Adolfo Rosati

How local stakeholders perceive agroforestry systems: an Italian perspective

This paper reports the results of a study conducted in Italy, within the AGFORWARD (2014–2017) project, aimed at promoting innovative agroforestry practices in Europe. Agroforestry offers a means for maintaining food production whilst addressing some of the negative environmental effects of intensive agriculture. This study aims to elicit the positive and negative points of view and perceptions of local stakeholders in Italy in relation to three types of agroforestry systems. The Participatory Research and Network Development was implemented in three workshops conducted in Sardinia, Umbria, and Veneto regions, and applied adopting a common methodological protocol. Qualitative data were obtained using open discussions with stakeholders on key issues, challenges and innovations. Quantitative data were obtained from stakeholders completing questionnaires during the workshops. A statistical analysis was applied to elicit the differences in stakeholders’ positive and negative perceptions in relation to production, management, environment and socio-economy aspects. Although the participants in the study came from different geographical and socioeconomic contexts with varied educational and cultural backgrounds, the different professional groups (farmers, policy-makers and researchers) and the three workshops generally shared similar perceptions of the benefits and constraints. The effects of agroforestry on production and the environment were generally perceived as positive, whilst those related to management were generally negative. The process of bringing the groups together seemed to be an effective means for identifying the key research gaps that need to be addressed in order to promote the uptake and maintenance of agroforestry.

Fruit production and branching density affect shoot and whole-tree wood to leaf biomass ratio in olive

The amount of shoot stem (i.e., woody part of the shoot) dry matter per unit shoot leaf dry matter (i.e., the shoot wood to leaf biomass ratio) has been reported to be lower in short shoots than in long ones, and this is related to the greater and earlier ability of short shoots to export carbon. This is important in fruit trees, since the greater and earlier carbon export ability of shoots with a lower wood to leaf biomass ratio improves fruit production. This ratio may vary with cultivars, training systems or plant age, but no study has previously investigated the possible effect of fruit production. In this study on two olive cultivars (i.e., Arbequina, with low growth rate, and Frantoio, with high growth rate) subject to different fruit production treatments, we found that at increasing fruit production, shoot length and shoot wood to leaf biomass ratio were proportionally reduced in the new shoots growing at the same time as the fruit. Specifically, fruit production proportionally reduced total new-shoot biomass, length, leaf area and average shoot length. With decreasing shoot length, shoot diameter, stem mass, internode length, individual leaf area and shoot wood to leaf biomass ratio also decreased. This may be viewed as a plant strategy to better support fruit growth in the current year, given the greater and earlier ability of short shoots to export carbon. Moreover, at the whole-tree level, the percentage of total tree biomass production invested in leaves was closely correlated with branching density, which differed significantly across cultivars. By branching more, Arbequina concentrates more shoots (thus leaves) per unit of wood (trunk, branches and root) mass, decreasing wood to leaf biomass ratio at the whole-tree level. Therefore, while, at the shoot level, shoot length determines shoot wood to leaf biomass ratio, at the canopy level branching density is also an important determinant of whole-tree wood to leaf biomass ratio. Whole-tree wood to leaf biomass ratio is likely to affect the canopys ability to export carbon (i.e., towards fruits), as shoot wood to leaf biomass ratio affects the carbon export ability of the shoot.

Resource investments in reproductive growth proportionately limit investments in whole-tree vegetative growth in young olive trees with varying crop loads

