Effects of irrigation on vegetation, mesofauna and organic matter decomposition in Mediterranean vineyards

Increasing temperatures and resulting stronger spring and summer drought have exponentially increased irrigation in Mediterranean vineyards. So far, little is known about the potential effects of irrigation on vineyard agroecosystems. The aim of this study is to assess the effect of vineyard irrigation on vegetation, soil mesofauna, the decomposition of organic matter, grapevine yield and berry sugar content. Five pairs of vineyards were selected in South-eastern France (Luberon), each comprising an irrigated and a non-irrigated vineyard. The irrigated vineyards received on average 60 mm of water which doubles usual summer rainfall. Under-vine vegetation and soil mesofauna were analysed during the growing season (April) and the following summer drought (August). Organic matter decomposition was tested using tea bags that were buried from January to May in the grapevine row. We found a significant difference in vegetation cover between treatments in April but not in the following August. Springtail and mite abundance were only different between treatments in August being higher in irrigated vineyards. In August, we also found significant differences between treatments in the structure of the soil mesofauna community. The effect of irrigation on the decomposition of organic matter was not significant. Grapevine yield was higher in irrigated vineyards but no effect on the chlorophyll index of grapevine leaves was found. This study highlighted the effect of irrigation showing that even moderate irrigation has significant effects on Mediterranean vineyard ecosystems. The strong increase of irrigated vineyards advocates for further research to obtain a better understanding of irrigation consequences under different pedoclimatic conditions.