Linda Scattolin

Vertical distribution of the ectomycorrhizal community in the top soil of Norway spruce stands

The vertical distribution of the ectomycorrhizal (ECM) community was studied in four old high-mountain Norway spruce (Picea abies [L.] Karst.) stands in northern Italy. The aim was to verify if the variability in the community structure could be explained by characteristics of the organic and mineral soil horizons. The community structure was evaluated in terms of both fungal species and their ability to explore soil (exploration types). From the 128 humus profiles sampled over the two study periods, 31 ECM species were recorded. The study demonstrated that the number of both non-vital tips and vital non-mycorrhized tips decreases with soil depth, from organic to mineral horizons, while the number of ectomycorrhizal tips mainly increases with soil depth. A preference was found of some ECM species and exploration types for specific organic or mineral soil layers and their features, especially moisture and available nitrogen. These results can help in understanding how the functional role of the single consortia and the ecological features determining this “adaptive diversity” in ectomycorrhizal communities could be of major importance to assess the resilience in forest soil ecosystems.

The ectomycorrhizal community structure in high mountain Norway spruce stands

The species composition of ectomycorrhizal (ECM) fungal communities can be strongly influenced by abiotic and biotic factors, which determine interactions among the species such as resource partitioning, disturbance, competition, or relationships with other organisms. To verify whether ectomycorrhization of the root tips and composition of the ECM community in Norway spruce vary according to site features and if ECM species peculiar to these environmental variables can be detected, ten comparable stands differing in bedrock pH and exposure were selected and studied. The results demonstrated that tips vitality and ectomycorrhization degree do not change significantly either on the same tree, or among trees growing in the same stand, whereas they differ greatly with bedrock pH and exposure, even if no spatial or temporal trend were found. ECM species composition revealed instead a significant connection with the two environmental features, with a few species significantly associated to them. The results suggest that pH/exposure patterns play a primary role in the adaptive selection of ECM species constituting the consortium.

Sistotrema is a genus with ectomycorrhizal species − confirmation of what sequence studies already suggested

The ectomycorrhizal status of Sistotrema sp. is shown by morphological–anatomical and molecular identification, confirming earlier reports about Sistotrema DNA in ectomycorrhizae (ECM). For molecular identification of the ECM nuclear rDNA ITS sequences obtained from mycorrhizal root tips and fruitbodies of Sistotrema sp. were compared. Blast searches using the Sistotrema sp. sequences as query were performed in GenBank and UNITE for comparison with previously published Sistotrema sequences. The morphological–anatomical characterization of the ECM used well-established protocols for the examination of all mantle parts and rhizomorphs in different sections and views including detailed illustrations. The ECM are irregularly monopodial–pyramidal, whitish ochre to yellow ochre, and woolly. Older ones become more greyish and silvery at some patches. Diagnostic anatomical characteristics are irregularly inflated emanating and rhizomorph hyphae, ampullately inflated clamps, and the occurrence of yellow drops within the hyphae. The plectenchymatous mantle shows ring-like arranged hyphae, and a slightly gelatinous matrix. The ECM of Sistotrema sp. are compared to those of other species that form distinctly ampullate hyphae in rhizomorphs, too. The anatomically most similar ECM to those of this Sistotrema specimen are those of Hydnum repandum.

A geostatistical model to describe root vitality and ectomycorrhization in Norway spruce

Abstract The spatial distribution of vital root tips and ectomycorrhizal (ECM) communities in forest soils is characterized by patchiness at a microscale level, mostly related to the distribution patterns of biotic and abiotic factors. A geostatistical model was applied to verify if spatial analyses could be useful in identifying an appropriate sampling method to study root tip vitality, ectomycorrhization and the ECM community. Root samples were collected from two high mountain Norway spruce forests (Trentino province, Italy) following a geometrical design. Laboratory microscopic and geostatistical ordinary kriging analyses were used to map tip vitality and ectomycorrhization degree, ECM richness and distribution grouped in “exploration types” (amount of emanating hyphae or presence and differentiation of rhizomorphs). Spatial gradients of the examined features existed at plant level, associated to the up-downslope direction (root tip vitality and ectomycorrhization, ECM richness) and distance from the stem base (ECM exploration types). The effectiveness of the geostatistical model used demonstrates that a geometrical sampling design, associated to spatial mapping techniques, can be useful in research where the tree, and not the forest, is the subject (mycological and phytopathological studies).