It has long been debated whether tree growth is source limited, or whether photosynthesis is adjusted to the actual sink demand, directly regulated by internal and environmental factors. Many studies support both possibilities, but no studies have provided quantitative data at the whole-tree level, across different cultivars and fruit load treatments. This study investigated the effect of different levels of reproductive growth on whole-tree biomass growth across two olive cultivars with different growth rates (i.e., Arbequina, slow-growing and Frantoio, fast-growing), over 2 years. Young trees of both cultivars were completely deflowered either in 2014, 2015, both years or never, providing a range of levels of cumulated reproductive growth over the 2 years. Total vegetative dry matter growth over the 2 years was assessed by destructive sampling (whole tree). Vegetative growth increased significantly less in fruiting trees, however, the total of vegetative and reproductive growth did not differ significantly for any treatment or cultivar. Vegetative growth over the 2 years was closely (R2 = 0.89) and inversely related to reproductive growth across all treatments and cultivars. When using data from 2015 only, the regression improved further (i.e., R2 = 0.99). When biomass was converted into grams of glucose equivalents, based on the chemical composition of the different parts, the results indicated that for every gram of glucose equivalent invested in reproductive growth, vegetative growth was reduced by 0.73-0.78 g of glucose equivalent. This indicates that competition for resources played a major role in determining tree growth, but also that photosynthesis was probably also enhanced at increasing fruit load (or downregulated at decreasing fruit load). The leaf area per unit of trunk cross sectional area increased with deflowering (i.e., decreased with reproductive growth), suggesting that water relations might have limited photosynthesis in deflowered plants, which had much greater canopies. Net assimilation rate (NAR) increased with reproductive growth and decreased with plant size. Net assimilation rate was also negatively correlated with the leaf area per unit of trunk cross sectional area, suggesting that water relations might have contributed to decreasing NAR at increasing plant size.

Advances in European agroforestry: results from the AGFORWARD project

In global terms, European farms produce high yields of safe and high quality food but this depends on the use of many off-farm inputs and the associated greenhouse gas emissions, loss of soil nutrients and other negative environmental impacts incur substantial societal costs. Farmers in the European Union receive support through a Common Agricultural Policy (CAP) that comprises direct payments to farmers (Pillar I) and payments related to rural development measures (Pillar II). This paper examines the ways in which agroforestry can support European agriculture and rural development drawing on the conclusions of 23 papers presented in this Special Issue of Agroforestry Systems which have been produced during a 4-year research project called AGFORWARD. The project had the goal of promoting agroforestry in Europe and focused on four types of agroforestry: (1) existing systems of high nature and cultural value, and agroforestry for (2) high value tree, (3) arable, and (4) livestock systems. The project has advanced our understanding of the extent of agroforestry in Europe and of farmers’ perceptions of agroforestry, including the reasons for adoption or non-adoption. A participatory approach was used with over 40 stakeholder groups across Europe to test selected agroforestry innovations through field trials and experiments. Innovations included improved grazing management in agroforestry systems of high nature and cultural value and the introduction of nitrogen fixing plants in high value timber plantations and olive groves. Other innovations included shelter benefits for arable crops, and disease-control, nutrient-retention, and food diversification benefits from integrating trees in livestock enterprises. Biophysical and economic models have also been developed to predict the effect of different agroforestry designs on crop and tree production, and on carbon sequestration, nutrient loss and ecosystems services in general. These models help us to quantify the potential environmental benefits of agroforestry, relative to agriculture without trees. In view of the substantial area of European agroforestry and its wider societal and environmental benefits, the final policy papers in this Special Issue argue that agroforestry should play a more significant role in future versions of the CAP than it does at present.

Partitioning of Dry Matter into Fruit Explains Cultivar Differences in Vigor in Young Olive (Olea europaea L.) Trees

