Integrating riparian Nothofagus antarctica forests to the study of beaver invasion on Tierra del Fuego

SOLER ESTEBAN, ROSINA MATILDE; MARTÍNEZ PASTUR, GUILLERMO; LENCINAS, MARIA VANESSA; ANDERSON, CHRISTOPHER

Mard el Plata

Congreso; 2º World Conference on Biological Invasions and Ecosystem Functioning (BIOLIEF); 2011

From 30-40% of riparian forests on Tierra del Fuego Island are affected by beaver (Castor canadensis), an invasive species that drastically modifies both the structure and function of Nothofagus forests. Previous studies have not included N. antarctica (ñire) in this landascape, even though it has great ecological importance as a pioneer species of non-forested environments and key reproductive strategies for habitat restoration. This study evaluated the effect of beaver impact on forest structure and natural regeneration of N. antarctica and resprouting response on Tierra del Fuego. Ten abandoned sites were selected in monospecific ñire forests. In each site, forest structure affected by beaver was determined. Then, each site was divided into pre-dam area, dam, flooded area and a wooded area (from the edge of impact to the maximum cutting distance). The natural regeneration (number, age, height, origin) was quantified using 1 m2 plots in each sector, and the % of stump regrowth in the wooded area was estimated using 100 m2 quadrants (near- and far-impact). We found seedlings (5-7 years old) grew in the pre-dam area (5 ind m-2), flooded area (23-42 ind m-2) and forest (3 ind m-2), with 7.8 cm average height. The origin was 80-92% agamic in the pre-dam and flooded areas, and 100% from seeds in the forest. Also, 46% of the stumps resprouted with 4-85 cm in length. The presence of seedlings in the abandoned sites may indicate that N. antarctica could be able to regenerate these forests in scenarios including beaver eradication. It is therefore essential to include the time since abandonment for each site in future analysis.