Surviving after an eruption: Ecosystem dynamics and mycorrhizae in Nothofagus pumilio forests affected by the 2011 Puyehue Cordón-Caulle tephra

MOGUILEVSKY, DENISE; FERNÁNDEZ, NATALIA V.; PUNTIERI, JAVIER G.; OUTES, VALERIA; FONTENLA, SONIA B.

FOREST ECOLOGY AND MANAGEMENT

ELSEVIER SCIENCE BV

Año: 2021 vol. 479

0378-1127

Volcanic eruptions affect ecosystems drastically, and ectomycorrhizal fungi (EM) may play a critical role inforest regeneration. Nothofagus species are usually ectomycorrhizal. The 2011 Puyehue Cordón-Caulle volcaniccomplex (PCCVC) eruption covered vast areas of N. pumilio forests with thick tephra deposits. The main objectivesof this work were to characterize the forest environment following tephra deposition, and to analyze thenatural regeneration and development of N. pumilio and associated EM communities. Three study sites wereselected and sampled two and three years after the PCCVC eruption. Two sites had a thick tephra layer (50 cm);in one of them most of the tree layer was dead (Highly Affected-Tephra) whereas in the other, most of the adulttrees were alive (Affected-Tephra). The third site had minimal tephra deposition (Non-Affected).Physicochemical properties of the substrate, biological environmental factors and EM behavior of N. pumilioseedlings and adults were evaluated in all three sites. The physicochemical properties of the substrate andenvironmental characteristics differed among sites. Both seedlings and adults had EM in all three sites. Thefrequency of six-month-old seedlings with EM (40%) and their colonization values (< 12%) were significantlylower in both tephra-affected sites than in the Non-affected site (100% and 80 %, respectively). However, all the18-month-old seedlings from the tephra-affected sites had EM and their colonization increased almost to thevalue of the seedlings from the Non-Affected site. In both tephra-affected sites N. pumilio seedlings were associatedwith some exclusive fungal species, which could have a primary successional role. The early, increasingEM colonization recorded in seedlings after the eruption supports the idea of the strong dependence ofNothofagus trees on this symbioses, and highlights that this mutualism could be an effective adaptive mechanismunder stressful conditions. Our findings also suggest that EM symbiosis in N. pumilio persists even after a severedisturbance and is regulated by several factors such as time after eruption, availability and type of mycorrhizalinoculum, plant development and physicochemical substrate composition.