IMBIV   05474
INSTITUTO MULTIDISCIPLINARIO DE BIOLOGIA VEGETAL
Unidad Ejecutora - UE
artículos
Título:
The effect of altitude and grazing on seedling establishment of woody species
Autor/es:
MARCORA, P.; RENISON, D.; PAIS BOSCH, A.; CABIDO, M; TECCO, P
Revista:
FOREST ECOLOGY AND MANAGEMENT
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2013 p. 300 - 307
ISSN:
0378-1127
Resumen:
Understanding the factors that determine altitudinal distribution of species is very important to evaluate
the influence of global change. Although climate is the major driver of vegetation distribution, other factors,
such as herbivory by livestock, can be more important locally and regionally. Despite its importance,
the altitudinal range distribution of species and how it is influenced by climate and livestock are generally
unknown. In the Sierras Grandes Mountains of central Argentina, woodlands of lower and upper altitudes
are interrupted by an intermediate vegetation belt devoid of forest. Traditionally, this pattern was
assumed to be determined by climate, although recent studies suggest that forest distribution would be
driven by livestock grazing. However, the potential altitudinal range distribution of the principal woody
species of these forests and how it is affected by livestock are still poorly known. In this study, we used an
experimental approach to evaluate seedling survival and growth ? with and without livestock presence ?
of the three principal woody species of the mountain woodlands along the entire altitudinal gradient of
Sierras Grandes. In January 2009, we planted seedlings of Polylepis australis, Maytenus boaria and
Escallonia cordobensis inside and outside livestock exclosures at seven altitudinal sites established every
200?400 m asl, from 940 m asl to 2700 m asl (i.e., maximum altitude of Sierras Grandes). During the
three following winters, we evaluated seedling survival and height and measured stocking rates.
Although the three species were able to sprout after browsing, livestock markedly reduced seedling
survival and height. Inside the exclosure, the three species successfully survived and grew along the
entire gradient, including the altitudinal belt devoid of forest. Furthermore, after three growing seasons
P. australis and E. cordobensis flowered inside the exclosure at the altitudes where seedlings reach greater
heights (2200 m asl and 1200 and 1600 m asl, respectively). We suggest that under the current high
stocking rates, livestock would strongly hinder seedling establishment of the three principal woody
species at most altitudes of Sierras Grandes. Our findings are in agreement with the assumption that
the present altitudinal belt devoid of forest is not climatically driven; rather, livestock is the major factor
of current forest distribution.