Seasonal carbon balance of 'Sangiovese' grapevines in two different central Italy environments

Seasonal carbon balance, expressed as grammes of dry matter accumulated per vine, was obtained using a daily time-step model (Stella software) which sums the daily difference between the estimated photosynthesis and respiration along the growing season. The model requires climatic, vegetative, and physiological input. Minimum and maximum air temperature, day-length, and available light were daily measured. Shoot growth, leaf area, and cluster dry weight were determined every 15 days. Finally, physiological parameters were monthly measured, as following 1) submodel Photosynthesis: maximum photosynthetic rate, photochemical efficiency, canopy extinction coefficient, light interception by the canopy; 2) sub-model Respiration: trends of a and b coefficients of the exponential response of the respiration rate to temperature in leaf, cluster, shoot and old wood. The trial was performed on grapevine cv. Sangiovese during 2001 growing season. Two mature spur-pruned and cordon trained vineyards were located on South-exposed hillsides near Perugia (IV, Inland-vineyard, Umbria region, 150 km from the sea) and near Ancona (MV, Maritime-vineyard, Marche region, 10 km from the sea). In MV, which was characterized by a higher air temperature and lower rainfall during the summer, the above ground accumulated dry matter per vine during the entire season was reduced by about 12% compared to IV (1907 vs 2149 g vine(-1)). The parameters which were most affected by the warmer conditions were the photochemical efficiency, the maximum photosynthetic rate and the respiration rate. In the MV about 49% of dry matter produced by the vine during the season was respired, whereas in the IV this percentage was only 36%. In both vineyards, the highest respiration rate was shown by leaves, followed by shoots, clusters, and old wood. In conclusion, data from destructive measurements showed good agreement with data estimated using Stella software. Conditions of drought and high temperature limited the seasonal dry matter production of the grapevines and increased the amount of carbon respired. Therefore, grapevine cultivars that are more sensitive to water deprivation, like Sangiovese, need great attention during the midsummer, especially in the Mediterranean areas, to avoid the critical periods which can be characterized by limiting supply/demand balance of the vine and undesirable dry matter allocation between different organs which will consequently reduce vine yield and grape quality.