Agro-climatic zoning of Spanish forests naturally producing black truffle

Abstract

Black truffle is a highly appreciated edible fungus that grows wild in southwestern Europe, although its cultivation has recently spread to other continents. In Spain the widespread exploitation of wild truffles began only after 1950, whereas plantations play a relevant role in truffle production from the late 1990s. However, most plantations continue to apply empiric practices not taking into account local environmental conditions. The identification of environmental factors driving black truffle distribution and yield could help to optimise cultivation practices, but no agro-climatic zoning is currently available for this fungus in Spain. This study characterises the climate of Spanish forests naturally producing black truffle, defines an agro-climatic zoning for the fungus and examines the climatic patterns across its spatial distribution. The examined forests presented climatic ranges coherent with the available experts' surveys, except for an extended low end in annual precipitation. The clustering identified three agro-climatic zones, with dry environments tending to be dominant. The principal components analysis indicated that the examined forests tended to cluster along water availability and temperature gradients. Only in one of the zones mean precipitations during the vegetative period were similar to those characterising optimum years for black truffle fruiting, thus suggesting that plantations could benefit from practices increasing soil water content. Similarly, the results suggested that in two of the zones plantations could benefit from practices increasing soil temperature in winter and early spring. The study provides a basis for large-scale planning of truffle cultivation and identification of research priorities in Spain.