Ecology of forests on the western slopes of the Peruvian Andes
Dry cloud forests on the western slopes of the Peruvian Andes were mapped from aerial photographs, 306 stands being recorded from 4o50'S to 12o47'S. The frequency and area of these stands, as well as most parameters analyzed in the eight sample sites, show a steep decreasing latitudinal trend and are strongly correlated with the latitudinal rainfall gradient. The mean area of the forest stands decreases from 115 ha in northern Peru to 42 ha in central Peru. The number of species recorded decreases along the study area from 52 to 13 and there is a well defined latitudinal sequence of species. Mean density and basal area per hectare of stems ≥10 cm gbh decreases from 2995 individuals and 79.91 m^2 in the north to 500 individuals and 17.27 m^2 in central Peru. The vertical structure is similar throughout the study area, emergent trees reaching on average 22 m and the main canopy 12 m in the north and 13 m and 7 m respectively in central Peru. Regeneration is very active in northern Peru. Juveniles have been found for a high proportion of species, including all common ones, and most species show a logarithmic decline in number of stems with increasing girth. There is a steep decreasing trend towards central Peru, where few species regenerate, mostly shrubs. The pattern found may be the result of the combined effect of grazing and a climatic change towards drier conditions evidenced in the regeneration pattern of most sites.