporadic trees with valuable timber production. At this purpose, a limited number of target trees are selected and favored by localized thinning. In this study, the effectiveness of the proposed tree-oriented approach was compared with the customary coppice management by a financial evaluation. Results showed that the tree-oriented approach is a reliable silvicultural alternative for supporting valuable timber production in mixed oak coppice forests.

The issue of soil exhaustion or soil sickness, referring to the progressive loss of soil quality and decrease in fertility, has increased considerably in the last decades. Recent models predicted that around 200,000 km2 of degraded agricultural land in Europe will be abandoned between 2000 and 2040. Accordingly, this research aims at identifying an adequate forest management that might recover low fertility soils through an increase of soil organic matter (SOM) and soil quality, improving the ecosystem services of those areas. Thus, a former agricultural site was identified in Brusciana (FI) where, for the past 18 years, various forest associations for wood production have been established, namely white poplar and common walnut (K), which were also planted intercropped with other species such as hazelnut (C), Italian alder (A), and autumn olive (E). These forest stands were compared also to an adjacent agricultural field (X). Preliminary analyses on the topsoil (0-10 cm) showed a general low concentration of SOM (10-70 mg/g), although lowest values were found in X and highest in A, while the others were intermediate. The same trend was followed by soil urease enzyme, while β-glucosidase was lower in the agricultural field in comparison to the other stands, where no significance difference were reported Regarding the acid phosphomonoesterase, significant differences were found between A and X, while the remaining stands showed similar values. We have computed the AI3 index as a reference for soil quality, which showed a better values in A compared to X, indicating that soil quality increased up to 4 times compared to the beginning of the experiment, while the other values were comparable. In conclusion, our preliminary results showed that afforestation of tired agricultural soils improved soil organic matter and soil quality, in particular in the stands where Italian alder were planted.

International audience; Mixed-species plantations containing non-nitrogen (N)-fixing species and N-fixing species have the potential to increase the productivity and the ecophysiological performance of the target tree species in comparison to monoculture. However, there are few and conflicting data on the effects of fixed N transfer on species water use efficiency in the short, medium and long term. In this paper, we evaluate the productivity and intrinsic water use efficiency (WUEi), i.e., the ratio of photosynthesis (A) to stomatal conductance (gs), in Quercus robur L. (pedunculate oak) stands growing in monoculture and in combination with Alnus cordata Loisel. (Italian alder) in a ratio of 25% (stand F25%) and 50% (stand F50%). We analyzed δ13C in tree rings as a proxy of the inter-annual changes in WUEi, while the influence of the stomatal conductance was explored through δ18O data. Our results indicate a considerable increase in cumulative basal area (BAI) and in WUEi in the two mixed stands during the period 1990–2002, largely resulting from an increase in N availability, due to the N-fixing species that induced an enhancement of A. After 2002, the differences between the three stands in terms of N% in tree rings, BAI and WUEi leveled off, when natural mortality or management practices decreased the competitive ability of Italian alder. Our study shows the importance of intercropping with a suitable N-fixing species to ensure high levels of productivity and water use efficiency of the target tree species in a Mediterranean-type agroforestry system, but also the need to understand how species interaction changes in time and space with a view to setting the management criteria to maximize tree performance.

