Increased evapotranspiration demand in a Mediterranean climate might cause a decline in fungal yields under global warming.

Wild fungi play a critical role in forest ecosystems, and its recollection is a relevant economic activity. Understanding fungal response to climate is necessary in order to predict future fungal production in Mediterranean forests under climate change scenarios. We used a 15-year data set to model the relationship between climate and epigeous fungal abundance and productivity, for mycorrhizal and saprotrophic guilds in a Mediterranean pine forest. The obtained models were used to predict fungal productivity for the 2021-2080 period by means of regional climate change models. Simple models based on early spring temperature and summer-autumn rainfall could provide accurate estimates for fungal abundance and productivity. Models including rainfall and climatic water balance showed similar results and explanatory power for the analyzed 15-year period. However, their predictions for the 2021-2080 period diverged. Rainfall-based models predicted a maintenance of fungal yield, whereas water balance-based models predicted a steady decrease of fungal productivity under a global warming scenario. Under Mediterranean conditions fungi responded to weather conditions in two distinct periods: early spring and late summer-autumn, suggesting a bimodal pattern of growth. Saprotrophic and mycorrhizal fungi showed differences in the climatic control. Increased atmospheric evaporative demand due to global warming might lead to a drop in fungal yields during the 21st century.

Age class influence on the yield of edible fungi in a managed Mediterranean forest.

Lack of information and difficulty in predicting wild edible sporocarp yields is blocking its integration in forest management. In the Mediterranean area, this nontimber forest product has increased its market value, consumption demand, and interest over the last decade. In this work, sampling year and stand age effects are analyzed in order to advance knowledge of edible fungi community structure, dynamics, and production. Weekly autumnal sporocarp monitoring was performed from 1997 to 2011 in a Pinus pinaster managed forest in central Spain. After applying a random stand age-stratified survey, 21 plots of 150 m(2) have been set with three per stand age class. The forest age classes have been defined as follows: 0-10 years, mixture of parent and regenerated trees, 11-20, 21-40, 41-60, 61-90, and over 90 years. A total of 153 species belonging to 56 genera were recorded, 55 of which are edible. The production of edible sporocarps was 19.8 kg ha(-1), representing 31 % of total production. Sporocarp production presents a sharp interannual variability with autumns 62 times more productive than others. The most abundant edible species in terms of fresh weight per hectare has been Lactarius deliciosus with 7.0 kg ha(-1). Edible fungi yields registered a significant decline in 10 years following regenerative cutting. The presence of parent trees significantly increases production with regard to the first class. The highest production of edible species occurs in the middle age, 41-60 years, and in the following classes, a decrease is produced. L. deliciosus production registered differences with age, manifesting in a high yield in young stands (11-20 years) and significant recovery in woodlands near to the cutting.

Persistence and detection of black truffle ectomycorrhizas in plantations: comparison between two field detection methods.

Owners of black truffle (Tuber melanosporum) plantations are concerned about the persistence of its mycorrhizas and mycelium in the soil, especially until the appearance of the "truffle burn" areas and the triggering of sporocarp production, at least 5-7 years after planting truffle-inoculated seedlings. During this period, the farmer does not know whether his management is promoting black truffle development. To study the presence and abundance of T. melanosporum ectomycorrhizas in plantations, two sampling methods, direct sampling of root tips and soil core collection, are compared by analyzing 48 evergreen oak trees (Quercus ilex) inoculated with truffle. Those trees are grouped by age (<6, 6-9, >9 years old) and presence or absence of truffle production. T. melanosporum was present in 46 out of the 48 studied trees, and its ectomycorrhizas appeared in 65% of the ectomycorrhizal tips. Its abundance is significantly higher with productive trees and young trees. Direct sampling of root tips and soil core collection were equally effective in detecting this species, although soil core collection proved a better method to also evaluate ectomycorrhizal fungal diversity. To detect the presence of T. melanosporum in a given plantation, three samples suffice, with a single sample per random tree. Although the presence of mycorrhizas is not a sure sign of the future success of a black truffle plantation, its absence influences managers as to whether to continue culturing truffles in a plantation.

Soil physical properties influence "black truffle" fructification in plantations.

