Ecosystem response to natural and anthropogenic disturbances in the Andean cloud forest of Ecuador

Gall midges were found in herbarium specimens of bamboo, Guadua paniculata and Fargesia nitida. The Brazilian cecidomyiids were Contarinia sp. and the Chinese specimens were related to the rice gall midge, Orseolia oryzae. No bamboo of any species has been previously described as a host plant for cecidomyiids.; Repeat aerial photography and ground observation were used to quantify changes in land use near Pasochoa Volcano, Ecuador. Fractions of the study region were assigned to natural (paramo, cloud forest) and managed (crop, pasture) landscape categories. These data showed a 7.2% decrease in land used for grazing and agriculture, a 4.6% increase in paramo, and a 2.2% increase in woody vegetation, between 1956 and 1987. Fire and grazing are likely caused for the increase in high-elevation grassland and the new woody cover was due to an increase in the extent of the bamboo, Chusquea, that colonized disturbed areas.; Interactions among plant colonists following disturbance influence species diversity of forests. Paired plots (bamboo intact, bamboo removed) were established. Species composition was interpreted in terms of biotic and abiotic environmental factors. Detrended correspondence analysis indicated that the abundance of non-bamboo species was most strongly influenced by the presence of Chusquea. Slope and aspect were the most important abiotic factors in determining species composition.; Vegetation reorganization was studied on the floodplain and on landslide sites in mid-elevation Andean forest following the 1987 earthquakes in northeastern Ecuador. Disturbed and undisturbed sites were sampled using transects and small quadrats. Tessaria integrifolia dominated the floodplain a year after the earthquakes. The number of individuals of that species per unit ground area was negatively correlated with distance from the floodplain (p {dollar}<{dollar} 0.001). Other floodplain colonizers, Gynerium sagittatum and Piper spp., became more prominent later. Chusquea sp. became established on a landslide site two years post-earthquake. Cluster analysis was used to classify the sites according to their similarity based on relative species abundance. The undisturbed forest was similar (0.76) to the upper landslide zone, and dissimilar (0.18) to the floodplain. These data suggest that distance from potential immigrants affects the species composition of early colonizers. Landslide disturbances are among the factors that create and maintain high organismal diversity on Andean watersheds.