Black truffle winter production depends on Mediterranean summer precipitation

Joaquin Latorre,Paul J Krusic,Simon Egli,Fernando Martínez-Peña,Daniel Oliach,Ulf Büntgen

doi:10.1088/1748-9326/ab1880

Abstract

The unprecedented price inflation of Black truffles, recently exceeding 5000 Euro kg−1 (in Zurich), is a combined result of increasing global demands and decreasing Mediterranean harvests. Since the effects of long-term irrigation and climate variation on symbiotic fungus-host interaction and the development of belowground microbes are poorly understood, the establishment and maintenance of truffle plantations remains a risky venture. Using 49 years of continuous harvest and climate data from Spain, France and Italy, we demonstrate how truffle production rates, between November and March, significantly rely on previous June–August precipitation totals, whereas too much autumnal rainfall affects the subsequent winter harvest negatively. Despite a complex climate-host-fungus relationship, our findings show that southern European truffle yields can be predicted at highest probability (r = 0.78, t-stat = 5.645, prob = 0.000 01). Moreover, we demonstrate the reliability of national truffle inventories since 1970, and question the timing and dose of many of the currently operating irrigation systems. Finally, our results suggest that Black truffle mycorrhizal colonization of host fine roots, the sexualisation of mycelium, and the formation of peridium are strongly controlled by natural summer rainfall. Recognising the drought-vulnerability of southern Europe’s rapidly growing truffle sector, we encourage a stronger liaison between farmers, politicians and scientists to maintain ecological and economic sustainability under predicted climate change in the Mediterranean basin.

Highlights

16 km2 of arable land in northeastern Spain and southern France are transformed each year into new plantations of the (Périgord) Black truffle (Tuber melanosporum Vittad, an Ascomycota; hereinafter ‘truffle’), with slightly smaller units in northcentral Italy
Our results suggest that Black truffle mycorrhizal colonization of host fine roots, the sexualisation of mycelium, and the formation of peridium are strongly controlled by natural summer rainfall
While there is a sharp rise in Spanish summer precipitation and truffle winter production from 2012 to present, the French data present a much slower, though continuous increase since around 2003

Summary

Introduction

16 km of arable land in northeastern Spain and southern France are transformed each year into new plantations of the (Périgord) Black truffle (Tuber melanosporum Vittad, an Ascomycota; hereinafter ‘truffle’), with slightly smaller units in northcentral Italy This booming industry substantially contributes to rural economies and cultural identity (Samils et al 2008, Büntgen et al 2017). Many plantations are irrigated, an increase in the frequency and intensity of Mediterranean summer droughts is expected to affect both, the quality and quantity of the subsequent truffle winter harvest (Büntgen et al 2012, Thomas and Büntgen 2019) This is alarming since warming in southern Europe is predicted to exceed global rates by 25% (Cramer et al 2018), notably with summer temperatures rising at a pace 40% larger than the worldwide mean (Lionello and Scarascia 2018). This trend will be associated with more heatwaves and a reduction in summer precipitation of around 10%–15% over the Mediterranean truffle producing regions (Fischer and Schär 2010, Büntgen et al 2012, Jacob et al 2014, Vautard et al 2014, Thomas and Büntgen 2019)

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