New decision support tools for Portuguese viticulture are urging under a climate change context. In the present study, heat and chilling accumulation conditions of a collection of 44 grapevine cultivars currently grown in Portugal are assessed at very high spatial resolution (similar to 1km) and for 1981-2015. Two bioclimatic indices that incorporate non-linear plant-temperature relationships are selected for this purpose: growing degree hoursGDH (February-October) and chilling portionsCP (October-February). The current thermal growing conditions of each variety are examined and three clusters of grapevine cultivars are identified based on their GDH medians, thus assembling varieties with close heat accumulation requirements and providing more physiologically consistent information when compared to previous studies, as non-linear plant-temperature relationships are herein taken into account. These new clusters are also a complement to previous bioclimatic zoning. Ensemble mean projections under two anthropogenic-driven scenarios (RCP4.5 and RCP8.5, 2041-2070), from four EURO-CORDEX simulations, reveal a widespread increase of GDH and decrease of CP, but with spatial heterogeneities. The spatial variability of these indices throughout Portugal is projected to decrease (strongest increases of GDH in the coolest regions of the northeast) and to increase (strongest decreases of CP in the warmest regions of the south and west), respectively. The typical heat accumulation conditions of each cluster are projected to gradually shift north-eastwards and to higher-elevation areas, whereas insufficient chilling may represent a new challenge in warmer future climates. An unprecedented level of detail for a large collection of grapevine varieties in Portugal is provided, thus promoting a better planning of climate change adaptation measures.
Santos, JA; Costa, R; Fraga, H
New insights into thermal growing conditions of Portuguese grapevine varieties under changing climates
Theoretical And Applied Climatology