Developing a Carbon Balance Model for ‘Kyoho' Table Grapes Under Double Cropping Production System In Subtropical Climate

To develop a carbon balance model for grapevines in Taiwan’s subtropical climate, we adopted the basic structure of ‘Vitisim’, a model designed for wine grapes in New York. Climatic inputs and growth parameters were then adjusted and compared using data collected in a commercial vineyard from the beginning of the second cropping season in 2008. Canopy development and canopy light interception were measured on mature ‘Kyoho’ table grapevines (Vitis vinifera L. x V. labrusca L.) trained with an overhead horizontal trellis. Selected buds for winter crops were forced on late August after the first harvest. Shoot and berry development in the second cropping season were therefore under the gradual shortened day length and decreased temperature, in contrast to the first cropping or vines in temperate regions. Day length during the second cropping season decreased from 44760 s.d^-1 at bud break to 38220 s.d^-1 at harvest, in comparison to 41500-54000 s.d^-1 in New York, 46140-56568 s.d^-1 in Italy, and 43620-49140 s.d^-1 in the first cropping season in Taiwan. Average daily radiation was also lower in the second cropping season in central Taiwan (10.79 MJ^.m^-2.d^-1) than that in the first cropping season (16.13 MJ^.m^-2.d^-1) and that in the normal growing season in New York (16.03 MJ^.m^-2.d^-1). There was no difference among the first cropping season, the second cropping season, and the N.Y. growing season on heat accumulation from bud break to full bloom based on 10^oC, but the heat accumulation from bud break to harvest for the second cropping season in Taiwan was 1450 degree days, slightly longer than 1393 degree days in N.Y. Maximum canopy light interception for grapevines trained with the horizontal trellis system in Taiwan was 41%, similar to that of vines trained with a hedge row trellis in N.Y. In the second cropping season leaf fall began 108 days after bud break, sooner than that of 160 days in N.Y. Gas exchange parameters of ‘Kyoho’ grapevines were measured on potted vines. Maximum photosynthesis rate of ‘Kyoho’ grapevines was 14.5 μmol.m^-2.s^-1. In early Oct. 2008 a tropical storm (typhoon) partially defoliated the vines and temporary reduced LAI by 67%. Our model simulation indicated that this typhoon damage might have reduced total seasonal fixed CO₂ by 7.1%. By leaf fall, 724 g. CO₂ per square meter of the vineyard were fixed in the second cropping season in Taiwan, less than 1583 g CO₂ in N.Y.