Viticultural practices in Jumilla (Murcia, Spain): a case study of agriculture and adaptation to natural landscape processes in a variable and changing climate

Abstract

This study examines viticultural practices near Jumilla (Murcia, SE Spain). It focuses on a site with extensive rock fragment (RF) covers on vineyard soils, their probable origins and the effects surface RF have on vines and soil properties, and also discusses the expected impacts of climate change during the 21st century. Data about vitivinicultural activities, substrates, and vineyard characteristics were obtained through extended interviews and fieldwork during three summer seasons. Vineyards occupy an extensive Quaternary-age, colluvial/alluvial glacis at 650–760 m below Sierra Molar, an Upper-Cretaceous mountain range that supplies white dolomitic limestone and calcareous marl clasts for RF. Regional climate is semiarid; rainfall is 313 mm/year, average temperature is 14.9 °C; a significant seasonal moisture deficit (≥478 mm/year) occurs during hot summers. Agricultural crops in the property are exclusively rainfed; no irrigation is utilized. This is facilitated by RF layers, which reach 100% groundcover and ≤30 cm thickness. Rock fragments occur naturally in the soil; RF are not placed on the fields, but accumulate by a combination of downslope transport from mountains by several geomorphic processes, and from agricultural tillage. RF covers show a layered structure; larger RF at the surface rest on a thin horizon of smaller fragments, over a thinner basal layer of even smaller particles lying unconformably on fine earth; this vertical stratification is generated by the sieving effect. The main pedological effects of RF include: improved infiltration and water storage, decreased runoff, lower evaporation rates, soil protection from rainsplash compaction and erosion, lower maximum temperatures, and greater sunlight reflection due to high rock albedo. By the late 21st century, Jumilla may experience higher seasonal temperatures, ~5–7 °C+ during summer, and 3–4 °C+ in winter, and a ~17–36% reduction of annual rainfall; the combination will cause greater evapotranspiration and vine stress. Several possible strategies to minimize the effects of climatic change are discussed.