& Key message This study developed and tested models to predict the belowground biomass and root/shoot ratio using aboveground field measures. The predictive power of such indirect measurement is useful for a rapid and reliable assessment of the biomass of the Mediterranean species. & Context Forest biomass estimation has been simplified by the availability of indirect methodologies for automatic measuring. However, most of the information on forest root systems is largely unexplored due to the difficulty in estimating belowground biomass (BGB) at large scale. A plausible approach to investigating forest BGB is to establish a relationship between a number of dendrometric parameters related to the aboveground vegetation (AGB) (e.g., tree diameter and height) and the belowground component of the total biomass. & Aims This work presents findings for indirect measurements of BGB in the typical Mediterranean landscapes focusing on sclerophyllous vegetation, specifically Phillyrea latifolia L. The purpose of the present study is twofold: (a) to develop a model explaining the BGB distribution of P. latifolia based on field data for dendrometric parameters, and (b) to understand how the ratio between BGB and AGB varies according to stem diameter as a proxy of plant growth. & Methods A total of 50 P. latifolia plants were randomly selected in the study areas and considered for excavation. Individual plants were analyzed to determine AGB and BGB development. A number of models were developed and tested to predict the BGB and root/shoot ratio using aboveground field measures. Allometric equations were employed to predict the AGB and BGB and relative partitioning in the Phillyrea community. & Results Models for P. latifolia AGB and BGB estimation that include crown diameter and stem height measures augment the models' predictive power. When used alone, the predictive power of the root collar diameter appears to be overestimated, while its effect is stronger for a subset of observations with larger crown diameter and stem height. The root/shoot ratio values of plant species typically related to the Mediterranean context seem to be largely superior to the ratio values of trees and forests. & Conclusions The model is ideally suited to incorporate indirectly measured tree height for a rapid and reliable assessment of the biomass of single Mediterranean species. Further research might include replication of the same studies in different geographic areas of the Mediterranean and in-depth analyses of AGB.

The aim of the current paper is to focus on the processes that rule transactions among firms, trying to highlight coordination forms. In stable social networks exchange occurs because of certain social elements, such as trust and reputation, which have a good influence on clarifying the expectations of the parties involved and on audit cost reductions. In this case social capital represents the coordination form that enables such relationships. To prove this statement we analyzed the network of socioeconomic relationships in the organic olive oil supply chain in the Sierra de Segura (Andalusia).

- Social capital and economic firm performances: an application to the organic extravirgin olive oil net-chain in the province of Bari The supply chains of niche market goods like organic products are rapidly evolving. Compared to the conventional supply chains, these are more risky andmarket oriented. Therefore, to build stable networks along and among the chains is becoming an increasingly valuable as a competitive factor. The firms use these networks to exchange tangible and intangible assets. Structural social capital embedded in business networks could influence the firms' competitiveness. In this perspective it can be worthwhile for the possible normative suggestion for policy makers to consider the control over strategic resources spread in the environment out of the firm, as a competitive advantage source, together with the firm's internal resources. The external environment is characterized by a net of inter-firms relationships, which pertain to trade exchange, information exchange, shared norms and resources' association. The strategic resources inside the network, especially information, constitute an asset that companies need to improve their competitive advantage. The structure of relationships enabling the access to those resources, constitute the social capital (sc) which is revealed in the modalities with which firms place themselves in the net: higher the sc, the higher the economic performance. This study aims to show the significance of structural sc in influencing the firms' economic performances in agribusiness. We will try to test this hypothesis by analyzing the organic olive oil production system in the Province of Bari. In this study we refer to the form of sc linked to the firm's position inside the net-chain and to the idea of structural holes. Specifically, we decided to measure sc in terms of network constraints - a more constrained entrepreneurial activity implies less structural holes and therefore less sc. As for the firm performance measures, there are several indexes that could be appropriate: from the well known roi (Return on Investment) and ros (Return on Sale), to revenue. Actually, we selected the last one (revenue). It in fact the results are easier to find, and the productive structure of the firms involved in the organic olive oil processing can be considered quite homogeneous. To measure the structure of the relational web we adopt the Social Network Analysis (sna), a method based on the analysis of the actors (individuals, firms, and institutions) involved in a particular context and on the relationships between them. The subject of the analysis is the extra-virgin organic olive oil net-chain in the province of Bari. A set of economic institutions and organizations both located in this province and out of this territory but involved in processing and in trading the extravirgin organic olive oil. The results obtained, show that also in agribusiness netchains, as the organic olive oil, firms gain a higher competitive advantage if the are able to be central in the network of relationships, both horizontal and vertical, assuming an intermediary role in the transactional and informational flows. Further studies are still necessary, since the analysis completely disregards some key factors of competitiveness (although recognizing their relevance), which are not directly connected to the structure of relationships of the netchain as the relational social capital (e.g. trust, norms and expectations) and cognitive social capital (e.g. shared view, common language).JEL Code: L14Key words: social capital, network analysis, netchain, economic performance, organic olive oil

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