Cloud forests on rock outcrop and volcanic soil differ in indicator tree species in Veracruz, Mexico

Abstract

The tropical montane cloud forest (TMCF) of central Veracruz, Mexico, predominantly grows on volcanic substrate from the Quaternary (2–0.08 Mya), but in very small areas it grows on shallow soils over limestone rock outcrops from the Cretaceous (90 Mya). Our objective was to contrast the vegetation structure and tree species composition of forest communities growing on rock outcrops (FOR) with nearby forests on prevalent volcanic soil (FOV). Results show that species richness and vegetation structure were similar between FOR and FOV. However, a clear difference was revealed by indicator species analysis (ISA), and multinomial classification model (CLAM). ISA and CLAM, respectively, identified 14 indicators and 13 specialists in FOR, whereas, they identified 7 indicators and 14 specialists in FOV. Some FOR indicators were Cercis canadensis, Clusia guatemalensis, Garrya laurifolia, Ostrya virginiana and Quercus pinnativenulosa. Some FOV indicators were Carpinus tropicalis, Clethra macrophylla, Liquidambar styraciflua and Quercus xalapensis; these species are also common in several Mexican TMCF. Our study demonstrates that the tree community on rock outcrops differs from the surrounding forest on volcanic soils; this is of particular interest because of its different species assemblage and contribution to the high beta diversity of the region.