A Floristic Study of Volcan Mombacho Department of Granada, Nicaragua

Abstract

Volcdn is a moderate sized (1,345 m elev.), quiescent volcano with one of two cloud forests in southwestern Nicaragua. Of 457 species listed, 80 are pteridophytes and 87 are orchids. The species richness of these groups may be accounted for by their high fecundity and dispersibility. This study has revealed only one endemic species. Since is the apparent northern range limit of several orchid species, it is suggested that the flora of the cloud forest has most of its affinities with Costa Rica. The lack of several wide ranging species on which are known only as far south as northern Nicaragua further supports this contention. As with most of tropical America, the cloud forests of are threatened by exploitation of their natural resources. Volcan (Fig. 1) is a quiescent, much eroded, and well vegetated volcano located near the city of Granada, Nicaragua. Mombacho is a modification of the Nahuatl Mopachotepetl meaning inclined mountain (Mantica, 1973). It is located at 1 1050'N latitude, 85059'W longitude (see map, Fig. 2), and is the fifth largest of the quaternary volcanos in western Nicaragua forming a chain from El Salvador to Costa Rica (Mooser et al., 1958). With a maximum elevation of 1,345 m, is somewhat lower than several other Nicaraguan volcanos, the highest of which is 1,745 m. It is, however, perhaps the most massive with a basal diameter of about 7 km. Its U-shaped crater rim is 1.5 km in diameter and the crater floor is about 750 m lower than the highest peak. The lowest point on the crater rim is 1,080 m. Besides the highest peak of the southeast crater rim, there is a second peak on the northwest rim with an elevation of 1,222 m. Adjacent to this peak is a large flat area appropriately called de las Flores. Within this area are two small vegetated craters each of unknown depth and about 200 m in diameter. Eastward from Plan de las Flores lies a trough-shaped valley over 1.5 km across extending northeast from the crater rim for a distance of 3.5 km. Aerial photographs reveal a number of lava flows extending down the sides of Mombacho, but these features have been obscured in the northeast valley and the open south side of the crater rim by later seismic events. The lava flows are for the most part fully vegetated, and their basal limits are sharply defined where they meet