# A Review of the Potential Climate Change Impacts and Adaptation Options for European Viticulture
## 4 Potential Climate Change Impacts
### The Role of Soils under Changing Climates  
Within the complex interactions between soil, plant functioning, fruit quality, and an evolving climate, the role of soils, the changes associated with soils, and the impacts resulting from these changes onto the soil-plant-atmosphere-continuum have been the least studied [149]. However, soil temperature has increased, at least at a rate similar to air temperature, over the past more than 100 years [150], and this has also been shown for soils in a vineyard region [151]. In the latter study, summer (NH; June, July, August (JJA)) soil temperatures (50 cm depth) were about 6 \({}^{\circ}\)C warmer than autumn temperatures (September, October, November (SON)) over most of the last century until about 1980. After this, JJA temperatures increased much faster than SON temperatures and reached average values today around 4 \({}^{\circ}\)C higher than about 40 years ago and about 8 \({}^{\circ}\)C warmer than SON temperatures [151]. These temperature increases are much larger than those observed over the same period for air temperature, and there is a high propensity that this already has profound effects on microbial community characteristics and activity [152]. Soils store about 2500 billion tons of carbon--more carbon than the atmosphere (780 billion tons) and plants (560 billion tons) combined on the planet [152] and, depending on cultivation practices, part of the carbon may be either released or additional carbon may be sequestered by the soil. A change in temperature may also alter the potential emission of some greenhouse gases from the soil, but this strongly interacts with soil water content [153].  
The temperature may play a potent role, because, depending on organic matter content; water holding capacity; pore size distribution; precipitation rates; and other climate variables, such as solar radiation, the temperature has a large effect on the mineralization rate [154; 155]. A comparison of the simulated rates of nitrogen mineralization during the growing season, for 30 year periods since 1961, showed increasing rates over the past 50 years, with substantial differences between soils [156; 157]. This analysis suggested that modifications in temperature and water relations in some vineyard sites already had a substantial impact on the release of nitrogen, which might have increased the risk for bunch rot development on these sites. However, independent measurements to validate model simulations are lacking, and a recent study on warming effects on microbial communities in temperate vineyard soils, which would be involved in N mineralization, did not find substantial changes [158].  
Soil temperature also has a direct effect on root and shoot hydraulics, which will affect the transpiration rate, which is so far under-rated in the quantification of possible climate change effects on plant water use. These increases in hydraulic conductance have been attributed to changes in membrane fluidity and permeability [159; 160], or changes in water viscosity [161], but most likely are a combination of both [162]. For a vineyard situation, attempts have been made to estimate these currently hypothetical changes, and the results show substantial possible effects on transpiration [151].