INVESTIGADORES
FARJI-BRENER Alejandro Gustavo
artículos
Título:
Slope orientation enhances the nurse effect of a paramo shrub, Hypericum irazuense (Hyperaceae) in Costa Rica
Autor/es:
FARJI-BRENER, AG
Revista:
JOURNAL OF TROPICAL ECOLOGY
Editorial:
Cambridge University Press
Referencias:
Lugar: Cambridge; Año: 2009 vol. 25 p. 331 - 335
ISSN:
0266-4674
Resumen:
Positive interactions between plants can structure plant communities and increase biological diversity. Several works have documented that the magnitude of nurse effect increases along environmental severity gradients at large spatial scales. We evaluated whether the nurse effect of Hypericum irazuense (Hypericaceae) changes when environmental stress varies at small spatial scales. In a Costa Rican Paramo, we sampled the vegetation beneath the crown of H. irazuense shrubs and adjacent open areas in both west and the nearest east slope. The east slope was considered a more stressful environment because it receives solar radiation in the morning (which is often sunny) whereas the west slope receives solar radiation during the afternoon (which is often cloudy). Plant richness was higher in the west than in the east slope, and higher under H. irazuense canopy than in control plots. However, the strength of the nurse effect was greater in the east slope. Our results reveal that H. irazuense acts as nurse plant and confirm that the magnitude of this effect increases with environmental stress, even in stress gradients at scales of several meters.  Because east and west slopes are similar with respect to soil type, herbivore pressure and other types of disturbances, the amelioration of soil temperatures is probably the mechanism through which H. irazuense improves plant species richness. This effect allowed less heat-tolerant plant species to grow under nurse plants. Our findings indicate that in a high-mountain, stressed environments, nurse shrubs may be disproportionately important in maintaining and restoring plant biodiversity.