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Abstract: Cellulose and lignin degradation dynamics was monitored during the leaf litter decomposition of three typical species of the Mediterranean area, Cistus incanus L., Myrtus communis L. and Quercus ilex L., using the litter bag method. Total N and its distribution among lignin, cellulose and acid–detergent–soluble fractions were measured and related to the overall decay process. The litter organic substance of Cistus and Myrtus decomposed more rapidly than that of Quercus. The decay constants were 0.47 year−1, 0.75 year−1 and 0.30 year−1 for Cistus, Myrtus and Quercus, respectively. Lignin and cellulose contents were different as were their relative amounts (34 and 18%, 15 and 37%, 37 and 39% of the overall litter organic matter before exposure, for Cistus, Myrtus and Quercus, respectively). Lignin began to decrease after 6 and 8 months of exposure in Cistus and Myrtus, respectively, while it did not change significantly during the entire study period in Quercus. The holocellulose, in contrast, began to decompose in Cistus after 1 year, while in Quercus and Myrtus immediately. Nitrogen was strongly immobilized in all the litters in the early period of decay. Its release began after the first year in Cistus and Myrtus and after 2 years of decomposition in Quercus. These litters still contained about 60, 20 and 90% of the initial nitrogen at the end of the experiment (3 years). Prior to litter exposure nitrogen associated with the lignin fraction was 65, 54 and 37% in Cistus, Myrtus and Quercus, while that associated with the cellulose fraction was 30, 24 and 28%. Although most of the nitrogen was not lost from litters, its distribution among the litter components changed significantly during decomposition. In Cistus and Myrtus the nitrogen associated with lignin began to decrease just 4 months after exposure. In Quercus this process was slowed and after 3 years of decomposition 8% of the nitrogen remained associated with lignin or lignin-like substances. The nitrogen associated with cellulose or cellulose-like substances, in contrast, began to decrease from the beginning of cellulose decomposition in all three species. At the end of the study period most of the nitrogen was not associated to the lignocellulose fraction but to the acid–detergent–soluble substance (87, 88 and 84% of the remaining litter nitrogen). [Copyright &y& Elsevier]

• Truffles play a pivotal role in soil food web dynamics. • There is a gap of knowledge in the effect of truffles on soil microbial communities. • Here, truffles were associated with changes in soil chemistry and biological activity. • A reduction in soil quality was also observed in association with truffle presence. Truffles contribute both directly and indirectly to important dynamics in the soil web, being involved in a large number of ecological functions that are crucial for terrestrial ecosystems. Despite this, the interrelationships between true truffles, i.e. hypogeous ectomycorrhizal fungi producing valuable fruiting bodies, and other elements of the soil system are largely unknown. In this study, we aimed to shed new light on whether and how much Tuber aestivum affects soil microbial activities (evaluated as enzyme activities), abundance (assayed as soil DNA content) and bacterial genetic diversity along with soil chemical properties. We compared chemical and biological variables inside and outside brûlés (i.e. areas inhabited by truffles with scarce vegetation cover around host plants) in two seasons, namely spring and summer, using both a linear mixed model and a multivariate two-block partial least squares approach. The areas with truffle presence had higher pH but lower organic carbon and nitrogen content. Similarly, all enzyme activities were lower inside the brûlé than outside, with the exception of peroxidase. A soil quality index (i.e. AI3) based on three enzyme activities (β-glucosidase, acid phosphomonoesterase and urease) indicated a reduction in soil quality inside the brûlé. Overall, soil DNA content responded to an interaction of truffle presence/absence and season, while bacterial genetic diversity indexes were higher in spring. Despite the observational nature of this study, results point out that T. aestivum can be considered a key species in the soil where it is present as it was associated with changes in chemistry as well as microbial activity that were generally more conspicuous than mere seasonal effects, although the causative nature of these associations still needs to be confirmed. [ABSTRACT FROM AUTHOR]

The fungal mycelium ingrowth and the rates of mass loss and respiration of needle litter of Pinus pinea, Pinus laricio, Pinus sylvestris, and Abies alba were investigated, in three coniferous forests, over a 3-year period by means of a composite set of incubations. In the early stages, the fungal flora of the decomposing needles was dominated by dematiaceous hyphomycetes and coelomycetes. Basidiomycetes reached a peak after 6 months on pine needles, but were absent from the N-rich needles of A. alba. Soil fungi (Penicillium, Trichoderma, Absidia, Mucor sp. pl.) became most frequent in later stages. At the end of the study period, the total mycelium amount showed the lowest values in all pine needles incubated in the P. laricio forest and the highest ones in P. pinea needles incubated in the P. pinea forest. In all data sets, as in data for boreal forests examined for comparison, the concentration of litter fungal mycelium versus litter mass loss followed a common exponential model. However, in later stages, the amount of litter fungal mycelium was very close to that of the humus at the incubation site, thus supporting the hypothesis of a logistic growth pattern. Respiration rates of decomposing litters varied with season and decreased with litter age to values close to those of the humus at the incubation site. Respiration of water-saturated litter was negatively correlated with the total mycelium concentration, and this was consistent with the observation that in far-decomposed litter only a minor fraction of the total mycelium is alive. [Copyright &y& Elsevier]