Temporal response of belowground and aboveground organisms to microclimate changes in irrigated mediterranean vineyards.

As a major adaptation to climate change in European crop production, irrigation is constantly increasing, particularly in Mediterranean agroecosystems. However, changes in microclimatic conditions due to irrigation may affect agroecosystem components, including soil organisms, ground-dwelling arthropods and their associated ecological functions. This study analyses the short-term effects of irrigation on Mediterranean vineyard ecosystems during the summer drought period. Soil microorganisms (phospholipid fatty acid analysis), enzymatic activity, soil respiration, organic matter decomposition, mesofauna and ground-dwelling arthropods were analysed in South-eastern French vineyards. We set up a randomised block design in two vineyards, each comprising 12 blocks with one irrigated and one non-irrigated plot per block. All response variables were measured four times: before irrigation, during irrigation, two days after irrigation, and one month later following the first rainfall. Effects of irrigation were analysed using mixed models. Irrigation exclusion reduced the abundance and activity of microorganisms, the abundance of mites and springtails, and soil respiration. It also affected the decomposition of organic matter, as evaluated using the tea bag method. The duration of these effects varied from a few hours for microorganism abundance to one month for mesofauna abundance. No differences remained after the drought period, when late summer precipitations compensated for differences in soil moisture. As drought periods may become more frequent and severe, the effects of irrigation are likely to increase. This may lead to long-term changes in soil community composition and associated functions. Our study highlighted the need for long-term monitoring of irrigation effects, as irrigation will likely become standard practice in future.