Field practices for adapting Mediterranean viticulture to climate change

Abstract

Field practices for adapting Mediterranean viticulture to climate change Mediterranean viticulture is being affected by climate change, which threatens wine typicity and, therefore, the whole viticulture sustainability. The main factors expected to affect grapevine cultivation are water scarcity, warm air temperature and the increase in the air carbon dioxide concentration, and impact of these factors will be mainly the: i) advancing of grapevine phenology, thereby decoupling berry technological and phenolic composition and ii) increasing vine water requirements. This PhD Thesis aimed at evaluating the effects of different field practices to adapt Mediterranean grapevine cultivation to climate change. Three experiments were performed in Valencia (Spain) to assess the effects of 1) regulated deficit irrigation; 2) training systems architecture and; 3) canopy management. The main responses evaluated were vineyard water-use efficiency (WUE) and grape composition. Experiment 1 was undertaken for three seasons in a drip-irrigated, cv. Muscat of Alexandria/161-49C vineyard to define the most sustainable irrigation strategy for white winegrapes in eastern Spain. For this, four treatments were tested: (i) Control, irrigated at 100% of estimated crop evapotranspiration (ETc) for the entire season; (ii) sustained deficit irrigation (SDI), irrigated at 50% of Control; (iii) early deficit (ED), where pre-veraison irrigation was withheld, followed by 100% ETc; and (iv) late deficit (LD), irrigated as in the Control until veraison and thereafter at 25% ETc until harvest. Results showed that yield in ED and LD was reduced 25 and 15%, respectively, compared to that of the Control, while yield under SDI did not differ significantly from that of the Control and was similar to that of the ED and LD treatments. All the deficit irrigation treatments had some carry-over effects on vine performance due to a significant decrease in shoot fruitfulness and in cluster mass due to smaller berries. Experiment 2 highlights that the response to the minimizing of the radiation load intercepted by the canopy is cultivar-dependent and that decreasing the radiation load in the Mediterranean vineyards could have positive effects on the whole vine's WUE. The effectiveness of the LLR technique seemed to depend on its final impacts on leaf area-to-fruit ratio and vine water status, the cultivar's photosynthetic compensation capacity and the environmental conditions. Therefore, under low vigour vine conditions, severe defoliation might not be advisable for adapting Bobal and Tempranillo to global warming due to the detrimental effects on red wine quality. On the contrary, the results of deficit irrigation and row orientation experiments provided novel insights on WUE as possible techniques to alleviate vineyard water scarcity. Therefore, the field practices studied are effective in adapting Mediterranean viticulture to climate change in terms of water stress. On the other hand, the impacts of the studied techniques in terms of thermal stress alleviation were not fully positive. Hence, further research is needed to determine the possibility of using other field practices, besides LLR, to couple berry sugars and phenolic maturity.