Recent invasion of buffel grass (Cenchrus ciliaris) of a natural protected area from the southern Sonoran Desert

Abstract

THE CENTRO ECOLÓGICO DE SONORA IS A NATURAL PROTECTED AREA WHERE THE NATURAL VEGETATION REMAINED UNDISTURBED AT LEAST UNTIL 1997. SINCE THEN, CENCHRUS CILIARIS HAS BECOME A PROMINENT ELEMENT OF THE VEGETATION BECAUSE OF DISTURBANCE. CLIMATE, SOIL PROPERTIES, POPULATION STRUCTURE AND BIOLOGICAL ACTIVITY FOR C. CILIARIS WERE STUDIED TO GAIN UNDERSTANDING OF THE ECOLOGICAL MECHANISMS THAT FAVORED THE INVASION BY THIS EXOTIC GRASS. MEAN AIR TEMPERATURE AND ANNUAL RAINFALL WERE 24.8°C AND 302 MM. THE SOIL WAS A LOAMY-SAND THAT WAS POOR IN MOST NUTRIENTS, BUT PARTICULARLY RICH IN PHOSPHORUS. PENNISETUM CILIARE WAS THE MOST ABUNDANT SPECIES AT THE CENTRO ECOLÓGICO, REPRESENTING OVER ONE THIRD OF TOTAL PLANT GROUND COVER. BASAL AREA FOR INDIVIDUAL PLANTS RANGED FROM LESS THAN 1 CM2 TO ALMOST 1 M2. LIVING LEAVES PER PLANT INCREASED WITH PRECIPITATION, PEAKING AT 199 LEAVES IN MARCH 2005, AND NO LIVING LEAVES WERE FOUND AFTER 103 DAYS WITHOUT RAIN. THE ENVIRONMENTAL CONDITIONS PREVALENT AT CENTRO ECOLÓGICO ARE VERY FAVORABLE FOR C. CILIARIS, WHOSE ESTABLISHMENT WAS APPARENTLY TRIGGERED BY A MAJOR DISTURBANCE CAUSED BY THE DEVELOPMENT OF HOUSING PROJECTS.