Low vigor and early and abundant production are desirable traits for modern tree crops. In olive, most cultivars are too vigorous and cannot be successfully constrained in the small volume allowed by the straddle harvester used in the so-called superhigh-density (SHD) orchards. Only few cultivars appear to have sufficiently low vigor to be suitable for this system. These cultivars combine low vigor with earlier and higher yield. This study investigated the hypothesis that differences in vigor between Arbequina, a low vigor and the most commonly used cultivar in SHD orchards, and Frantoio, a highly vigorous cultivar not suitable for such orchards, are related to their differences in early bearing and consequent differences in dry matter partitioning into fruit. Young trees of both cultivars were deflowered either in 2014, 2015, both years, or neither one, resulting in a range of cumulative yields over the 2 years. Tree trunk crosssectional area (TCSA) was measured at the beginning of each year. This was closely related to total tree mass, as assessed at the beginning and at the end of the experiment. Cumulative yield, in terms of fruit dry matter, was also assessed. TCSA increased less in fruiting trees in both years. As expected, when not deflowered, ‘Frantoio’ was less productive and more vigorous than ‘Arbequina’. However, there was no difference in TCSA increment when both cultivars were completely deflowered. TCSA increments were closely inversely related to yield across all treatments and cultivars (R = 0.90). The regressions improved further when data from 2015 only were used (R = 0.99). The results represent the first quantitative report showing that differences in vigor among cultivars can be completely explained in terms of different dry matter partitioning into fruit, supporting the hypothesis that early bearing is a major cause, rather than merely a consequence, of lower vigor in young ‘Arbequina’ trees. These results provide new understanding on vigor differences across cultivars, which will be useful for breeding and selection of new genotypes. The higher productivity of modern fruit tree cultivars, compared with wild trees, is mostly related to their higher partitioning of dry matter into fruit [i.e., higher harvest index (HI)] (Patrick, 1988), rather than to differences in photosynthetic abilities (Loomis, 1983). In cultivated species, HI often reaches 75% (Cannell, 1985), whereas it is much lower in wild species. The increase in HI is obtained both by a shorter initial unproductive period (i.e., early bearing) and by maintaining higher partitioning into fruit in the mature tree (more abundant yield, relative to tree size) to the detriment of vegetative growth (Archbold et al., 1987; Forshey and McKee, 1970). In fact, reproductive and vegetative growth are in competition for the available resources and one inhibits the other (Grossman and DeJong, 1995a, 1995b; Kramer and Kozlowski, 1979; Spurr and Barnes, 1980). Because of this competition, it has long been assumed that reducing vegetative growth is essential to bring about early and abundant fruiting (Browning, 1985). Containing plant vigor, e.g., by controlled water stress (Mitchell et al., 1989); containing root volume with drip irrigation (Mitchell and Chalmers, 1983) or by root pruning (Geisler and Ferree, 1984); dwarfing rootstocks (Avery, 1970; Preston, 1958); and shoot removal, chemical control of vegetative growth, or both (Mulas et al., 2011; Rugini and Pannelli, 1992; Williams et al., 1986), all result in enhanced yield. However, the opposite is also true: once reproduction starts, the crop will compete with, and reduce, vegetative growth and, therefore, vigor, as shown also by modeling (Grossman and DeJong, 1994; Smith and Samach, 2013). This is the case for mature trees of many species (Berman and DeJong, 2003; Costes et al., 2000; Lauri and T erouanne, 1999; Salazar-García et al., 1998; Stevenson and Shackel, 1998), including olive (Castillo-Llanque and Rapoport, 2011; Connor and Fereres, 2005; Dag et al., 2010;Lavee, 2007;Monselise andGoldschmidt, 1982; Obeso, 2002; Rallo and Su arez, 1989). In young trees, the removal of all blossoms or fruits results in dramatic increases in growth relative to the fruiting trees (Chandler and Heinicke, 1926; Embree et al., 2007; Forshey and Elfving, 1989;Mochizuki, 1962; Verheij, 1972). Similarly, earlier and more abundant fruiting (i.e., higher partitioning into fruit) is at least one of the mechanisms involved in the effect of dwarfing rootstocks (Avery, 1970; Preston, 1958) and in some cases, the only mechanism (Lliso et al., 2004), although in other cases, it is probably not the only one. In fact, defruiting apple trees on dwarfing rootstocks allows tree vigor to increase dramatically, but still less than in trees with more vigorous rootstocks (Avery, 1969; Barlow, 1964). It could be argued, therefore, that early and abundant fruiting is not just a consequence of lower vigor, but once