Evaluating tree-herbivory interactions in Nothofagus antarctica with livestock use and the need of multi-scale approach

SOLER R.; MARTÍNEZ PASTUR G.; CELLINI J.M.; LENCINAS M.V.; PERI P.L.

Temuco

Congreso; Congreso Latinoamericano de IUFRO de Ecología de Paisajes y Segundo Congreso Latinoamericano de IALE; 2016

IALE

The use of forest by livestock could have substantial effects on forest structure and dynamics, via grazing and trampling. It can affect tree seedling establishment, survival and community structure and composition. However, the type and magnitude of livestock impact on forest ecosystems is determined by livestock type, grazing regime, but also by the landscape structure (e.g. forest-steppe edge, forest patch size). We present results of different studies about herbivory impact on Nothofagus antarctica recruitment in forests used for livestock in Tierra del Fuego (TDF) and compared findings for stand- versus landscape-level studies to determine lessons for tree-herbivore interactions and management. At stand level, livestock reduce density and total height ofseedling but in some cases the influence of canopy cover determine high survival rate. Moreover, there is a cumulative effect of livestock and wild ungulates (e.g. guanacos) herbivore on tree recruitment. For example, areas grazed only by guanacos (livestock exclusion) support the same seedling density and did not reduce browsing damage compared to areas grazed by all type of herbivores. On the other hand, recent evidence shows that type of livestock causes different degree of soil compaction, regardless grazing period. For example, fieldssupporting heavy animals (cattle) during a short period increase soil compaction compared with lighter animals (sheep) grazing year-round influencing seedling growth. Moreover, cattle and sheep graze differently over different habitat types (ñire forest, riparian meadows and grasslands). Landscape studies show higher browsing pressure but also greater seedling density in forest-grasslands edges than inside forest patches. Moreover, some landscape metrics (e.g. exposition) influence such recruitment dynamic determining some vulnerable areas to herbivory. Currently more and more ranches are converting sheep production for cattle production. In this context, a multi-scale perspective can prove valuable to contextualize existing information for sustainable livestock management in TDF.