fungal ecology 5 (2012) 591e599 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/funeco Spatial distribution and ecological variation of re-discovered German truffle habitats a, € b,c a d b Ulrich STOBBE *, Ulf BUNTGEN , Ludger SPROLL , Willy TEGEL , Simon EGLI , Siegfried FINKa aInstitute of Forest Botany and Tree Physiology, Albert-Ludwigs-University of Freiburg, 79085 Freiburg, Germany bSwiss Federal Research Institute WSL, 8903 Birmensdorf, Switzerland cOeschger Centre for Climate Change Research, 3013 Bern, Switzerland dInstitute for Forest Growth IWW, Albert-Ludwigs-University of Freiburg, 79085 Freiburg, Germany article info abstract Article history: Several truffle species (Tuber spp.) are highly prized by chefs and gourmets with some À Received 22 July 2011 commanding prices of up to V9.000 kg 1 on international markets. Their ecological drivers Revision received 5 December 2011 and geographical patterns, however, often remain a puzzle. Truffle species in Germany are Accepted 24 January 2012 classified as Very Rare or even Extinct on the national Red Lists, while historical literature Available online 28 March 2012 described their sporadic existence. Here we present evidence of seven Tuber species Corresponding editor: (T. aestivum, T. brumale, T. excavatum, T. fulgens, T. macrosporum, T. mesentericum, T. rufum), Anne Pringle discovered at 121 sites in Southwest Germany. The valuable Burgundy truffle (T. aestivum) occurred at 116 sites. An unexpected abundance of Tuber spp. associated with 13 potential Keywords: host plants along wide ecological gradients in a region far outside the traditional Mediter- Climate change ranean truffle foci in France, Italy and Spain, is likely indicative of possible responses to Cultivation potential climate change, and also suggests ample truffle cultivation potential north of the Alpine arc. Host vegetation ª 2012 Elsevier Ltd and The British Mycological Society. All rights reserved. Site characteristics Spatial distribution Truffle habitat Tuber aestivum Introduction 2007), whereas many species do not have culinary value to humans (Pacioni et al. 1990). For spore dispersal, an array of Truffles are hypogeous fruit bodies of ascomycete fungi wildlife animals, including boar, mice and squirrel, is attrac- belonging to the genus Tuber (Trappe 1979). To date, it is ted by the aromatic compounds and consumes the fruit bodies widely accepted that Tuber spp. occur exclusively in associa- after digging them out. The spores then pass unharmed tion with certain host plants and only under specific ecological through the digestion system and are dispersed with the dung habitat characteristics, including a narrow range of climatic in potentially new habitats (Trappe & Claridge 2010). Although conditions (Hall et al. 2007). The worldwide number of Tuber many physiological parts of the distribution strategy of spp. remains unclear, but it is assumed to exceed 180 species Tuber spp. are understood, the overall bio-geographical and (Bonito et al. 2010). Some of these have outstanding commer- site-ecological requirements of many species still remain À cial value and command prices up to V9.000 kg 1 (Hall et al. unclear (Buntgen€ et al. 2011). Aside from the traditional truffle * Corresponding author. Tel.: þ49 (0) 761 2033655; fax: þ49 (0) 761 2033650. E-mail address: [email protected] (U. Stobbe). 1754-5048/$ e see front matter ª 2012 Elsevier Ltd and The British Mycological Society. All rights reserved. doi:10.1016/j.funeco.2012.02.001 592 U. Stobbe et al. cultivation hotspots in France (Midi-Pyrenees and Provence for Tuber melanosporum and Burgundy for Tuber aestivum), Methods Northern and Central-Italy (both species) and Central Spain for T. melanosporum, newly discovered truffle grounds like the The research area in Southwest Germany (Baden- € Swedish island of Gotland, have gained in importance with Wurttemberg) is adjacent to well-known truffle habitats in a concomitant impact on its rural economy (Weden et al. 2009). France (Burgundy and Lorraine) and Switzerland (Jura). Addi- Detailed insight on the Burgundy truffle (T. aestivum syn. tionally, the climate is similar to the mentioned regions and uncinatum; Weden et al. 2005), which is assumed to be most there is an abundance of calcareous geological formations, widespread across Europe, is therefore not only of particular essential for the growth of almost all Tuber spp. (Sourzat 2002; scientific interest but also of enormous economic value (Hall Weden et al. 2004; Hall et al. 2007). Search areas were defined et al. 2003). on the basis of geology and site characteristics in the southern A decline in truffle harvest across the Mediterranean Rhine valley, the Hegau region and the southern Swabian Jura, area, possibly