induced, it becomes a cause of the reduction in vigor. Whether different partitioning into fruit (i.e., difference earliness and abundance of fruiting) could be the cause of differences in vigor among different cultivars has not been studied. In olive, as for other fruit trees, vigor reduction and early and abundant production are also desirable traits (Rallo et al., 2007; Tous et al., 1999), but few cultivars possessing these traits have been identified, despite much research on reduced vigor or even dwarf cultivars (Barranco, 1997; Le on Moreno, 2007; Sonnoli, 2001). Nor has it been possible to successfully induce these traits in traditional olive cultivars by grafting, despite much research on olive rootstocks (Baldoni and Fontanazza, 1990; Barranco, 1997; Pannelli et al., 1992, 2002; Troncoso et al., 1990). Recently, the so-called SHD orchards have been developed, using the few cultivars found to have sufficiently low vigor and early yield. SHD olive orchards, if indeed technically and economically viable, are important for the olive industry because they allow continuous (i.e., straddle harvester) mechanical harvesting (Rallo et al., 2007; Tous et al., 1999), thus greatly reducing costs and hand labor requirements. However, the straddle harvester requires small-canopy trees (Camposeo et al., 2008; Tous et al., 2006) and traditional cultivars tend to ‘‘escape’’ from the small volume allowed, thus requiring intense pruning, which stimulates vegetative growth and reduces fruiting (Jerie et al., 1988). SHD Received for publication 27 Nov. 2017. Accepted for publication 23 Feb. 2018. We gratefully acknowledge Darcy Gordon for language editing. Co-first author. Corresponding authors. E-mail: adolfo.rosati@ crea.gov.it or franco.famiani@unipg.it. This is an open access article distributed under the CC BY-NC-ND license (http://creativecommons. org/licenses/by-nc-nd/4.0/). HORTSCIENCE VOL. 53(4) APRIL 2018 491 orchards also require early and abundant fruiting if they are to be economically viable (De Benedetto et al., 2003). It is important, therefore, to understand the mechanisms implicated in early and high production and reduced canopy size. So far, the cultivars that proved most suitable for SHD olive orchards are Arbequina, Arbosana, and Koroneiki (Tous et al., 2006), three cultivars characterized by low vigor compared with most traditional cultivars (Rosati et al., 2013; Tous et al., 2006). However, they are also characterized by early and abundant bearing, as well as low alternate bearing (Caruso et al., 2012; Díez et al., 2016; Farinelli and Tombesi, 2015; Godini et al., 2011; Moutier, 2006; Moutier et al., 2008). Trees of these cultivars produce large crops, relative to their size, already in the second and third year after transplanting. Given the competition between crop and vegetative growth, we hypothesize that early bearing is implicated in the difference in vigor between such cultivars and more traditional ones that do not fruit until much older. In a previous study (Rosati et al., 2017), we found that tree growth, in terms of both tree diameter and canopy volume increments, was inversely related to tree yield across 12 cultivars in young olive trees. Similarly, Di Vaio et al., (2013) found that across 20 cultivars, the least vigorous tended to have greater early yields. However, correlation does not prove causality and only by defruiting the trees it would be possible to test whether fruiting is indeed a cause, rather than a mere consequence, of reduced vigor in early-bearing low-vigor cultivars. In this article, we test the hypothesis that earlier and more abundant bearing is the cause, or one of the causes, of reduced vigor. To test this hypothesis, we compared the initial growth of deflowered, partially deflowered (i.e., in alternate years), and control fruiting trees in Arbequina, the cultivar most used in SHD orchards, and in Frantoio, a traditional cultivar much more vigorous than Arbequina (Rosati et al., 2013; Vivaldi et al., 2015). Materials and Methods The study was carried out at the Department of Agricultural and Environmental Sciences of the University of Perugia. Oneyear-old plants, originated from rooted cuttings, were grown in 9.5-L pots. The trees were grown outdoors for two seasons (2014 and 2015). The trees were regularly fertigated using a drip irrigation system, avoiding any water and nutrient stress. A total of 48 ‘Arbequina’ and 48 ‘Frantoio’ trees were used. Initially, we planned to deflower half of the plants during the first season and then half of each treatment in the second season. ‘Frantoio’, however, had no flowers the first season and only ‘Arbequina’ could be deflowered. Therefore, only 24 ‘Frantoio’ plants were retained in the experiment. In 2015, instead, both cultivars bore inflorescences and could be deflowered. To avoid confusion, we, therefore, called the different treatments fruiting (Fr) and not fruiting (NF), whether naturally or because deflowered. Therefo