Although the important effects of pH and carbonate content of soils on "black truffle" (Tuber melanosporum) production are well known, we poorly understand the influence of soil physical properties. This study focuses on physical soil characteristics that drive successful production of black truffles in plantations. Seventy-eight Quercus ilex ssp. ballota plantations older than 10 years were studied in the province of Teruel (eastern Spain). Soil samples were analyzed for various edaphic characteristics and to locate T. melanosporum ectomycorrhizae. The influence of cultivation practices, climatic features, and soil properties on sporocarp production was assessed using multivariate analyses. Low contents of fine earth and silt and high levels of bulk density, clay content, and water-holding capacity appear to promote fructification. Watering is also highly positive for truffle fructification. We develop and discuss a logistic model to predict the probability of truffle fructification in field sites under consideration for truffle plantation establishment. The balance between water availability and aeration plays a crucial role in achieving success in black truffle plantations.

Seasonal dynamics of Boletus edulis and Lactarius deliciosus extraradical mycelium in pine forests of central Spain.

The annual belowground dynamics of extraradical soil mycelium and sporocarp production of two ectomycorrhizal fungi, Boletus edulis and Lactarius deliciosus, have been studied in two different pine forests (Pinar Grande and Pinares Llanos, respectively) in Soria (central Spain). Soil samples (five per plot) were taken monthly (from September 2009 to August 2010 in Pinar Grande and from September 2010 to September 2011 in Pinares Llanos) in eight permanent plots (four for each site). B. edulis and L. deliciosus extraradical soil mycelium was quantified by real-time polymerase chain reaction, with DNA extracted from soil samples, using specific primers and TaqMan® probes. The quantities of B. edulis soil mycelium did not differ significantly between plots, but there was a significant difference over time with a maximum in February (0.1576 mg mycelium/g soil) and a minimum in October (0.0170 mg mycelium/g soil). For L. deliciosus, significant differences were detected between plots and over time. The highest amount of mycelium was found in December (1.84 mg mycelium/g soil) and the minimum in February (0.0332 mg mycelium/g soil). B. edulis mycelium quantities were positively correlated with precipitation of the current month and negatively correlated with the mean temperature of the previous month. Mycelium biomass of L. deliciosus was positively correlated with relative humidity and negatively correlated with mean temperature and radiation. No significant correlation between productivity of the plots with the soil mycelium biomass was observed for any of the two species. No correlations were found between B. edulis sporocarp production and weather parameters. Sporocarp production of L. deliciosus was positively correlated with precipitation and relative humidity and negatively correlated with maximum and minimum temperatures. Both species have similar distribution over time, presenting an annual dynamics characterized by a seasonal variability, with a clear increase on the amounts of biomass during the coldest months of the year. Soil mycelial dynamics of both species are strongly dependent on the weather.

Edible sporocarp production by age class in a Scots pine stand in Northern Spain.

With the aim of increasing knowledge of community structure, dynamics and production of ectomycorrhizal fungi, edible sporocarp yields were monitored between 1995 and 2004 in a Pinus sylvestris stand in the northeast zone of the Iberian Peninsula. A random sampling design was performed by stand age class according to the forest management plan: 0-15, 16-30, 31-50, 51-70 and over 71-years-old. Eighteen 150 m plots were established and sampled weekly every year from September to December. One hundred and nineteen taxa belonging to 51 genera were collected, 40 of which were edible and represented 74% of the total biomass. Boletus edulis, Lactarius deliciosus, Cantharellus cibarius and Tricholoma portentosum sporocarps, which are considered to be of high commercial value, represented 34% of the total production. B. edulis and L. deliciosus were the most remarkable and abundant species, and both were collected in more than 60% of the samplings. B. edulis fructified every year of the experiment; its mean production was 40 kg/ha and year and its maximum productivity was more than 94 kg/ha in 1998. The age class with the largest production of this taxa was the fourth (51-70 years), with 70 kg/ha. L. deliciosus only failed to fructify one autumn (2000); its mean production was almost 10 kg/ha and its maximum productivity close to 30 kg/ha in 1997. The maximum productivity of this species was found in the second (16-30 years) and fifth (71-90 years) stand age classes, with 18 and 16 kg/ha, respectively. Advances in this field can certainly offer new insights into factors affecting sporocarp production.