No abstract

The European black truffle is a mycorrhizal fungus native to Spanish Mediterranean forests. In most Spanish regions it was originally commercially harvested in the second half of the 20th century. Experts agree that wild truffle yields suffered a sharp decline during the 1970s and 1980s. However, official statistics for Spanish harvest are scarce and seemingly conflicting, and little attention has been paid to the regime for the exploitation of truffle-producing forests and its implications on the sustainability of this resource. Trends in harvest from 1969 to 2013 and current harvesting practices were analyzed as a case study, taking into account that Spain is a major truffle producer worldwide, but at the same time truffles have only recently been exploited. The available statistical sources, which include an increasing proportion of cultivated truffles since the mid-1990s, were explored, with estimates from Truffle Harvesters Federation showing higher consistency. Statistical sources were then compared with proxies for wild harvest (rents from truffle leases in public forests) to corroborate time trends in wild harvesting. Results suggest that black truffle production is recovering in recent years thanks to plantations, whereas wild harvest is still declining. The implications of Spanish legal and institutional framework on sustainability of wild truffle use are reviewed. In the current scenario, the decline of wild harvest is likely to continue and eventually make commercial harvesting economically unattractive, thus aggravating sustainability issues. Strengthening of property rights, rationalization of harvesting pressure, forest planning and involvement of public stakeholders are proposed as corrective measures.

The ectomycorrhizal fungus Tuber melanosporum fruits in association with Quercus in natural forests of Spain.Some of these stands are managed to keep an open canopy and meet the habitat requirements of the fungus.However, there are few quantitative studies analysing in these forests the relationship between soil environment and T. melanosporum. Eight forest stands which produce T. melanosporum have been monitored for six years in order to characterise the below-ground ectomycorrhizal community and to assess its temporal dynamics after experimental canopy opening. The brûlé, the ground where T. melanosporum fruits, shows a distinct ectomycorrhizal community, characterised by lower density of active ectomycorrhizal tips, lower morphotype richness per soil volume, higher abundance of T. melanosporum and lower abundance of Cenococcum geophilum than soil closest to the trunk of the host Q. ilex. Opening the canopy has not stimulated an increase in T. melanosporum, suggesting that a shift in the soil environment alone will not trigger the formation of new truffières in the short term. The dry climate of these truffières may be a factor, as T. melanosporum abundance appears to be sensitive to annual weather conditions.

The wild production of the highly appreciated fungus Tuber melanosporum is negatively affected by canopy closure in the stand. Habitat improvement has been proposed as a tool to recover the production in close forests, but evaluations based on scientific monitoring are still lacking. This study analyses the short-term effect of a pilot project on improvement of T. melanosporum reproduction habitat. The results support the project hypothesis that the canopy closure was hampering truffle fruiting in the larger brûlés. The silvicultural treatment alone has not triggered a clear positive response in all the truffières, suggesting that complementary actions are necessary to ensure their sustainability. Weather conditions provoke a year-to-year variation in the fruiting and determine the responsiveness of the truffières to the treatment.

No abstract

Abandoned charcoal hearths constitute a very particular habitat for spontaneous fruiting of Tuber melanosporum, leading some harvesters to hypothesise that the fungus could benefit from the alterations that these soils underwent. However, ecological mechanisms involved in this relation are not fully elucidated yet. As a first step to understand it, the influence of long-term soil alteration on the symbiotic stage of T. melanosporum and on selected soil properties considered key to fruiting was assessed by conducting a greenhouse bioassay and a field observational study. In the bioassay, percent root colonisation and relative abundance of T. melanosporum were significantly lower in hearth than in control soils. Hearth soils showed significantly lower resistance to penetration, larger temperature fluctuation, reduced plant cover and reduced herbaceous root abundance. The results do not support the hypothesis that soil from historical charcoal hearths currently enhances development of T. melanosporum mycorrhizas. However, whether this is due to increased infectivity of native ectomycorrhizal communities or to worse conditions for development of T. melanosporum mycorrhizas remains unresolved. Native ectomycorrhizal communities in hearths showed altered composition, although not a clear change in infectivity or richness. Direction of change in hearth soil properties is compared to alteration occurring in soils spontaneously producing T. melanosporum. The interest of these changes to improve T. melanosporum fruiting in plantations is discussed.

No abstract

El embalse San Roque se encuentra a 11 km de la ciudad de Carlos Paz y a 40 de la ciudad de Córdoba y una de las funciones es brindar agua a gran parte de la ciudad y sus alrededores. Debido a que recibe un alto aporte de nutrientes provenientes principalmente de la actividad antrópica constituye un ecosistema favorable para el desarrollo de comunidades algales. El objetivo general del trabajo fue evaluar el estado trófico del embalse a través de índices de eutrofización e indicadores biológicos. Se llevaron a cabo muestreos estacionales desde febrero de 2014 hasta febrero de 2016, en el muro de cierre de embalse y la desembocadura de los tributarios. Se midieron parámetros físicos y químicos y determinaron nutrientes. Se realizó la identificación taxonómica de las especies, se calculó la biomasa fitoplanctónica mediante el biovolumen y clorofila a y se estimó el índice de estado trófico. Se determinaron un total de 204 Taxa. El componente dominante del fitoplancton fue el dinoflagelado Ceratium furcoides y como subdominante la diatomea Aulacoseira granulata. De acuerdo al índice de estado trófico ubicamos al embalse San Roque en estado eutrófico, condiciones indeseables en un ambiente utilizado para provisión de agua potable.