A life-form classification from Neotropical Gramineae is proposed for 113 native species from eastern lowland Bolivia. A factor analysis was performed on a correlation matrix of 51 vegetative attributes to identify ‘character suites,’ which were then used as the basis for the classification. The principal types are arboreal, liana, shrub-like, forb-like, bunch grass with basal foliage, bunch grass with basal and caulescent foliage, caespitose annuals, elongate rhizomes, turf grass, stoloniferous, and decumbent (the last category is further divided into subgroups: -perennial, -indefinite, -floating aquatic, and -vine-like). A key component of the life-form classification is the morphology of leaf blades, with five major patterns recognized: elongate and inrolled, elongate and conduplicate, elongate and flat with an attenuate base, short and broad with an amplexicaule base, and short and broad with a pseudopetiole.
The distribution and relative abundance of three major photosynthetic categories were compared with life-form and habitat preference. Photosynthetic type of individual species was identified based on leaf anatomy. C4-(XyMS −) species predominated in cerradao, cerrado, campo rupestre, valleyside campos, and seasonally inundated savanna, as well as on granite outcrops. C4-(XyMS + ) species were relatively rare in all habitats, but were significantly more abundant in the xeric microenvironments of granite outcrops. C3 species predominated in semi-deciduous forest and increased in relative abundance in wetland habitats. Caespitose annuals and bunch grass species were predominantly C4 type, while arboreal and liana species were uniformly C3 type. Grasses classified as decumbent or shrub-like were predominantly C3 type, while rhizomatous, stoloniferous, and forblike grasses were a mixture of C3 and C4 type.
The intent of the study was to group morphological characteristics objectively in order to derive a life-form classification specific for the Gramineae. Comparisons of the relative abundance of the various life-forms in a broad range of habitat types provide a descriptive assessment of the adaptive value of these characteristics.