related to increasing temperature means and whereas the acidic areas of the Black Forest were excluded. decreasing precipitation totals (Buntgen€ et al. 2011), and Potential sites were identified using presence of suitable trees a decreasing supply with rising market prices has subse- or shrubs, biological structures like forest edges, topograph- quently led to an upsurge in interest in truffle cultivation ical features like relief and exposure, while unlikely areas (Martin 2011). An expected humidity loss in the Mediterranean such as agricultural land were excluded. Well-trained truffle basin, especially in summer (Gibelin & Deque 2003; Thuiller dogs of the breeds Bracco francese and Lagotto romagnolo were 2007), is likely to further add to this issue. In contrast, habi- used to locate truffles between 2008 and 2011. The dogs are tats suitable for fungal growth in more northern parts of the able to detect the odour of many hypogeous fungi and do not temperate European forest zone are likely to increase due to discriminate between different Tuber species or other species a slight temperature increase (Buntgen€ et al. 2011), associated such as Choiromyces meandriformis and Melanogaster spp. The with extended vegetation periods and less frequent and severe dogs often explored areas, which were unlikely to be truffle frost events (Menzel & Fabian 1999; Menzel et al. 2003). Indeed, habitats, and surprisingly, yielded additional findings. Most various species-specific geographical range shifts, mostly sites were frequently visited throughout the 3-yr inventory to towards higher elevations and northern latitudes, have been assess truffle occurrence in different seasons, and thus gain reported (Burrows et al. 2011) and may also account for a spatial insight into their intra-annual phenology. expansion of truffle habitats in tandem with improved growth Wherever truffle fruit bodies were found, geographical conditions of their host plants (Buntgen€ et al. 2011). coordinates were determined by GPS, and all tree and shrub Historical German literature described the occurrence of species were recorded to describe the characteristic floristic different Tuber spp., as well as the utilisation of T. aestivum composition of the truffle site. The relative proportion of tree mainly for manufacturing sausage (Leberwurst; Hesse 1891). species at 71 T. aestivum sites was also systematically Hesse (1891) also provided information on the harvesting of observed to assess its likely hosts. Geological parent material € T. aestivum throughout Germany and described several new was defined by the LGRB map-server (Regierungsprasidium species including Tuber debaryanum, Tuber exiguum, Tuber Freiburg 2011). Temperature and precipitation data from 73 w 2 murinum, Tuber rutilum and Tuber scruposum. To our knowl- meteorological stations within the research area ( 2 500 km edge, very little information about the ecology and distribu- with a 10 km buffer zone) was obtained from the DWD tion of Tuber spp. has been published since then, and many (Deutscher Wetterdienst; Federal Ministry of Transport, species have even been regarded as extinct, or near so (Ludwig Building and Urban Development). Site locations were illus-  & Schnittler 1996). The Red List of German Mushrooms trated on 10 10 km gridded high-resolution maps allowing (Ludwig & Schnittler 1996), the Red List of Baden-Wurttemberg€ evaluation against the Red Lists (Winterhoff & Krieglsteiner Mushrooms (Winterhoff & Krieglsteiner 1984), and an atlas 1984; Ludwig & Schnittler 1996). of fungal distribution (Krieglsteiner 1993) are currently the The identity of each fruit body was determined from only sources that contain information on truffle distribution macroscopic and microscopic features following Pacioni € in Germany. Other publications partly describe diversity, (1981), Breitenbach & Kranzlin (1984), Sourzat (2002), the geography and ecology, but do not provide a sufficient over- internet platform Tuberkey (University of Parma 2006), Hall view (Pacioni 1981; Breitenbach & Kranzlin€ 1984; Gerhardt et al. (2007), and the key provided by Trappe & Castellano 1996). In contrast, ample truffle findings have been reported (2007). Microphotographs were prepared using a ZEISS Axio- e  from countries nearby Germany, such as France (Chevalier phot light microscope at 50 400 magnification fitted with & Frochot 1997a), Switzerland (Swiss Federal Institute for a ZEISS Axiocam MRc 5 digital camera. The shape (net struc-  m Forest, Snow and Landscape Research WSL 2010), Austria ture or spines on the surface) and size (length width in m) (Urban et al. 2004), Denmark (Global Biodiversion Information of the spores were the most important features. Facility GBIF 2009) and Poland (Hilszczanska~ et al. 2008;