The role of two different training systems in affecting carbon sequestration capability in hazelnut orchards

Energ. Ecol. Environ. https://doi.org/10.1007/s40974-020-00202-1 ORIGINAL ARTICLE The role of two different training systems in affecting carbon sequestration capability in hazelnut orchards Mirko U. Granata1 1 • Rosangela Catoni1 • Francesco Bracco1 Department of Earth and Environmental Sciences, University of Pavia, Via S. Epifanio 14, 27100 Pavia, Italy Received: 8 June 2020 / Revised: 27 October 2020 / Accepted: 28 October 2020  The Author(s) 2020 Abstract As a part of a larger study concerning the carbon sequestration capability by hazelnut orchards in Italy, we analyzed the total amount of carbon dioxide (CO2) removed over the year from the atmosphere through the net assimilation rates in two hazelnut orchards in Piedmont (i.e., the second region in Italy for surface and production). In particular, considering the key role played by the structural traits in affecting carbon sequestration potential, we assessed the impact of two different training systems widely diffused in the region: single trunk in orchardA and bush-like in orchardB. The results showed that plants in orchardA and orchardB sequestered 10.6 ± 1.8 and 25.7 ± 4.2 kg (CO2) plant-1 month-1, respectively. Higher CO2 sequestration in the plants in orchardB was due to their higher leaf area index relative to plants in orchardA. The mean CO2 sequestration from orchardA and orchardB per area was 4.25 ± 1.72 and 8.57 ± 3.41 Mg (CO2) ha-1 month-1, respectively. We also estimated the total amount of CO2 emission by the management over the entire production season in 157.335 kg CO2eq ha-1 by summing the contribution of diesel fuel, machinery and fertilization practices and considering that the total amount of CO2 sequestered by the two hazelnut orchards over the entire study period was estimated in 26 Mg (CO2) ha-1 in orchardA, and in 51 Mg (CO2) ha-1 in orchardB, they had an effective positive role as carbon sink at this local level. Keywords Hazelnut orchard  Training systems  Carbon sequestration  Leaf area index & Rosangela Catoni 1 Introduction In the scenario of expected climatic change (temperature increases and water deficits) related to the greenhouse effect, there has been an increasing interest on the carbon (C) cycle in terrestrial ecosystems (Don et al. 2012). The global warming is now clearly recognized as a major threat to natural and socioeconomic systems, and the global community is searching for cost-effective ways to slow the build-up of atmospheric carbon dioxide (CO2) concentrations and minimize its impact (Kirschbaum 2006). The Kyoto protocol to the United Nations framework convention on climate change (1997) establishes the principle that carbon sequestration can be used by participating nations to help meet their respective net emission reduction targets for carbon dioxide (CO2) and other greenhouse gases. In fact, by sequestering a large amount of atmospheric C, terrestrial ecosystems are thought to offer a mitigation strategy for reducing global warming (Schimel et al. 2001). Specifically, the Article 3.4 of the Kyoto Protocol recommended, among the allowed activities, forest management, cropland management, grazing land management and revegetation (Smith 2004). In particular, among the cropland context, orchards in comparison with annual crops have structural characteristic allowing them to sequester significant quantities of atmospheric C for longer periods with smaller annual fluctuations (Smaje 2015). This different performance of the orchards is due to, on the one hand, their long life cycle, which allows them to accumulate C in permanent organs such as trunk, branches and roots and in the soil through rhizo-deposition and, on the other hand, to a low or null soil tillage, which preserves soil organic matter from mineralization (Scandellari et al. 2016). Nevertheless, in spite of the strategic role of orchards, their C 123 M. U. Granata et al. potential has been only partially explored, with studies conducted regarding olive (Nardino et al. 2013; Sofo et al. 2005), palm (Navarro et al. 2008), apple (Zanotelli et al. 2015), peach (Sofo et al. 2005) and pear (Zhang et al. 2013). The landscape of Mediterranean region is largely dominated by orchards (Aguilera et al. 2015), and one of the most widely diffused is represented by hazelnut orchard (Corylus avellana L). Among the Mediterranean region, Italy is one of the major hazelnut productions worldwide, being second only to Turkey. In Italy, the hazelnut production surface is located mainly in four regions: Lazio, Piedmont, Campania and Sicily, covering 98% of the entire Italian production area (Istat 2019). The present work is part of a larger study on the carbon sequestration capability of hazelnut orchards, which first covered orchards in Lazio region, with data that have been extended to include the nearby Campania region (Granata et al. 2020). The current study is focalized on the role of carbon sinks in hazelnut orchards in Piedmont, that based on the latest updates on the surface devoted to this culture, ranks as the second region in Italy for surface and production (24,555 ha and 39,997 tons, respectively, data from Istat 2019). In Piedmont, the hazelnut cultivation became really important and expanded in the late 1980s (Godone et al. 2014). Over time, there has been a significant increase in hazelnut surfaces in Piedmont, with a stronger trend than in the rest of Italy which reflects an increased interest of landowners toward hazelnut and its economical potential (Valentini and Me 2002). In particular, the nut production is based on a single cultivar ‘tonda gentile delle Langhe,’ selected directly by farmers for its good environmental adaptability to Piedmont climate and for the excellent quality of the kernel (Valentini et al. 2014). In Piedmont, the traditional cultivation of this cultivar expects different training systems in open forms such as the bush or single trunk. In both cases, choosing the right distance between plants is necessary to ensure adequate ventilation and lighting as well as allowing the mechanized cultivation practices such as pruning and harvesting. Thus, based on the soil fertility, water availability and the training systems, the planting distance inside the hazelnut orchards may vary from 5 9 4 m (plant density 500 plants ha-1) to 6 9 6 m (plant density 278 plants ha-1) (Comunità Montana Alta Langa, 2009). The aim of this work was to analyze the CO2 sequestration capability of mature hazelnut orchards in Piedmont in two areas where hazelnut plants were subjected to two different training systems (bush vs single trunk), but similar in terms of plants densities (333 vs 400 plants ha-1). The objectives of the study were 1) to compare the CO2 sequestration in the two orchards with respect to the different training systems, 2) to measure the seasonal pattern of CO2 sequestration during the year and 3) to 123 contextualize the obtain CO2 sequestration capability in the Italian sc (...truncated)