The ectomycorrhizal community in Mediterranean old-growth Quercus ilex forests along an altitudinal gradient

The Mediterranean coastal region is considered a “hot spot” of both biodiversity and climate change, as global average air temperatures and atmospheric CO2 concentrations are increasing with subsequent impacts on regional precipitation patterns. The main goal of this study, performed in the largest Mediterranean holm oak forests (Sardinia Island, Italy), was to verify whether the vitality of root tips and the composition of the ectomycorrhizal community of holm oak change with the altitudinal gradient. The results demonstrated that the altitude does not significantly affect the vitality and the degree of ectomycorrhization of the root tips, while significant differences were observed in the ectomycorrhizal community composition, correlated with both the altitude and the Southward exposition of the root systems, both associated to the increase of xeric and drought conditions at the soil level. This study should help to integrate the understanding of forest ecology and forecast modelling, to improve the management strategies of the Mediterranean oak forests in the future.

The ectomycorrhizal community in urban linden trees and its relationship with soil properties

The aim of this study was to verify if root tip vitality and ectomycorrhization in 16 mature urban linden (Tilia vulgaris Hayne) trees, growing in roadside and park side sites, at moderately and strongly declining levels, could be associated with main soil properties. From the 738 soil and root samples collected over the four study periods, 52 ectomycorrhizae were recorded. The study demonstrated that the number of non-vital, vital non-mycorrhizal and mycorrhizal tips never differed significantly, neither among samples collected beneath the same tree nor among trees belonging to the same site and decline class, with the exception of the number of vital non-mycorrhizal tips showing significant differences among sites. Significant differences in ectomycorrhizal community composition between sites and between decline classes were found. This result may be related to the variation of the environmental variables as a whole rather than to the influence of a single or few factors, even if capability, permanent wilting point and available water are the soil parameters most significantly related to diversity in ectomycorrhizal community.

A sampling method to describe the Norway spruce ectomycorrhizal community at plant level

Abstract To verify the possibility of developing a sampling method to accurately describe the Norway spruce ectomycorrhizal community at plant level, research was conducted in four comparable monospecific forests on healthy, mature and coeval Norway spruce trees. The results showed that the lowest number of tips per root core can characterize the community changes from site to site, with tree species, age and sampling design being constant. This highlights the importance of ectomycorrhizal species distribution, which is not an intrinsic character of ectomycorrhizal species, and probably changes with the environmental and fungal community features. The research demonstrated, in accordance with a theoretical ectomycorrhizal distribution, the effectiveness of an encoded geometrical sampling design consisting of the collection of 24 root samples from each of the four unrelated plants, along four perpendicular directions and at six fixed distances from the collar, and with the observation of 10 randomly selected ectomycorrhizal tips per sample.

Linden tree stress detection: Chlorophyll–nitrogen contents and ectomycorrhizal community

Urban trees are frequently subjected to stress-causing environmental factors and cultural practices, requiring a permanent monitoring of their health condition. Stress detection in woody plants usually relies on a visual assessment of symptoms: inventories are mostly based on the parameters of the percentage of foliage reduction and leaf colour, both of which require a subjective interpretation. The main goal of this study was to detect whether the foliar chlorophyll (Chl) and nitrogen contents of linden trees, in an urban environment, can be useful and objective diagnostic indicators of the plant health and physiological performance, and whether it was possible to evaluate these data through a quick technique. Furthermore, as the ectomycorrhizal (ECM) community is a well-known bioindicator of the plant health status, its potential association with both variations in the Chl content and the different degrees of tree decline was verified. By determining the mathematical relationship between the instrument (SPAD-502) readings, the foliar Chl and nitrogen contents and the association with significant variations in the ECM community, the different stages of the visual symptoms of decline were accurately determined. This approach should help to integrate the methodology used for tree health inventories with new universal methods that do not entail individual interpretation.