干旱区生态环境知识资源中心

A fire in the Monte Desert brought about an abrupt decrease in grass cover and the subsequent invasion by forbs. This led bird species that fed on seeds and buds on the ground to segregate spatially between burned and unburned sites (while there was food in the burned habitat). Owing to the disappearance of food resources from the burned sites, four bird guilds withdrew from those sites, while the generation of new resources led to the selection of the burned habitat by two guilds scarcely represented in the unburned area. These modifications in habitat use brought about a decrease in local bird diversity and an increase in regional bird diversity. The structural simplification of the habitat in burned sites may account for the decrease in local diversity, according to the theory of habitat selection. The increase in regional diversity may be a consequence of the complementary spatial distributions between burned and unburned areas of species belonging to different guilds (either stressed or favored by the disturbance). The intermediate disturbance hypothesis explains satisfactorily the increase in regional bird diversity after the fire.