Predicted climate change will increase the truffle cultivation potential in central Europe

Anthropogenic climate change significantly impacts the distribution of ectomycorrhizal fungi, crucial for both natural ecosystems and agriculture. Species are shifting towards higher latitudes and elevations, leading to habitat expansion or contraction. Predicting these distributional changes relies heavily on species distribution models (SDMs), also known as niche models. These models correlate species occurrence with abiotic factors like climate, soil, and elevation to forecast future distributions. While simpler correlative SDMs have limitations, they remain the most practical approach for many species, including fungi. This study focuses on two commercially valuable truffle species, the Burgundy truffle (*Tuber aestivum*) and the Périgord truffle (*Tuber melanosporum*), to investigate the impact of climate change on their cultivation potential in Central Europe. Both truffle species are ectomycorrhizal fungi with high economic value, currently cultivated across Europe (Burgundy) and primarily in the Mediterranean (Périgord). The study investigates the potential of cultivating these truffles in the Czech Republic considering the predicted changes in climate and existing environmental information.

The study conducted a comprehensive literature review of 57 scientific publications to define the ecological requirements for both Burgundy and Périgord truffles. The review focused on temperature (annual means, January and July extremes), precipitation (annual totals and summer amounts), elevational ranges, host tree species, and soil pH. Each requirement was assigned a range of values representing the species' viable ecological range, categorized into five suitability classes (1-5), with 5 representing optimal conditions. The relative importance of each parameter (soil pH, annual temperature, precipitation, and elevation) was determined using rank sum methods based on expert judgment from the literature.

The study area was limited to the Czech Republic (49–51°N and 12–19°E), encompassing diverse biogeographic zones and geological bedrock types suitable for truffle cultivation (high-calcium limestone karst, secondary and tertiary deposits, and Quaternary sediments). Favorable soils included fertile chernozems, phaeozems, and calcareous leptosols below 300–400 m a.s.l. Climatological data for 2020 (baseline) and 2050 (future) were obtained from a network of 268 climatological stations, using regression kriging with altitude as a predictor to interpolate temperature and precipitation into a 500 × 500 m grid. Future climate was modeled using the delta-change approach, combining averages from five Global Climate Models (GCMs) under three Representative Concentration Pathways (RCPs) – 2.6, 4.5, and 8.5. Soil pH data were compiled from the State Land Office and Forest Management Institute, extrapolating field measurements to cover 64% of the Czech Republic. Elevation data were obtained from a high-resolution LIDAR mapping database. A multicriteria analysis, incorporating weighted scores for each environmental parameter, was used to generate suitability maps for truffle cultivation. The weighted scores were summarized into final suitability values, representing the overall suitability for truffle cultivation. The final suitability values were then converted into percentages. The distribution maps were created using ArcGIS Pro.

Optimal growth conditions for Burgundy truffles were estimated as ~10 °C annual temperature, 19.8 °C July temperature, 2.1 °C January temperature, ~700 mm annual precipitation (~160 mm in summer), a pH of ~7.5, and an ideal elevation of ~-570 m a.s.l. For Périgord truffles, the optimum conditions included ~12 °C annual temperature, 20.5 °C July temperature, 3.8 °C January temperature, ~780 mm annual precipitation (~140 mm in summer), a pH of ~8, and an elevation of ~620 m a.s.l. Under current (2020) conditions, ~14% of the Czech Republic (8486 km²) is highly suitable for Burgundy truffle cultivation, while only ~8% (6418 km²) is suitable for Périgord truffles. Under low- and mid-emission scenarios (RCP 2.6 and 4.5) Burgundy truffle cultivation potential will slightly expand, however high-emission scenarios (RCP 8.5) will result in a reduction in suitable areas. Périgord truffle suitability will increase substantially under all future climate scenarios, with a significant expansion of highly suitable areas, driven by rising temperatures. The overall potential cultivatable area will change minimally under all scenarios, with the moderate and highly suitable areas expanding substantially. The rate of change in suitable land for Périgord truffles is predicted to be much faster than that of Burgundy truffles.

The model's uncertainties include the limited data on truffle occurrences in the Czech Republic and the challenges in validating the model due to the strict protection of Burgundy truffles and the uncertainties associated with PCR detection methods for mycorrhizae. While Burgundy truffles showed some resilience to climate change under low-emission scenarios, high-emission scenarios could negatively impact their production due to increased summer droughts. Conversely, Périgord truffles are predicted to significantly benefit from warming, expanding their potential cultivation areas northward. The increased risk of agricultural drought under future climate scenarios highlights the potential role of irrigation in mitigating these effects, particularly in regions of southern Moravia and central Bohemia, which have been identified as potentially suitable locations for truffle cultivation in the Czech Republic. The availability of drought-tolerant oak species, common truffle hosts, supports this.

This study provides valuable insights into the potential for truffle cultivation in central Europe under future climate scenarios. While acknowledging inherent uncertainties, the findings suggest that climate change may create new opportunities for cultivating both Burgundy and Périgord truffles, particularly in regions with alkaline soils. This could offer significant ecological and economic benefits. Further field research is crucial to validate the model's predictions and guide sustainable truffle cultivation practices.

The study's limitations include the reliance on correlative niche models, which may oversimplify complex ecological interactions. The limited historical data on truffle occurrences in the Czech Republic also impacts the accuracy of the model. The model does not explicitly account for changes in host tree distribution, which could influence truffle growth, and the lack of validation data for the model's predictions are further limitations of the study.