Correction to: Advances in European agroforestry: results from the AGFORWARD project

In the original publication of the article, the copyright line was incorrect in Springer link. The correct copyright line should read as “The Author(s) 2018”. The original article has been corrected.

Growth Is Inversely Correlated with Yield Efficiency across Cultivars in Young Olive (Olea europaea L.) Trees

The modern olive industry is increasingly interested in olive cultivars that start producing early and remain relatively small, because they are suitable for super highdensity orchards. Some cultivars are better suited to this than others but it is not clear why. Understanding the mechanisms that lead to early production and reduced canopy size is therefore important. The object of this study was to investigate whether differences in vigor across olive cultivars are related to earliness and abundance of bearing. We analyzed tree growth and productivity in young coetaneous trees of 12 olive cultivars, grown together in the same orchard. Trunk diameter increased over the observation period, reaching significantly different values across cultivars. Canopy volume also increased, reaching 2-fold differences between the minimum and the maximum values. Cumulative yield increased, reaching up to 3-fold differences. When the cumulative yield at the end of the experiment was plotted against the final trunk diameter, no correlation was found. A significant correlation was found when cumulative yield was plotted against the increment in trunk diameter during the observation period for which yield data were collected. This relationship improved (i.e., R rose from 0.57 to 0.83) when yield efficiency [i.e., cumulative yield per unit of final trunk cross-sectional area (TCSA) or per unit of canopy volume] was used instead of yield. These results clearly showed that trees that produced proportionally more (i.e., higher yield efficiencies) grew less.We conclude that, in young olive trees, vigor is inversely related to early bearing efficiency, which differs significantly across cultivars. The results support the hypothesis that early and abundant bearing is a major factor in explaining differences in vigor across olive cultivars. The olive industry requires canopy reduction to allow super high-density orchards which permit earlier production and continuous mechanical harvesting (Rallo et al., 2007; Tous et al., 1999). This has stimulated much research into reduced vigor or even dwarf cultivars (Barranco, 1997; Le on Moreno, 2007; Sonnoli, 2001) and dwarfing rootstocks (Baldoni and Fontanazza, 1990; Barranco, 1997; Pannelli et al., 1992, 2002; Troncoso et al., 1990). Some cultivars, such as Arbequina, Arbosana, and Koroneiki, are better suited than others for super highdensity orchards which require smallcanopy trees (Camposeo et al., 2008; Tous et al., 2006) but it is not clear why. Understanding the mechanisms that lead to early and high production and reduced canopy size is therefore very important. It is generally assumed that such cultivars have an inherent low vigor, and that this trait is the key factor for their suitability to super high-density orchards. It has also been shown that these cultivars exhibit greater branching associated with smaller diameters of trunk, branches, and shoots, resulting in higher yield efficiency and a greater number of fruiting shoots in the small canopy volume allowed in super high-density systems (Rosati et al., 2013). Therefore, the lower tree size results, at least in part, from the different branching characteristics, which concentratemore shoots in a small canopy volume, without necessarily implying lower shoot growth. However, the low vigor of such cultivars is also associated with the ability to produce more and earlier (Camposeo et al., 2008; Tous et al., 2003, 2006). It is possible, therefore, that the low vigor (reduced growth) of early-bearing cultivars could derive from their higher early productivity. If a tree spends more of the available resources into producing fruits, it can only grow less as a result (Grossman and DeJong, 1994). Competition between vegetative and reproductive growth is well established in several tree species (Berman and DeJong, 2003; Costes et al., 2000; Lauri and T erouanne, 1999; Salazar-García et al., 1998; Stevenson and Shackel, 1998) including olive (Castillo-Llanque and Rapoport, 2011; Connor and Fereres, 2005; Dag et al., 2010; Fern andez et al., 2015; Monselise and Goldschmidt, 1982; Rallo and Su arez, 1989). However, very few studies considered young trees and no relationship between tree initial growth and cumulative yield was found (Moutier, 2006). It is important to consider that absolute yield is a size-dependent parameter and it is possible that, if less productive young trees grow faster, they will eventually become bigger enough to outyield the smaller, albeit more yield-efficient, trees. A more thorough analysis of growth and productivity, the latter expressed as yield efficiency, might reveal a relationship between tree growth and yield. In this article, we test the hypothesis that the initial growth of young olive trees is inversely related to their yield efficiency. Materials and Methods The trial was carried out in an olive orchard located at the experimental farm of the CREAOLI, near Spoleto in central Italy (42 48#48

Combining livestock and tree crops to improve sustainability in agriculture: a case study using the Life Cycle Assessment (LCA) approach

N, 12 39#15

Plant density and genotype effects on wild asparagus (Asparagus acutifolius L.) spear yield and quality

