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ŠUMARSKI LIST 11-12/2021 str. 47     <-- 47 -->        PDF

richness recorded in our research was similar to the one obtained in three declining pedunculate oak stands in western Poland where a total of 18 ECM fungal species was revealed and ECM fungal species richness ranged from 11 to 15 taxa (Bzdyk et al. 2019). Also, in the forest of the Taurus mountains in Central Germany, 18 different ECM genera and species were determined on sessile oak (Schirkonyer et al. 2013), while in Ireland 21 ECM taxa were found on native oaks Q. petrea and Q robur (O’Hanlon and Harrington, 2012).
On average, three ECM fungi were recorded in soil samples from sites Info center and Brankovac. This is considerably lower in comparison to oak stands in Austria where eight morphotypes w&1077;re found averagely (Kovacz et al. 2000) and in the forest of Q. ilex in Spain where on average seven species were recorded (de Roman and de Miguel, 2005). Shannon-Weaver index per soil sample at sites Info center and Brankovac with values 0.7 and 0.9, respectively, is considerably lower compared to the ones recorded in oaks stands in Austria where vital trees had Shannon-Weaver index 1.3-1.5 (Kovacz et al. 2000) and in the Q. ilex forest in Spain where this index was 1.2 in the burned stand and 1.3 in the control stand (de Roman and de Miguel 2005). However, if we compare total values of Shannon-Weaver index calculated for sites Info center and Brankovac (2.3 and 2.1, respectively) with the ones obtained by Kovacz et al. (2000) in Austria for aggregated soil samples taken under vital trees (in the range 2.6-2.7) we can conclude that these values are comparable.
The low average number of ECM fungal taxa and value of Species richness and Shannon-Weaver index per soil sample could be explained by the lack of precipitation, which is characteristic for the studied sites during September and October, when sampling was conducted. Also, the summer season in 2017 was one of the warmest for the period 2010-2017 (Galić et al. 2018). Drought caused dying out of a large number of roots and consequently high number of old, non-turgescent, and nonmycorrhizal roots were observed in soil samples (data not shown), while the number of ECM fungal taxa per soil sample was decreased. Bzdyk et al. (2019) suggest that the number of vital and non-vital ECM roots is influenced by short-term factors such as local droughts, but these factors do not influence total ECM diversity which is supposed to be more susceptible to long-term trends.
At both sites, ECM community was made up of a few abundant taxa and a larger number of rare taxa. This is in accordance with numerous studies (Courty et al. 2008, O’Hanlon and Harrington 2012, Suz et al. 2014, Rosinger et al. 2018, Bzdyk et al. 2019). It is assumed that a large number of taxa present at low frequencies may constitute biological insurance for adaptation to changing environmental conditions. Namely, a more diverse ECM community that includes rare ECM species is important in case if ecological conditions change, as some dominant ECM fungi might not be adapted to the new conditions (Penna et al. 2010, O’Hanlon and Harrington 2012).
Ectomycorrhizal fungi determined as Lactarius quietus, Cenococcum geophilum, and Tomentella sublilacina were recorded at both studied sites from Fruška gora. Similarly, the most abundant ECM fungi on temperate oaks across nine European countries were Lactarius quietus, Cenococcum geophilum, and Russula ochroleuca (Suz et al. 2014). Moreover, in a temperate oak forest Lactarius quietus, Tomentella sublilacina, Cenococcum geophilum, and Russula sp.1 were abundant and present all year long (Courty et al. 2008). Lactarius quietus is an oak specialist which was recorded as one of the most abundant and frequently occurring ECM fungi on temperate oaks across Europe (Voříšková et al. 2013, Bzdyk et al. 2019). Cenococcum geophilum is a species complex that is the most widely distributed making symbiosis with over 200 tree hosts (LoBuglio 1999). C. geophilum is also known for its ability to withstand extreme conditions, especially drought, but it is frequently found on oaks across Europe (de Roman and Miguel 2005, Schirkonyer et al. 2013).
Families Russulaceae, Cortinariaceae and Thelephoraceae were reported to be dominant in temperate and Mediterranean oak forests (Courty et al. 2008, Richard et al. 2011). Moreover, research of ectomycorrhizae in temperate oak forests across Europe revealed that the most abundant family was Russulaceae, followed by Gloniaceae, Thelephoraceae, and Cortinariaceae (Suz et al. 2014). A higher number of ECM fungal taxa belonging to the phylum Basidiomycota in comparison to Ascomycota obtained in our study is concordant to many previous studies (Richard et al. 2011, Suz et al. 2014; Bzdyk et al. 2019 etc.)
Classification of ectomycorrhizae based on ETs connects ECM fungal morphology with their ecology (Agerer 2001). Each exploration type has different functional traits and different capabilities to take up and translocate nutrients and to store carbon (Hobbie and Agerer 2010). Furthermore, it was proven that ETs have site indication value, particularly in relation to nutrients availability and soil composition (Rudawska et al. 2011).
At both sites on the mountain Fruška gora, contact and short-distance ETs dominated. According to Bzdyk et al. (2019), the contact ET is considered well adapted to soil layers rich in organic matter and to relatively nutrient-rich conditions. In contrast, ETs with abundant mycelial biomass, such as the long-distance ET, were found to be well adapted to nutrient-poor conditions, especially poor in nitrogen (N) (Hobbie and Agerer 2010). Usually, mycorrhizae with contact, short- and medium-distance smooth ETs seem to use labile, mainly inorganic N, while medium distance fringe and mat, and long-distance ETs are believed to use organic N and have degradation enzymes with the strongest potential activities (Lilleskova et al. 2011, Suz et al. 2014).