Il presente lavoro riguarda lo studio degli accrescimenti di cinque piantagioni di noce comune (Juglans regia L) in relazione alle caratteristiche stazionarie e alle varie ipotesi di consociazione che li caratterizzano, localizzate in varie località del centro-nord Italia, realizzati in varie epoche e con criteri progettuali differenti tra loro, e distinte in due tipologie di impianti: monociclici monobiettivo e policiclici multi-obiettivo. Per gli impianti monociclici, sono stati analizzati gli accrescimenti in diametro e altezza del noce per i singoli impianti, al sesto e tredicesimo anno di età, sulla base delle varie tesi, presenti all’interno di ogni singola piantagione, e in particolar modo alla percentuale e alle specie azotofissatrici consociate (Alnus cordata L, Elaeagnus umbellata T, Alnus Cordata L + Elaeagnus umbellata T). In seguito è stata effettuata una comparazione complessiva delle tre piantagione analizzate, con l’obiettivo di valutare l’effetto delle consociazioni e la loro interazione con le differenti condizioni stazionali. I risultati mostrano come, in condizioni di fertilità scarsa e media, l’effetto della consociazione ha effetti positivi sull’accrescimento del noce, se confrontato con quello in purezza, sia rispetto all’altezza che in termini di accrescimento diametrico. In terreni a media-bassa fertilità, l’effetto delle azotofissatrici sul noce si traduce in accrescimenti maggiori e in una migliore qualità delle piante, che quindi presentano una forma più slanciata e un fusto più dritto. In condizioni di fertilità elevata, l’effetto delle azotofissatrici sul noce risulta essere secondario. Anche per i policiclici è stata effettuata l’analisi per ogni singolo impianto, per valutarne lo sviluppo a scala locale. Si tratta di due impianti dove il noce è consociato con il pioppo ibrido I214, con specie ad elevata produttività (i.e. biomassa) e con alcune piante accessorie. In questi impianti, le piante di noce e pioppo presentano due disposizioni diverse dei filari: per fila singola uno, per fila binata l’altro. Non essendoci differenze particolari in termini di specie consociate e di condizione stazionarie, per il noce il confronto tra i differenti impianti ha riguardato il modulo di impianto (in file singole e binate), le distanze nella fila e la consociazione con le specie da biomassa (Short rotation coppice, SRC). I risultati mostrano come il noce a 8 metri consociato con SRC di nocciolo sia quello più sviluppato, rispetto a quello consociato con SRC di carpino nero. Essendo un impianto dove i prodotti attesi riguardano anche il pioppo e le specie da biomassa, è stata effettuata una analisi sintetica per descriverli. Il pioppo in fila singola registra i diametri maggiori, indipendentemente dalla distanza a cui è messo a dimora. Nelle biomasse si registra una maggiore produttività da parte del nocciolo nell’impianto in fila binata, anche se bisogna sottolineare la differente epoca di stima delle biomasse nelle due piantagioni. This study concerns the analysis of five plantations of common walnut (Juglans regia L), in relation to the stationary characteristics and the different hypothesis of intercropping that characterize them, from various places in Northern and Central Italy, which were established at different times and through alternative techniques, and grouped into the following two types: single-objective monocyclic, and multi-objective polycyclic. For the monocyclic plantations, both the diameter and height increment of the walnut were assessed for each plantation, at the sixth and the thirteenth year of age, according to the alternative management strategies previously defined for each plantation and in particular to the percentage and nitrogen-fixing species intercropping (Alnus cordata L, Elaeagnus umbellata T, Alnus cordata L + Elaeagnus umbellata T). Then, a comparison between the three plantations was carried out, in order to evaluate the effect of intercropping, as well as and their response to different site conditions. The results show that in medium-low fertility conditions, the consociation has positive effects on the walnut growth, if compared with the same in pure stands, regarding both the diameter and height increment. In medium-low fertility conditions, the effect of nitrogen-fixing on the walnut results in a higher individual growth and in an increased wood quality. In these cases, the stems are more slender and straighter. In high fertility conditions, the effects of the nitrogen-fixation on the walnut seem to be secondary. Even for the polycyclic plantations, the analysis for each individual plant was carried out, in order to evaluate their growth at the local scale. In these two plants, the walnut is associated with the I214 hybrid poplar, especially for the production of biomass, with some other species. In these plants, walnut and poplar species have two different row arrangements: single row and double row. Considering that in this case there are no large differences between terms of secondary species and site conditions, the comparison between the different systems for the walnut concerned the implant module (in single and double rows), the distances between the rows, and intercropping with biomass species (Short rotation coppice, SRC). The results show that the walnut trees at 8 meters is the most developed if associated with the hazel SRC, in comparison with that associated with the hornbeam SRC. Being a plant where the expected products also concern the poplar and biomass species, it was carried out summary analysis to describe them. The poplar in single row has larger diameters, regardless of the distance to which it is planted. Concerning the results in biomass production, a higher productivity is obtained in common hazel plants on twin-rows, despite the two plantations have different ages. Dottorato di ricerca in Scienze agro-forestali, delle tecnologie agro-industriali e del territorio rurale. I sistemi forestali (XXVIII ciclo)