DIVERSIDAD FLORÍSTICA DE UN BOSQUE NUBOSO EN PACTO, PICHINCHA - ECUADOR

Abstract

In july 2003 we carried out a botanic research in the evergreen foothill forests of the Sardinas river basin, in the area of Pacto, province of Pichincha (coordinates 78°51.37’W - 00°12’N, 78°51.39’W - 00C11.23'N, altitude 770 - 1100 m). We applied a linear model of 50 X 4 m X 5 transects (0.1 ha) at three sites of different altitudes in the river basin; we look for species with DBH > 2.5 cm. Botanic samples are kept in the Alfredo Paredes herbarium (QAP). We calculated the corrected Simpson Diversity Index and the Sorensen’s Similarity Index for the three sites. In the first sampling site (lower part of the river) we found 208 individuáis of 61 species. The Diversity Index (DI) was 17.9; the most common species were Iriartea deltoidea, Theobroma gileri, Pitcairnia clarkii, Miconia barbinervis and Pentagonia ?. In the second sampling site (middle part of the river) we found 174 individuáis of 75 species; the DI was 25.66. The most common species were Faramea cf. oblongifolia, Geonoma undata, Otoba novogranatensis, Wettinia radiata and Inga leiocalycina. In the third sampling site we found 155 individuáis of 65 species; the DI was 25.76. The most common species were O. novogranatensis, Faramea fragrans, Ocotea cf. floccifera, Eugenia cf. florida and Tovomita weddelliana. For the three sites, the Dl’s pointed to a mean to low diversity. The sampling sites had a different density, a mean to low alpha diversity and similar species number; however, the composition of the vegetation and the altitude were different. The percentage of similarity between the sampling sites ranged from 27 to 37.1%. Beta diversity in the Sardinas river basin consisted of 149 species. Fifteen species (10 %) were found throughout the altitudinal gradient and 20 species (13.4 %) were endemic, including Virola reidii and Matisia grandifolia, recorded from Esmeraldas, and Pitcairnia clarkii from Bilsa - Esmeraldas. The forests of the Sardinas river basin are among the last remnants in fhe hills of the western Andes in the Pichincha province. These forests are important regulators of the water volume of the upper basin; they also present a high endemism and are the distributional limit of several species of the Coastal región.