Impact of different natural thermic environments on the regeneration dynamics of two Nothofagus species across elevation in the Southern Andes

CAGNACCI J; LÍA MV; MARTINEZ-MEIER, A.; ESTRAVIS BARCALÁ, M.; MARCHELLI P; ARANA ,MV; GONZALEZ POLO, M; PASTORINO, M.J,

Bariloche

Conferencia; Adapting forest ecosystems and wood products to biotic and abiotic stress; 2019

INTA - INRA

A widely accepted paradigm in forest ecology proposes that patterns of relative abundance among forest?s mature trees are largely influenced by biotic and abiotic processes that operate most intensely at the earliest life-cycle stages. Therefore, traits expressed early in development such as germination and seedling establishment may be under strong selective pressure by the environment, and their adjustment to changing climates may ultimately influence species´ responses to global climate change (GCC). Here we used different thermal environments generated across altitude in an old-growth temperate Patagonian forest as a natural laboratory to study the response of regeneration ? seedling energence and mortality- of Nothofagus obliqua and N. pumilio to different climatic scenarios. These are two iconic species of sub-Antarctic forests, which co-exist in contrasting and non-overlapping thermal niches. Whereas N. obliqua is predominant at the warmer and lower environments at 650-850 m above the sea level (a.s.l.), N. pumilio inhabits the colder and higher montane environments, above 1000 m a.s.l. We simulated germination pulses during two different years and three altitudes; 680, 930 and 1340 m a.s.l., which comprise different thermal environments inside and outside species´ natural ranges. We scored seedling emergence and survival every 30 days during two consecutive years for each independent experiment. Our results indicate that the different environments established across elevation influenced neither the percentage of emerging seedlings nor the dynamics of seedling mortality in both species. However, at the end of the first growth season, N. obliqua showed relatively higher percentages of seedlings at 930 m a.s.l., in the upper and colder boundary of its distribution range. In contrast, we didn´t find significant differences in final percentages of seedlings of N. pumilio at the different altitudinal levels, although seedlings inhabiting the warmer and lower environments showed a significant reduction in leaf area, which suggest that plants were growing under stress. Taken together, our results indicate that seedling performance of N. obliqua and N. pumilio is favoured in colder environments. Results reported here were consistent across the two independent experiments and will be discussed in the context of forest regeneration in response to GCC.