Carbon sequestration in orchards and vineyards

I sistemi arborei possono agire da accumulatori netti di CO2 grazie alla loro capacità di stoccare carbonio organico nelle strutture permanenti e nel suolo. In questo articolo vengono esaminati tre importanti sistemi arborei da frutto quali melo, vite e olivo, che sono stati oggetto dell’ “International Workshop on Carbon Sequestration in Horticultural Crops” tenutosi a Pisa il 30 ottobre 2018. La comprensione delle relazioni che intercorrono tra le variabili ambientali, i processi fisiologici e la gestione agronomica riveste un ruolo cruciale per una corretta stima dei flussi e dell 'allocazione del carbonio in frutteti e vigneti.

Climate change, caused by unprecedented concentrations reached in the atmosphere by major greenhouse gases, is responsible for detrimental effects also on agricultural ecosystems. Woody tree crops, representing significant portions of land surface in many regions, have intrinsic features that allow them to potentially act as net CO2 sink, storing it as organic carbon in their permanent structure and in the soil. Taking advantage of the outcomes of the “International Workshop on Carbon Sequestration in Horticultural Crops”, organized by the Italian Horticultural Society (SOI) and held in Pisa on the 30th of October 2018, this paper reviews the major findings in the assessment of carbon fluxes in three fruit tree systems: vineyards, apple and olive orchards. In general, the gross primary productivities (GPP) of the examined woody agroecosystems are comparable with those of temperate forests, with higher efficiency in allocating the synthesized carbon in new biomass, possibly due to lower growth and maintenance costs. However, the carbon storing capacity is highly variable in time and space and it is strongly dependent on climatic conditions and orchard management. The major factors influencing orchards net ecosystem production (NEP) includes the seasonal environmental conditions, planting density, irrigation and soil management, with water supply and cover crops producing positive ecosystems services not limited to carbon sequestration. The orchard net ecosystem carbon budget (NECB) is determined by considering the lateral carbon fluxes, with the harvesting of fruits and the use of organic fertilizers and soil improvers representing the most influential practices. In general, higher carbon storage capacity of fruit tree systems is possible through an intensification of ecological practices, adopting strategies that aims at minimizing negative environmental effects such as nutrient leaching, soil erosion, loss of biodiversity, while maintaining high yield performance. Understanding the relationships between physiological processes and specific management practices and environmental variables, either via long term monitoring experiments and/or the calibration of specific models, is crucial to get a clearer picture of the carbon fluxes occurring in changing growing conditions, and to predict the response of the orchard under different scenarios.