Vineyard mulching as a climate change adaptation measure: Future simulations for Alentejo, Portugal

Climate change projections for the next decades are expected to bring important challenges to the Portuguese viticulture. More specifically, for the wine region of Alentejo, in Southern Portugal, the projected warming and drying are expected to have detrimental impacts on grapevine physiology and ultimately on yields. The present study assesses the adaptation potential of mulching for maintaining current grapevine yield levels in the region. For this purpose, the STICS process-based crop model was used to simulate future (2021-2080) grapevine yields in the 8 sub-regions of Alentejo (with Denomination of Origin). Several datasets for weather variables, soil characteristics, topographic features and management practices were defined independently for each sub-region. Simulations comprise both non-mulching and mulching experiments over the next 60 years, under the climate change scenario RCP8.5. Although both non-mulching and mulching simulations suggest a gradual yield decrease in the future, mulching mitigates these decreases by 10 to 25%. Furthermore, the results show that mulching can reduce the yield decreasing trend, from -0.75%/year to -0.66%/year. In effect, mulching is expected to provide yield gains over the full simulated time period, being the benefits particularly apparent towards the end of the target period (2061-2080; warmest years of simulation). Mulching is a cost-effective adaptation measure that may be easily adopted by growers on the short-term. Nonetheless, this strategy alone might not be enough to fully mitigate yield losses and additional / complementary measures should be envisioned to warrant the sustainability of the Alentejo winemaking sector under futures climates.