NATURAL FOREST SUCCESSION AFTER A VOLCANIC ERUPTION: MYCORRHIZAL AND FUNGAL COMMUNITIES RELATED TO SEEDLING REGENERATION

MOGUILEVSKY DENISE; CARRON AYELÉN; FERNÁNDEZ NATALIA; PUNTIERI JAVIER; CORNEJO RIVAS PABLO; FONTENLA SONIA

Bariloche

Simposio; II International Symposium: Mycorrhizal Symbiosis in South America; 2019

UNComahue - IPATEC - INIBIOMA - CONICET

The 2011 Puyehue Cordón Caulle´s eruption affected large areas of Nothofagus pumilio (lenga) forests. In some places a 50 cm thick tephra layer buried the understory vegetation and provided a brand new substrate for plants and microorganisms. After the eruption, abundant seedling regeneration of N. pumilio took place, but there is no information about its ectomycorrhizal behaviour and the importance of this symbiosis for this natural process. The ectomycorrhizal (EM) symbiosis is present in all Nothofagus species, and colonization rates in mature N. pumilio trees are in general ≥70%. Our objective was to analyse how tephra influenced N. pumlio´s EM colonization, seedling development and root fungal communities over time. In 2013, in a forest with high tephra deposition we buried 15 pots into the tephra layer, which were filled with soil obtained from under the tephra. Two six-month-old seedlings that were growing in the tephra were transplanted into each pot (?soil seedlings?, SS) and nearby seedlings remained growing in the tephra (?tephra seedlings?, TS). One, four and five years after the experiment was established (2014, 2017 and 2018) we collected seedlings from both substrates (SS and TS) in addition to roots from adult trees. We analysed several morphometric measures of the seedlings and EM abundance in seedlings and adults. For studying the composition of different rhizosphere fungal communities we performed several Denaturing Gradient Gel Electrophoresis (DGGE). Total DNA was extracted from the rhizosphere and nested PCRs were carried out, using different sets of primers for analysing three different fungal communities, Total Fungi (ITS1F-ITS4), Ascomycetes (ITS1F-ITS4A) and Basidiomycetes (ITS1F-ITS4B). All the individuals had EM. The first year (2014), EM colonization was lower in TS (49%) than in SS and adults (75% and 70%, respectively). In 2017 and 2018 the EM colonization was similar between all samples (63-86%). For the morphometric measures, in the first year, no differences were found between TS and SS, but in 2017 SS were bigger than TS, and in 2018 SS seedlings were smaller than TS. For the three fungal communities analyzed, in 2014 there was a clear separation between TS and SS, but in 2017 they were more similar to each other. These results suggest that tephra is becoming an appropriate substrate for N. pumilio development. Tephra allows the germination and survival of N. pumilio seedlings, has EM infective capacity, and favours root colonization over time. After a high-impact disturbance, the re-establishment of the native inoculum in tephra and the occurrence of EM in N. pumilio seedlings seem to be important factors for the forest regeneration.