Freezing tolerance in grasses along an altitudinal gradient in the Venezuelan Andes

Published in Oecologia

Marquez EJ, Rada F, Fariñas M

Publication year 2006

Instituto de Ciencias Ambientales y Ecológicas (ICAE), Facultad de Ciencias, Universidad de Los Andes, Mérida, 5101, Venezuela

Edjuly J. Márquez, Fermín Rada & Mario R. Fariñas

Universidad Nacional Experimental Francisco de Miranda, Centro de Investigación en Ecología y Zonas Aridas (CIEZA), Calle Mapararí, entre callejón las Flores y Cristal, Coro 4101-A, Edo. Falcón, Venezuela

Edjuly J. Márquez

IAI Program


IAI Project CRN040


The tropical high Andes experience greater daily temperature oscillations compared to seasonal ones as well as a high frequency of night frost occurrence year round. Survival of organisms, under such environmental conditions, has been determined by selective forces which have evolved into adaptations including avoidance or tolerance to freezing. These adaptations have been studied in different species of trees, shrubs and perennial herbs in páramo ecosystems, while they have not been considered in grasses, an important family of the páramo. In order to understand survival of Poaceae, resistance mechanisms were determined. The study was performed along an altitudinal gradient (2,500-4,200 m a.s.l.) in the páramo. Supercooling capacity and frost injury temperature were determined in nine species in order to establish cold resistance mechanisms. Grasses registered a very low supercooling capacity along the altitudinal gradient, with ice formation between -6 and -3°C. On the other hand, frost injury temperature oscillated between -18 and .7°C. Our results suggest that grasses exhibit freezing tolerance as their main cold resistance mechanism. Since grasses grow at ground level, where greatest heat loss takes place, tolerance may be related to this life form as reported for other small life forms.