E, 356 m above sea level). Selfrooted trees were planted in 1986 and measurements began in 1990 on five trees of each of 12 cultivars studied, namely ‘Vocio’, ‘San Felice’, ‘Rosciola’, ‘Raio’, ‘Raia’, ‘Pocciolo’, ‘Marchigiana’, ‘Leccino’, ‘Frantoio’, ‘Dolce Agogia’, ‘Correggiolo’, and ‘Borgiona’. The cultivars were placed in rows (i.e., one row per cultivar) and border rowswere not used. Along the row (20 trees), the five representative trees were sampled at random along the whole length of the row (excluding border trees), to avoid possible differences due to position, even though the soil was uniform. Tree spacing was 5 · 5 m and the trees were trained to a cone shape. In order not to interfere with tree growth, pruning was limited to the minimum necessary to train the trees to a cone shape. Other field practices were carried out as traditionally done in the area, including chemical fertilization with N, P, and K, and natural Received for publication 19 July 2017. Accepted for publication 29 Sept. 2017. We thank Darcy Gordon for language editing and for critical review of the manuscript. Co-first author. Corresponding authors. E-mail: adolfo.rosati@ crea.gov.it or franco.famiani@unipg.it. This is an open access article distributed under the CC BY-NC-ND license (http://creativecommons. org/licenses/by-nc-nd/4.0/). HORTSCIENCE VOL. 52(11) NOVEMBER 2017 1525 green mulch mowed two to three times per year. Parameters measured annually, from 1990 (year 1) to 1996 (year 7), included trunk diameter, from which TCSA was calculated, tree yield, and basal diameters and height of the canopy from which canopy volume was calculated, assuming a cone-shaped canopy. Yield efficiency was calculated as the cumulative yield over the studied period divided by the TCSA, or by the canopy volume, at the end of the period. Cultivar differences in the various parameters measured were statistically analyzed by analysis of variance (ANOVA), according to a completely randomized design, and averages were compared by using the Student– Newman–Keuls test. Relationships between parameters were evaluated by calculating the coefficients of determination (R) and the statistical significance of the fits. Results and Discussion Tree diameter increased over time with large variation among cultivars (Fig. 1). Vocio, the cultivar reaching the largest diameter, had values about 45% greater than Borgiona, the smallest cultivar. Results of the ANOVA for the final diameter are reported in Table 1. The different tree growth here found is similar to what has been found in previous studies (Farinelli and Tombesi, 2015; Vivaldi et al., 2015). Canopy volume increased over time with larger variations among cultivars than for trunk diameter (Fig. 2): ‘Raio’ reached the largest canopy volume, more than double that of ‘Pocciolo’, the smallest. Results of the ANOVA for the final canopy volume are reported in Table 1. Cumulative yield increased over the observed period, reaching more than 3-fold differences between the most and the least productive cultivars (Fig. 3). Results of the ANOVA for the final cumulative yield are reported in Table 1. To assess whether tree growth was affected by yield, we plotted the cumulative yield obtained over the 7-year observation period against the final trunk diameter and found no significant relationship (Fig. 4) as previously found (Moutier, 2006). The lack of correlation was because trees were of dissimilar size at the start of the experiment, and the final diameter was not a good parameter to indicate tree growth during the period over which yield was evaluated. Final diameter represents tree growth from the beginning of the tree life, but yield data were not collected before 5 years from transplanting, when all cultivars had at least some fruits, although other cultivars had already produced more extensively. Therefore, to compare tree growth and yield over the same period, the diameter increment during the observed period was used in place of the final diameter. When cumulative yield was plotted against the diameter increment over the same observation period, a significant relationship was found (Fig. 5). However, the relationship was much improved (i.e., R = 0.83 instead of 0.57 and significance of the relationship was P# 0.01) when yield efficiency was used in place of yield, both when efficiency was expressed in terms of yield per unit cross-sectional area (Fig. 6) or unit of canopy volume (Fig. 7). This indicates that a poor (or lack of) relationship between growth and cumulative yield derives from growth dynamics. In fact, trees that initially produce less (i.e., lower yield efficiency) and grow more can eventually become bigger enough to outyield trees that initially producedmore and thus remained smaller. These results point at the importance of correctly evaluating growth and yield parameters. Because of the growth dynamics described above, yield alone does not represent a good parameter to evaluate whether tree